CA1103665A

CA1103665A - Preparation of esters of thiocarbamic acids involving use of phase transfer catalysts

Info

Publication number: CA1103665A
Application number: CA285,552A
Authority: CA
Inventors: Harold M. Pitt
Original assignee: Stauffer Chemical Co
Current assignee: Stauffer Chemical Co
Priority date: 1976-09-03
Filing date: 1977-08-26
Publication date: 1981-06-23
Also published as: JPS5334722A; ZA775331B; IT1091119B; DE2738628A1; PL108414B1; FR2363551A1; ES462081A1; NL7709711A; AU2850877A; DD132432A5; HU175829B; CS207480B1; IN145874B; GB1538643A; SU921464A3; PL200632A1; FR2363551B1; IL52868A; AR219718A1; IL52868A0

Abstract

\
Abstract of the Disclosure Ester of thiocarbamic acids are prepared by a process comprising (a) reacting a carbamyl chloride with a mercaptan in the presence of (i) an aqueous solution of a caustic agent, and (ii) a catalytic amount of a phase transfer catalyst; (b) separating the organic ant aqueous phases; and (c) recovering the thiocarbamic acid enter from the organic phase

Description

11~)3665 Back~round of the Invention The esters of thiocarbamic acids are useful for a variety of purposes. Some are active herbicides, others are effective for inhibiting the growth of micro-organisms such as bacteria, and still others are active insecticides. The S following is a group of processes representative of those known in the art ~or the preparation of these compounds.

U.S. Patent No. 2,983,747 employs zinc chloride as a catalyst in the direct reaction of carbamyl chlorides with mercaptans to produce various thiocarbamic esters. Although the reaction can be conducted without the use of a solvent, a solvent inert to the catalyst, such as an organic solvent, m~st ~e used if a solvent is employed.

U.S. Patent 2,913,327 teaches the preparation of the sodium salt of a mercaptan followed by reaction with a carbamyl chloride in the presence of a solvent. The use of the sodium salt of the mercaptan causes problems of filtration and solids handling. The use of a solvent reduces reactor capacity throughout. In addition, solvent recovery can be a problem.
Furthermore, the hydrogen evolved during the preparation of the sod~wm salt causes a disposal problem.

U.S. Patent 3,133,947 describes the preparation of esters of thiocarbamic acids by a process comprising reacting a secondary or primary amine with carbonyl sulfide in the presence of a basic material which may be any amine, including a tertiary amine, and thereafter reacting the intermediate with an organic

-2- ~

l~iO3665 sulfate, such as a dialkyl sulfate, or a diallyl sulfate. This process is unfavorable because of the special gas handling equipment required for the carbonyl sulfide addition. Further, alkyl sulfate values are lost, thus adding to the expense of the overall process.

U.S. Patent 3,8~6,524 teaches the preparation of thiocarbamic acid este~s by reaction of a carbamyl chloride with a mercaptan in the presence of an aqueous solution of a caustic agent. This process requires considerable agitation in order to form a high interfacial area between the two liquid phases~ as well as a high caustic concentration in order to achieve the desired conversion and product purity.

In view of the problems as enumerated hereinabove, wh~ch are encountered in the prior art processes, it is the object of this invention to provide a process for the preparation of esters of thiocarbamic acids which provides high yields as well as a savings in starting materials and operating expenses.

In another aspect, it is an object of this invention to provide a novel use for a phase transfer catalyst, in enhancing the reaction between a carbamyl chloride and a mercaptan in the presence of an aqueous solution of a caustic agent to produce a thiocarbamic acid ester.

