WO1996004793A1 - Methods and compositions for prolonging the release of carbon disulfide in soil - Google Patents

Methods and compositions for prolonging the release of carbon disulfide in soil Download PDF

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Publication number
WO1996004793A1
WO1996004793A1 PCT/US1995/009433 US9509433W WO9604793A1 WO 1996004793 A1 WO1996004793 A1 WO 1996004793A1 US 9509433 W US9509433 W US 9509433W WO 9604793 A1 WO9604793 A1 WO 9604793A1
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composition
group
organic
cations
soil
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PCT/US1995/009433
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French (fr)
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Donald C. Young
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Entek Corporation
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C329/00—Thiocarbonic acids; Halides, esters or anhydrides thereof
    • C07C329/02—Monothiocarbonic acids; Derivatives thereof
    • C07C329/04—Esters of monothiocarbonic acids
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
    • A01N47/00—Biocides, pest repellants or attractants, or plant growth regulators containing organic compounds containing a carbon atom not being member of a ring and having no bond to a carbon or hydrogen atom, e.g. derivatives of carbonic acid
    • A01N47/02—Biocides, pest repellants or attractants, or plant growth regulators containing organic compounds containing a carbon atom not being member of a ring and having no bond to a carbon or hydrogen atom, e.g. derivatives of carbonic acid the carbon atom having no bond to a nitrogen atom
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
    • A01N59/00—Biocides, pest repellants or attractants, or plant growth regulators containing elements or inorganic compounds
    • A01N59/04—Carbon disulfide; Carbon monoxide; Carbon dioxide

