CA1066616A - Water-soluble, liquid concentrates of s-methyl-((methylcarbamoyl)oxy)-thioacetimidate and methyl n',n'-dimethyl-n-((methylcarbamoyl)oxy)-1-thiooxaminidate - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Chemically and physically stable insecticidal, nematocidal, water-soluble, liquid concentrates of (a) S-methyl-[(methylcarbamoyl)oxy]-thioacetimidate, and (b) methyl N',N'-dimethyl-N-[(methylcarbamoyl)oxy]-1-thiooxamimidate when dissolved in an appropriate solvent, preferably methanol and water, in the presence of a small amount of acid,display solubility synergism.

Description

BACK~ROUND OF TXE INVENTION

The use of CH3-C=N-O-C-NHCH3 (methomyl) O O
Il 11 .
and (CH3)2N-C-C=NOC-NH-CH3 (oxamyl) as insecticldes and nematocides is well known ln the art.
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On occasion one may wlsh to applg these materials together in order to get the beneflt of both.
In tho~e lnstances, a slngle product containing both compounds provides economies of packaging and shipping, makes it more convenient to prepare -; .....
a spray solutlon and avoids do~age errors.
It is there~ore de~irable to maximize the amount of active ingredient, methomgl and oxamyl, which can b- transported in a single container.
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SUMMARY OF THE INYENTION
According to this invention, methomyl and oxamyl 1~ certain ratlos can be dissolved in designated ~olwnts, at a pH of about 2.8 - 3.2 with the unexpected result that the tota~ amount, expressed as grams o~
active per 100 gram~ oi solvent, is greater than the total o~ the amounts oi each which could be dissolved separately in the same solvent system.

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The lnitial welght ratios of methomyl to oxamyl to be dls~olved to constitute the concentrates of thls invention can be from about 2:1 to about 1:2.5.
The ~olvent systems which can be utllized include methanol/water containing from about O to 70 weight percent water, acetone/water contalnlng from about O to 70 welght percent water; or cyclohexanone/cyclo;
hexanol/methanol/water containlng from about 20-92 weight percent cyclohexanone and cyclohexanol pro-vlded at least 35% o~ this component i~ cyclo-hexanone, about 3-25 weight percent methanol and at least about 5 weight percent water.
m e pH o~ the system must be acidic and in general sufficient acid is needed to maintain a pH of about 2.8 - 3.1.
Other additlves such as colorant~ may be lntro-duced lnto the concentrates if desired.
Methomyl ~nd oxamyl may be chBracterlzed by the ~ollowing formulae: S-methyl- ~ methylcarbamoyl)ox ~ -thioacetlmidate (methomyl) and methyl N',N'-dimethyl-N-methylccarbamoyl)ox~7-1-thiooxamimidate (oxa~yl).

DETAILED DESCRIPTION OF THE INVENTION
In more detail, the lnstant invention relates to the unexpected ~lnding that when one combine~ methomyl and -~ -oxamyl in a designated solvent, unexpected solubllity synergism is ob~erved. m at is to say, when one adds both methomyl and oxamyl, in the deslgnated ratlo, to a designated solvent, one 18 able to dlssolve an unexpectedly lar~e ~mount o~ total mlxed active ingredient in the aolvent. ~ependlng ~pon the lo~eat :

~ ~0666~6 temperature which the solution must withstand without crystalllzation, one can obtain a concentration of 1 to 5 lbs. of total active ingredient per U.S. gallon of solution. The weight ratio of methomyl to oxamyl is about 2:1 to about 1:2.5, preferably about 1.5:1 to 1:1.5 and most preferably about 1:1 to 1:1.5.
m e solvents may be a system of methanol/~ater ;~
containing from about O - 70 weight percent water; acetone/-water containing from about O - 70 weight percent water;
or cyclohexanone/cyclohexanol/methanol/water contalning from about 20-92 weight percent cyclohexanone and cyclohexanol provlded at least about 35% of thls component is cyclohexanone, about 3-25 welght percent methanol and at lea~t about 5%
~ater. The preferred solvent ls a system of methanol/water contalning from about O - 79 percent ~ater, most preferably about 20 - 50 percent.
The p~ may vary from about 2.8 to 3.2; the most preferred acld to be utlllzed is phosphoric acid, but other aclds such aR acetic, citric and sulfurlc acld are also ACCeptable 80 long as the desired pH i8 obtained. In a preferred embodiment, phosphoric acid in the amount of about 0.4 to o.6 weight percent i~ utllized. If desired, warnlng agents may be added such as dyes, colorants, or odor-produclng chem~cals. Typically, a colorlng agent would be added ln an amount from about 0.01 - 0.10 percent. Suitable colorlng agents would be MARASPERSE~, a product of the Amerlcan Can Company, LIGNOSOLS* sold by Lignosol Chemical6 Company, or organic dyes such as FD & C Blue No. 1, FD & C Red No. 3 (773 erythrosine) or FD & C Yellow No. 5 (640 tartrazlne).
In fact, any colorlng agent~ that do not react chemically * denotes trade mark ~ ' . , .

