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研究了醛和二苯基N-无取代硫亚胺(Ⅰ)反应生成腈的机理。(Ⅰ)跟对位取代苯甲醛的反应速度按Hammett方程作图,得到正的ρ值(ρ=+2.4)。测得活化焓和活化熵分别为△H~≠=23.1 kcal/mole和△S~≠=-5.1 e.u。(苯甲醛)。用氘代苯甲醛PhCDO观测到同位素效应(k_H/k_D=2.0)。以上观察结果表明,反应起初是经过氮原子亲核加成到羰基中的碳原子上,接着脱出氢氧阴离子和决定反应速度的质子。
The mechanism of reaction of aldehydes with diphenyl N-unsubstituted sulfilimines (Ⅰ) to form nitriles was studied. The reaction rate of (Ⅰ) with para-substituted benzaldehyde is plotted according to the Hammett equation and a positive ρ value (ρ = + 2.4) is obtained. The activation enthalpy and activation entropy were measured as △ H ~ ≠ = 23.1 kcal / mole and △ S ~ ≠ = -5.1 e.u. (Benzaldehyde). Isotope effects were observed with deuterated benzaldehyde PhCDO (k_H / k_D = 2.0). The above observations show that the reaction is initiated by the nucleophilic addition of the nitrogen atom to the carbon atom in the carbonyl group followed by the removal of the hydroxide anion and the proton which determines the reaction rate.