Definitions

  • the present invention relates to (a) carbon disulfide precursors and (b) methods for prolonging the release of carbon disulfide in soil.
  • Carbon disulfide and carbon disulfide precursors have been used to treat soil to control pests. However, shortly after treatment (i.e., generally less than about 4 days) there is very little or no pesticidal activity left. Accordingly, there is a need to prolong pesticidal activity after treating soil with carbon disulfide or a carbon disulfide precursor.
  • the present invention satisfies the need for prolonged pesticidal activity by providing compositions which exhibit extended pesticidal activity when applied to soil.
  • the composition comprises a combination of carbon disulfide precursors. More
  • composition comprises (a) at least one compound selected from monomeric
  • inorganic and organic cations a is the valence of M; b is a positive integer (i.e., 1 or a whole number greater than 1); c is at least 4; d is a positive integer, provided that a «b equals 2 ⁇ d; e is a positive integer; f is a positive integer; g is the valence of X; h is the valence of Y; i is a positive integer, provided that 2 ⁇ f equals (g + h)i; and X and Y are independently selected from the group consisting of inorganic cations and organic cations, provided that when g is 2 or greater there is no Y (and h, therefore, is zero); and (b) a xanthate having the formula
  • composition comprises a compound having the formula
  • the conversion rate increases with increasing temperature up to about 43.3°C (110°F). Above about 43.3°C (110°F) the conversion rate starts decreasing due to the denaturing of the responsible bacteria.
  • the moisture dependence of the conversion rate is due to the fact that water is one of the essential reactants in the sulfuric acid-forming reaction.
  • perthioxanthates it is believed that the charge density on perthioxanthates is less than on corresponding thiocarbonates.
  • perthioxanthates are thought to be more thermodynamically stable than corresponding thiocarbonates.
  • perthioxanthates are believed to decompose in the soil at a slower rate than corresponding thiocarbonates.
  • perthioxanthates also exhibit an extended release of carbon disulfide in soil because, instead of decomposing directly to carbon disulfide,
  • perthioxanthates first break down into xanthate and elemental sulfur.
  • the elemental sulfur gradually converts in situ to sulfuric acid, with the sulfuric acid reacting with the generated xanthate to form carbon disulfide and other reaction products.
  • compositions within the scope of the present invention exhibit pesticidal activity significantly longer than other carbon disulfide-generating compounds.
  • compositions within the scope of the present invention exhibit herbicidal activity at carbon disulfide application rates which do not elicit herbicidal activity from individual applications of either the thiocarbonate or xanthate components of the composition.
  • the monomeric thiocarbonates employed in the present invention have the formula (M +a ) b ((CS c ) -2 ) d where M is selected from the group consisting of
  • thiocarbonates are present); and d is a positive integer, provided that a ⁇ b equals 2 ⁇ d. Any number of monomeric thiocarbonates differing in b, c, and/or d values and/or M cationic species can be present in the compositions of the present invention.
  • oligomeric thiocarbonates used in the invention, these compounds have the formula where e is a positive integer or mixed number (generally 5 or less; e can be a mixed number when a plurality of different oligomeric thiocarbonates are present); f is a positive integer; g is the valence of X; h is the valence of Y; i is a positive integer, provided that 2 ⁇ f equals (g + h)i; and X and Y are independently selected from the group consisting of inorganic and organic cations, provided that when g is 2 or greater there is no Y. Any number of oligomeric thiocarbonates differing in e, f, g, h, and/or i values and/or X and/or Y cationic species can be present in the compositions of the present invention.
  • Preferred inorganic cations for M, X, and/or Y are ammonium ion, alkali metal cations (especially sodium and potassium), alkaline earth metal cations (especially magnesium and calcium), and transition metal cations (especially the micronutrients zinc, iron, manganese, copper, and molybdenum).
  • R 1 R 2 R 3 R 4 Q + where R 1 , R 2 , R 3 , and R 4 are independently selected from the group consisting of hydrogen and C 1 -C 50 organic groups (provided that at least one of R 1 , R 2 , R 3 , or R 4 is an organic group), Q + is selected from the group consisting of nonmetals, semi-metals, and metalloids, and the total number of carbon atoms in the organic cation is 1 to 60.
  • the organic groups can be derived from
  • each R 1 , R 2 , R 3 , and R 4 comprises up to about 20 carbon atoms and the total number of carbon atoms in the organic cation is 1 to 40.
  • each of R 1 , R 2 , R 3 , and R 4 is a hydrocarbyl group having from 1 to about 8 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl, isobutyl, hexyl, octyl, phenyl, and benzyl), with the total number of carbon atoms in the organic cation being 24 or less.
  • the most preferred hydrocarbyl groups are alkyl groups, especially alkyl groups having from 1 to about 4 carbon atoms.
  • Q is preferably nitrogen, phosphorus, arsenic, or antimony, with the corresponding organic cations being primary, secondary, tertiary, and quaternary ammonium, phosphonium, arsonium, and stibonium cations. More preferably, the organic cation is a quaternary ammonium cation.
  • the xanthates employed in the present invention have the formula
  • R 5 is an organic group, such as described above with respect to R 1 to R 4 ;
  • Z is selected from the group
  • inorganic cations and organic cations consisting of inorganic cations and organic cations, such as the inorganic and organic cations discussed above with respect to M, X and Y; and j is the valence of Z (i.e., a positive integer such as 1, 2, 3, etc.).
  • the monomeric and oligomeric thiocarbonates as well as the xanthates are preferably water soluble.
  • water soluble means that the compound in question can form an aqueous solution containing at least about 10 weight percent of the compound at 20°C.
  • the monomeric and oligomeric thiocarbonate and the xanthate compounds employed in the present invention form aqueous solutions comprising at least about 20, even more
  • the preferred alkaline earth metals are magnesium and
  • alkali metals sodium and potassium because monomeric thiocarbonates containing these particular alkaline earth and alkali metals tend to be more soluble and less expensive than monomeric
  • hexathiocarbonate (where a equals 1, b equals 2, c equals 6, and d equals 1) decomposes according to the following chemical reactions:
  • oligomeric thiocarbonates decompose in soil through the following sequential reactions:
  • Thiobacillus species which are ubiquitous in soil, slowly oxidize elemental sulfur to sulfuric acid (i.e., a strong acid) which produces a local pH of less than about 2.
  • sulfuric acid i.e., a strong acid
  • the xanthates and thiocarbonates are simultaneously applied to the soil (usually in the form of an aqueous solution), the xanthates are in the same locality as the above-generated sulfuric acid.
  • the sulfuric acid reacts with xanthates to release carbon disulfide in accordance with the following chemical reaction:
  • the moles of elemental sulfur generated by the complete decomposition of the thiocarbonates present in the composition of the present invention can be
  • composition comprises y different oligomeric thiocarbonates and z different monomeric thiocarbonates, N O1 is the number of moles of a first oligomeric
  • N O2 is the number of moles of a second oligomeric thiocarbonate having m O2 repeating
  • N M1 is the number of moles of a first monomeric
  • N M2 is the number of moles of a second monomeric thiocarbonate having c M2 ⁇ d M2 sulfur atoms
  • N Mz is the number of moles of a zth monomeric thiocarbonate having c Mz ⁇ d Mz sulfur atoms.
  • N xanthate the stoichiometric relationship between the number of moles of generated elemental sulfur and the total number of moles of decomposable xanthate anion
  • N xanthate 2 (e O1 ⁇ f O1 ⁇ N O1 + e O2 ⁇ f O2 ⁇ N O2 + . . . + e Oy ⁇ f Oy ⁇ N Oy + d M1 (c M1 - 3 ) N M1 + d M2 (c M2 - 3 ) N M2 + . . . +
  • the thiocarbonate compound(s) are preferably present in the composition in a stoichiometric excess (e.g., 1.01, 1.05, or 1.1 times the stoichiometric concentration).
  • composition of the present invention comprises one mole of sodium
  • composition comprises a perthioxanthate having the formula
  • R 5 , Z, and j are as described above and t is a positive integer or mixed number, e.g., 1, 2, 3, 3.6, 4, or more (t can be a mixed number when a plurality of different perthioxanthates are present) .
  • t is a positive integer or mixed number, e.g., 1, 2, 3, 3.6, 4, or more (t can be a mixed number when a plurality of different perthioxanthates are present) .
  • the higher the integer t the more stable the perthioxanthate and the longer the delayed release of carbon disulfide.
  • the perthioxanthates are preferably water soluble, and preferably form aqueous solutions comprising at least about 20, even more preferably at least about 30, and most preferably at least 40, weight percent of such compounds.
  • Z is an alkaline earth metal
  • Z is preferably selected from magnesium and calcium
  • Z is preferably selected from sodium and potassium because these
