2-nitrotoluene

Phototransformation in air

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

phototransformation in air

Type of information:

(Q)SAR

Adequacy of study:

other information

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

results derived from a (Q)SAR model, with limited documentation / justification

Principles of method if other than guideline:

Method: other (calculated): with AopWin v. 1.91

GLP compliance:

no

Details on test conditions:

Sensitiser (for indirect photolysis): OH
Sensitiser concentration: 500000 molecule/cm³

- Rate constant (for indirect photolysis): 0.0000000000007722 cm³/(molecule*sec)
- Degradation in % (for indirect photolysis): 50 after 20.8 day(s)

Executive summary:

EPI Suite (AopWin v. 1.91) calculation

Sensitiser (for indirect photolysis): OH Sensitiser concentration: 500000 molecule/cm³

- Rate constant (for indirect photolysis): 0.0000000000007722 cm³/(molecule*sec)
- Degradation in % (for indirect photolysis): 50 after 20.8 day(s)

Reference 2

Endpoint:

phototransformation in air

Type of information:

other: EU Risk Assessment

Adequacy of study:

other information

Reliability:

other: EU Risk Assessment

Rationale for reliability incl. deficiencies:

other: No reliability is given as this is a summary entry for the EU RAR.

GLP compliance:

not specified

Specific details on test material used for the study:

- Analytical purity: not specified

EU Risk Assessment (2008):

 

When released to the atmosphere, 2-nitrotoluene is expected to exist entirely in the vapour phase. The dominant removal mechanisms would be reaction with photochemically generated hydroxyl radicals (estimated half-life 8h) and direct photolysis. The rate at which 2-nitrotoluene reacts with OH radicals has been measured experimentally; the velocity constant KOH was 0.7·10-12cm3·molecule-1·s-1 (Meylan and Howard, 1993), equivalent to a half-life period (t1/2) of 23 days, assuming a mean tropospheric OH radical concentration of 5·105molecules per cm3. In view of the UV absorption of 2 -nitrotoluene in the sunlight range (wavelenght >295 nm) there is a possibility of direct photolysis under tropospheric conditions (BUA, 1989).

 

The photochemical reaction of 2-nitrotoluene was studied by Nojima and Kanno (1977). One millilitre of a solution of 2-nitrotoluene in hexane (4.46·10-5moles/ml) was taken in a litre reaction vessel, followed by removal of n-hexane and substitution with air or nitrogen free from nitrogen oxides. The residual nitrotoluene in air was irradiated atl>300 nm for 5 hours and this yielded nitrophenol derivatives. From this results it might be considered that the compound was converted at first to the corresponding phenol and cresol by the liberation of nitrogen monoxide through the nitronitrite rearrangement, followed by nitration with nitrogen dioxide, which was produced by the oxidation of nitrogen monoxide in the excess of oxygen in air, finally to give nitrophenols. When 2-nitrotoluene was irradiated in nitrogen the nitro group turned into the hydroxyl group and o-cresol was obtained. The yields of the products of both photochemical reaction with air and with nitrogen are the following:

Rate of disappearance of o-nitrotoluene	Products (yield)
79% - reaction with air	2-methyl-6-nitrophenol (6.1%)
	2-methyl-4-nitrophenol (7.5%)
71% - reaction with nitrogen	o-cresol (8.5%)

 

Precipitation

A 2-nitrotoluene lifetime of 20 days, based upon the reaction with hydroxyl radicals, may lead to a certain removal of 2-nitrotoluene from the atmosphere by precipitation. Even so, it is unlikely to be transported long distances from its point of emission and possible concentrations due to precipitation of 2-nitrotoluene from the atmosphere are therefore expected to be larger next to the point of emission.

Executive summary:

EU Risk Assessment (2008):

When released to the atmosphere, 2-nitrotoluene is expected to exist entirely in the vapour phase. The dominant removal mechanisms would be reaction with photochemically generated hydroxyl radicals (estimated half-life 8h) and direct photolysis. The rate at which 2-nitrotoluene reacts with OH radicals has been measured experimentally; the velocity constant KOH was 0.7·10-12cm3·molecule-1·s-1 (Meylan and Howard, 1993), equivalent to a half-life period (t1/2) of 23 days, assuming a mean tropospheric OH radical concentration of 5·105molecules per cm3. In view of the UV absorption of 2 -nitrotoluene in the sunlight range (wavelenght >295 nm) there is a possibility of direct photolysis under tropospheric conditions (BUA, 1989).

