4-Chloro-3-fluorobenzaldehyde: Experimental (XRD, FT-IR and Raman) and DFT studies
Makaleler > Tam Makale · 2014
Yazarlar: Cemal PARLAK, Chandraju Sadolalu Chidan KUMAR, Hoong Kun FUN, Guerkan KESAN, Lydia RHYMAN, Ponnadurai RAMASAMİ, Siddegowda CHANDRAJU, Ching Kheng QUAH
JOURNAL OF FLUORINE CHEMISTRY, SCI Expanded İndekslerine Giren Dergi, Uluslararası, 2014, cilt 163, ss 7-15
DOI: 10.1016/j.jfluchem.2014.03.014
Özet
The structure of 4-chloro-3-fluorobenzaldehyde (CFB, C7H4ClFO) has been characterized by single-crystal X-ray diffraction, FT-IR and Raman techniques. The conformational isomers, optimized geometrical parameters, normal mode frequencies and corresponding vibrational assignments of CFB have been examined using the density functional theory method, with the Becke-3-Lee-Yang-Parr functional and the 6-311+G(3df,p) basis set. Reliable vibrational assignments and molecular orbitals have been investigated by the potential energy distribution. CFB crystallizes in monoclinic space group P2(1)/c with the O-cis conformation. In order to examine the effect of fluorine on the conformational preference, the chloro- and bromo-analogs of CFB have also been studied theoretically. It is observed that CFB prefers the O-cis conformation while the chloro- and bromo-analogs prefer the O-trans conformation. Although the free energy difference between the O-cis and O-trans conformers is less than 0.2 kcal/mol, the free energy rotational barrier is at least 8.4 kcal/mol [B3LYP/6-311+G(3df,p)]. MP2/aug-cc-pVDZ computations reveal that these free energies remain almost unaffected. The atypical characteristic of fluorine affecting conformational isomerism is observed. In addition, there is a good agreement between the experimentally determined structural parameters and vibrational frequencies of CFB and those predicted theoretically. (C) 2014 Elsevier B.V. All rights reserved.