  • perthioxanthate to xanthate and elemental sulfur the subsequent in situ conversion of the generated elemental sulfur to sulfuric acid, and the eventual reaction of the sulfuric acid with the xanthate to form carbon disulfide and other reaction products.
  • the decomposition of perthioxanthates in soil can be represented as follows:
  • the Thiobacill ⁇ s species present in soil can theoretically oxidize each of the above t ⁇ j generated elemental sulfurs to sulfuric acid as follows:
  • compositions of the present invention can also be present in the composition of the present invention.
  • water is generally present, with the composition preferably being an aqueous solution.
  • the composition preferably also contains a base and/or a sulfide having the formula
  • D is selected from the group consisting of organic and inorganic cations such as discussed above with respect to M, X, and Y; k is the valence of D; m is a positive integer; n is 1 or any whole or mixed number greater than 1 (and preferably from 1 to about 5); and p is a positive integer, provided that k «m equals 2p.
  • the preferred organic and inorganic cations for D are the same as preferred in the case of M, X, and Y.
  • the base employed preferably has a significant solubility in water. More preferably, the base is a water soluble inorganic base, with the most preferred bases being alkali metal and ammonium hydroxides.
  • the sulfide and/or base can be added to the thiocarbonate-containing aqueous solution or, more typically, is present in the thiocarbonate-containing aqueous solution as a result of using a stoichiometric excess of sulfide and/or base during the synthesis of the thiocarbonates.
  • a stoichiometric excess of sulfide and/or base is employed, the amount of sulfide and/or base used in the reaction is generally at least about 1.01, preferably at least about 1.02, more preferably about at least 1.04, and most preferably at least about 1.08 equivalents of sulfide and/or base per equivalent of carbon disulfide employed in the reaction.
  • the amount of added sulfide and/or base usually corresponds to at least about 0.01, preferably at least about 0.02, more
  • Hardness-complexing agents can also be used to retard precipitation of insoluble carbonates, e.g., calcium carbonate, which tend to plug drip irrigation emitters and sprinkler nozzles.
  • exemplary hardness- complexing agents are alkali metal hexametaphosphates (e.g., sodium hexametaphosphate and potassium
  • compositions of the present invention can further be combined with other agricultural chemicals to provide a multifunctional product.
  • the compositions can be combined with solid or liquid
  • ammoniacal compounds includes ammonia, ammonium- containing compounds (e.g., ammonium nitrate and ammonium sulfate), and ammonium-forming compounds (e.g., urea and biuret)). Techniques for synthesizing various monomeric and oligomeric thiocarbonates are respectively described in U.S.
  • Patent 5,256,424 and U.S. Patent 5,288,753 these patents being incorporated herein in their entireties by reference.
  • Other monomeric and oligomeric thiocarbonates can be made using analogous reactions.
  • a monomeric tetrathiocarbonate is commercially available; EnzoneTM brand sodium tetrathiocarbonate is sold by UNOCAL and extensively used in agricultural applications. Methods for preparing xanthates are well known to those skilled in the art and various xanthates are, in fact, commercially available.
  • the perthioxanthates can be prepared using different methodologies. In one procedure, the
  • perthioxanthates are prepared by reacting a xanthate having the formula (R 5 OCS 2 ) j Z +j (where R 5 , Z, and j are as previously defined) with sulfur for a sufficient period of time (e.g., about 3 hours) in a basic solution.
  • a xanthate having the formula (R 5 OCS 2 ) j Z +j where R 5 , Z, and j are as previously defined
  • perthioxanthates are prepared by reacting the above- described xanthate with a monomeric thiocarbonate having the formula (M +a ) b ((CS c ) -2 ) d (where M, a, b, c, and d are as previously defined) for a convenient period of time
  • the synthesis can be represented as follows: Na + (C 2 H 5 OCS 2 )- + Na 2 (CS 4 ) -2 ⁇ Na + (C 2 H 5 OCS 3 )- + Na 2 (CS 3 ) -2
  • the perthioxanthates are prepared by reacting the above- described monomeric thiocarbonate with a salt of an alcohol having the formula E +q (OR 6 ) -1 where E is selected from the group consisting of organic and inorganic cations such as discussed above with respect to D, M, X, and Y; q is the valence of E; and R 6 is an organic group.
  • E is selected from the group consisting of organic and inorganic cations such as discussed above with respect to D, M, X, and Y; q is the valence of E; and R 6 is an organic group.
  • the preferred organic and inorganic cations for E are the same as preferred in the case of D, M, X, and Y; and the preferred organic groups are the same as preferred for R 1 , R 2 , R 3 , and R 4 .
  • thiocarbonate and the salt of an alcohol is conducted for a convenient period of time (e.g., about 2 hour) in water.
  • a convenient period of time e.g., about 2 hour
  • the synthesis can be represented as follows:
  • any convenient pressure preferably, at atmospheric pressure.
  • compositions of the present invention can be employed as agricultural biocides in any application where tetrathiocarbonates as well as oligomeric
  • thiocarbonates can be used. They can be utilized in or on soil for the control of a wide variety of plant and animal pests, including insects, rodents, fungi,
  • compositions of the present invention can also be used as herbicides, especially pre- emergence herbicides, for the control of undesirable plants.
  • the herbicidal activity of the thiocarbonate- and xanthate-containing compositions is very surprising in view of the fact that these compositions exhibit herbicidal activity at carbon disulfide application rates which do not elicit herbicidal activity from individual applications of either the thiocarbonate or xanthate components of the composition.
  • compositions are generally applied as a solution by spraying onto the soil surface. More
  • compositions are added to and then applied as part of irrigation water.
  • concentration of releasable carbon disulfide in the aqueous solution is typically about 50 to about 10,000, preferably about 100 to about 5,000, more preferably about 1,000 to about 3,000, and most preferably about 2,000, ppmw.
  • the water slows the diffusion of the carbon disulfide from the soil into the air, and thus prolongs contact between the carbon disulfide and soil pests.
  • Injection into the soil, using a shank or knife, is also a useful method for applying the
  • the injectors are usually either closely spaced to treat essentially the entire field area, or spaced such that only the plant growing beds are treated.
  • the application rate for a particular situation depends on many factors, such as the pest or pests to be controlled, the crop to be protected and its stage of growth, soil moisture and other conditions, and the like.
  • the compositions provide beneficial effects at application rates as low as about 0.45 kg (1 1b), preferably at least about 2.27 kg (5 1b), of
  • the compositions are applied at rates of about 4.54 kg (10 lb) to about 226.80 kg (500 1b), preferably less than about 112.40 kg (250 1b), more preferably less than about 56.70 kg (125 1b), and most preferably from about 6.80 kg (15 1b) to about 34.02 kg (75 1b), releasable carbon disulfide content per acre. If the compositions are applied in a localized manner, for example under the drip lines of trees, the effective application rate can be much higher than the average per acre, since only the soil in the root zones is actually treated.
  • compositions can be mixed with the loose soil from the hole, which is then placed around the roots of the new tree. This controls pests in and around the planting hole and provides a healthier environment for the new tree to become established.
  • compositions of the present invention generally contain little, or no,
  • the perthioxanthates is typically less than about 10 to 100.
  • the mole ratio is less than about 5 to 100, more preferably less than about 1 to 100, even more preferably less than about 0.5 to 100, and most preferably less than about 0.1 to 100.
  • thiocarbonate compounds or the perthioxanthates will be less than 0.05 to 100, more frequently less than about 0.01 to 100, even more frequently less than about 0.005 to 100, and most frequently less than about 0.001 to 100.
  • Example 1 and Comparative Examples 1-2 were replicated four times using the following procedure per replication or treatment.
  • Unsterilized, sandy loam soil about 1,000 g was placed in a 2,000 ml beaker and saturated with about 250 ml water.
  • each beaker was treated with about 1,500 ppmw of carbon disulfide derived from either a solution comprising ethyl xanthate and EnzoneTM brand sodium tetrathiocarbonate (Example 1) or straight EnzoneTM brand sodium tetrathiocarbonate
  • Each of the control and carbon disulfide- treated beakers was then inoculated daily with about 10 ml of an active suspension of Phytophthora Parasitica .
  • Example 1 and Comparative Examples 1-2 were not sterilized and,
  • Enzone/ethyl xanthate solution in Example 1 weed seeds germinated in all soil samples treated with either Enzone (i.e., in Comparative Example 1) or ethyl xanthate (i.e., in Comparative Example 2). Accordingly, the fact that the same total carbon disulfide equivalent application rate was employed in Example 1 and comparative Examples 1-2 indicates that the thiocarbonate-xanthate composition of the present invention exhibits synergistic herbicidal activity--especially synergistic pre-emergence herbicidal activity.