Phase transfer catalysts are known for their ability to promote reactions between reactants residing in separate but contiguoUc liquid phases by transfering one reactant across the interface. The use of phase transfer catalysts in alkyl halide ilO3665 displacement reactions, dichlorocyclopropanation of alkenes, oY~idation of alkenes, and other reactions is taught in C. M.
Starks~ J. Am. Chem. Soc. 93 ~1), 195-199 (1971). Other uses are disclosed in W. P. Weber, G. W. Gokel, and I. K. Ugi, An~ew. Chem. Internat. Edit. 11 (6), 530-531 (1972), H. E. Hennis, L. E. Thompson, and J. P. Long, I & EC Prod. Res. and Dev. 7 (2), 96-101 (1968), and British Patent 1,227,144.

il~ 366~5 Summary and Brief Description of the Invention This in~ention relates to a novel method of preparing members of the class of compounds known as thiocarbamates. More particularly, this invention relates to the method of preparing esters of thiocarbamic acids by the reaction of an appropriate carbamyl chloride and requisite mercaptan in the presence of (i) an aqueous solution of a caustic agent, and (ii) a catalytic amount of a phase transfer catalyst.

Generally, any mercaptan or carbamyl chloride can be us~d in the instant process. The general reaction scheme can be represented as follows:
_ OH- R ~ R
NCCl $ RS - ~ ~ NC SR + Cl R / R ~
in which examples of mercaptans and carbamyl chlorides which can be used ~re those in which R represents:

alkyl, having 1 to 12 carbon atoms, in~lusîve;
haloalkyl, having 1 to 12 carbon atoms, inclusive, preferably chloro- or bromo-~ubstituted alkyl;
alkylthioalkylene, having a total of from 2 to 10 carbon atoms, înclusive;
alkoxyalkylene, having a total of from 2 to 10 carbon atoms, inclusive;
cycloal~yl, having 3 to 7 carbon atoms, înclusive;
alkenyl, having at least 1 double bond and from 2 to 8 carbon atoms, inclusive;

~;1)36~5 alkynyl, h~v ~g at least one triple bond and from 3 to 6 carbon atoms, inclusive, for example: isobutynyl, 3-methyl-butyn-(l)yl(3);
phenyl;
naphthyl;
benzyl;
c~-alkyl benzyl, in which the alkyl has 1 to 4 carbon atoms, inclusive;
substituted phenyl wherein the substituents include alkoxy having 1 to 4 carbon atoms, inclusive, nitro, chloro, trifluoro, methyl, for example: o-methoxy, m-butoxy, p-nitro,

3,4-dinitro, 2,4-dinitro;
substituted naphthyl, wherein said substituents include alkoxy, nitro, chloro, bromo, trifluoromethyl;
halo~lkenyl, in which alkenyl has 2 to 6 carbon atoms, inclusive, and halo is chloro, bromo, iodo, or fluoro, for example: 2,3-dichlcroallyl, 3,4,4-trifluoro-3-butenyl, 2-bromoallyl, and the like;
cyclohexenyl;
substituted benzyl, wherein the substituents are, for example:
chlorine, bromine, fluorine, methyl-p-methyl, o-methyl, 2,4-dimethyl, 2,6-dimethyl, 2,4-dichloro, 3,4-dichloro, ar,~r,ar-trichloro, 5-chloro-2-methoxy, nitro;
carboalkoxy~lkyl, having from 2 to 8 c~rbon atoms, inclusive;
phenyl thioethyl;
phenyl oxyethyl;
pyrimidyl;
pyridyl;
indazolyl;

^6-~)3665 quinolyl;
isoquinolyl;
furyl; and dibenzofuryl;

Rl and R2 independently represent:

alkyl, having from 1 to 12 carbon atoms, inclusive;
slkenyl, having at least 1 double bond and from 2 to 8 carbon atoms, inclusive;
haloalkyl, having from 1 to 12 carbon atoms, inclusive, where kalo is chloro, fluoro, or bromo;
cyano-substituted alkyl, having from 2 to 6 carbon atoms, inclusive;
alkynyl, having at least one triple bond and from 3 to 6 carbon atoms, inclusive, for example: propargyl, isobutynyl, and the like;
cyclohexenyl;
haloalkenyl, having from 2 to 8 carbon atoms, inclus~ve, where halo is chloro, fluoro, or bromo;
benzyl;
substituted-benzyl, in which the substituents are, for example:
chloro, lower alkoxy having 1 to 4 carbon atoms, inclusive, cyano, nitro and trifluoromethyl;
hal.oalkoxy, having 1 to 8 carbon atoms, inclusive, where halo is chloro, fluoro, or bromo;
alkoxy, having 1 to 8 carbon atoms, inclusive;
alkenyloxy, having at least 1 double bond and from 2 to 8 carbon atoms, inclusive;
nitroalkoxy, having 1 to 6 carbon atoms, inclusive;

