Solvent-induced E/Z isomerization of 2-(furylmethylidene)-1-hydrazinecarbothioamide: The N–H⋅⋅⋅O intramolecular hydrogen bond as promoting factor

It is proved by the 1H and 13C data that the thiosemicarbazone with the furyl substituent is synthesized as the E isomer. However, this thiosemicarbazone undergoes the solvent-induced E/Z isomerization when standing in chloroform, despite the fact that the other thiosemicarbazones with a heteroaryl or aryl substituent do not exhibit such phenomenon. It is established that the N–H⋅⋅⋅O intramolecular hydrogen bond in the Z isomer of furyl...