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Abstract

A composition comprising (a) a perthioxanthate and/or (b) a combination of (i) a thiocarbonate selected from the group consisting of oligomeric thiocarbonates, monomeric thiocarbonates containing at least 4 sulfur atoms, or combinations thereof and (ii) a xanthate exhibits prolonged pesticidal activity and synergistic herbicidal activity when applied to soil.

Description

METHODS AND COMPOSITIONS FOR PROLONGING THE RELEASE OF
CARBON PISULFIDE IN SOIL
BACKGROUND
The present invention relates to (a) carbon disulfide precursors and (b) methods for prolonging the release of carbon disulfide in soil. Carbon disulfide and carbon disulfide precursors have been used to treat soil to control pests. However, shortly after treatment (i.e., generally less than about 4 days) there is very little or no pesticidal activity left. Accordingly, there is a need to prolong pesticidal activity after treating soil with carbon disulfide or a carbon disulfide precursor.
SUMMARY OF THE INVENTION The present invention satisfies the need for prolonged pesticidal activity by providing compositions which exhibit extended pesticidal activity when applied to soil. In one embodiment, the composition comprises a combination of carbon disulfide precursors. More
specifically, in this version the composition comprises (a) at least one compound selected from monomeric
thiocarbonates having the formula
(M+a)b((CSc)-2)d, and/or oligomeric thiocarbonates having the formula
Figure imgf000003_0001
where M is selected from the group consisting of
inorganic and organic cations; a is the valence of M; b is a positive integer (i.e., 1 or a whole number greater than 1); c is at least 4; d is a positive integer, provided that a«b equals 2·d; e is a positive integer; f is a positive integer; g is the valence of X; h is the valence of Y; i is a positive integer, provided that 2·f equals (g + h)i; and X and Y are independently selected from the group consisting of inorganic cations and organic cations, provided that when g is 2 or greater there is no Y (and h, therefore, is zero); and (b) a xanthate having the formula
(R5OCS2)jZ+j where R5 is an organic group; Z is selected from the group consisting of inorganic and organic cations; and j is the valence of Z. (As used in the specification and claims, the term "inorganic cation" means a cation devoid of any carbon atom; the term "organic cation" means a cation containing at least one carbon atom; and the term
"organic group" means a group containing at least one carbon atom.) In another embodiment, the composition comprises a compound having the formula
Figure imgf000004_0001
where R5, Z, and j are as described above and t is a positive integer. (Hereinafter, the above compounds will be referred to as "perthioxanthates".) Without being bound by any particular theory of operation, it is believed that the simultaneous soil application of the xanthate and the above-described monomeric and/or oligomeric thiocarbonate yields a prolonged release of carbon disulfide due to the initial release of carbon disulfide and elemental sulfur from the decomposition of the thiocarbonate, the gradual or delayed in situ conversion of the elemental sulfur to sulfuric acid, and the subsequent production over time of additional carbon disulfide because of the reaction of the sulfuric acid with the xanthate. (The conversion rate of elemental sulfur to sulfuric acid is temperature and moisture dependent. More particularly, below about 15.6°C (60°F) there is negligible conversion of elemental sulfur to sulfuric acid, whereas above about 15.6°C
(60°F) the conversion rate increases with increasing temperature up to about 43.3°C (110°F). Above about 43.3°C (110°F) the conversion rate starts decreasing due to the denaturing of the responsible bacteria. The moisture dependence of the conversion rate is due to the fact that water is one of the essential reactants in the sulfuric acid-forming reaction.)
Regarding perthioxanthates, it is believed that the charge density on perthioxanthates is less than on corresponding thiocarbonates. In other words,
perthioxanthates are thought to be more thermodynamically stable than corresponding thiocarbonates. Hence,
perthioxanthates are believed to decompose in the soil at a slower rate than corresponding thiocarbonates. In addition, perthioxanthates also exhibit an extended release of carbon disulfide in soil because, instead of decomposing directly to carbon disulfide,
perthioxanthates first break down into xanthate and elemental sulfur. The elemental sulfur gradually converts in situ to sulfuric acid, with the sulfuric acid reacting with the generated xanthate to form carbon disulfide and other reaction products. As shown below in the comparative examples, compositions within the scope of the present invention exhibit pesticidal activity significantly longer than other carbon disulfide-generating compounds. In
addition, compositions within the scope of the present invention exhibit herbicidal activity at carbon disulfide application rates which do not elicit herbicidal activity from individual applications of either the thiocarbonate or xanthate components of the composition. DETAILED DESCRIPTION OF THE INVENTION
The monomeric thiocarbonates employed in the present invention have the formula (M+a)b((CSc)-2)d where M is selected from the group consisting of
inorganic and organic cations; a is the valence of M; b is a positive integer; c is 4 or any whole or mixed number above 4 (e.g., 5, 5.3, 6, 7, etc; c can be a mixed number when a plurality of different monomeric
thiocarbonates are present); and d is a positive integer, provided that a·b equals 2·d. Any number of monomeric thiocarbonates differing in b, c, and/or d values and/or M cationic species can be present in the compositions of the present invention.
Regarding oligomeric thiocarbonates used in the invention, these compounds have the formula
Figure imgf000007_0001
where e is a positive integer or mixed number (generally 5 or less; e can be a mixed number when a plurality of different oligomeric thiocarbonates are present); f is a positive integer; g is the valence of X; h is the valence of Y; i is a positive integer, provided that 2·f equals (g + h)i; and X and Y are independently selected from the group consisting of inorganic and organic cations, provided that when g is 2 or greater there is no Y. Any number of oligomeric thiocarbonates differing in e, f, g, h, and/or i values and/or X and/or Y cationic species can be present in the compositions of the present invention.
Preferred inorganic cations for M, X, and/or Y are ammonium ion, alkali metal cations (especially sodium and potassium), alkaline earth metal cations (especially magnesium and calcium), and transition metal cations (especially the micronutrients zinc, iron, manganese, copper, and molybdenum).
If an organic cation is chosen for M, X, and/or Y, the most suitable are of formula
R1R2R3R4Q+ where R1, R2, R3, and R4 are independently selected from the group consisting of hydrogen and C1-C50 organic groups (provided that at least one of R1, R2, R3, or R4 is an organic group), Q+ is selected from the group consisting of nonmetals, semi-metals, and metalloids, and the total number of carbon atoms in the organic cation is 1 to 60. The organic groups can be derived from
aliphatic, alicyclic, or aromatic compounds, and include straight chain, branched chain, and cyclic structures. The organic groups can be, for example, substituted or unsubstituted alkyl, alkenyl, alkynyl, aryl, arylalkyl, or alkylaryl groups, and can include heteroatoms such as oxygen, sulfur, nitrogen, and phosphorus. Preferably, each R1, R2, R3, and R4 comprises up to about 20 carbon atoms and the total number of carbon atoms in the organic cation is 1 to 40. More preferably, each of R1, R2, R3, and R4 is a hydrocarbyl group having from 1 to about 8 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl, isobutyl, hexyl, octyl, phenyl, and benzyl), with the total number of carbon atoms in the organic cation being 24 or less. The most preferred hydrocarbyl groups are alkyl groups, especially alkyl groups having from 1 to about 4 carbon atoms.
