TERT-BUTYL CONFORMATIONAL NBO ANALYSES IN DIPIVALOYLMETHANE

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Nekoei A.R.; SAFARZADEH S.

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Seminar Paper

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

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Title

TERT-BUTYL CONFORMATIONAL NBO ANALYSES IN DIPIVALOYLMETHANE

Author(s)

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

Keywords

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Abstract

CONFORMATIONAL ISOMERISM IS A FORM OF STEREOISOMERISM IN WHICH THE ISOMERS CAN BE INTERCONVERTED EXCLUSIVELY BY ROTATIONS ABOUT FORMALLY SINGLE BONDS. SUCH ISOMERS ARE GENERALLY REFERRED TO AS CONFORMATIONAL ISOMERS OR CONFORMERS AND SPECIFICALLY AS ROTAMERS; IN THE SENSE THAT THERE EXISTS A ROTATIONAL ENERGY BARRIER THAT NEEDS TO BE OVERCOME TO CONVERT ONE CONFORMER TO ANOTHER. THE FORCES UNDERLYING THE BARRIER TO ROTATION AROUND FORMALLY SINGLE BONDS HAVE BEEN THE FOCUS OF NUMEROUS STUDIES [1-2].THERE ARE STRONG EVIDENCES POINTING OUT THAT HYPERCONJUGATION IS INVOLVED, WITH APPRECIABLE IMPORTANCE, IN A REPRESENTATIVE NUMBER OF SITUATIONS [3]. ROTATIONAL BARRIERS PLAY A FUNDAMENTAL ROLE IN THE MOLECULAR SIMULATION. WITH THIS REGARD, ALL CONFORMERS OF THE ENOL FORM OF DIPIVALOYLMETHANE (DPM) COMPOUND HAVE BEEN STUDIED BY CONSIDERING THE ROTATION OF THE T-BUTYL GROUPS, IN BOTH SIDE OF HYDROXYL AND CARBONYL, ABOUT THE C-C BONDS.THE RELATIVE ENERGIES OF ALL CONFORMERS AND ALSO THE BARRIER HEIGHTS FOR INTERNAL ROTATIONS HAVE BEEN EVALUATED.ALL CALCULATIONS IN THIS STUDY HAVE BEEN PERFORMED BY THE GAUSSIAN 03W AND NBO 5.0 PROGRAM PACKAGES. THE FULL GEOMETRY OPTIMIZATIONS FOR THE ENOL FORMS OF DPM HAVE BEEN CARRIED OUT USING B3LYP LEVEL OF DENSITY FUNCTIONAL THEORY (DFT), AT 6-31G (D), 6-311G (D, P) AND 6-311++G (D, P) BASIS SETS. THE VIBRATIONAL FREQUENCIES HAVE BEEN ALSO CALCULATED AT THESE LEVELS. ALL CALCULATIONS SHOW THAT ONLY TWO CONFORMATIONS OF THE ENOL FORMS ARE STABLE. IN THE MOST STABLE FORM, ONE T-BUTYL GROUP IS IN STAGGERED POSITION WITH ITS NEARBY C-O SINGLE BOND (HYDROXYL SIDE), AND THE SECOND T-BUTYL GROUP IS IN THE ECLIPSE POSITION RESPECT TO ITS NEARBY CARBONYL GROUP. THE OTHER LESS STABLE ENOL CONFORMER IS THE FORM IN WHICH BOTH T-BUTYL GROUPS ARE IN THE STAGGERED POSITION WITH RESPECT TO THE C-O AND C=O BOND. ALL OTHER ENOL CONFORMATIONS DO NOT SHOW ANY STABILITY AND TURN TO THE TWO AFOREMENTIONED STABLE CONFORMERS, UPON FULL OPTIMIZATION. THE REASONS OF THESE STABILITIES HAVE BEEN EVALUATED BASED ON THE MOLECULAR STRUCTURE, THE INTRAMOLECULAR HYDROGEN BONDING, 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). TERT-BUTYL CONFORMATIONAL NBO ANALYSES IN DIPIVALOYLMETHANE. IRANIAN CHEMISTRY CONGRESS. SID. https://sid.ir/paper/915525/en

Vancouver: Copy

Nekoei A.R., SAFARZADEH S.. TERT-BUTYL CONFORMATIONAL NBO ANALYSES IN DIPIVALOYLMETHANE. 2013. Available from: https://sid.ir/paper/915525/en

IEEE: Copy

A.R. Nekoei, and S. SAFARZADEH, “TERT-BUTYL CONFORMATIONAL NBO ANALYSES IN DIPIVALOYLMETHANE,” presented at the IRANIAN CHEMISTRY CONGRESS. 2013, [Online]. Available: https://sid.ir/paper/915525/en

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