with the other formulation ingredients may be utilized.
Combinations of coloring agents are also suitable. MARASPERSE
CB, or FD & C Blue No. 1 are the preferred coloring agent. -The preparation of both methomyl and oxamyl is well known to one skilled in the art. For instance, the preparation of methomyl and its various uses as an insecti-cide, nematocide etc. are included in U.S. Patent 3,639,633 to James B. Buchanan. The preparation of oxamyl and it~
uses for various purposes such as an insecticide, miticide, -or nematocide are taught in U.S. Patent 3,530,220 to Buchanan.
As woula be expected, the concentrates of the instant invention are useful ~or controlling insects, other arthropod pests and pestiferous mollusks and nematodes.
m e methomyl, oxamyl, acid and any other ingred-ients ~uch as coloring agents may be mixed in conventional equipment by conventional means. For instance, they may be mixed as rollows: The solvent sy~tem and acid are added to a glass-lined or stainless steel kettle equipped with a stirring mochanism and facil~ties ~or blanketing the kettle with nitro-gen or other inert gas to reduce the ~ire hazard of the flam-mable solvents. ~he active ingredients and the warning agent such as a coloring agent are added to the kettle ~hile stir-rlng, stirring i~ continued until the active ingredients and coloring agent are dissolved. The solution can the be flltered by techniques known in the art. A "sparkler" filter may be used.
Example l Formulations o~ the following compo~itions are prepared by dissolving the methomyl, oxamyl and coloring agent where applicable, in the solvent system and acid at ~. i :

` ~066616 ambient temperature. The solution i~ clarlfied by filtration techniques known in the art. -~
A. methomyl---------------------- 22 lb.
oxamyl--------7~ -------- 22 lb.
MARASPERSE CB-`-L------------- 0.025 lb. :;
CH~OH------------------------- 33.3 lb. :~ ~
H2~--------------------------- 22.1 lb - . -85% H3PO~---------------______ 0.33 lb. . -~
B. methomyl---------------------- 20 lb. ~ -yl ~~~~~~~~~~~r~r------ 10 lb.
F.D. & C. Blue No. 1-~-'------ 0.01 lb.
CH~OH------------------------- 62.7 lb. ~ :
H2~--------------------------- 6.9 lb. -85% H P4----------___________ 0.33 lb- . ..
C. methomyl---------------------- 15 lb.
oxamyl-----------------__----- 15 lb. :
acetone----------------------- 52 lb. ::
~ater------------------------- 13 lb. : -85% H3P04--------------------- 5 lb.
D. methomyl---------------------- 20 lb.
ox~myl------------------------ 30 lb. :~
cyclohexanone----------------- 27 lb.
C~30H-------__________________ 4.5 lb.
wa~er--------------------~~~~~ 13.5 lb.
5~ H3P4 ~~~~~~--------___ 5 lb.