Q is preferably nitrogen, phosphorus, arsenic, or antimony, with the corresponding organic cations being primary, secondary, tertiary, and quaternary ammonium, phosphonium, arsonium, and stibonium cations. More preferably, the organic cation is a quaternary ammonium cation.
The xanthates employed in the present invention have the formula
(R5OCS2)j Z+j where R5 is an organic group, such as described above with respect to R1 to R4; Z is selected from the group
consisting of inorganic cations and organic cations, such as the inorganic and organic cations discussed above with respect to M, X and Y; and j is the valence of Z (i.e., a positive integer such as 1, 2, 3, etc.).
The monomeric and oligomeric thiocarbonates as well as the xanthates are preferably water soluble. (As used in the specification and claims, the term "water soluble" means that the compound in question can form an aqueous solution containing at least about 10 weight percent of the compound at 20°C.) More preferably, the monomeric and oligomeric thiocarbonate and the xanthate compounds employed in the present invention form aqueous solutions comprising at least about 20, even more
preferably at least about 30, and most preferably at least 40, weight percent of the compound. Accordingly, with respect to M of the monomeric thiocarbonates, the preferred alkaline earth metals are magnesium and
calcium, and the preferred alkali metals are sodium and potassium because monomeric thiocarbonates containing these particular alkaline earth and alkali metals tend to be more soluble and less expensive than monomeric
thiocarbonates containing other alkaline earth or alkali metals.
As noted above, it is believed that the
simultaneous soil application of the xanthate and the above-described monomeric and/or oligomeric thiocarbonate yields a prolonged release of carbon disulfide due to the initial release of carbon disulfide and elemental sulfur from the decomposition of the thiocarbonate, the gradual or delayed in situ conversion of the elemental sulfur to sulfuric acid, and the subsequent production over time of additional carbon disulfide because of the reaction of the sulfuric acid with the xanthate. More specifically, monomeric thiocarbonates decompose in soil through the following sequential reactions: (M+a)b((CSc)-2)d → (M+a)b((Sc-2)-2)d + dCS2
(M+a)b((Sc-2)-2)d → (M+a)b((Sc-3)-2)d + dS° (M+a)b((Sc-3)-2)d → (M+a)b((Sc-4)-2)d + dS°
...
(M+a)b((S2)-2)d → (M+a)b((S)-2)d + dS°
To illustrate a specific example, sodium
hexathiocarbonate (where a equals 1, b equals 2, c equals 6, and d equals 1) decomposes according to the following chemical reactions:
Na2CS6 → Na2S4 + CS2
Na2S4 → Na2S3 + S°
Na2S3 → Na2S2 + S°
Na2S2 → Na2S + S°
In addition, oligomeric thiocarbonates decompose in soil through the following sequential reactions:
Figure imgf000010_0001
((e+1) ·f)CS2 + (X+gY+h)iSf + (e·f)S°
Thus, when e is 2 and f, g, h, and i are each 1, the decomposition of the oligomeric thiocarbonate occurs as follows:
Figure imgf000010_0002
Furthermore, Thiobacillus species, which are ubiquitous in soil, slowly oxidize elemental sulfur to sulfuric acid (i.e., a strong acid) which produces a local pH of less than about 2. This oxidation process can be represented as follows:
Figure imgf000011_0001
Because the xanthates and thiocarbonates are simultaneously applied to the soil (usually in the form of an aqueous solution), the xanthates are in the same locality as the above-generated sulfuric acid. The sulfuric acid reacts with xanthates to release carbon disulfide in accordance with the following chemical reaction:
2(R5OCS2)jZ+j + JH2SO4→ (2·j)R5OH + Z2(SO4)j + (2·j)CS2
For example, when Z is a monovalent cation (e.g., sodium) and j is 1, the xanthate-sulfuric acid chemical reaction is as follows:
2(R5OCS2)Na + H2SO4 → 2R5OH + Na2(SO4) + 2CS2
Similarly, when Z is a divalent cation (e.g., calcium) and j is 2, the following chemical reaction ensues:
2(R5OCS2)2Ca + 2H2SO4 → 4R5OH + 2Ca(SO4) + 4CS2
Likewise, when Z is a trivalent cation (e.g., ferric iron) and j is 3, the chemical reaction can be
represented as follows:
2(R5OCS2)3Fe + 3H2SO4 → 6R5OH + Fe2(SO4)3 + 6CS2 Thus, for each mole of elemental sulfur produced from thiocarbonate decomposition, one mole of sulfuric acid is produced, with each mole of sulfuric acid reacting with two moles of xanthate anion (i.e., (R5OCS2)-) to generate two moles of additional carbon disulfide. Accordingly, each mole of produced elemental sulfur theoretically results in the conversion of two moles of xanthate anion to two moles of carbon disulfide.
The moles of elemental sulfur generated by the complete decomposition of the thiocarbonates present in the composition of the present invention can be
calculated using the formula
(eO1 · fO1 · NO1 + eO2 · fO2 · NO2 + ... + eOy · fOy · NOy + dM1 ( cM1 - 3 ) NM1 + dM2 ( cM2 - 3)NM2 + . . . +
dMz(cM2 - 3 ) NMz) where the composition comprises y different oligomeric thiocarbonates and z different monomeric thiocarbonates, NO1 is the number of moles of a first oligomeric
thiocarbonate having eO1 repeating (- S - (C = S) - S) units taken fO1 times, NO2 is the number of moles of a second oligomeric thiocarbonate having mO2 repeating
(- S - (C = S) - S) units taken fO2 times, NOy is the number of moles of a yth oligomeric thiocarbonate having mOy repeating (- S - (C = S) - S) units taken fOy times, NM1 is the number of moles of a first monomeric
thiocarbonate having cM1·dM1 sulfur atoms, NM2 is the number of moles of a second monomeric thiocarbonate having cM2·dM2 sulfur atoms, and NMz is the number of moles of a zth monomeric thiocarbonate having cMz·dMz sulfur atoms.
Accordingly, since each generated mole of elemental sulfur theoretically reacts with two moles of xanthate anion to generate two additional moles of carbon disulfide, the stoichiometric relationship between the number of moles of generated elemental sulfur and the total number of moles of decomposable xanthate anion (shown in the following formulas as "Nxanthate") can be represented by the formula
Nxanthate = 2 (eO1 · fO1 · NO1 + eO2 · f O2 · NO2 + . . . + eOy · fOy · NOy + dM1 (cM1 - 3 ) NM1 + dM2 (cM2 - 3 ) NM2 + . . . +
d Mz ( CM2 - 3 ) NMz)
To ensure that substantially all the xanthate present in the composition reacts to form additional carbon
disulfide, the thiocarbonate compound(s) are preferably present in the composition in a stoichiometric excess (e.g., 1.01, 1.05, or 1.1 times the stoichiometric concentration).
To illustrate, when the composition of the present invention comprises one mole of sodium
hexathiocarbonate (Na2CS6) and one mole of
tetraethylammonium hexathiodicarbonate
((C2H5)4N(CS3CS3)N(C2H5)4), eO1, fO1, NO1 each equals 1, cM1 equals 6, each of dM1 and NM1 equals 1, and the general formula for calculating the amount of elemental sulfur generated upon the complete decomposition of these thiocarbonates is
(eO1·fO1·NO1 + dM1(cM1 - 3)NM1)
Substituting the known values in the above simplified formula gives
(1·1·1 + 1· (6-3) ·1) = 4 Thus, since each mole of generated elemental sulfur theoretically reacts with two moles of xanthate anion to generate additional carbon disulfide, a composition comprising one mole of sodium hexathiocarbonate and one mole of tetraethylammonium hexathiodicarbonate can, in theory, stoichiometrically react with 8 moles of xanthate anion.
In another version of the invention, the composition comprises a perthioxanthate having the formula
Figure imgf000014_0001
