The "Nitration of toluene to 4-nitrotoluene, 2-nitrotoluene and 2,4-dinitrotoluene" is a very important reaction in chemical industry, but difficult to perform in the laboratory. The desired products are produced as an isomeric mixture. The pruification of this mixture is very problematic. Thus selectivity and yield are evaluated as low for this experiment.

Accordingly the mass efficiency of this experiment is very low compared to other NOP experiments .

For educt and products there are almost complete (eco)toxicological data sets available. Toluene exhibits only low acute toxicity and no chronic toxicity. Of the products especially 2,4-dinitrotoluene is potentially hazardous. While this substance posesses only low to average acute toxicity, it is a carcinogen. The same holds true for the byproduct 2,6-dinitrotoluene and the product 2-nitrotoluene which features a low limit value (technical guidance concentration in Germany) of 0,5 mg/m³. Besides there is evidence for reproductive toxicity of 2-nitrotoluene. The product 4-nitrotoluene and the byproduct 3-nitrotoluene are of low acute toxicity, but there is evidence for mutagenic and carcinogenic effects also, which have been predicted by theoretical evaluation methods. The permissible air concentration for these two substances is 28 mg/m³ in Germany.

In contrast the solvents used for extraction and recrystallization, ethanol, methanol (with significant higher acute toxicity than ethanol, but without mutagenicity or carcinogenic potential), cyclohexane and acetic acid ethyl ester used for thin layer chromatography are of low acute toxicity. Only n-hexane which is also used in thin layer chromatography for reaction control exhibits neurotoxicity. The inorganic educt and reagents fuming nitric acid and the concentrated sulfuric acid are very hazardous because of their very corrosive properties, but this danger can easily be averted by appropriate safety measures. During the nitration reaction very toxic nitrogen oxide gases may be produced. All other inorganic auxiliary substances do not pose any hazard to human health .

Additionally the nitrated toluenes possess only low biodegradability, but a medium toxicity for aquatic organisms, and many of them have been classified accordingly as dangerous to the environment. Most of the solvents used like ethanol, methanol, acetic acid ethyl ester and n-hexane are only slightly toxic to aquatic organisms and are biologically easily degradable. Only cyclohexane has been classified as as dangerous to the environment because of its low biodegradability. If released to the environment the nitrogen oxides produced by this reation may also cause an increase in tropospheric ozone concentrations.

Summed up this experiment has a low economic efficiency (in the laboratory) and (for a standard laboratory) inacceptable toxicological risks as well as a relatively high environmental persistence of the products. Thus we evaluate it with the "red light".