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Optimum geometries and relative energies for cytosine, thymine, uracil, the imino tautomer of cytosine, the enol tautomer of thymine, and the enol tautomer of uracil by the MINDO /2 SCF MO method
Author(s) -
Zielinski Theresa Julia,
Rein Robert
Publication year - 1978
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560140615
Subject(s) - tautomer , thymine , cytosine , mindo , uracil , chemistry , enol , computational chemistry , crystallography , stereochemistry , molecule , dna , organic chemistry , biochemistry , catalysis
A MINDO /2 SCF MO geometry optimization of cytosine (C), thymine (T), uracil (U), the imino tautomer of cytosine (C*), the enol tautomer of thymine (T*), and the enol tautomer of uracil (U*)was made. The optimized geometries for cytosine, thymine, and uracil agree well with crystallographic data. The optimized geometries for the tautomers show the correct trends in bond lengthening and bond angle except for the C4—O4 length and C4—O4—H angle of T* and U*. The energies of tautomerization were found to be 10.3, −9.0, and −14.2 kcal/mol for C⇌C*, T⇌T*, and U⇌U*, respectively, when optimized geometries are used. The overestimation of the C4—O4—H angle is speculated to arise because of an inadequacy in the parametrization of the one‐center integrals in MINDO /2.