$~Q36~i5 phenyl;
substituted-phenyl, in which the substitutents are, for example:
chloro, bromo, nitro, cyano, alkoxy having 1 to 4 carbon atoms, inclusive, phenyl and the like;
phenoxy-substituted alkyl, in which alkyl has from 1 to 4 carbon atoms, inclusive;
naphthyl;
furfuryl, tetra-hydrofurfuryl;
cycloalkyl, having from 3 to 7 carbon atoms, inclusive;
heterocyclic oxygen, nitrogen or sulfur-containing ring groups, for example: pyridyl, ~hienyl, f~ryL, pyranyl, pyrimidinyl, indolyl, quinolyl~ isothioazolyl, piperidyl, piperazinyl, morpholinyl and the like;
alkyl-substituted pyridyl, where alkyl h~s from 1 to 4 carbon atoms, inclusive; and Rl and R2 taken together with the nitrogen to which they are attached represent heterocyclic groups, e.g., pyrryl, pyrrolidyl, pyrazolyl, pyrazolinyl, piperldinyl~ imidazolyl, indolyl, ~ ~methylindolyl, aziridinyl, carbazolyl, morpholinyl, 3-azablcyclo-[3.2.2]nonanyl-3, polyalkylen~mine, having 3 to 6 carbon atoms, inclusive, alkyl-substituted piperidine, for example, 5-ethyl^2-methyl piperidine.

The advantages of the present inven~ion over the closest prior art~ U. S. Patent 3,836,524, are as follows:

1) a rnuch lower concentration of caustic solution will produce the same conversion and purity, ~ ~ 36~65 2) a lower excess of mercaptan with respect to carbamyl chloride will produce the same conversion, 3) less agitation is needed, and

4) reaction times are sharply reduced.

Detsiled Description of the Invention As stated hereinabove, the process of the present invention comprises reacting a carbamyl chloride with a mercaptan in the presence of (i) an aqueous solution of a caustic agent, and (ii) a catalytic amount of 8 phase transfer catalyst. The components of the reaction mixture can be added in any order, for example:
(a) a mixture of the mercaptan and the phase transfer catalyst can be added to the caustic solution, and the resulting mixture ~hen added to the carbamyl chloride;
(b) a mixture of the phase transfer catalyst, the lS mercaptan, and the carbamyl chloride can be sdded to the caustic solution; or (c) the phase transfer catalyst can be added to the carbamyl chloride which is then added to a mixture of the mercaptan and the caustic solution.

The lat~er is the preferred mode of addition for carbsmyl chlorides and mercaptans in general. Mode (b) is preferred when the mercaptide salt is insoluble in the caustic solution. In any case, the resulting reaction mixture forms two liquid phases: an organic phase containing the carbamyl chloride, and an aqueous phase containing the caustic and the mercaptan.

~3U665 The term "phase transfer catalyst" is used herein to represent any catalyst which facilitates the transfer of a chemical species from one liquid phase to another. Examples of such catalysts are quaternary salts having the formula (R3R4R5R6M) X
wherein R3, R4, R5, and R6 are hydrocarbon radicals selected ir.dependently from the group consisting of alkyl, alkenyl, aryl, alkaryl, aralkyl, and cycloalkyl radicals; M is a member selected from the group consisting of nitrogen, phosphorus, arsenic, antimony, and bismuth, preferably nitrogen or phosphorus; and X is an anion which will dissociate from the cation in an aqueous environment, preferably a halide ion or a hydroxyl ion, most preferably chloride or bromide.

