Substituent, temperature and solvent effects on keto-enol equilibrium in symmetrical pentane-1,3,5-triones. Nuclear magnetic resonance and theoretical studies

Novak, Predrag; Škare, Danko; Sekušak, Sanja; Vikić-Topić, Dražen (2000) Substituent, temperature and solvent effects on keto-enol equilibrium in symmetrical pentane-1,3,5-triones. Nuclear magnetic resonance and theoretical studies. Croatica Chemica Acta, 73 (4). pp. 1153-1170. ISSN 0011-1643

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Abstract

Keto-enol tautomeric equilibrium in several beta -triketones has been investigated using NMR spectroscopy and theoretical methods. The equilibrium involves two slow and two fast enolization processes in solution. In solvents of low polarity and at room temperature, the predominant tautomeric species is the dienol form. However, the equilibrium is significantly shifted to the more polar triketo form on raising the temperature up to 140 degreesC and by using solvents of higher polarity. Structures and stabilities of both long and short-lived tautomeric forms, as well as transition-state structures and barrier heights of enolization processes, were calculated using semiempirical and density functional quantum chemical methods.

Item Type:	Article
Uncontrolled Keywords:	pentane-1,3,5-triones; keto-enol equilibrium; nuclear magnetic resonance spectroscopy; quantum chemical calculations; tautomeric equilibria; ab-initio; gas-phase; geometry optimization; n-butane; derivatives; systems; complex; purine; energy
Subjects:	NATURAL SCIENCES > Chemistry
Divisions:	Division of Organic Chemistry and Biochemistry NMR Center
Projects:	Project title Project leader Project code Project type Istrazivanja statičkih i dinamičkih svojstava molekula Aleksandar Sabljić 00980605 MZOS Molekularni receptori s policikličkim jedinicama Kata Majerski 00980702 MZOS
Depositing User:	Dražen Vikić-Topić
Date Deposited:	21 Nov 2013 14:13
URI:	http://fulir.irb.hr/id/eprint/1043

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