Calmon, Jean P. published the article 《Thermodynamic functions of enolization of aliphatic β-diketone》. Keywords: diketone enolization thermodn functions; enolization thermodn functions diketone.They researched the compound: 2,6-Dimethyl-3,5-heptanedione( cas:18362-64-6 ).Safety of 2,6-Dimethyl-3,5-heptanedione. Aromatic heterocyclic compounds can be divided into two categories: single heterocyclic and fused heterocyclic. In addition, there is a lot of other information about this compound (cas:18362-64-6) here.
The following data were determined (β-diketone, % enol form at 33°C. equilibrium constant for the keto-enol tautomer at 33°C., enthalpy of enolization -ΔH in kcal./mole, and entropy of enolization -ΔS at 33°C. in cal./mole/°K.): Ac2CH2, 79.5, 3.89, 2.8, 6.45; AcCH2COEt, 80.5, 4.09, 3.0, 7.0; iso-PrCOCH2Ac, 89, 7.88, 3.2, 6.35; iso-BuCOCH2Ac, 90, 8.87, 3.3, 6.45; tert-BuCOCH2Ac, 93.5, 14.30, 3.9, 7.45; tert-BuCH2COCH2Ac, 94, 15.65, 3.45, 5.8; iso-BuCOCH2COEt, 90.5, 9.81, 3.7, 7.55; iso-BuCOCH2COPr, 92, 11.40, 3.4, 6.3; iso-BuCOCH2COPr-iso, 95, 20.30, 4.45, 8.55; (iso-BuCO)2CH2, 93.5, 14.60, 3.3, 5.8; (iso-PrCO)2CH2, 94, 15.95, 3.7, 6.6; tert-BuCOCH2COPr-iso, 96, 23.15, 4.65, 8.95; (tert-BuCO)2CH2, 98.5, 58.9, 4.9, 8.25. The data were determined from the N.M.R. spectra of the β-diketone. The variations in the entropies are attributed to resonance stabilization of the enol form and to the steric effects of the substituents which destabilize the keto form. The strong neg. entropy is explained by a chelated enolic structure which is more rigid than the diketo form.
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Reference:
Thiazole | C3H3NS – PubChem,
Thiazole | chemical compound | Britannica