where R5, Z, and j are as described above and t is a positive integer or mixed number, e.g., 1, 2, 3, 3.6, 4, or more (t can be a mixed number when a plurality of different perthioxanthates are present) . In general, the higher the integer t, the more stable the perthioxanthate and the longer the delayed release of carbon disulfide.
The perthioxanthates are preferably water soluble, and preferably form aqueous solutions comprising at least about 20, even more preferably at least about 30, and most preferably at least 40, weight percent of such compounds. Hence, when Z is an alkaline earth metal, Z is preferably selected from magnesium and calcium, and, when Z is an alkali metal, Z is preferably selected from sodium and potassium because these
particular cations tend to render the perthioxanthates more soluble and less expensive than corresponding perthioxanthates containing other alkaline earth or alkali metals. As previously noted, it is believed that the soil application of the perthioxanthates yields a
prolonged release of carbon disulfide because of, among other reasons, the initial decomposition of the
perthioxanthate to xanthate and elemental sulfur, the subsequent in situ conversion of the generated elemental sulfur to sulfuric acid, and the eventual reaction of the sulfuric acid with the xanthate to form carbon disulfide and other reaction products. In the presence of oxygen and water, the decomposition of perthioxanthates in soil can be represented as follows:
(R5OCS - S - St)jZ+j → (R5OCS - S - St-1)jZ+j + jS°
(R5CS - S - St-1)jZ+j → (R5OCS - S - St-2)jZ+j + jS°
...
(R5OCS - S - S)jZ+j → (R5OCS - S)jZ+j + jSº
The Thiobacillυs species present in soil can theoretically oxidize each of the above t·j generated elemental sulfurs to sulfuric acid as follows:
Figure imgf000015_0001
The sulfuric acid produced during the latter process reacts with in situ formed xanthate to release carbon disulfide in accordance with the following
chemical reaction:
(R5OCS - S)jZ+j + t·jH2SO4→ jCS2 + jROH + Z+j(HSO4)j +
(t·j-j)H2SO4
One or more optional ingredients can also be present in the composition of the present invention. For example, water is generally present, with the composition preferably being an aqueous solution. In addition, to enhance the stability of the thiocarbonates and the perthioxanthates in the aqueous solution, the composition preferably also contains a base and/or a sulfide having the formula
(D+k)m((Sn)-2)p where D is selected from the group consisting of organic and inorganic cations such as discussed above with respect to M, X, and Y; k is the valence of D; m is a positive integer; n is 1 or any whole or mixed number greater than 1 (and preferably from 1 to about 5); and p is a positive integer, provided that k«m equals 2p. The preferred organic and inorganic cations for D are the same as preferred in the case of M, X, and Y.
The base employed preferably has a significant solubility in water. More preferably, the base is a water soluble inorganic base, with the most preferred bases being alkali metal and ammonium hydroxides.
The sulfide and/or base can be added to the thiocarbonate-containing aqueous solution or, more typically, is present in the thiocarbonate-containing aqueous solution as a result of using a stoichiometric excess of sulfide and/or base during the synthesis of the thiocarbonates. When a stoichiometric excess of sulfide and/or base is employed, the amount of sulfide and/or base used in the reaction is generally at least about 1.01, preferably at least about 1.02, more preferably about at least 1.04, and most preferably at least about 1.08 equivalents of sulfide and/or base per equivalent of carbon disulfide employed in the reaction. On the other hand, when additional sulfide and/or base is added to the thiocarbonate-containing aqueous solution, the amount of added sulfide and/or base usually corresponds to at least about 0.01, preferably at least about 0.02, more
preferably at least about 0.04, and most preferably at least about 0.08 equivalents of sulfide and/or base per equivalent of carbon disulfide in solution.
Hardness-complexing agents can also be used to retard precipitation of insoluble carbonates, e.g., calcium carbonate, which tend to plug drip irrigation emitters and sprinkler nozzles. Exemplary hardness- complexing agents are alkali metal hexametaphosphates (e.g., sodium hexametaphosphate and potassium
hexametaphosphate). The compositions of the present invention can further be combined with other agricultural chemicals to provide a multifunctional product. For example, the compositions can be combined with solid or liquid
fertilizers such as urea, ammonia, ammonium nitrate, calcium nitrate, as well as other sources of plant nutrients. Since the thiocarbonates and perthioxanthates inhibit nitrification, they reduce the rate at which ammoniacal compounds, such as fertilizers, nitrify in the soil. (As used in the specification and claims, the term "ammoniacal compounds" includes ammonia, ammonium- containing compounds (e.g., ammonium nitrate and ammonium sulfate), and ammonium-forming compounds (e.g., urea and biuret)). Techniques for synthesizing various monomeric and oligomeric thiocarbonates are respectively described in U.S. Patent 5,256,424 and U.S. Patent 5,288,753, these patents being incorporated herein in their entireties by reference. Other monomeric and oligomeric thiocarbonates can be made using analogous reactions. In addition, a monomeric tetrathiocarbonate is commercially available; Enzone™ brand sodium tetrathiocarbonate is sold by UNOCAL and extensively used in agricultural applications. Methods for preparing xanthates are well known to those skilled in the art and various xanthates are, in fact, commercially available.
The perthioxanthates can be prepared using different methodologies. In one procedure, the
perthioxanthates are prepared by reacting a xanthate having the formula (R5OCS2)jZ+j (where R5, Z, and j are as previously defined) with sulfur for a sufficient period of time (e.g., about 3 hours) in a basic solution. For example, in the case of sodium ethyl xanthate, the synthesis can be conducted in a sodium hydroxide solution in accordance with the following reaction scheme:
Na+(C2H5OCS2)- + 2Sº → Na+(C2H5OCS3)- + Sº
In another synthesis procedure, the
perthioxanthates are prepared by reacting the above- described xanthate with a monomeric thiocarbonate having the formula (M+a)b((CSc)-2)d (where M, a, b, c, and d are as previously defined) for a convenient period of time
(e.g., about 1 hour) in water. For example, in the case of sodium ethyl xanthate and sodium tetrathiocarbonate, the synthesis can be represented as follows: Na+(C2H5OCS2)- + Na2(CS4)-2 → Na+ (C2H5OCS3)- + Na2(CS3)-2
In a third synthesis procedure, the perthioxanthates are prepared by reacting the above- described monomeric thiocarbonate with a salt of an alcohol having the formula E+q(OR6)-1 where E is selected from the group consisting of organic and inorganic cations such as discussed above with respect to D, M, X, and Y; q is the valence of E; and R6 is an organic group. The preferred organic and inorganic cations for E are the same as preferred in the case of D, M, X, and Y; and the preferred organic groups are the same as preferred for R1, R2, R3, and R4.
The reaction between the monomeric
thiocarbonate and the salt of an alcohol is conducted for a convenient period of time (e.g., about 2 hour) in water. To illustrate, in the case of the sodium salt of ethanol and sodium tetrathiocarbonate, the synthesis can be represented as follows:
Na+(C2H5O)- + Na2(CS4)-2 → Na+(C2H5OCS3)- + Na2(S)-2 Each of the above perthioxanthate synthesis procedures can be conducted at or above ambient
temperature (preferable, at a temperature of about 30° to about 90°C) and at any convenient pressure (preferably, at atmospheric pressure).
The compositions of the present invention can be employed as agricultural biocides in any application where tetrathiocarbonates as well as oligomeric
