The Solvolysis of Heteroaromatic Analogs of Benzyl Substrates And Oxygen-17 NMR Study of Heteroaromatic Ketones

• Main Authors: Duann, Yeh-Fang, 段葉芳
• Other Authors: Liu Kwang-Ting
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/82105266050107639019

博士 === 國立臺灣大學 === 化學系 === 86 === A linear relationship δ=24.6σ++556.3 could be useful in estimating the σ+value for furan and thiophen . The substituent constants σ+value for those- five membered heteroaromatic ring were determined from 17O NMR substituent chemical shifts of the carbonyl group in trifluroacetyl derivatives . The σ+values were found to be -1.08 for 2-furyl , -0.29for 3-furyl , -1.02 for 2-thienyl and -0.52 for 3-thienyl, respectively . Nucleophilic solvent participation was found in the solvolysis of primary and secondary-α-methylbenzyl halide , whereas , the solvolysis mechanism for secondary- α-tert-butylbenzyl derivatives was a limiting SN1 process . Variation of ρvalue was found in the solvolysis of secondary-α-tert- butylbenzyl derivatives with the number of data points from electron donor to electron withdrawing substituent on the benzene ring . It suggested the possibility of acceleration of the deactivate substrate due to the increasing significance of solvation to the leaving group . The σ+value for 2-furyl and 3-furyl , and 2-thienyl and 3-thienyl group were found to be -1.05,-0.596,-0.931 and -0.545 , respectively , from extrapolation or interpolation of solvolysis rate data in Hammett-Brown relationship logk=σ+ρ . Significant difference between this and previous study by 17O chemical shift for 3-furyl group was noteed. α-Tert-butylpyridinylmethyl derivatives and some five-membered two- heteroatom analogous were prepared and were solvolyzed . Poor linear correlation between logk and YX or YBnX by using Grunwald -Winstein equation. The range of σ+value of 3-pyridinyl and 2-thiazoyl were 0.450~0.631 and -0.066~0.008 , respectively , from interpolation of solvolysis rate data in Hammett-Brown relationship logk=σ+ρ. Solvolysis of α-tert-butyl(1-naphthyl)methyl and α-tert-butyl(2- naphthyl)methyl bromides were studied . The σ+values were found to be -0.237 and - 0.189 , respectively .