As used in the description of R3, R4, RS, and R6 above:
~he term "alkyl" refers to a monovalent straight or branched chain saturated aliphatic hydrocarbon group of 1 to 25 carbon atoms, inclusive, e.~g., methyl, ethyl, propyl, i-propyl, n-butyl, s-butyl, t-butyl, n-octyl, 2-methyloctyl, decyl, 6-methylundecyl, dodecyl, and the like;
the term "alkenyl" refers to a monovalent straight or branched chain aliphatic hydrocarbon of ~ to 25 carbon atoms, inclusive, and containing at leas~ one double bond, e.g., allyl, butenyl, butadienyl~ and the like;
the tenm "aryl" refers to a monovalent monocyclic or bicyclic aromatic hydrocarbcn group, i.e., phenyl and naphthyl;

llV366~

the term "alkaryl" refers to an aryl groups as defined above, in which at least one hydrogen atom is substituted by an alkyl group as defined above, e.g., tolyl, xylyl, mesityl, ethylphenyl, and the like;
the term "aralkyl" refers to an alkyl group as defined above, in which a hydrogen atom is substitutet by an aryl or alkaryl group as defined above, e.g., benzyl, phenethyl, methyl-benzyl, naphthylmethyl, and the like; and the term "cycloalkyl" refers to a monovalent cyclical sat~rated hydrocarbon group of 4 to 8 carbon atoms, inclusive, i.e., cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl.

Mixtures of such quaternary salts may likewise be utili~ed in the practice of the invention. Double or multi-functional quaternary salts in which the general formula (R3R4R5R6M)+ X ~s repeated a plurality of times with the same or different substituent combinations, can also be utilized effectively.

The most preferred phase transfer catalysts are tetra-n-butylphosphoni~m chloride, hexadecyltributylphosphonium bromide, benzyltriethylammonium chloride, benzyltriethylammonium bromide, tricaprylylmethylammonium chloride, and dimethyldicocoammonium chloride~ The latter two catalysts are manufactured by General Mil~ Co., Chemical Division, Kankakee, Illinois, and are Q
alternatively designated by the names "Aliquat 336" and llAliq~at 221'i, respectively.

c~

~036~s The term "catalytic amour.t" is used herein to represent any amount of phase transfer catalyst which will enhance the progress of the reaction. The amount of catalyst normally will range from about 0.2 to about 5.0 weight % of the reaction mixture, preferably from about 0.5 to about 1.0 weight %.

The ratio of reactants employed in the instant process can vary widely. Normally, the mole ratio of mercaptan (RSH) to carbamyl chloride (R *2NCOCl) is at least about 1Ø The preferred ratio of mercaptan to carbamyl chloride is at least about 1.1.

The mole ratio of caustic agent to mercaptan is at least about 0.5, however, the preferred ratio of caustic agent to mercaptan is at least about 1Ø Thus, in the most preferred form, this process is carried out with an excess of caustic agent.
The term "caustic agent" is used herein to mean any inorganic material which will sufficiently produce hydroxyl ions in an aqueous solution to function in this process. The nature of the caustic agent must produce sufficient alkalinity in an aqueous solution to inhibit or suppress the hydrolysis of the mercaptide RS ion to the mercaptan according to the equation:

RS + H20 ~SH + OH
The caustic agents contemplated for use in this process include, among others, sodium hydroxide, potassium hydroxide, barium hydroxi~e, and the like, and m~xtures thereof. The caustic agent is supplied to the reaction scheme as an aqueous solution which can range from about 5% to about 50%, such that the solution is 1 ~0 36~5 liquid. For example, when using sodium hydroxide, the preferred range of caustic solution is about 10% to about 30% by weight.

The conditions of the reaction can be varied rather extensively without having an appreciable effect on the yield or quality of the product. The temperature of the reaction can range from about 10C to about 100C and preferably from about 20C to about 80C. Within the temperature l~mit~ specified herein, it is found that esters of thiocarbamic acids can be prepared and that the undesirable by-product acids of the corresponding urea will be minimized. The selected temperature also determines the rate of the reaction; that is, the time required to economically and feasibly arrive at the product with a negligible amount of carbamyl chloride remaining. The reaction time, therefore, will depend upon several interacting factors, such as temperature and degree 15- of agitation.

Although agitation is not essent~al to the efficient progress of the reaction, there is still an advantage to be gained in reaction time by the use of agitation to increase the interfacial area between the two liquid phases. Agitation can be ~0 achieved, for example, by the use of stirrers, baffle plates within the reaction vessel, turbulence columns and the like.

