1,2-dichlorobenzene

Phototransformation in air

Administrative data

Endpoint:

phototransformation in air

Type of information:

other: BUA report

Adequacy of study:

other information

Reliability:

other: BUA report

Rationale for reliability incl. deficiencies:

other: BUA report

Data source

Reference

Reference 1

Reference Type:

other: BUA report

Title:

Unnamed

Year:

1990

Reference 2

Reference Type:

publication

Title:

Laboratory experiments to assess the importance of photochemical transformation during the atmospheric transport of chlorinated aromatic pollutants

Author:

Bunce NJ, Landers JP, Langshaw JA, Nakai JS

Year:

1987

Bibliographic source:

Proc - APCA Annu Meet, 80th (Vol 6), 87/96.2, 1-16

Reference 3

Reference Type:

publication

Title:

An assessment of the importance of direct solar degradation of some simple chlorinated benzenes and biphenyls in the vapor phase

Author:

Bunce NJ, Landers JP, Langshaw JA, Nakai JS

Year:

1989

Bibliographic source:

Environ Sci Technol, 23: 213-218

Reference 4

Reference Type:

publication

Title:

Reactions of disubstituted benzenes with OH in the gas phase: Benzene, o-, m-, and p-dichlorobenzene and p-chloroaniline

Author:

Wahner A, Zetzsch C

Year:

1982

Bibliographic source:

Comm Eur Communities (Rep), EUR 7624, Phys-Chem Behav Atmos Pollut, 138-148

Reference 5

Reference Type:

publication

Title:

Rate constants for the addition of OH to aromatics (benzene, p-chloroaniline, and o-, m-, and p-dichlorobenzene) and the unimolecular decay of the adduct. Kinetics into a quasi-equilibrium. (Part 1)

Author:

Wahner A, Zetzsch C

Year:

1983

Bibliographic source:

J Phys Chem, 87, 4945-4951

Reference 6

Reference Type:

publication

Title:

Measurements of some potentially hazardous organic chemicals in urban environments

Author:

Singh HB, Salas LJ, Smith AJ, Shigeishi H

Year:

1981

Bibliographic source:

Atmos Environ, 15: 601-612

Reference 7

Reference Type:

publication

Title:

The significance of quantum yield during determination of environmental photochemical degradability of organic compounds

Author:

Parlar H, Korte F

Year:

1979

Bibliographic source:

Chemosphere, 8: 797-807

Reference 8

Reference Type:

publication

Title:

Umwandlung von Organohalogenverbindungen unter abiotischen Bedingungen [in German]

Author:

Gäb F, Parlar H

Year:

1979

Bibliographic source:

Forschungsbericht (03 7114). Spez Ber Kernforschungsanlage Jülich, Jül-Spez-45, Organohalogenverb Umwelt, 180-197

Reference 9

Reference Type:

publication

Title:

Photoformation of polychlorinated biphenyls from chlorinated benzenes

Author:

Uyeta M, Taue S, Chikasawa K, Mazaki M

Year:

1976

Bibliographic source:

Nature, 264: 583-584

Materials and methods

Principles of method if other than guideline:

BUA report

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

1,2-dichlorobenzene

EC Number:

202-425-9

EC Name:

1,2-dichlorobenzene

Cas Number:

95-50-1

Molecular formula:

C6H4Cl2

IUPAC Name:

1,2-dichlorobenzene

Results and discussion

Any other information on results incl. tables

BUA report:

Several publications on the photochemical degradation of 1,2-dichlorobenzene in air were summarized in the assessment of the BUA report 53 (1990). The reliability of these publications was not assignable because references were only cited as secondary literature.

Although the quantum yield for the irradiation of gaseous o-dichlorobenzene with light of wavelength 254 nm at 23 °C is 0.63 +/- 0.04, direct photolysis is not a degradation pathway of any consequence in the environment since o-dichlorobenzene does not absorb enough in the wavelength range encountered in tropospheric sunlight.

In a further publication, the following rate constant for the reaction between OH radicals and o-dichlorobenzene in the atmosphere at room temperature (22 °C) were calculated:

KOH = (4.2 +/- 0.2) x 10^-13 cm3/(molecule*s)

When allowance is made for the mean global OH radical concentration in the troposphere, which current knowledge puts at 5 x 10^5 molecules/cm3, the halflife, t0.5, computes to 38 +/- 2 days.

A further reaction rate constant of KOH = 0.3 x 10^-12 cm3/(molecule*s) at 300 K was assumed and a mean OH radical concentration of 10^6 molecules/cm3, t0.5 = 27 days. For an OH radical concentration of 5 x 10^5 molecules/cm3, the half-life would be 53 days.

In the atmosphere, photo-induced dechlorination to chlorobenzene is also possible. A quantum yield of 0.244 was determined for this reaction when o-dichlorobenzene dissolved in n-hexane was irradiated with light of wavelength 271 nm, the wavelength of maximum absorption.

The formation of trichlorobiphenyls and hydrogen chloride has been described when o-dichlorobenzene is exposed to sunlight for up to 56 days, i.e., to light of wavelength of at least 300 nm, in a sealed borosilicate glass flask.

Applicant's summary and conclusion

Executive summary:

BUA report:

Several publications on the photochemical degradation of 1,2-dichlorobenzene in air were summarized in the assessment of the BUA report 53 (1990). The reliability of these publications was not assignable because references were only cited as secondary literature.

Although the quantum yield for the irradiation of gaseous o-dichlorobenzene with light of wavelength 254 nm at 23 °C is 0.63 +/- 0.04, direct photolysis is not a degradation pathway of any consequence in the environment since o-dichlorobenzene does not absorb enough in the wavelength range encountered in tropospheric sunlight.

In a further publication, the following rate constant for the reaction between OH radicals and o-dichlorobenzene in the atmosphere at room temperature (22 °C) were calculated:

KOH = (4.2 +/- 0.2) x 10^-13 cm3/(molecule*s)

When allowance is made for the mean global OH radical concentration in the troposphere, which current knowledge puts at 5 x 10^5 molecules/cm3, the halflife, t0.5, computes to 38 +/- 2 days.

A further reaction rate constant of KOH = 0.3 x 10^-12 cm3/(molecule*s) at 300 K was assumed and a mean OH radical concentration of 10^6 molecules/cm3, t0.5 = 27 days. For an OH radical concentration of 5 x 10^5 molecules/cm3, the half-life would be 53 days.

In the atmosphere, photo-induced dechlorination to chlorobenzene is also possible. A quantum yield of 0.244 was determined for this reaction when o-dichlorobenzene dissolved in n-hexane was irradiated with light of wavelength 271 nm, the wavelength of maximum absorption.

The formation of trichlorobiphenyls and hydrogen chloride has been described when o-dichlorobenzene is exposed to sunlight for up to 56 days, i.e., to light of wavelength of at least 300 nm, in a sealed borosilicate glass flask.