抄録
The influence of d6-benzene on the nuclear magnetic resonance (NMR) spectra of N-vinyl-2-pyrrolidone (VP) was investigated. It was found that the orientation of amide group in VP to benzene was different from that in dimethylformamide (DMF) or methylpyrrolidone (MP) owing to repulsion of π-electron between vinyl group in VP and benzene ring. Subsequently the complex formation between DMF, MP, or VP and aromatic ring in ajmaline was also confirmed, in which the individual amide group in DMF, MP, or VP was oriented against aromatic ring in ajmaline as well as against benzene. In addition, it was recognized that polyvinylpyrrolidone (PVP) formed the complex with benzene in a slightly different orientation from that of VP with benzene because of the steric hindrance of PVP. It became apparent, however, that the resulting orientation was similar to that between VP and benzene when the chain length of PVP was relatively shorter. With increasing molecular weight of PVP, pyrrolidone ring would be considered to tend to lie at a certain angle to the plane of the benzene ring. Moreover, the complex formation of DMF, MP, or VP with ajmaline was regarded to be weaker than that with benzene from the association constant (Kn). Consequently, on the basis of the Kn value of PVP with benzene, the possibility of interaction between PVP and ajmaline was discussed.
