Journal of Molecular Structure, ( ISI ), Volume (873), Year (2008-4) , Pages (79-88)

Title : ( Structure and vibrational assignment of the enol form of 3-chloro-pentane-2,4-dione )

Authors: Sayyed Faramarz Tayyari , Mansoureh Zahedi Tabrizi , Raheleh Afzali , Somayeh Lale , Hassan Ali Mirshahi ,

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Molecular structure of 3-chloro-pentane-2,4-dione (known as a-chloroacetylacetone, ClAA) has been investigated by means of ab initio and Density Functional Theory (DFT) calculations and the results were compared with those of its parent, pentane-2,4-dione (known as acetylacetone, AA). The harmonic vibrational frequencies of the cis-enol form were calculated at the B3LYP level of theory using 6- 311G** and 6-311++G** basis sets. We also calculated the anharmonic frequencies at B3LYP/6-31G** level of theory. The calculated frequencies and the Raman and IR intensities were compared with the experimental results. According to the theoretical calculations, at the B3LYP/6-311++G** level, the hydrogen bond strength for ClAA is 68.7 kJ/mol, about 2.3 kJ/mol stronger than that in AA. This result is in agreement with the OH/OD stretching, the OH/OD in-plane bending, and O  O stretching frequencies. The 1H chemical shifts for ClAA and AA are computed at the B3LYP/6-311++G** level using the GIAO method. The calculated difference chemical shift of the enolated proton in ClAA and AA is in excellent agreement with the experimental results. Natural bond orbital (NBO) analyses indicate that, in spite of electron withdrawing nature of Cl atom, the steric effect increases the hydrogen bond strength


, Vibrational spectra; a, Chloroacetylacetone; NBO; Intramolecular hydrogen bond; Anharmonicity
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author = {Tayyari, Sayyed Faramarz and Zahedi Tabrizi, Mansoureh and Afzali, Raheleh and Lale, Somayeh and Mirshahi, Hassan Ali},
title = {Structure and vibrational assignment of the enol form of 3-chloro-pentane-2,4-dione},
journal = {Journal of Molecular Structure},
year = {2008},
volume = {873},
month = {April},
issn = {0022-2860},
pages = {79--88},
numpages = {9},
keywords = {Vibrational spectra; a-Chloroacetylacetone; NBO; Intramolecular hydrogen bond; Anharmonicity},


%0 Journal Article
%T Structure and vibrational assignment of the enol form of 3-chloro-pentane-2,4-dione
%A Tayyari, Sayyed Faramarz
%A Zahedi Tabrizi, Mansoureh
%A Afzali, Raheleh
%A Lale, Somayeh
%A Mirshahi, Hassan Ali
%J Journal of Molecular Structure
%@ 0022-2860
%D 2008