O,O-diethyl hydrogen phosphorodithioate

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1997

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study is a publication with detailed description of the method used.

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

publication

Title:

Kinetics and Mechanism of Hydrolysis of Di-Ethyl Dithiophosphate in Acid Media

Author:

Patil, R. et al

Year:

1997

Bibliographic source:

Asian Journal of Chemistry, Vol. 9, No. 3, 407-410

Materials and methods

Test guideline

Qualifier:

no guideline followed

Deviations:

not applicable

Principles of method if other than guideline:

Reactions using diethyl dithiophosphate were carried out at 98°C employing 5E-04 mol/dm3 solution of diester which was subsequently followed by the Allen's modified method of colorimetric estimation of organic phosphate in aqueous media maintaining constant ionic strength by means of HCl and NaCl.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

O,O-diethyl hydrogen phosphorodithioate

EC Number:

206-055-9

EC Name:

O,O-diethyl hydrogen phosphorodithioate

Cas Number:

298-06-6

Molecular formula:

C4H11O2PS2

IUPAC Name:

O,O-diethyl sulfanylphosphonothioate

Details on test material:

- Name of test material (as cited in study report): diethyl dithiophosphate

Radiolabelling:

no

Study design

Analytical monitoring:

not specified

Estimation method (if used):

Not applicable

Number of replicates:

Not applicable

Positive controls:

not specified

Negative controls:

not specified

Statistical methods:

Not applicable

Results and discussion

Transformation products:

not specified

Details on hydrolysis and appearance of transformation product(s):

The rate of hydrolysis of diethyl dithiophosphate was studied in HCl (0.1 - 7 mol/dm3). The pseudo first order rate constants were determined from which it is clear that the rste of reaction increases up to 4 mol/dm3 HCl but further increase in acid molarity decreases the rate as it can be attributed to the complete conversion of the ester (basic) molecule into their respective conjugate acid species with the lowering of concentration of a nucleoplhile (water), which plays its role in rate determining step of bimolecular hydrolytic reaction.

Other kinetic parameters:

In order to determine whether or not there is an effect of ionic strength or presence of acid catalysis, kinetic runs were made at three different ionic strength (1.0, 2.0 and 3.0) which were maintained by adequate mixture of NaCl and HCl. Hydrolysis at each ionic strength is represented by a linear curve that makes a positive slope. From the study of ionic strength, the total rates contributed by conjugate acid and neutral were calculated.

Details on results:

Arrhenius parameters were determined for the hydrolysis at 3.0 and 5.0 mol/dm3 HCl. The magnitude of these parameters falls in the range of bimolecular reaction. Bimolecular nature of reaction is further supported by additional parameters suggesting that water involved as a proton transfer agent is the rate determining step. Comparative kinetic data also support the bimolecular nature of hydrolysis involving attack of water molecule on phosphorous of the diester involving P-O bond fission.

Any other information on results incl. tables

No other information.

Applicant's summary and conclusion

Validity criteria fulfilled:

not applicable

Conclusions:

A bimolecular nature of hydrolysis of diethyl dithiophosphate is proposed.

Executive summary:

Investigation of the hydrolysis of diethyl dithiophosphate was carried out by using Allen's modified method of colorimetry, in aqueous solution medium from 0.1 to 7.0 mol/dm3 HCl at 98°C.

Based on the results obtained, a bimolecular nature of hydrolysis involving attack of water molecule is proposed.