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~ 10666~6 E. methomyl~ -------------- 15 lb.
oxamyl----------~ ----- 15 lb.
cyclohexanone----------------- 15.6 lb.
cyclohexanol------------------ 19.5 lb.
CH30H-------__________________ 9.75 lb.
water------------------------- 20.15 lb. -85~ H3P04----------~ ----__ 5 lb.
(1) Available from American Can Co.
(2) Available from H. Kohnstramm & Co. Inc., ~-New York or Chicago.
Example 2 Methomyl and oxamyl were added to varlous methanol:water solvent systems ranging rrom 100% CH30H
to 40~ CH30H:60~ H20. ffle methomyl and oxam~l were dis~olved separately or comblned in a 1:1 weight ratio in the solvent systems at room temperature at a concentration exceeding the ~olubility limlt at -6C. Each sample wa~ seeded with methomyl and/or oxamyl at _6C and allo~ed to crystallize untll equilibrium was establish- `~
ed. The supernatant liquid Or each sample was aasayed rOr methomyl and/or ox~myl by liquid chromatography.
The rollo~ing re~ults were obtained.

80LBEILITY QF ~En~L AND OXUoL (1:1 WT. ~ArIo) I~ CHbO~Ha4 A~ ~C I~ GM3/100 GM~ 80LVDNT
th Actl~c~ 1~ 801~nt Mcthomyl Mothcmyl ~u~l 801v~nt Meth~l OY myl ~ ~m~l Alone la Alone in R~ gmsgm- Solv~nt gms ~olveat loO/0 63.9 80 143.9 30.7 33.3 90/10 66.4 92.0158.4 29.9 40.6 80/20 58.1 87.o145.1 26.3 44.7 7/3 43.~ 52.796.5 20.8 42.2 60/4~ 35.5 53.288.7 15.5 39.7 50/~o 23.7 33.357. 10.5 29.0 40/60 18.8 33.752.5 6.2 20~9 ~., , , . . ' , ,.,.. ?:~
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1066616 ~ ~

The table illustrates that ln a common solutlon, both the total comblned amount of actlves as well a~ the amount of each lndlvidual component ha~ been lncreased over what a ~olution Or each actlve lngredient alone ln that solvent could contaln.
Flgures 1 and 2 show a plot of the solublllty data of Example 2. Curve 1 of Flgure 1 plots the solu-blllty o~ methomyl alone in the various methanol/
water solvents. Curve 2 of Flgure 1 plots the solu-10 blllty Or methomyl ln the presence of oxamyl. Curve ~ -

3 of Flgure 2 plot~ the solubll~ty of oxamyl alone ln the various methanol/water solvents. Curve 4 Or Figure 2 plots the solubility Or oxamyl ln the presence of methomyl. m e shaded areas between curves 1 and 2 and between curves 3 and 4 represent the lncrease ln solubillty derived from havlng both methomyl and ox~myl present.

` 1066616 Solubillty of Methomgl and Oxamyl (2:1 wt. ratio) in CH30H/H20 at -6C
Methomyl and oxamyl were added to various methanol:water solvent systems ranging from 100 wt.
% CH30H to 30 wt. ~ CH30H:70 wt. ~ H20. me methomyl and oxamyl were dlssolved in a 2:1 weight ratio of 50 wt. % methomyl to 25 wt. ~ oxamyl in the eolvent 3ystems. me samples were equilibrated at -6C ln a constant temperature freezer after which they were seeded with methomyl and oxamyl crystals to ensure crystallization of both materials. After crystal-llquid equilibrium was assured, liquid was removed at -6C and assayed for methomyl and oxamyl. Solids were also removed at -6C, washed with hexane ~nd dried.
me solids were then dissolved in methanol to yield a 10 wt. ~ solution. mis solutlon was evaluated by thin layer chromatography (TIC) to ensure the solids consisted of both methomyl and oxamgl. All solids were composed Or the mixture. me following assays uero obtalned on the liquids.

gOLUBILITY OF ~DC~HOMYL IUID OXAMYL (2:1 WT. RA~IO) IN C~90~/H p A~ -6C D GM8/100 GM8 80LVENT
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80th ~ctlv-~ in 801vent Methcmyl Methomyl Oxamyl Solvent Metbomyl Oxamyl ~ Oxamyl Alone i~ Alone in ~O~/~H20 eD8 gms gm~801~nt 0m~801~ent gms 100/0 82.5 113 195.5 30.7 33.3 90/10 73~7 106 179.7 29.9 40.6 80/20 59,8 94,7154.5 26.3 44.7 70/30 34.2 89.1123.3 20.~ 42.2 60/40 ~5.2 99.2154.4 15.5 39.7 50/50 46.1 96.6142.7 10.5 29.0 40/60 42.2 100 142.2 6.2 20.9 30/70 24.1 57.481.5 -- -_ g _ .
, The above data lllustrate that the solubility of both methomyl and oxamyl is increased in methanol:water solvent systems when a 2:1 wt. ratio of methomyl to oxamyl is dlssolved initially. Furthermore, the total amount of active ingredient in a given solutlon, when both oxamyl and methomyl are present in combin-ation in solutlon is much greater than the sum of the lndlvidual components dissolved in separate solutions. In addition, the quantity of solvent needed to di~solve given quantitles Or oxamyl and methomyl when in mixture is less than 1/3 the quantlty of solvent needed to dlssolve the oxamgl and methomgl lndivldually.

