The oxidative detoxification of 2, 4, 6-trinitrotoluene (TNT) has been an extraordinary challenge since its large scale use during the Second World War. Oxidation of TNT requires brutal conditions such as dichromate and concentrated sulfuric acid and days of reaction time. TNT contamination in soil and in water is more severe in military bases, explosive manufacturing plants and ammunition facilities. An attractive alternative approach employs a reductive strategy involving electrochemical reduction of the nitro groups to amines (Wang et al. Electroanalysis, 2011  , 23, 1193-1204). The fully reduced product (2, 4, 6- tri-aminotoluene) can then be easily functionalized to phenols using century �old classic diazonium ion chemistry (Sandmeyer reaction). In a recent electrochemical study (Chua et al Journal of Physical Chemistry, 2012  , 116, 4243-4251), Cyclic voltammetry of TNT indicated a remarkable selectivity; the first reductive step involved the ortho-nitro group.  Using 2, 4-dinitrotoluene as a model compound, we have studied the selectivity of reduction (if any) by nano-iron particles. The nano-iron particles were generated in situ by the reduction of ferrous ammonium sulfate (complexed with citrate) by sodium borohydride (Ranu et al; Chemical Communications, 2012  , DOI: 10.1039/c2cc3099h; first published on the WEB on 10 April 2012, Royal Society of Chemistry). Using stoichiometric conditions of reactants (1 mmol nitro compound: 3 mmol nano-iron particles), the reduction product was purified by silica chromatography (hexane �ethyl acetate; 2:1) and analyzed by 500 MHz 1H-NMR. The integrated NMR spectra was used to estimate the observed ortho/pararatio. Interestingly, the reduction at the para-position was preferred to the reduction of the ortho-nitro group (para: ortho = 60:40). This result conflicts with the electrochemical measurements where there was remarkable selectivity (100%) for the reduction of the ortho nitro group. With a 10-fold excess of Fe NPS to TNT, complete reduction to 2, 4, 6-triaminotoluene was achieved. We will present both Cyclic Voltammetry and product analysis studies.

Reductive detoxifiaction of 2, 4, 6-trinitrotoluene (TNT) by Fe nanoparticles

247th National Meeting (2014)

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