Ground states of σ-bonded molecules. Part XII. MINDO/1 studies of inversion barriers, rotational barriers, tautomerism, and hydrogen bonding

Abstract

a tThe MI N DO/1 method has been used to study barriers to inversion of trivalent nitrogen, keto-enol tautomerisrn, and chelation by hydrogen bonding in enols from p-dicarbonyl compounds. The results seem to agree quite well with experiment.Austin, Austin, Texas 7871 2, U.S.A. PREVIOUS papers of this series have described a semi-good estimates of heats of formation. In its original empirical SCF MO treatment of compounds formed from form 2b (MINDO/l) the method failed to give correct carbon, hydrogen, nitrogen, and oxygen, based on the molecular geometries. The calculations had to be method' and using parameters chosen to give

Sensitized ketonization of ethyl acetoacetate. A method for the determination of triplet quantum yields

“…4 The formation of the diketone from trans-EAA is a relaxation process and it should favorably occur rather than rotation around the C4-Cs double bond. 23 The values for QT determined by the method described above are somewhat higher than these obtained by sensitized isomerization of simple olefins.16"18 A combination of the last method with heavy atom quenching14 leads, however, to good agreement with our data, as well as with those determined by sensitized phosphorescence of biacetyl. 15,19 Following eq 5, the rate parameters kAT for triplet quenching by this electron resonance mechanism was calculated and the obtained value, feAT = 4.8 X 109 M"1 s"1, is near the limit of diffusion control.…”

Gas phase UV-visible spectra of reacting hydroaromatics systems

“…4 The formation of the diketone from trans-EAA is a relaxation process and it should favorably occur rather than rotation around the C4-Cs double bond. 23 The values for QT determined by the method described above are somewhat higher than these obtained by sensitized isomerization of simple olefins.16"18 A combination of the last method with heavy atom quenching14 leads, however, to good agreement with our data, as well as with those determined by sensitized phosphorescence of biacetyl. 15,19 Following eq 5, the rate parameters kAT for triplet quenching by this electron resonance mechanism was calculated and the obtained value, feAT = 4.8 X 109 M"1 s"1, is near the limit of diffusion control.…”