International Journal of Chemical Kinetics p. 514 - 523 (2012)
Update date:2022-08-05
Topics:
Taha, Ahmed A.
The objective of this study is to test the suitability of the extended Hammett-Brown equation, log (kXX/kHH) = ρ+∑σ+, in depicting satisfactorily additive effects of electronegative atom-bearing substituents, which are known to possess diverse and multicomponent influences on the side chain reactions of polysubstituted benzenes. The equation has been used to correlate, for the first time, the additive effect of substituents in the specific rates of solvolysis of 2-chloro-2-phenylpropanes (3b-3f) having 3-F,4-Me, 3-Br,4-Me, 3-I,4-Me, 3-Me,4-Me, or 3-MeO,4-Me substituents. The rates were determined titrimetrically at 288, 298, and 308 K using 90% aqueous acetone as solvent. Measured additive effects of these substituents on the solvolysis rate and activation parameters of the parent cumyl chloride (2-chloro-2-phenylpropane) are found to be well correlated using the equation given above. Plots of log (kXX/k HH) of 3b-3f together with mainly di-, but also tri- and mono-substituted cumyl chlorides from previous studies against ∑σ+ give a linear correlation coefficient of 0.990 as a measure of the validity of the equation to depict such systems. The halogen substituents' extent of conformity with additivity reflected in their relative (kobsd/kcalcd) rate ratios is found to correlate with the steric size of substituents. Plots of rate ratios against Taft's steric factor of each halogen give a linear correlation coefficient of 0.994 for the 3-halo substituents. The 3,4-dimethyl substituents' relative rate ratio of 1.03 shows excellent additivity, whereas the 3-methoxy-4-methyl ratio of 1.43 shows the methoxy group to be far less deactivating than predicted. Similar trends were found for the free energy of activation (δG? - δG 0?) differences, which correlated linearly with a coefficient of 0.983 with Taft's steric factor of halogen atoms.
View MoreJiaxing Trustworthy Import And Export Co.,Ltd
Contact:+86-573-82030555
Address:Room 1202, Unit B, Charming plaza,No.1558 East Zhongshan Road , Jiaxing City, Zhejiang Province, China.
Chengdu King-tiger Pharm-chem. Tech. Co., Ltd
Contact:028-85317716
Address:Tianfu Life Science Park, No. 88 South Keyuan Road, Gaoxin District, Chengdu City, Sichuan Province, PRC.
Shanghai Korey Pharm Co.,Ltd.(expird)
Contact:021-61840961 021-61840962
Address:No.157,Zhuguang Rd, Qingpu, Shanghai, China
website:http://www.debyesci.com
Contact:+85221376140
Address:Rm. 19C, Lockhart Ctr., 301-307 Lockhart Rd., Wan Chai
Contact:+86-512-69561895
Address:No.111, Building A4, 218 Xinghu Street, Suzhou Industrial Park, P. R. China
Doi:10.1007/s11164-012-0724-5
(2013)Doi:10.1016/j.poly.2017.12.021
(2018)Doi:10.1016/0223-5234(91)90120-C
(1991)Doi:10.3390/molecules14104190
(2009)Doi:10.1016/0040-4039(91)80487-Q
(1991)Doi:10.1021/ja3047975
(2012)