thiocarbonates can be used. They can be utilized in or on soil for the control of a wide variety of plant and animal pests, including insects, rodents, fungi,
nematodes, acarids, bacteria, arachnids, gastropods, and worms. While soil application of the compositions can be accomplished either prior to planting or after plant growth is established, the compositions of the present invention can also be used as herbicides, especially pre- emergence herbicides, for the control of undesirable plants. The herbicidal activity of the thiocarbonate- and xanthate-containing compositions is very surprising in view of the fact that these compositions exhibit herbicidal activity at carbon disulfide application rates which do not elicit herbicidal activity from individual applications of either the thiocarbonate or xanthate components of the composition.
The compositions are generally applied as a solution by spraying onto the soil surface. More
commonly, the compositions are added to and then applied as part of irrigation water. The concentration of releasable carbon disulfide in the aqueous solution is typically about 50 to about 10,000, preferably about 100 to about 5,000, more preferably about 1,000 to about 3,000, and most preferably about 2,000, ppmw. (The water slows the diffusion of the carbon disulfide from the soil into the air, and thus prolongs contact between the carbon disulfide and soil pests.) Injection into the soil, using a shank or knife, is also a useful method for applying the
compositions. In soil injection, the injectors are usually either closely spaced to treat essentially the entire field area, or spaced such that only the plant growing beds are treated.
The compositions of the present invention are effective as soil fumigants over a wide range of
application rates. The application rate for a particular situation depends on many factors, such as the pest or pests to be controlled, the crop to be protected and its stage of growth, soil moisture and other conditions, and the like. Generally, the compositions provide beneficial effects at application rates as low as about 0.45 kg (1 1b), preferably at least about 2.27 kg (5 1b), of
releasable carbon disulfide content per acre of soil treated, and as high as about 907.18 kg (2000 1b), usually less than about 453.59 kg (1000 1b), releasable carbon disulfide content per acre. Typically, for the overall fumigation of cultivated fields, the compositions are applied at rates of about 4.54 kg (10 lb) to about 226.80 kg (500 1b), preferably less than about 112.40 kg (250 1b), more preferably less than about 56.70 kg (125 1b), and most preferably from about 6.80 kg (15 1b) to about 34.02 kg (75 1b), releasable carbon disulfide content per acre. If the compositions are applied in a localized manner, for example under the drip lines of trees, the effective application rate can be much higher than the average per acre, since only the soil in the root zones is actually treated.
Another example of soil application is in the planting of trees, or the replacement of diseased or dead trees, in an orchard. When the planting hole is dug or the old tree is removed, the compositions can be mixed with the loose soil from the hole, which is then placed around the roots of the new tree. This controls pests in and around the planting hole and provides a healthier environment for the new tree to become established.
Since trithiocarbonates do not generate
elemental sulfur when they decompose, trithiocarbonates do not participate in the sequential reactions discussed above for decomposing xanthates to release carbon
disulfide. Accordingly, the compositions of the present invention generally contain little, or no,
trithiocarbonates. In fact, in the compositions of the present invention, the ratio of the total moles of trithiocarbonates to either (a) the total moles of thiocarbonate compounds (namely, the sum of all moles of monomeric thiocarbonates having the formula
(M+a)b((CSc)-2)d, and all moles of oligomeric thiocarbonates having the formula
Figure imgf000022_0001
where M, a, b, c, d, e, f, g, h, i, X, and Y are as defined above) or (b) the perthioxanthates is typically less than about 10 to 100. Preferably, the mole ratio is less than about 5 to 100, more preferably less than about 1 to 100, even more preferably less than about 0.5 to 100, and most preferably less than about 0.1 to 100.
Frequently, the ratio of the total moles of
trithiocarbonates to either the total moles of
thiocarbonate compounds or the perthioxanthates will be less than 0.05 to 100, more frequently less than about 0.01 to 100, even more frequently less than about 0.005 to 100, and most frequently less than about 0.001 to 100. COMPARATIVE EXAMPLES
The following examples compare the efficacy of an exemplary composition within the scope of the present invention to other carbon disulfide-generating compounds. EXAMPLE 1 AND COMPARATIVE EXAMPLES 1-2
Protocol Each of Example 1 and Comparative Examples 1-2 were replicated four times using the following procedure per replication or treatment. Unsterilized, sandy loam soil (about 1,000 g) was placed in a 2,000 ml beaker and saturated with about 250 ml water. Next, each beaker was treated with about 1,500 ppmw of carbon disulfide derived from either a solution comprising ethyl xanthate and Enzone™ brand sodium tetrathiocarbonate (Example 1) or straight Enzone™ brand sodium tetrathiocarbonate
(Comparative Example 1) or ethyl xanthate (Comparative Example 2). In addition, untreated beakers (i.e., beakers not treated with any carbon disulfide or carbon disulfide precursors) were used as controls.
Each of the control and carbon disulfide- treated beakers was then inoculated daily with about 10 ml of an active suspension of Phytophthora Parasitica .
At periodic intervals shown below in Table A, approximately 100 mg of soil from each beaker was added to agar plates (petri dishes). After about 48 hours, the number of Phytophthora Parasitica propagules on each agar plate was counted. The results of these tests are reported in Table A as percent control, where Percent Control = (1-NPT/NPC) 100% with NPT denoting "number of propagules from treated sample" and NPC denoting "number of propagules from untreated control."
Figure imgf000024_0001
As shown by the data set forth in Table A, the Enzone/ethyl xanthate solution gave good initial results, then dropped off, but by the seventh day was giving increasingly better results. In fact, after 14 days, the Enzone/ethyl xanthate solution gave nearly the same results as it had given initially.
In contrast, Enzone by itself gave good initial results, but became substantially ineffective by the fourth day; and ethyl xanthate never exhibited any effectiveness at all.
Furthermore, the soil used in Example 1 and Comparative Examples 1-2 was not sterilized and,
therefore, contained weed seeds. While no weed seeds germinated in the soil samples treated with the
Enzone/ethyl xanthate solution in Example 1, weed seeds germinated in all soil samples treated with either Enzone (i.e., in Comparative Example 1) or ethyl xanthate (i.e., in Comparative Example 2). Accordingly, the fact that the same total carbon disulfide equivalent application rate was employed in Example 1 and comparative Examples 1-2 indicates that the thiocarbonate-xanthate composition of the present invention exhibits synergistic herbicidal activity--especially synergistic pre-emergence herbicidal activity.
Although the present invention has been
described in detail with reference to some preferred versions, other versions are possible. For example, instead of applying a single thiocarbonate- and xanthate- containing solution to soil, a thiocarbonate-containing solution and a separate xanthate-containing solution can be simultaneously applied to the soil. Therefore, the spirit and scope of the appended claims should not necessarily be limited to the description of the
preferred versions contained herein.

