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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 17, Number 8
BKCSDE 17(8)
August 20, 1996 

Steric Effect on the Molecular Hyperpolarizabilities of β-Nitrostyrene Derivatives
Bong Rae Cho*, Jong Tae Je, Hyun Soo Kim, Seung Joon Jeon, Ok-Keun Song, C. H. Wang
The steric effect on the first order hyperpolarizability of the β-nitrostyrene derivatives has been investigated by comparing the β values and the dihedral angles between the aryl and nitroalkenyl groups. In general the β value increased with the electron-donating ability of the substituent. The larger β value for 3,4-dimethoxy-β-nitrostyrene than that for p-methoxy-β-nitrostyrene has been attributed to the lower charge transfer energy for the former. The most striking substituent effect was observed in the β-methyl-β-nitrostyrene derivatives. Thus the β values for 3,4-dimethoxy- and p-methoxy derivatives of the latter decreased to near zero, probably because of the large distortion from planarity caused by the steric repulsion between the β-methyl and the aryl groups. The larger β value for p-dimethylamino-β-methyl-β -nitrostyrene has been interpreted with an increased electron-donating ability of the substituent and increased co-planarity.
693 - 695
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