Abstract
Rates for reactions of substituted phenacyl bromides with imidazole and those of substituted imidazoles with phenacyl bromide were measured by an electric conductivity method. The rates were accelerated by electron-withdrawing substituents of phenacyl bromide and these reactions obeyed well both the linear free energy relationship and the isokinetic relationship. The relation between pKa's of substituted imidazoles and reaction constants fit the Bronsted rule. However, the case of 2-methylimidazole deviated far from this rule exerting steric hindrance. The reaction proceeded much faster in acetonitrile than in methanol and the observed ratio, k2 (acetonitrile)/k2 (methanol), was considerably larger than the value calculated from the Kirkwood equation.
치환 phenacyl bromide와 imidazole과의 반응 및 phenacyl bromide와 치환imidazole과의 반응속도를 전기전도도법으로 측정하였다. 반응속도는 phenacyl bromide의 전자 끄는기에 의하여 촉진되었으며 이 반응은 linear free energy relationship과 isokinetic relationship에 잘 맞았다. 반응속도와 imidazole의 pKa사이에는 Bronsted rule이 잘 적용되었으나 2-methylimidazole의 경우에는 위치장애현상으로 인해 여기서 벗어났다. Acetonitrile 용매하에서는 methanol 용매하에서보다 Kirkwood식에서 예상되는 것보다 훨씬 빠르게 반응속도가 관찰되었다.
