Study of polynitrodimethylbenzenes, polynitrodimethylbiphenyls and related compounds

• Main Author: Walsh, Moyra
• Published: Kingston University 1996
• Subjects: 547; Chemistry
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318191

A study of the reaction of various weak bases with 1,3-dimethyl-2,4,6-trinitrobenzene (DMTNB) in dimethyl sulphoxide (DMSO) has been carried out. Conductance results indicated formation of a benzyl-type anionic species by abstraction of a methyl hydrogen from DMTNB. This was confirmed by spectroscopic techniques. Proton NMR studies of the reaction of base with 1,3-dimethyl-2,4,6-trinitrobenzene (DMTNB) 2,2',4,4',6-pentanitro-3,5'-dimethylbiphenyl (PNDMBP) and 2,2',4,4',6,6'-hexanitro-3,3' -dimethylbiphenyl (HNDMBP) showed the formation of mono-anionic species at low mole ratios of base and dianionic species at higher mole ratios of base to polynitroaromatic compound. The kinetics of the reaction of diethylenetriamine with DMTNB in DMSO and in DMSO/methanol have been studied and the values for the activation energy, enthalpy of reaction and entropy of reaction have been determined. A parametric study has been carried out on the reaction of base with DMTNB in the presence of cupric chloride, and the separation and identification of products from the reaction has been. attempted. Although none of the products could be characterised unambiguously, structures for the products, which could be polymeric in nature, have been tenatively suggested. Attempts have also been made to separate and characterise the products from the reaction of base with PNDMBP and HNDMBP in the presence of cupric chloride, but again the structures of the products could not be assigned unambiguously. Differential scanning calorimetry (DSC) has been used to study the thermal decomposition ofDMTNB, 1,3-dicarboxy-2,4,6-trinitrobenzene (DCTNB), 1,3-bis-(2- hydroxyethyl)-2,4,6-trinitrobenzene (DHTNB), PNDMBP and HNDMBP, and of mixtures of these compounds with weak bases in various mole ratios. The exothermic decomposition temperature, the enthalpy of decomposition and the activation energy of decomposition of the compounds have been determined, as well as the exothermic decomposition temperature of mixtures of these compounds with base. It has been oufnd that the presence of base lowers the exothermic decomposition temperature of the polynitroaromatic compound ie. the base sensitizes the decomposition of the compounds studied. The thermal decomposition of some solid state charge-transfer complexes formed between tetrathiafulvalene (TTF) and 9- methylanthracene (9-MA) as eletron donors and DMTNB, DCTNB, PNDMBP, HNDMBP and 2,4,6-trinitrotoluene (TNT) as eletron acceptors has been investigated by differential scanning calorimetry. The effect of complexation on the thermal behaviour of the donor and acceptor molecules has been noted, and the enthalpy of decomposition and activation energy for decomposition of selected complexes has been determined. A range of charge transfer complexes have been prepared using using various donors and acceptors and their composition characterised as 1:1 donor to acceptor. The eletrical conductivity of the complexes have been measured and iy has been found out that, although some had conductivity in the semiconductor range, the majority were insulators. The oxidation potential of the donors and the reductionpotentials of the acceptors have been determined using cylic voltammetry. The relative eletron acceptor abilities of DCTNB, PNDMBP and HNDMBP have been evaluated for their reduction potential values. The effect of interaction in solution between donor and acceptor species on the oxidation/ reduction potentials of the species has been investigated. The values for the eletron affinity of DMTNB, DCTNB and PNDMBP have been obtained from measurements on the visible absorption spectra of the complexes formed between these compounds and a number of anthracene derivatives.