以半經驗分子軌域法計算芳香基環丙烷所得電荷密度與以核磁共核振儀所測其化學位移之比較

Correlation of the Charge Densities of Carbons of Cyclopropane in the Cyclopropylarenes from Semi-empirical Calculation with their Substituent Chemical Shifts from C-13 NMR Studies

林孝道(Shaw-Tao Lin) ； 楊富媚(Fu-May Yang) ； 楊惠如(Huey-Ju Yang) ； 林文忠(Wen-Chung Lin)

《化學》 54卷1期 (1996/03) Pp. 17-23

https://doi.org/10.6623/chem.1996003

摘要

利用半經驗式分子軌域法計算環丙烷系列中三個碳原子核之電荷密度，並與Hammett σ，σ^+，σ^-值及由核磁共振法形成之取代基化學位移(SCS)值分別做比較。由理論計算所得之C_α，C_7電荷密度(AMI, MNDO)與Hammett σ，σ^-值及SCS有良好之線性關係。可能鹵素所導致之場效應而使理論計算之電荷密度值呈現不規則性。一般而言，AM1及MNDO仍然可應用於環丙烷之碳化學位移變化之預測。

關鍵字

半經驗式計算 ； 化學位移 ； Hammett函數 ； 場效應 ； 共振效應 ； 芳百基環丙烷

並列摘要

The charge densities of carbon of cyclopropane ring in the cyclopropylarenes were calculated by means of semi-empirical molecular orbtial methods (AMI, MNDO, PM3). Correlations between the charge densities of carbon, Hammell σ, σ^+, σ^- constants and substituent chemical shifts(SCS) from ^(13)C NMR studies were made. The charge densities of C_σ C_7 (from AMI, MNDO) can well be correlated with Hammell σ, σ^- as well as SCS. The presence of halogens on C_β resulted in higher field effect and the changing of substituents did not affect the consistency of the charge densities. In general, methods of AMI and MNDO can be applied to the prediction of the chemical shifts of carbon on the cyclopropyl series.

並列關鍵字

Semi-empirical calculations ； Charge density ； Chemical shift ； Hammett constant ； field effect ； Resonance effect ； Arylcyclopropane