Dimethyl carbonate

Phototransformation in air

Administrative data

Endpoint:

phototransformation in air

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: well documented study

Data source

Reference

Reference Type:

publication

Title:

Atmospheric loss processes of dimethyl and diethyl carbonate.

Author:

Katrib Y, Deiber G, Mirabel P, Le Calvé S, George C, Mellouki A, Le Bras G

Year:

2002

Bibliographic source:

J Atmos Chem 43: 151-174 (2002)

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Absolute rate coefficient data are reported for the OH radical reaction with dimethyl carbonate in the temperature range 263-372K. OH radicals were produced by pulsed laser photolysis of H2O2 at 248 nm. The concentration of OH radicals was monitored at various reaction times ranging from 10 µs to 10 ms by pulsed laser induced fluorescence. A Nd:YAG pumped frequency doubled dye laser was used to probe the OH radical at 282 nm, the subsequent fluorescence was detected by a photomultiplier. The output pulse from the photomultiplier was integrated for a preset period by a gated charge integrator. Typically the fluorescence signal resulting from 100 probe laser shots was measured for 10 to 15 different delay times and averaged to generate OH concentration-time profiles over at least three lifetimes. For the kinetic measurements, carbonate/H2O2 mixtures in helium diluent were flowed slowly through the cell, so that each photolysis/probe sequence interrogated a fresh gas mixture and reaction products did not build up in the cell. All experiments were carried out under pseudo-first-order conditions with [carbonate]>> [OH], the initial concentration of OH being lower than 2 × 10E11 molecule/cm³. The concentrations of the carbonates were calculated from their mass flow rates, temperature and pressure in the reaction cell.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Dimethyl carbonate

EC Number:

210-478-4

EC Name:

Dimethyl carbonate

Cas Number:

616-38-6

Molecular formula:

C3H6O3

IUPAC Name:

dimethyl carbonate

Details on test material:

- Name of test material (as cited in study report): dimethyl carbonate
- Substance type: ester
- Physical state: liquid
- Analytical purity: >99% (obtained from Fluka), further purified by repeated freeze-pump-thaw cycles and fractional distillation
- Impurities (identity and concentrations): not reported

Study design

Light source:

other: laser

Light spectrum: wavelength in nm:

248

Reference substance:

no

Results and discussion

% Degradation

% Degr.:

50

Sampling time:

22.9 d

Test condition:

25°C; 1 x 10E6 OH/cm³

Applicant's summary and conclusion

Validity criteria fulfilled:

not applicable

Conclusions:

Half-lives in the range between 15.3 and 45.8 d can be calculated for the photodegradation of dimethyl carbonate by reaction with OH radicals in dependance of the OH concentration.

Executive summary:

The OH reaction rate coefficient of dimethyl carbonate was determined using laser photolysis - laser induced fluorescence. Based on the kinetic data a rate coefficient k (OH)=0.35 x 10E-12 cm³/molecule x s was obtained. Taking into account the reaction rate coefficient and OH radical concentrations of 5 x 10E5 OH/cm³ (24 h day) and 1.5 x 10E6 OH/cm³ (12 h day) resulted in half-lives of 45.8 and 15.3 d, respectively. The calculation of the tropospheric half-life using a OH radical concentration of 1 x 10E6 OH/cm³ as cited in this publication yielded a value of 22.9 d.