THEORETICAL STUDY ON CONFORMATIONAL ISOMERS OF ACETYL ACETONE, NBO ANALYSES

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Nekoei A.R.; SAFARZADEH S.

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Seminar: IRANIAN CHEMISTRY CONGRESS
Year:2013 | Issue:16

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Title

THEORETICAL STUDY ON CONFORMATIONAL ISOMERS OF ACETYL ACETONE, NBO ANALYSES

Author(s)

Nekoei A.R. | SAFARZADEH S. | Issue Writer Certificate

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Abstract

IN METHYLATED MOLECULES, THE METHYL GROUP CAN ROTATE AROUND A SINGLE BOND SO THAT DURING A FULL 360° ROTATION IT THRICE ENCOUNTERS AN UNSTABLE AND A RELATIVELY STABLE CONFORMATION.THE ENERGY DIFFERENCE BETWEEN THESE TWO CONFORMERS GIVES RISE TO POTENTIAL BARRIER TO THIS ROTATION. THE QUANTUM MECHANICAL NATURE OF THIS HINDERED ROTATION IN MOLECULES WAS RECOGNIZED IN THE EARLY YEARS OF QUANTUM THEORY [1]. CONFORMATIONAL ANALYSIS IS A FUNDAMENTAL SUBJECT IN ORGANIC AND PHYSICAL CHEMISTRY. HOWEVER, NOT EVERY QUESTION CONCERNING THE CONFORMATION ANALYSIS IS SIMPLE TO ANSWER. A B -DICARBONYL COMPOUND, WITH AT LEAST ONE ALPHA PROTON, PREDOMINANTLY EXISTS AS CONJUGATEDCIS -ENOL FORM [2]. OVER THE YEARS, THE KETO-ENOL TAUTOMERIC EQUILIBRIUM AND THE STRUCTURE OF BOTH KETO AND ENOL FORMS OF B-DICARBONYL HAVE BEEN THE SUBJECTS OF INTENSIVE STUDIES USING A LARGE VARIETY OF DIFFERENT METHODS [2]. ACETYLACETONE (AA) IS A WELL-KNOWN MEMBER OF B-DICARBONYL COMPOUNDS. A FULL CONFORMATIONAL ANALYSES OF AA, WITH SPECIAL ATTENTION ON THE CONFORMATIONS OF TWO METHYL GROUPS IN THE SIDE OF CARBONYL AND HYDROXYL GROUPS, IN ITS ENOL FORM, HAVE BEEN THE SUBJECT OF THE PRESENT WORK BY MEANS OF AB INITIO AND DENSITY FUNCTIONAL THEORY (DFT) CALCULATIONS. ALL QUANTUM MECHANICAL CALCULATIONS HAVE BEEN PERFORMED USING GAUSSIAN 03W PACKAGE PROGRAM AND NBO 5.0 SOFTWARE. ALL POSSIBLE ENOL CONFORMATIONS OF AA HAVE BEEN FULLY OPTIMIZED AT HF AND HYBRID DENSITY FUNCTIONAL B3LYP LEVELS, USING 6-31G (D), 6-311G (D, P) AND 6-311++G (D, P) BASIS SETS. THE VIBRATIONAL FREQUENCIES HAVE BEEN CALCULATED AT THE SAME LEVEL. ALSO VISUAL ANALYSES HAVE BEEN MADE WITH THE GAUSSVIEW 3.0 PACKAGE. THE OBTAINED RELATIVE STABILITIES IN ALL LEVEL OF CALCULATIONS SHOW THAT, IN THE MOST STABLE ENOL FORM OF AA, THE HYDROXYL AND THE NEARBY METHYL GROUPS ARE IN THE STAGGERED POSITION, BUT THE CARBONYL AND ITS NEARBY METHYL GROUPS ARE IN THE ECLIPSE POSITION RESPECT TO EACH OTHER. THE DETAILED REASONS HAVE BEEN INVESTIGATED BY COMPARING THE MOLECULAR STRUCTURE, THE INTRAMOLECULAR HYDROGEN BONDING, VARIETIES OF HYPERCONJUGATION INTERACTIONS, ATOMIC NATURAL BOND ORBITAL (NBO) CHARGES, SECOND ORDER PERTURBATION THEORY ANALYSES OF DONOR-ACCEPTOR CHARGE TRANSFER IN NBO BASIS, DIPOLE MOMENTS AND POLARIZABILITIES.

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APA: Copy

Nekoei, A.R., & SAFARZADEH, S.. (2013). THEORETICAL STUDY ON CONFORMATIONAL ISOMERS OF ACETYL ACETONE, NBO ANALYSES. IRANIAN CHEMISTRY CONGRESS. SID. https://sid.ir/paper/915102/en

Vancouver: Copy

Nekoei A.R., SAFARZADEH S.. THEORETICAL STUDY ON CONFORMATIONAL ISOMERS OF ACETYL ACETONE, NBO ANALYSES. 2013. Available from: https://sid.ir/paper/915102/en

IEEE: Copy

A.R. Nekoei, and S. SAFARZADEH, “THEORETICAL STUDY ON CONFORMATIONAL ISOMERS OF ACETYL ACETONE, NBO ANALYSES,” presented at the IRANIAN CHEMISTRY CONGRESS. 2013, [Online]. Available: https://sid.ir/paper/915102/en

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