Belova Natalya V, Girichev Georgiy V, Shlykov Sergey A, Oberhammer Heinz
Ivanovo State University of Chemistry and Technology, Ivanovo 153460, Russia.
J Org Chem. 2006 Jul 7;71(14):5298-302. doi: 10.1021/jo060603e.
The tautomeric properties of acetoacetamide, CH3C(O)CH2C(O)NH2, have been investigated by gas electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 approximations with 6-31G(d,p) and 6-311++G(3df,pd) basis sets). GED results in a mixture of 63(7)% enol tautomer and 37(7)% diketo form at 74(5) degrees C. Only one enol form with the O-H bond adjacent to the methyl group (CH3C(OH)=CHC(O)NH2) and only one diketo conformer (with dihedral angles tau(O=C(CH3)-C-C) = 31.7(7.5) degrees and tau(O=C(NH2)-C(H2)-C(O)) = 130.9(4.5) degrees ) are present. The calculated tautomeric composition varies in a wide range depending on the quantum chemical method and basis set. Only the B3LYP method with small basis sets reproduces the experimental composition correctly.
已通过气体电子衍射（GED）和量子化学计算（采用6 - 31G(d,p)和6 - 311++G(3df,pd)基组的B3LYP和MP2近似方法）研究了乙酰乙酰胺（CH3C(O)CH2C(O)NH2）的互变异构性质。在74(5)摄氏度下，GED结果表明存在63(7)%的烯醇互变异构体和37(7)%的二酮形式的混合物。仅存在一种O - H键与甲基相邻的烯醇形式（CH3C(OH)=CHC(O)NH2）和一种二酮构象异构体（二面角tau(O = C(CH3)-C - C) = 31.7(7.5)度，tau(O = C(NH2)-C(H2)-C(O)) = 130.9(4.5)度）。根据量子化学方法和基组的不同，计算得到的互变异构组成在很宽的范围内变化。只有采用小基组的B3LYP方法能正确再现实验组成。