Solubllity of Methomyl and Oxamyl 1:2.5 wt. ratio - -in CH~3OH:H20 at -6C
Exa~ple 3 was repeated by dlssolving methomyl and oxamyl ln a 1:2.5 weight ratio in the ssme solvent systems under the same conditions. me ~ollowing methomyl and oxamyl ~olubilities at -6C were found.
TLC lndlc~ted the solids in each sample contained both materlals.

80LUBILIrY OF METEOMYL AND OXANYL (1:2.5 wr. RA~IO) IN C~OH/E20 ~ -6C IN GMS/100 GMB SOLVEDr Both ~ctlve~ in Solvent Methomyl Methomyl Oxamgl Sol~ont Mbthomyl Oxamyl ~ Oaa~yl Alone in Alone i~
gms emsgms 801vent gm~ Sol~ent gm~
100/0 71.1 72.3143.4 30.7 33.3 90 ~ 0 59.9 76.4146.3 29.9 40.4 ~
80/20 57.3 73.7131.0 26.3 44.8 `
70/30 22.0 46.168.1 20.6 42.3 60/40 44.0 74.8118.8 15.5 39.6 50/50 41.1 74.0115.1 10.5 29.1 40/60 28.8 51.680.4 6.2 20.9 30/70 15.6 34.75-3 . .
' ' - 10 - .;

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^ ~066616 Methomgl and/or oxamyl were added to a solvent system conslsting of 60~ cyclohexanone~ 10~ methanol and 30~ water at room temperature at a concentra-tlon higher than the solubility limit at -6C. The methomyl and oxamyl wete added together, at weight ratios of 2~ 1 and 1:2.5. m e solutions were cooled to -~C and seeded with methomyl and/or oxamyl to initiate crystallization. me solutions remained at -6C until equilibrlum was a~sured. The supernatant liquid in each sample was analyzed for methomyl and oxamyl by liquid chromatography. m e ~ollowing results were obtained.

SOLUBILITY OF MET~OMYk A~D OXAMYL
(2:1, 1:1 and 1:2.5 wr. RArIOS) D CYCLOHBXANONE~ CH3OH
AND ~2 AT -6C IN GMS/100 GMS SOLVENT
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Both Active~ in Solvent Methomyl Methomyl Oxumyl Nothomyl/Oxamyl Methomyl Oxumyl ~ Ox~myl Alone in Alo~e in ratio p~s ~ms gms Solvent ~8 Solvent ~ms 2:1 64.8 84.8 149.6 29.5 48.4 1:1 46.2 80.1 126.3 29.5 48.4 1:2.5 66.6 82.7 149.3 29.5 48.4 -- -- .

Methomyl and Oxamyl Solubility In Cyclohexanone, Cyclohexanol, CH30H and H20 at -6C

Methomyl and oxamyl were dissolved separately and in weight ratio~ of 1:1, 2:1 and 1:2.5 methomyl to oxamyl in a solvent system consisting Or 30 wt. ~

, . : , . , ~
, cyclohexanone, 30 wt. % cyclohexanol, 30 wt. ~ water ~-and 10 wt. % methanol. m ese solutions were equilibrated at -6C and ~eeded with methomyl and/or oxamyl crystals. m e samples of liquid and so~ids remained at -6C until solid-llquid equilibrium was ~ -assured. A llquid sample was removed from each at -6C and assayed for methomyl and/or oxamyl.
Sol~ds were also isolated at -6C, washed, dried and ~ -~
dlssolved in CH30H to yield a 10~ solution whlch was analyzed by TLC to ensure both methomyl and oxamyl crystals were present ln the solids of the comblnatlon sample. All such solids contained both oxamyl and methomyl.