The photochemical reaction of 2-nitrotoluene was studied by Nojima and Kanno (1977).

When 2-nitrotoluene was irradiated in nitrogen the nitro group turned into the hydroxyl group and o-cresol was obtained. The yields of the products of both photochemical reaction with air and with nitrogen are the following:

Rate of disappearance of o-nitrotoluene	Products (yield)
79% - reaction with air	2-methyl-6-nitrophenol (6.1%)
	2-methyl-4-nitrophenol (7.5%)
71% - reaction with nitrogen	o-cresol (8.5%)

 

Reference 3

Endpoint:

phototransformation in air

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Principles of method if other than guideline:

- flash light photolysis/resonance fluorescence

GLP compliance:

no

Specific details on test material used for the study:

- Name of test material (as cited in study report): o-Nitrotoluene
- Analytical purity: not specified

Key result

Reaction with:

OH radicals

Rate constant:

0 cm³ molecule-1 s-1

The reactivity of o-nitrotoluene to OH radicals was determined experimentally. The velocity constant K_OH was 0.7×10^-12 cm³×molecule^-1×s^-1 for nitrotoluene, equivalent to a half-life period (t_1/2) of 23 days, assuming a mean tropospheric OH radical concentration of 5×10⁵ molecules/cm³ (Nolting et al., 1987). In view of the UV absorption of nitrotoluenes in the sunlight range (wavelength > 295 nm) there is a possibility of direct photolysis under tropospheric conditions.

Executive summary:

The reactivity of 2-nitrotoluene to OH radicals was determined experimentally. The velocity constant K_OH was 0.7×10^-12 cm³×molecule^-1×s^-1 for nitrotoluene, equivalent to a half-life period (t_1/2) of 23 days, assuming a mean tropospheric OH radical concentration of 5×10⁵ molecules/cm³ (Nolting et al., 1987). In view of the UV absorption of nitrotoluenes in the sunlight range (wavelength > 295 nm) there is a possibility of direct photolysis under tropospheric conditions.

Description of key information

For transported isolated intermediates according to REACh, Article 18, this endpoint is not a data requirement. However, data is available for this endpoint and is thus reported under the guidance of "all available data".

EU Risk Assessment (2008)

When released to the atmosphere, 2-nitrotoluene is expected to exist entirely in the vapour phase. The dominant removal mechanisms would be reaction with photochemically generated hydroxyl radicals (estimated half-life 8h) and direct photolysis. The rate at which 2-nitrotoluene reacts with OH radicals has been measured experimentally; the velocity constant KOH was 0.7·10-12cm3·molecule-1·s-1 (Meylan and Howard, 1993), equivalent to a half-life period (t1/2) of 23 days, assuming a mean tropospheric OH radical concentration of 5·105molecules per cm3. In view of the UV absorption of 2 -nitrotoluene in the sunlight range (wavelenght >295 nm) there is a possibility of direct photolysis under tropospheric conditions (BUA, 1989).

The photochemical reaction of 2-nitrotoluene was studied by Nojima and Kanno (1977).

When 2-nitrotoluene was irradiated in nitrogen the nitro group turned into the hydroxyl group and o-cresol was obtained. The yields of the products of both photochemical reaction with air and with nitrogen are the following:

Rate of disappearance of o-nitrotoluene	Products (yield)
79% - reaction with air	2-methyl-6-nitrophenol (6.1%)
	2-methyl-4-nitrophenol (7.5%)
71% - reaction with nitrogen	o-cresol (8.5%)

 

Nolting et al., 1987

The reactivity of 2-nitrotoluene to OH radicals was determined experimentally. The velocity constant KOH was 0.7×10-12 cm³×molecule-1×s-1 for nitrotoluene, equivalent to a half-life period (t1/2) of 23 days, assuming a mean tropospheric OH radical concentration of 5×10⁵ molecules/cm³. In view of the UV absorption of nitrotoluenes in the sunlight range (wavelength > 295 nm) there is a possibility of direct photolysis under tropospheric conditions.

Bayer Industry Services 2006 (EPI Suite (AopWin v. 1.91) calculation)

Sensitiser (for indirect photolysis): OH Sensitiser concentration: 500000 molecule/cm³

- Rate constant (for indirect photolysis): 0.0000000000007722 cm³/(molecule*sec)
- Degradation in % (for indirect photolysis): 50 after 20.8 day(s)

Key value for chemical safety assessment

Half-life in air:

23 d

Degradation rate constant with OH radicals:

0 cm³ molecule-1 s-1