Vibrational spectra and rotational isomerism of simple dialkyl dithioesters and N-acylglycine ethyl dithioesters, thiolesters, and dioxygenesters

Abstract

Simple dialkyl dithioesters and N-acylglycine ethyl dithioesters have been investigated by Raman, resonance Raman and infrared spectroscopies. Based on the data of isotopic substituted derivatives and a normal coordinate analysis, vibrational assignments have been proposed for methyl dithioacetate. Raman spectra of ethyl dithioacetate(CH 3C(=S)S ▪ CH 2CH 3) and methyl dithiopropionate (CH 3CH 2 ▪ C (=S)SCH 3) have provided fundamental knowledge on rotational isomerism about the bonds indicated. Raman, resonance Raman and FTIR spectroscopic studies on N-acylglycine ethyl dithioesters indicated the coexistence of three conformers in solution and a combined x-ray crystallographic-resonance Raman spectroscopic approach has been used to set up precise structure-spectra correlations for these conformers. The corresponding conformational states of N-acylglycine thiolesters and dioxygenesters are also discussed briefly.