The present invention may be practiced in a batch or batch-like fonm or in a continuous or continuous-like form. ~hen the invention is practiced in a manner resembling a ba~ch process, all the various species will be combined in steps detenmined by a uitable t~me sequence into a single body o~ liquid. When a ~ 1~ 3~ 5 continuous or continuous-like form is used, the desired reaction rate can be achieved by selecting a suitable type of agitation and appropriate reaction conditions. The choice`between the various types of process to be used will depend on the desired manufacturing conditions. The reaction vessel or vessels will preferably consis~ of non-corrosive materials, such as mild steel, which will not interfere with the principal reaction.

Upon completion of the process reaction, the thiocarba-mate ester product will rem-ain in the organic phase. Salt which may have precipitated during the reaction can be dissolved readily by the addition of water. The two liquid phases are subsequently separated. The organic phase is dried and the thiocarbamate ester is recovered therefrom. The product can be stripped of residual water and volatile components by purging with argon or nitrogen while heating. Further purification can be achieved by conventional purification techniques.

Specific examples are set forth below showing the prepara-tion of thiocarbamic acid esters by the process of the present invention. These examples are included for illustrative purposes only, and are not to be interpreted as imposing any limitations on the scope of the invention herein described. Such limitations are set forth in the appended claims.

EXAMPLES
General Procedure The general procedure used in the following exper~ments was as follows. An aqueous solution of sodium hydroxide was placed in an agitation flask equipped with a stirrer. The ~36~;5 appropriate mercaptan was added to the aqueous solution. To this - mixture was added the requisite carbamyl chloride with the phase transfer catalyst dissolved therein, while maintaining the flask and its contents at the indicated temperature At the end of the experiment water was added when necessary to dissolve any precip-itated salts, and the organic layer containing the thiocarbamic acid ester was separated. The organic layer was either heated under a vac~um or purged with nitrogen while heating to remove residual water and mercaptan. The reactants, products, catalysts, conditions and results are summarized and reported in the following Tables I, II, and III. The results are area percent from gas chromatography analysis of the material. In several instances, a weight percent purity also was determined and found to agree within experimental error to the gas chromatographic analysis.

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11~366S

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-19-.

Of particular interest in the data in Table III are comparisons between Experiments 8 and 8a, between 9 and 9a, and between 10 and lOa. Each pair demonstrates the progress of the reaction both with and without a phase transfer catalyst. The data show a striking ad~antage gained in each case in both reaction t~me and product purity by the use of the catalyst.
Although a comparison between Experiments 16 and 9a shows no advantage in the data presented to be gained by the use of benzyltriethylammonium chloride, an increase in rate, not shown in the table, did occur. The reaction did not proceed o completion since the catalyst was not soluble in the carbamyl chloride. A complete reaction will be achieved either when the same catalyst is used with a carbamyl chloride in which ~t is soluble, or when a different catalyst is used which is soluble in the carbamyl chloride used in Experiment 16. The ad~antage of a system where all components are soluble is thus apparent.
The ph~se transfer catalyst used may also act as an emulsifying agent, and thus facilitate mixing.

Compound Activity Data A3 ~tated hereinabove, the thiocarbamic acid esters prepared by the proces~ of the invention are useful as herbicides, gr~wth inhibitors, and insectic1des. Herbicide activlty of some of the compounts made in the above examples by the process of the invention was determined by the following screening procedures.

-~0-i~O3u66 5 Pre-emer~ence Herbicide Screenin~ Test Using an analytical bslance, 20 mg of the compound to be tested is weighed out on ~ piece of glassine weighing paper.
The paper and compound ~re placed in 8 30 ml wide-mouth bottle ~nd 3 ml of acetone containing 1% Tween 20~ (~ polyoxyethylene 5~ sorbit~n monolsurate) is added to dissolve the compound. If the msterifll is not soluble in ~cetone, another solvent ~uch as water~ alcohol or dimethylformsmide (DMF) is used instead. When DMF i8 u3ed, only 0.5 ml or less i8 used to dissolve the compound and then Another solvent is used to make the volume up to 3 ml.
IOE The 3 ml of solution is spr~yed unifonmly on the 30il contained in a ~mall fiber fl~t one day after planting weed seeds in the flat of soil. A No. 152 DeVilbiss atomizer is used to apply the Qpray using compressed air ~t a pressure of 5 lb/sq.in. The rAte of ~pplication is 8 lb/acre and the spr~y volume is 143 1~ g~l/acre.

