3-(2-Nitrovinyl)thiopene에 대한 n-butylmercaptan의 친핵성 첨가반응에 관한 연구

Abstract

3-(2-nitrovinyl) thiophene ( NVT )은 탄소-탄소 이중결합이 nitro기와 conjugate되어 있는 물질로서 여기에 친핵성시약인 n-bu-tylmercaption을 반응시켜, 산성에서 염기성에 이르는 넓은 PH영역( pH 0.05-11.50 )에 걸친 반응속도를, 25℃, 35℃, 45℃의 세 온도에서 흡광도 변화에 의한 NVT의 농도감소를 측정하여 반응속도식을 구하였으며 실험사실에 잘맞는 반응메카니즘을 제안하였으며, Arrhenius plot으로 부터 이 반응의 활성화에너지와 활성화엔트로피를 구하였다. pH 5.69이하에서는 NVT에 n-butylmercaptan의 중성분자가 첨가되고, pH5.69이상 pH 8.87까지는 n-butylmercaptan의 ion이 첨가되는 Michael반응이 일어나며, pH8.87이상에서는 mercaptide ion의 첨가반응과 함께 제거반응도 일어나는 것으로 생각되었다. 25℃, 35℃, 45℃의 각 온도에서 측정한 반응속도상수를 Arrhenius plot 하여, 활성화에너지 , frequency factor를 구하고, Eyring 식으로 부터 활성화엔트로피를 계산하여 비교하였더니, pH가 증가할수록 반응속도상수가 증가하고, 활성화에너지는 낮아지며, 활성화엔트로피는 증가함을 알 수 있었다.;The reaction kinetics and mechanism of the nucleo-philic addition reaction of n-butylmercaptan to 3-(2-nitrovinyl) thiophene(NVT) were investigated over the wide pH at various temperatures. The absorbance decrease of NVT along the reaction proceeds was checked by UV spectrophotometry. Rate equations were derived on the basis of three different PH regions, where it seemed that three different mechanisms exist at those PH range respectively. From the rate equation, one may conclude that the reaction mechanisms are different as follows 1) At lower PH(lower than 5.69) n-butylmercaptan molecules attack NVT. 2) At medium PH(from 5.69 to 8.87) n-butylmercaptide ions attack NVT. 3) At higher PH(higher than 8.87) n-butylmercaptide ions add to the NVT like Michael addition reaction but simultaneously elimination reaction occurs. The reaction were found to be second order overall of the reaction. Activation energy and activation entropy are different according to the PH. By this results we could predicted that the transition state.