The chemical behaviour of nitromethane in inert solvents examined through spectroscopic techniques.

Abstract

Nitromethane dissolved in carbontetrachloride or cyclohexane as inert solvents, exhibits some of its unique chemical properties in such solutions. Spectroscopic evidence reveals that the molecules are found as discrete entities in the concentration range of about 0.05-0.18 M. Beyond this concentration limit the molecules of nitromethane define a smooth but sharp inflexion point as the concentration increases signifying a transition region at which the formation of dimers by head to tail association of two of its molecules begins. The stability of the dimer is supported by ab initio and DFT calculations and its existence is implied by the results of calculated 1H and 13C NMR chemical shifts and confirmed by experimental 1H NMR evidence. In the transition region, only monomers and dimers of nitromethane coexist in dynamic equilibrium. By the end of the turn in the curve of inverse bandwidth against molar concentration of nitromethane, the dimer species start building up a more complex layered structure whose basic units are the dimers of nitromethane, at this point the curve defines a plateau of constant intensity and almost independent of the concentration of nitromethane in solution.