On the day preceding tre~tment, the fiber fl~t, which is 7 inches long, 5 inches wide and 2.75 inches deep , is filled to a depth of 2 inches with loamy sand soil. Seeds of seven different weed species are plsnted in individual rows using one species per 2~ row acro~ the width of the fl~t. The seeds are covered with soil so that they ~re pl~nted at a depth of O.S inch. The seeds used are h~iry crabgras~ (Di~itflria san~uinalis), yellow foxt~il (Sethria ~lauca), redroot pigweed (Am~ranthus retroflexu~), Indian mustard (Brassica ~uncea), curly dock (Rumex crispus), Z~ w~tergrass (Echinochloa crusgalli), snd red oat (Avena sativs).
Ample ~eeds are planted to give sbout 20 to 50 seedlings per row after emergence depending on the s~ze of the plants.

r~

1~ 6~5 Af~er trestment, the flats ~re placed in the greenhouse at a temperature of 70 to 8SF snd watered by sprinkling. Two weeks ~fter trestment the degree of injury or control is deter-mined by comp~rison with untreated check pl~nts of the same age.
The in~ury rating from 0 to lOOqo is recorded for each s~ecies - ~s percent control with 07O representing no in~ury and 1007o representing complete kill.

Post-emer~ence Herbicide Screenin~ Test Seeds of 8iX plant species, including halry crabgrass, watergr~ss~ red oat, mustard, curly dock and Pinto beans (Phaseolus vul~aris~ are planted in the Styrofoam flats as tes-; cribed above for pre-emergence screening. The flats ~re placedin the greenhouse st 70 to 85F and wstered daily with a sprinkler.
About 10 to 14 days after planting when the primary leaves of the bean p$ants are almost fully expanded and the first tri-foli~te le~ve~ re ~ust atarting to form, the plsnts ~re sprayed.
The spray is prepared by weighiQg out 20 mg of the test compound, dissolv~ng it in 5 ml of ~cetone cont~ining 1% Tween 2 ~ and then adding 5 ml of water. The solution is ~r~yed on the foliage using a No. 152 DeVilbiss Rtomizer at ~n sir pressure of 5 lb/
sq. ln. The ~pray concentration is 0.2 ~nd the rate is 8 lb/~cre.
The spray volume i9 476 gsl/~cre. In~ury r~tings sre recorded 14 days a~ter treatment. The rating ~ystem is the ~sme as des-cribed ~bove in ~e-emergence test.

The resul~s of these tests ~re shown in Table IV.

~1~3~5 TABLE IV

Herbicide ActivitY

Product of Percent Control at 8 lb/A
Experiment No. Pre-EmerRence Post-Emer~ence , 1 90 . 8 : 11 53 45 *

Aver~ge for seven plant species in ~he pre-emergence test and for ~ix plant specles in the post-emergence test.

