Tautomeric and conformational properties of acetoacetamide: electron diffraction and quantum chemical study.
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.
Belova
Natalya V
NV
Ivanovo State University of Chemistry and Technology, Ivanovo 153460, Russia. belova@isuct.ru
Girichev
Georgiy V
GV
Shlykov
Sergey A
SA
Oberhammer
Heinz
H
D000090:Acetoacetates / Q000737:chemistry*; D000577:Amides / Q000737:chemistry*; D004583:Electrons; D005740:Gases / Q000737:chemistry; D006860:Hydrogen Bonding; D008956:Models, Chemical; D008968:Molecular Conformation; D011789:Quantum Theory
D000090:Acetoacetates; D000577:Amides; D005740:Gases