L“*
potential by-products. did not lead to phate as starting materials under similar the determination of the compounds or condensation conditions as for Diazinon, breakdown products responsible for the the oxygen analog (0-Diazinon) was increased anticholinesterase activity of obtained. The purified and distilled distilled Diazinon, even occurring when product boils a t 123-5’ C. a t 0.03 mm. oxygen is carefully excluded. of mercury. This 0-Diazinon always T h e fact that none of the above cited contains. after distillation, small amounts Thioldiazinon of 2-isopropyl-4-methyI-6-hydroxypyrim- decomposition or by-products was able Using 2-iso~~ropyl-4-inethyl-O-merto explain the increased mammalian idine and probably small amounts of captopyrimidine for the condensation toxicity as well as the higher cholinT E P P lvhich may be formed due to the -with 0.0-diethyl [chlorophosphate,Thiolesrerase inhibition found in technical influence of heat. 0-Diazinon is con.diazinon should result. -\ \vide variety Diazinon indicated that a special study siderably less stable to hydrolysis than of reaction conditions \\-as chosen. Jvithwas needed to clarify the phenomena Diazinon. a t a p H of 7 the rate being out getting even :,mall amounts of a pure which can occur when technical Diazabout 10 times as high. T h e antiThioldiazinon. Lnder mildest condeninon or its formulations are stored. cholinesterase activity proved to be by sation conditions a t temperatures as loiv The results of this special study have been far higher than the anticholinesterase as 30’ C. t!ie reaction benveen 2-isoreporred (8). activity of Diazinon. 0-Diazinon could prop>-I- 4 - meth!-l - 6 - mercaptopyrimiexplain the higher cholinesterase inhibiLiterature Cited dine and 0.0-diethyl chlorophosphate tion of partly decomposed Diazinon. did not take ;>lacCH-!.,; ,!!-O-P/ (13) Suter, R.: Delley, R., Meyer, R . , diluted acid or alkali hydroxide solution Z . anal. Chem. 147, 173 (1955). CH 3 $‘OC,Hj (14) Suter, R., Meyer, R., J. R. Geigy did not eliminate the occurrence of the S.A.. Bade, Switzerland, private comspots. 0-Iliazinon munication, 1956. Further investigations based on paper Using 2-isopropyl-4-methyl-6-hydroxy- chromatography of technical, distilled, Received f o r review October 7 , 7957. Accepted July 21: 1958. and purified Diazinon, known and pyrimidine and 0,O-diethyl chlorophosA86 >86
ences in storage temperature and humidity. Catalytic Activity of Carrier. Another important factor of Aramite decomposition is the type of carrier used in the formulation. With few exceptions, most of the common commercial carriers exhibit catalytic activity at elevated temperahres (50 to 70 (2.). This property, which accelerates the rate of decomposition, is dependent on surface activity, porosity, and chemical composition of the diluent. T h e effect of this activity varies greatly with the type of carrier ( 7 , 2). Aramite begins to decompose almost immediately after formulation in a kaolin-type diluent, but in calcium carbonate decomposition of Aramite proceeds very slowly a t room temperature. In almost all fillers Aramite decomposes rapidly a t 50" C. unless stabilized. Stabilization of' Aramite by Glycols. Although technical Aramite contains 0.5% propylene (oxide, which prevents decomposition of the technical material in a storage a t normal warehouse temprratures, the formulated dusts or wettable powders should be further stabilized when they are stored at higher temperatures (35" to 50" C.). Laboratory and field studies have shown that propylene oxide volatilizes from wettable powders and dusts at 35" C . or higher. In Table I1 the effect of various glycols and some These tests other additives is given. were made in sealed glass containers. T h e half life of the wettable powder was significantly increased by the use of 47, propylene oxide? but it was not sufficient to warrant its use under commercial conditions. As shown in T,ible I the half life of Aramite was increased almost twentyfold when formulated Ivith Attaclay in which the moisture cont'mt was lowered from 0.6 to less than C.2YG',.This suggested that the addition of a humectant might accomplish similar inhibition, because the amount of the rnoisture content would be controlled within narrow limits. Glycerol increased the half life 13 times over that of a simihrly prepared unstabilized formula. This significant increase in stability led to the investigation of various glycols.
