ジオキサン中p-ニトロソフェノール互変異性混合物のエタノールによる酸触媒エーテル化反応

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The acid-catalyzed reversible etherification of the allelotrope of p-nitrosophenol (PNP) with ethanol in dioxane was studied kinetically togather with its reverse reaction, the acid-catalyzed reversible hydrolysis of p-nitrosophenetole (PNPT) in dioxane. Both reactions have another rate equation at more or less than 0.4 M water as follows : In the case of C_<H_2O>⪈0.4M and C_<H_2SO_4>=0.1N ; Rate_<forward>=(k_2-k^f_<-3h>C_<H_2O>+k_3C_<PNP>)C_<PNP>C_<EtOH> Rate_<reverse>=(k_<-2>-k^f_<3h>C_<H_2O>+k_<-3>C_<PNPT>)C_<PNPT>C_<H_2O> In the case of C_<H_2O>≨0.4 M and C_<H_2SO_4>=0.1N ; Rate'_<forward>={k_2-0.4k^f_<-3h>+k^f_<3h>(C_<H_2O>-0.4)+k_3C_<PNP>-k_<-4h>C_<PNP>(C_<H_2O>-0.4)}C_<PNP>C_<EtOH> Rate'_<reverse>={k_<-2>-0.4k^r_<3h>+k^r_<-3h>(C_<H_2O>-0.4)+k_3C_<PNPT>-k_<4h>C_<PNPT>(C_<H_2O>-0.4)}C_<PNPT>C_<H_2O> When the concentration of water is constant, the rate equation of the forward reaction was simplified in the following way. Rate_<forward>=(k_2'+k_3'C_<PNP>)C_<PNP>C_<EtOH> Isotope Effects on these rate constants were k_2'H/k_2'D=0.83 and k_3'H/k_3'D=2.58,respectively. Apparent activation parameters, ΔE_a and ΔS^=⃥ were obtained to be 2.1 kcal/mol, -72.4 e.u. for the forward reaction expressed by k_2' and 27.0 kcal/mol, 4.4 e.u. for the forward one expressed by k_3', respectively. Nucleophilic attack of oxygen atom of ethanol on the ring carbon attached to hydroxyl group of the allelotrope, is discussed as a probable mechanism.
公益社団法人日本薬学会の論文
1982-02-25

ジオキサン中p-ニトロソフェノール互変異性混合物のエタノールによる酸触媒エーテル化反応

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