SOLUBILITY OF MErHOMYL A~D OXAMeL ~:1, 1:1 AND 1:2.5 WT. RArI03) : - .
IN CYCLOHBXANO~E, CYCLOHEXANOL, CH30~ ADD H20 A~ _60C IN GMB/10O GM8 80LVE~r ~.
Both ~ctlve~ in 801vent Methomyl Methomyl Oxamyl Methomyl/Oxamyl Methomyl Oxamyl ~ Qxa~yl Alono ln Alone ln ratlo smo 0ms ~m~ 801ve~t ~m~ Sol~ent ~s 2:1 42.7 83.0 125.7 24.5 41.5 1:1 39.6 63.7 103.3 24.5 41.5 , :
1:2.5 40.2 61.B 102.0 24.5 41.5 Solublli~g of Methomyl and Oxamyl 80:20 St. Ratlo Acetone:H20 ~ -Methomyl and oxamyl were dissolved in a solvent system consl~ting of 80 wt. ~ acetone and 20 wt. %

water separately and in 1:1, ~:1 and 1:2.5 wt. ratios - 12 _ .

~ 06~ 6 of methomyI to oxamyl. These solutions were equilibrated at -6C and were seeded with methomyl and/or oxamyl.
m ey remained at -6C until solid-liquid equilibrlum was assured. Liquid was removed ~rom each sample at -6C and assayed for methomyl and ox~myl. Solids were also removed at -6C, washed, dried and dis-solved in methanol to yield a 10 wt. ~ solution which was evaluated by T$C for oxamyl and methomyl. Both were present in the solids ~rom combination samples.
The following results were obtained on the liquids removed from the samples.

SOLUBILIIY QF M2TEOMYL AND OXAMYL 2:1, 1:1 AND 1:2.5 WT~ RArIOS
IN 80:20 WT. ACETONe AND HDO IN GMS/100 GMS SOLYENT
Both Actives in Solvent Methomyl Metho~yl Oxa~yl Methomyl/Oxamyl Metho~yl Qxamyl ~ Oxamyl Alone in Alone in ratio ~m~ ema gms Solvent ~ms Solvent Kms 2:1 64.8 84.6 149.4 41.4 52.0 1:1 67.o 79.3 146.3 41.4 52.0 1:2.5 66.6 82.8 149.4 41.4 52.0 m e data in Examples 2-7 show that increases ln solubillty occur when ox~mgl and methomyl, both active insecticldes and nematocides, are dissolved together In the solvents taught. The lncreases allow slgnlflcant economles of solvent cost, packaging and shlpplng by greatly reduclng the solvent necessary.
m e magnltude o~ these inCrease~ is unexpected.

Claims (7)

CLAIMS:

1. An insecticidal and nematocidal composi-tion comprising (a) S-methyl-[(methylcarbamoyl)oxy]-thioacetimidate, and (b) methyl N',N'-dimethyl-N-[(methylcarbamoyl)oxy]-1-thiooxamimidate in a solvent, said solvent selected from solvent systems consisting of methanol/water containing from 0 to 70 weight percent water, acetone/water containing from about 0 to 70 weight percent water, and cyclohexanone/cyclohexanol/-methanol/water containing from about 20-92 weight per-cent cyclohexanone and cyclohexanol provided at least about 35% of this component is cyclohexanone, about 3-25 weight percent methanol and at least about 5 weight percent water, the ratio of (a) to (b) being 2:1 to about 1:2-1/2, said composition being maintained at a pH
of about 2.8 to 3.2.

2. A composition of Claim 1 wherein the solvent system is methanol and water containing from about 0-70 weight percent water.

3. A composition of Claim 2 wherein the ratio of (a) to (b) is 1-1/2:1 to 1:1-1/2.

4. The composition of Claim 2 wherein the pH
is maintained at the desired level by adding phosphoric acid to the composition.

5. The composition of Claim 2 wherein the ratio of (a) to (b) is about 1:1 to 1:1-1/2.

6. The composition of Claim 1 wherein the solvent system is methanol and water containing from about 20-50 weight percent water.

7. The composition of Claim 2 wherein a color-ing agent is also present.