BE596091A - - Google Patents

Description

       

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  "New thionophosphoric ester and its preparation process." The use of 0,0-dimethyl-0- (4-nitro-phenyl) -thionophosphate currently plays a dominant role in the control of harmful organisms . The disadvantage of this compound in practical application is the relatively high toxicity of this ester to warm-blooded living beings. We had already tried to

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 reduce this high toxicity by an adequate substitution in the phenyl residue.

   The known 0,0-dimethyl-0 (4-nitro-3-chlorophenyl) -thionophosphate (see French patent no. 1,076,507 of April 28, 1953 (Belgian patent 519,482) admittedly has a low toxicity with regard to warm-blooded living beings, but in practice this compound has not assumed the same importance as the aforementioned 0,0-dimethyl-0- (4-nitro-phenyl) -thionophosphate.



  Now, the Applicant has made the surprising observation that 0,0-dimethyl-0- (4-nitro-3-methyl-phenyl) -thionophosphate of formula
 EMI2.1
 not yet known to date, is characterized, for a low toxicity to warm-blooded living beings, by excellent insecticidal activity. While 0,0-dimethyl-0- (4-nitro-phenyl) -thionophosphate exerts in practice only a weak action on the devouring insects (caterpillars and beetles), 0,0-dimethyl-0 - (4-nitro-3-methylphenyl) -thionophosphate is excellent for the precise destruction of devouring insects.

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  This singular and practically desired effect was not to be expected due to the substitution of a methyl group in the 3-position of the phenyl.



  The examples which follow are given to illustrate the preparation and the activity of the new compound.



   Example 1
 EMI3.1
 61 g (0.4 mol) of 1-methyl-3-hydroxy-6-nitrobenzene (Stadel, Ann. 259 (1890) 210; PF 130 C) and 56 g (0.4 mol of carbonate of finely pulverized potassium in 250 cc of methyl ethyl ketone.



  After half an hour of heating at 60-70 C, 0.5 g of copper powder is added and 65 g (0.4 mole) of dimethylthiophosphoric acid chloride is then introduced dropwise; a weak exotherm occurs.



  After heating for 2 hours at 70-80 ° C., the mixture is left to cool, filtered with suction and the filtrate is washed with 250 cc of benzene. Then the filtrate is washed with water, until the complete disappearance of the yellow color. After drying over sodium sulfate,

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 the solvent is removed by distillation and one then obtains
104 g of a light brown, limpid oil. Yield: 94% of theory.



  The calculation gives for a molecular weight of 277.2:
N 5.05% S 11.57% P 11.18% We found: N 4.96 S 11.87% P II, 21 µ Toxic dose for rats by oral administration: LD50 = 500 mg / kg.



   Example 2 To a solution of the compound obtainable according to the process described above, in equal parts by weight of chlorobenzene, is added twice the amount of a commercial emulsifier based on benzyl-hydroxydiphenyl-polyglycolether. This mixture is made up with water to a concentration of 0.001% (active ingredient). This emulsion is sprayed, until dew forms, on bush beans (Phaseolus vulgaris) heavily infested with resistant forms of spinning moths (Tetranychus alteae Hanst). The evaluation, made after 24 or 28 hours, shows 100% destruction of the parasites.



   Example 3 When spraying or watering caterpillars (Plutella maculipennis) with an aqueous dilution

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 to 09004 ci of the following sprayable agent:
 EMI5.1
 
<tb> active <SEP> ingredient <SEP> 50 <SEP>%
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<tb> xylene <SEP> 30 <SEP>%
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<tb> a <SEP> nonyl-phenol <SEP> hydroxyethylated <SEP> 20 <SEP>%
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 they quickly suffer serious damage and succumb to 100 after 1 to 2 days.



   Example 4 When preparing an aqueous sprayable agent from 50% 0,0-dimethyl-0- (4-nitro-3-methylphenyl) -thionophosphate, 30% cyclohexanol and 20% non-emulsifier. ionogen, and if this agent is applied in a concentration of 0.001%, aphids (Doralis fabae) can be completely destroyed on Cineraria or Chrysanthemum.


    

Claims (1)

CLAIMS 1 Process for preparing an ester of thionophosphoric acid, characterized in that 3-methyl-4-nitrophenol is reacted with 0,0-dimethyl-thionophosphoric acid halides. 2 As a new industrial product, 0,0-dimethyl-0- (4-nitro-3-methylphenyl) -thionophosphate. 3 An agricultural pest control agent which is or contains the compound of claim 2. 4 Pest control method, characterized in that use is made of the compound according to claim 2.