Claims

1. A composition comprising at least (I) and/or (II), where:
(I) is a mixture comprising:
(a) at least one thiocarbonate compound selected from the group consisting of monomeric thiocarbonates having the formula
(M+a)b((CSc)-2)d, and oligomeric thiocarbonates having the formula
and
Figure imgf000026_0001
(b) a xanthate having the formula
(R5OCS2)jZ+j; and (II) is a compound having the formula
Figure imgf000026_0002
where :
a is the valence of M;
b is a positive integer;
c is at least 4;
d is a positive integer, provided that a·b = 2·d; e is at least 1;
f is a positive integer; g is the valence of X;
h is the valence of Y;
i is a positive integer, provided that
2·f = (g + h)i;
j is the valence of Z;
t is at least 1;
M is selected from the group consisting of inorganic and organic cations;
R5 is an organic group;
X and Y are independently selected from the group consisting of inorganic cations and organic cations, provided that when g is 2 or greater there is no Y;
Z is selected from the group consisting of inorganic cations and organic cations.
2. The composition of claim 1 comprising the mixture (I).
3. The composition of any one of claims 1-2 where:
the thiocarbonate compound comprises the monomeric thiocarbonate;
M and Z are independently selected from the
group consisting of inorganic cations and organic cations, the inorganic cations being selected from the group consisting of ammonium, alkali metals, alkaline earth metals, and transition metal cations, and the organic cations having the formula R1R2R3R4Q+;
R1, R2, R3, and R4, are independently selected from the group consisting of hydrogen and C1-C50 organic groups, provided that at least one of R1, R2, R3, and R4 is an organic group; and
Q+ is selected from the group consisting of nonmetals, semi-metals, and metalloids; and R5 is a C1-C50 organic group.
4. The composition of any one of claims 1-2 where:
the thiocarbonate compound comprises the oligomeric thiocarbonate;
X, Y, and Z are independently selected from the
group consisting of inorganic cations and organic cations, the inorganic cations being selected from the group consisting of ammonium, alkali metals, alkaline earth metals, and transition metal cations, and the organic cations having the formula R1R2R3R4Q+;
R1, R2, R3, and R4 are independently selected from
the group consisting of hydrogen and C1-C50 organic groups, provided that at least one of R1, R2, R3, and R4 is an organic group;
Q+ is selected from the group consisting of
nonmetals, semi-metals, and metalloids; and
R5 is a C1-C50 organic group.
5. The composition of claim 1 where:
the composition comprises the compound (II);
Z is selected from the group consisting of inorganic cations and organic cations, the inorganic cations being selected from the group consisting of ammonium, alkali metals, alkaline earth metals, and transition metal cations, and the organic cations having the formula R1R2R3R4Q+;
R1, R2, R3, and R4 are independently selected from
the group consisting of hydrogen and C1-C50 organic groups, provided that at least one of R1, R2, R3, and R4 is an organic group; Q+ is selected from the group consisting of nonmetals, semi-metals, and metalloids; and R5 is a C1-C50 organic group.
6. The composition of claim 1 where the thiocarbonate compound is selected from the group consisting of sodium tetrathiocarbonate, potassium tetrathiocarbonate, tetraethylammonium
hexathiodicarbonate, and tetramethylammonium
hexathiodicarbonate, and the xanthate is selected from the group consisting of sodium ethylxanthate and potassium ethylxanthate.
7. The composition of any one of claims 1-6 where the composition is a solution.
8. The composition of any one of claims 1-6 where the composition is a mixture of at least two solids, one solid being the thiocarbonate compound and another solid being the xanthate.
9. The composition of any one of claims 1-8 further comprising at least one sulfide having the formula
(D+k)m((Sn)-2)p where:
D is selected from the group consisting of organic and inorganic cations;
k is the valence of D;
m is a positive integer;
n is at least 1; and
p is a positive integer, provided that
k·m = 2p.
10. The composition of any one of claims 1-9 further comprising a base.
11. The composition of any one of claims 1-10 where the composition comprises at least a stoichiometric concentration of the thiocarbonate compound(s) based upon the concentration of the xanthate present in the
composition.
12. The composition of any one of claims 1-10 where the composition comprises less than a
stoichiometric concentration of the thiocarbonate
compound(s) based upon the concentration of the xanthate present in the composition.
13. A composition formed by reacting either (A) and (B) or (C) and (B) or (A) and (D) where:
(A) is at least one thiocarbonate compound selected from the group consisting of monomeric thiocarbonates having the formula
(M+a)b((CSc)-2)d, and oligomeric thiocarbonates having the formula
Figure imgf000030_0001
where:
M is selected from the group consisting of inorganic and organic cations;
a is the valence of M;
b is a positive integer;
c is at least 4; d is a positive integer, provided that a·b = 2·d; e is at least 1;
f is a positive integer;
g is the valence of X;
h is the valence of Y;
i is a positive integer, provided that
2·f = (g + h)i; and
X and Y are independently selected from the group consisting of inorganic cations and organic cations, provided that when g is 2 or greater there is no Y;
(B) is a xanthate having the formula
(R5OCS2)jZ+j where:
R5 is an organic group;
Z is selected from the group consisting of inorganic cations and organic cations; and
j is the valence of Z;
(C) is sulfur; and
(D) is a salt of an alcohol having the formula
E+q(OR6)-1 where:
E is selected from the group consisting of organic and inorganic cations;
q is the valence of E; and
R6 is an organic group.
14. An agricultural material comprising:
(a) the composition of any one of claims 1-13; and
(b) at least one material selected from the group consisting of carriers, extenders, coatings, binders, and fertilizers.
15. A method for prolonging the release of carbon disulfide in soil comprising the step of applying the composition or agricultural material of any one of claims 1-14 to the soil.
16. A method for prolonging the release of carbon disulfide in soil comprising the steps of:
(A) combining the composition or
agricultural material of any one of claims 1-14 with irrigation water to form a composition-irrigation water combination; and
(B) applying the composition-irrigation water combination to the soil.
17. A method for preventing the germination of seeds in soil, the method comprising the step of applying the composition or agricultural material of any one of claims 1-14 to the seed-containing soil.
18. A method for preventing the germination of seeds in soil, the method comprising the step of applying the composition or agricultural material of any one of claims 1-14 to the seed-containing soil at a carbon disulfide application rate which is herbicidally
efficacious for the composition or agricultural material in that seed-containing soil but herbicidally ineffective for (A) the thiocarbonate component of the composition or agricultural material when the thiocarbonate component is separately applied at the same carbon disulfide
application rate to a different sample of the same seed- containing soil and (B) the xanthate component of the composition or agricultural material when the xanthate component is separately applied at the same carbon disulfide application rate to a different sample of the same seed-containing soil.
19. A method for controlling vegetation growing in soil, the method comprising the step of applying the composition or agricultural material of any one of claims 1-14 to the vegetation-containing soil.
20. A method for controlling vegetation growing in soil, the method comprising the step of applying the composition or agricultural material of any one of claims 1-14 to the vegetation-containing soil at a carbon disulfide application rate which is herbicidally efficacious for the composition or agricultural material in that vegetation-containing soil but herbicidally ineffective for (A) the thiocarbonate component of the composition or agricultural material when the
thiocarbonate component is separately applied at the same carbon disulfide application rate to a different sample of the same vegetation-containing soil and (B) the xanthate component of the composition or agricultural material when the xanthate component is separately applied at the same carbon disulfide application rate to a different sample of the same vegetation-containing soil.
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US2574829A (en) * 1948-12-31 1951-11-13 Phillips Petroleum Co Preparation of organic sulfenyl xanthates, sulfenyl trithiocar-bonates, thiosulfenylxanthates and thiosulfenyl trithiocarbonates
US4078912A (en) * 1975-05-28 1978-03-14 Imperial Chemical Industries Limited Fertilizers containing nitrification inhibitor
US4242472A (en) * 1978-02-17 1980-12-30 Bridgestone Tire Company Limited Vulcanizable rubber composition improved in sulfur blooming with metal alkylxanthate
WO1984004230A1 (en) * 1983-05-02 1984-11-08 Union Oil Co Fumigation methods and compositions
EP0366226A1 (en) * 1988-10-28 1990-05-02 Union Oil Company Of California Stabilized thiocarbonate solutions and the use thereof for controlling soil pests
EP0426292A1 (en) * 1989-09-29 1991-05-08 Union Oil Company Of California Thickened fumigant compositions
WO1991009526A2 (en) * 1989-12-28 1991-07-11 Union Oil Company Of California Oligomeric thiocarbonates
WO1991013551A1 (en) * 1990-03-09 1991-09-19 Union Oil Company Of California Pelletized thiocarbonates for soil treatment

Patent Citations (8)

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Publication number Priority date Publication date Assignee Title
US2574829A (en) * 1948-12-31 1951-11-13 Phillips Petroleum Co Preparation of organic sulfenyl xanthates, sulfenyl trithiocar-bonates, thiosulfenylxanthates and thiosulfenyl trithiocarbonates
US4078912A (en) * 1975-05-28 1978-03-14 Imperial Chemical Industries Limited Fertilizers containing nitrification inhibitor
US4242472A (en) * 1978-02-17 1980-12-30 Bridgestone Tire Company Limited Vulcanizable rubber composition improved in sulfur blooming with metal alkylxanthate
WO1984004230A1 (en) * 1983-05-02 1984-11-08 Union Oil Co Fumigation methods and compositions
EP0366226A1 (en) * 1988-10-28 1990-05-02 Union Oil Company Of California Stabilized thiocarbonate solutions and the use thereof for controlling soil pests
EP0426292A1 (en) * 1989-09-29 1991-05-08 Union Oil Company Of California Thickened fumigant compositions
WO1991009526A2 (en) * 1989-12-28 1991-07-11 Union Oil Company Of California Oligomeric thiocarbonates
WO1991013551A1 (en) * 1990-03-09 1991-09-19 Union Oil Company Of California Pelletized thiocarbonates for soil treatment

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Title
CHEMICAL ABSTRACTS, vol. 55, no. 5, 6 March 1961, Columbus, Ohio, US; abstract no. 4859i, J.ZEMÀNEK: "The efficiency of new organic fungicides" *
CHEMICAL ABSTRACTS, vol. 95, no. 10, 7 September 1981, Columbus, Ohio, US; abstract no. 83047, J.MAJEWSKA ET.: "Spectrophotometric UV analysis of the products of hydrolysis of carbon disulfide" *
SBORNIK CESKOSLOV. AKAD. ZEMEDEL. VED ROSTLINNA VYROBA, pages 1105 - 1118 *
WLOKNA CHEM., vol. 6, no. 3, pages 367 - 372 *

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AU3148695A (en) 1996-03-07

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