~23~

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the preparation of a thiocarbamic acid ester which comprises:
(a) reacting a carbamyl chloride of the formula in which R1 and R2 are independently selected from the group consisting of hydrogen and the following substituted or unsubstituted groups: C1-C12 alkyl, C2-C8 alkenyl, C3-C6 alkynyl, phenyl, C7-C10 phenylalkyl, C3-C7 cycloalkyl, C5-C7 cycloalkenyl, C1-C8 alkoxy, C2-C8 alkenoxy, C2-C8 alkoxyalkyl, C2-C8 alkylthioalkyl, C3-C8 alkoxyalkenyl and C3-C8 alkylthioalkenyl;
wherein the substituents are independently selected from the group consisting of halo, cyano, nitro, trifluoromethyl, and alkoxy and alkyl having 1 to 4 carbon atoms; or R1 and R2 together with the nitrogen atom to which they are bound form a member selected from the group con-sisting of pyrryl, pyridyl, and C2-C6 polyalkylene-imine;
with a mercaptan having the formula R3SH, in which R3 is selected from the group consisting of the following sub-stituted or unsubstituted groups:
C1-C12 alkyl, C2-C8 alkenyl, C3-C6 alkynyl, phenyl, C7-C10 phenylalkyl, C3-C7 cycloalkyl, C5-C7 cycloalkenyl, C1-C8 alkoxy, C2-C8 alkenoxy, C2-C8 alkoxyalkyl, C2-C8 alkylthioalkyl, C3-C8 alkoxyalkenyl and C3-C8 alkylthio-alkenyl; wherein the substituents are independently selected from the group consisting of halo, cyano, nitro, trifluoromethyl, C1-C4 alkyl, and C1-C4 alkoxy;
in the presence of (i) an aqueous solution comprising of from 5 to 50%
by weight of an alkali or alkaline earth metal hydroxide, and (ii) a catalytic amount of a quaternary salt having the formula (R4R5R6R7M)+Q-in which:
M is a member selected from the group consisting of nitrogen, phosphorus, and arsenic;
Q- is an anion selected from the group consisting of chloride, bromide, iodide, and hydroxide; and R4, R5, R6, and R7 are independently selected from the group consisting C1-C25 alkyl, C2-C25 alkenyl, phenyl, C7-C10 alkylphenyl, C7-C10 phenylalkyl, and C4-C8 cycloalkyl; or any two of the groups R4, R5, R6 and R7 are joined to constitute a 5- or 6-membered heterocyclic ring containing the quaternized M atom plus a maximum of one non-adjacent nitrogen, oxygen, or sulfur atom; and (b) separating said ester from said aqueous solution.

2. A process for the preparation of a thiocarbamic acid ester which comprises:
(a) reacting a carbamyl chloride having the formula in which R1 and R2 are independently selected from the group consisting of Cl-C6 alkyl and C5-C7 cycloalkyl, or R1 and R2 together with the nitrogen atom to which they are bound from C4-C6 polyalkyleneimine, with a mercaptan having the formula R3SH in which R3 is selected from the group consisting of C1-C6 alkyl, phenyl, halo-substituted phenyl, benzyl, and halo-substituted benzyl, in the presence of, (i) an aqueous solution comprising of from 5 to 50%
by weight of a caustic agent selected from the group consisting of NaOH, KOH, and Ba(OH)2, and (ii) a catalytic amount of a quaternary salt having the formula (R4R5R6R7M)+Q- in which R4, R5, R6, and R7 are independently selected from the group consisting of C1-C25 alkyl, phenyl, and C7-C10 phenylalkyl, M is nitrogen or phosphorus, and Q- is chloride or bromide; and (b) separating said ester from said aqueous solution.

3. The process of Claim 2 in which the quaternary salt is selected from the group consisting of tetra-n-butylphosphonium chloride, hexadecyltributylphosphonium bromide, benzyltriethyl-ammonium chloride, benzyltriethylammonium bromide, tricaprylyl-methylammonium chloride, and dimethyldicocoammonium chloride.

4. The process of Claim 2 in which the quaternary salt is selected from the group consisting of tetra-n-butylphosphonium chloride, benzyltriethylammonium chloride, tricaprylylmethyl-ammonium chloride, and dimethyldicocoammonium chloride.

5. The process of Claim 2 in which the quaternary salt of step (a)(ii) is present in an amount ranging from about 0.2 to about 5.0 weight %.

6. The process of Claim 2 in which the quaternary salt of step (a)(ii) is present in an amount ranging from about 0.5 to about 1.0 weight %.

