Properties of Thiopyrones

The properties of pyrones will be dealt with in the following order  

The Hiickel approximation of the molecular orbital method (HMO method) can be used to interpret and predict the quantities of Sections IV,B, 1-3 from the energies of the molecular orbitals.64,05 The theoretical data for the quantities of Sections IV, B, 4 and 5 are obtainable from the expansion coefficients of the molecular orbitals. 

It is our aim to find certain structural similarities between pyrones and other organic compounds for a better understanding of their physical and chemical properties, and to utilize such similarities in predicting properties not yet studied experimentally. The following consideration relates to compounds of the y-pyrone type it is easily extended to a-pyrones. 

Quantum chemical calculations indicate a similarity between tropone (35) and 4//-pyran-4-one (l).66,87 Hence, the thiopyrones (3 and 6) should show a pseudotropone character, and the thiopyrones (4, 5, 7, and 8) may be compared with the tropothione (36), which has not yet been synthesized.33,38,53,98 The dipolar structures established by Arndt et al.2,0 in 1924 suggest the formal similarity of the 

Streitwieser, Jr., Molecular Orbital Theory for Organic Chemists, Wiley, New York, 1961. 

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