Structure and vibrational spectroscopy of methanesulfonic acid hydrazide: an experimental and theoretical study

A comprehensive study of the molecule of methanesulfonic acid hydrazide (MSH) is presented. The X-ray structure shows that in the crystal two centrosymmetrically oriented MSH molecules are Yield together by N-H ... N hydrogen bonding interactions. This feature is unprecedented for the known arylsulfonic hydrazide analogues. The energetics of the various MSH staggered conformers and the stabilisation due to dimerisation are evaluated by HF ab initio calculations. Moreover, the pathways that interconvert the conformers as well as their enantiomers are outlined. The transition states between conformers correspond to the eclipsed conformation about the S-N linkage while those between enantiomers require planarisation of the N atom bound to sulfur. Some interconversions require two steps and two barriers to be bypassed. The IR and Raman spectra of MSH have been recorded and a normal coordinate analysis (NCA) has been carried out. The assignments have been double-checked through the ab initio calculated frequencies. The latter techniques also allow evaluation of the normal modes of vibration due to interacting MSH monomers, which can be experimentally detected.