4-nitrotoluene

Endpoint summary

Description of key information

Phototransformation in air

The irradiation of p-nitrotoluene in air yielded the nitrophenol derivative: 4-methyl-2-nitrophenol (6.1%). Through these experiments it is noticed that the reaction did never afford the directly hydroxylated derivatives of the original nitrotoluenes. It might be considered from these results that  the photo-excited nitro compounds turned at first into the corresponding phenols, followed by nitration. When p-nitrotoluene was irradiated in nitrogen, the nitro group turned into a hydroxyl group. (Nojima, 1977)

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

In deviation from the U.S. EPA AOPWIN calculation program the calculated half-life is based on a mean OH radical concentration (sensitiser for indirect photolysis) of 500,000 OH radicals/cm3 as a 24 h average. (AOPWIN v. 1.89 (2000) calculation for 4-nitrotoluene, Bayer AG, 2002)

 

Hydrolysis

With regard to its chemical structure 4-nitrotoluene is not expected to hydrolyse under environmental conditions. (OECD SIDS, 2003, expert judgement)

 

Phototransformation in water

4-nitrotoluene may be susceptible to photolysis. Because nitroaromatic compounds absorb sunlight strongly in the ultraviolet and blue spectral region, they are generally susceptible to photochemical transformation in aquatic systems.

The following initial rates for photodegradation of 4-nitrotoluene in water were obtained (Dillert, 1997 and 1999):
- 0.49 µmol/lxmin
- 1.01 µmol/lxmin in the presence of 20 mmol/l H₂O₂ (photooxidation with hydrogenperoxide)
- 1.45 µmol/lxmin in the presence of 100 µmol/l Fe₂(SO₄)₃
- 14.5 µmol/lxmin in the presence of both 20 mmol/l H₂O₂ and 100 µmol/l Fe₂(SO₄)₃ (photo-Fenton-reaction)                        - 6.9 µmol/lxmin in the presence of TiO₂ (photocatalysis)
- 14.5 µmol/lxmin in the presence of 100 µmol/l Fe₂(SO₄)₃, without oxalate (photo-Fenton reaction)
- 60 µmol/lxmin in the presence of both 100 µmol/l Fe₂(SO₄)₃ and 150 µmol/l oxalate (photo-Fenton reaction)

Taking into account the averaged annual values that pertain to near-surface conditions at latitude 40°N and based on the obtained quantum yield a half-life can be derived for 4-nitrotoluene: t1/2 = 5.9 hours It was observed that the photodegradation in pure water is slower than in natural water. The photodegradation depends on the content in humic acid and nitrates, which is higher in natural water. (Simmons, 1986)

5-Nitro-o-cresol, p-cresol, 2-methylresorcinol and p-toluidine are intermediates which can be detected for some hours during the degradation of 4-nitrotoluene. Ammonia, nitrate and CO2 were formed in different ratios depending on the test conditions employed. Acetic acid, formic acid and trace amounts of formaldehyde were also formed. The authors conclude that 2 independent routes for initial degradation exist. Pseudo-first order photolytic degradation rate constant k1 is 0.045 1/min (concentration of test substance 0.0001 mol/l) which equals about 60 min half life for the removal of TOC.
k = 0.00000962 mol/l x min (Vohra, 2002)