TY - JOUR
A1 - Neuvonen, Kari
A1 - Neuvonen, Helmi
A1 - Koch, Andreas
A1 - Kleinpeter, Erich
T1 - Taft equation in the light of NBO computations introduction of a novel polar computational substituent constant scale sigma(q)* for alkyl groups
JF - Computational and theoretical chemistry
N2 - The validity of the Taft equation: log(k(R)/k(CH3)) = rho*sigma* + delta E-S was studied with the aid of NBO computational results concerning cyclohexyl esters RCOOC6H11 [R = Methyl, Ethyl, n-Propyl, Isopropyl, n-Butyl, Isobutyl, sec-Butyl, tert-Butyl, Neopentyl, CH(CH2CH3)(2), CH(CH3)C(CH3)(3), C(CH3)(2)CH2CH3, C(CH3)(2)C(CH3)(3), CH(CH3)(Np), CH(iPr)(tBu), C(Me)(Et)(iPr), C(Et)(2)(tBu) or C(Et)(iPr)(tBu)]. It was proved that the sigma*(alkyl) value is a composite substitutent constant including the polar and steric contributions. A novel computational sigma(q)* substituent constant scale is presented based on the NBO atomic charges of the alpha-carbon and the computational total steric exchange energies E(ster) of the cyclohexyl esters specified above. The method used offers a useful way to calculate sigma*(alkyl) values for alkyl groups for which experimental Taft's polar sigma* parameters are not available.
KW - NBO analysis
KW - Taft equation
KW - Polar substituent constant
KW - Steric effect
Y1 - 2012
U6 - http://dx.doi.org/10.1016/j.comptc.2011.11.044
SN - 2210-271X (print)
VL - 981
IS - 2
SP - 52
EP - 58
PB - Elsevier
CY - Amsterdam
ER -