7. The process of Claim 2 in which the reaction of step (a) occurs at a temperature from about 10°C to about 100°C.

8. The process of Claim 2 in which the reaction of step (a) occurs at a temperature from about 20°C to about 80°C.

9. The process of Claim 2 in which the mole ratio of mercaptan to carbamyl chloride in step (a) is at least about 1Ø

10. The process of Claim 2 in which the mole ratio of mercaptan to carbamyl chloride in step (a) is at least about 1.1.

11. The process of Claim 2 in which the caustic agent of step (a)(i) is sodium hydroxide.

12. The process of Claim 2 in which the mole ratio of caustic agent to mercaptan in step (a) is at least about 0.5.

13. The process of Claim 2 in which the mole ratio of caustic agent to mercaptan in step (a) is at least about 1Ø

14. The process of Claim 2 in which the concentration of the caustic solution of step (a)(i) ranges from about 5% to about 50% by weight.

15. The process of Claim 2 in which the concentration of the caustic solution to step (a)(i) ranges from about 10% to about 30% by weight.

16. The process of Claim 2 in which said carbamyl chloride is di-n-propylcarbamyl chloride, said mercaptan is ethyl mercaptan, and said quaternary salt is tricaprylylmethylammonium chloride.

17. The process of Claim 2 in which said carbamyl chlo-ride is diisobutylcarbamyl chloride, said mercaptan is ethyl mercaptan, and said quaternary salt is tricaprylylmethylammonium chloride.

18. The process of Claim 2 in which said carbamyl chlo-ride is di-n-propylcarbamyl chloride, said mercaptan is n-propyl mercaptan, and said quaternary salt is tricaprylylmethylammonium chloride or dimethyldicocoammonium chloride.

19. The process of Claim 2 in which said carbamyl chlo-ride is cyclohexyl ethylcarbam-1 chloride, said mercaptan is ethylmercaptan, and said quaternary salt is tricaprylylmethyl-ammonium chloride.

20. The process of Claim 2 in which said carbamyl chlo-ride is n-butylethylcarbamyl chloride, said mercaptan is n-propyl mercaptan, and said quaternary salt is tricaprylylmethylammonium chloride.

21. The process of Claim 2 in which said carbamyl chlo-ride is hexahydro-1H-azepine-1 carbamyl chloride, said mercaptan is p-chlorophenyl mercaptan, and said quaternary salt is tri-caprylylemethylammonium chloride.

22. The process of Claim 2 in which said carbamyl chlo-ride is hexahydro-1H-azepine-1 carbamyl chloride, said mercaptan is ethyl mercaptan, and said quaternary salt is tricaprylyl-methylammonium chloride.

23. The process of Claim 2 in which said carbamyl chlo-ride is cyclohexyl ethylcarbamyl chloride, said mercaptan is benzyl mercaptan, and said quaternary salt is tricaprylylmethyl-ammonium chloride or dimethyldicocoammonium chloride.

24. A process for the preparation of a thiocarbamic acid ester which comprises:
(a) reacting a carbamyl chloride having the formula in which R1 and R2 are independently selected from the group consisting of C1-C6 alkyl and C5-C7 cycloalkyl, or R1 and R2 together with the nitrogen atom to which they are bound from C4-C6 polyalkyleneimine, with a mercaptan having the formula R3SH in which R3 is selected from the group consisting of C1-C6 alkyl, phenyl, halo-substituted phenyl, benzyl, and halo-substituted benzyl, in the presence of, (i) an aqueous solution of a member selected from the group consisting of NaOH, KOH, and Ba(OH)2, and (ii) a catalytic amount of a quaternary salt having the formula (R4R5R6R7M)+Q- in which R , R , R6, and R7 are independently selected from the group consisting of C1-C10 alkyl, phenyl, and C7-C10 phenylalkyl, and have a total sum of 10 to 16 carbon atoms, M is nitrogen or phosphorus, and Q- is chloride or bromide; and (b) separating said ester from said aqueous solution.

25. The process of Claim 24 in which said carbamyl chlo-ride is di-n-propylcarbamyl chloride, said mercaptan is n-propyl mercaptan, and said quaternary salt is tetra-n-butylphosphonium chloride or benzyltriethylammonium chloride.

26. The process of Claim 24 in which said carbamyl chloride is hexahydro-1H-azepine-1 carbamyl chloride, said mer-captan is ethyl mercaptan, and said quaternary salt is tetra-n-butylphosphonium chloride.