Synthetic and mechanistic studies in polynitroaromatic chemistry.

This project developed from an industrial need for a plasticiser for explosives formulations which is easier to manufacture, more stable than those presently employed, but still based on a polynitroaromatic nucleus. The major aim of this programme was to produce new liquid or low melting polynitroaromatic compounds by simple routes. A literature search highlighted various molecular features which appeared to produce a low melting temperature in polynitroaromatic compounds. Using these features, four categories of compounds were identified as target compounds for a synthetic programme to produce low melting polynitroaromatic compounds. (A: Alkyltrinitrobenzenes; B: trinitrophenylpropanoate esters; C: 3-alkylpicrylethers; D: 3-alkyltrinitrobenzoate esters). 2,4,6-Trinitrotoluene (the preferred starting material for category A and B compounds) forms an anion in basic solution, which has been suggested as having nucleophilic characteristics 3. In fact, this work has shown that it displays very poor nucleophilic qualities, though reaction with p-nitrobenzyl bromide was successful. An ultraviolet and nmr spectroscopic study of this reaction provided evidence to suggest that O'-adduct formation facilitates an ionic substitution reaction; whereas in other cases such O-complex formation is not favoured and radical decomposition of TNT occurs.Three 3-alkylpicryl chlorides have been prepared from 3-alkylphenols as precursors for category C and D compounds. Attempts to prepare such compounds from TNT were unsuccessful. Partial reduction of TNT, to 2,4-diamino-6-nitrotoluene was achieved, but bromination of this compound proved to be uncontrollable, with 2,4-diamino-3,5-dibromo-6-nitrotoluene being the only product. The mechanism of this reaction is discussed.The preparation of 3-alkylpicryl ethers (category C compounds) was successfully achieved and numerous liquids or low melting solids were produced. 3-t-Butylpicryl chloride in reaction with certain alkoxides, displayed a competition between nitro group and halogen substitution, with up to 30% nitro group substitution being observed; a novel reaction in systems of this type. A series of low melting compounds have been prepared from 3-alkylpicryl halides using various sulphur and nitrogen nucleophiles.