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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 35, Number 5
BKCSDE 35(5)
May 20, 2014 

mPW1PW91 Calculated Structures and IR Spectra of the Conformational Stereoisomers of C-Cyanophenyl Pyrogallol[4]arene
Sangdoo Ahn*, Tae Jung Park, Jong-In Choe*
mPW1PW91, Conformer, Stereoisomer, IR spectrum, Cyanophenyl pyrogallol[4]arene
Molecular structures of the various conformational stereoisomers of 2,8,14,20-cyanophenyl pyrogallol[4]arenes 1 were optimized using the mPW1PW91 (hybrid Hartree-Fock density functional) calculation method. The total electronic and Gibbs free energies and the normal vibrational frequencies of the different structures from three major conformations (CHAIR, TABLE, and 1,2-Alternate) of the four stereoisomers [1(rccc), 1(rcct), 1(rctt), and 1(rtct)] were analyzed. The mPW1PW91/6-31G(d,p) calculations suggested that 1(rcct)1,2-A, 1(rctt)CHAIR, and 1(rtct)CHAIR were the more stable conformations of the respective stereoisomers. Hydrogen bonding is the primary factor for the relative stabilities of the various conformational isomers, and maximizing the π-π interaction between the cyanophenyl rings is the secondary factor. The calculated IR spectra of the more stable conformers [1(rctt)CHAIR, 1(rcct)1,2-A, 1(rtct)CHAIR] were compared with the experimental IR spectrum of 1(rctt)CHAIR.
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