Table II. Effect of Glycols and Other Additives on Aramite Stability in 15% Wettable Powders Containing Attaclay at 50' C. in Sealed Glass Jars Doys Stored
%
Addifive
None None Mineral oil D-Sorbit a1 Ethylene glycol mono-i\--butyl ether Ethylene glycol Diethylene glycol 2,3-Butylene glycol Propylene oxide 1,3-Butylene glycol G1y cer o1 Polyethylene glycol 400 Propylene glycol Dipropylene glycol
0 0 0 0 0
5 .O 5 .O 6.0 5.0 4.0
Table 111. Effect of Dipropylene Glycol in 3% Aramite Dust Formulations at 50" C. in Sealed Glass Jars Di-
Aramite
propylene Glvcol. Diluent
'70
'
ClearLaketalc None SoapstoneAt t aclay Xone Anhydritefiller None Clear Laketalc 3 0 SoapstoneAttaclay 1.0 2.0 Anhydrite filler 1 . O 2.0
Dovs
st0;ed
31 31 31 75 42 42 50 42
95 8 85 5 77.2 91.4
9 10 8 8
18 45 45 45 30 45 109 37 45 86
82 0 87 2 87 8 79 0 52 3 65.2 41.2 4.6 3.3 6.0
11 26 26 28 29 35 132 402 577 716
Table IV. Effect of Dipropylene Glycol on Aramite-Aldrin and Aramite-Dieldrin Formulations Stored at 50" C. for One Month
DecomDosition. '
%
54 49 45 3
(3.67, Aramite present) Aramite Dipropylene DecomGlycol, position,
'
75 42 80 56
5.23 5.24 3.71 4.25
All of the unsubstituted glycols tested inhibited the decomposition to some degree. Propylene, dipropylene, and polyethylene glycol 400 were the most effective additives investigated. Some of the glycols tested did not show any improvement over propvlene oxide. it'hen one of the hydroxy groups was blocked as in the case of ethylene glycol mono-AV-butyl ether (Table 11). the stabilizing influence was nullified. Apparently the glycol must contain two or more free hydroxyl groups to possess this stabilizing function. Table I11 illustrates the stabilizing effect of dipropylene glycol in several Aramite 3% dusts prepared with three different fillers. The optimum per cent of glycol necessary for adequate stabilization is dependent on the type of diluent used. This will vary between 2 and 5%. The glycol stabilizes Aramite in the presence of other chlorinated hydrocarbons such as DDT, DDD. methoxychlor, aldrin. dieldrin. and toxaphene when these are used alone or in combination. An illustration of the stabilizing function of dipropylene glycol in formulations of Aramite and aldrin or Ararnite and dieldrin is given in Table IV. I n the combination of tetraethyl pyrophosphate
Days
20 20 9 15
30 5 0 5 5 5 5 4
Holf life,
Aramite Decomposition, 70
-
Technicol Insecticide
Aldrin Dieldrin Dieldrin .4ldrin Dieldrin Dieldrin
%
%
%
2 0 1 0 2 .O 2.0 1. O 2.0
None None None
60 1 3 97 31 91.67 3.50 8.57 12.57
1 .O 1. O 1. O
with Aramite, the glycols were of no value in inhibiting the decomposition, because of the initial high acidity associated with technical tetraethyl pyrophosphate. This latter combination liberates sulfur dioxide \Tithin 24 hours. Dipropylene glycol has been used satisfactorily to stabilize Aramite dusts and wettable powders for several years ( 3 ) . The degree of stabilization afforded is dependent upon the choice of the glycol, the selection of the diluent. and the type of wetting agent, dispersant agent, or other additives incorporated. This necessitates that each formula be evaluated individually.
Literature Cited (1) Malina, M. A , , Goldman, A , ?Trademan. L., Bolen, P. B.? J. . ~ G R . FOOD CHEM. 4, 1038-42 (1956). (2) Naugatuck Chemical! Saugatuck, Conn., Aramite Technical Formulator's Handbook. (3) Yaffe, J., Cassil, C. C. (to Food Machinery and Chemical Corp.), U. S. Patent 2,832,716 (April 29! 1958). Received f o r review March 27, 7958. Accefifed July 15, 1958. Diaison of Agricultural and Food Chemistry, 13.3rd Meeting, ACS, San Francisco, Calif., April 1958.
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