Re-examination of the two factors affecting H-bonding:Rehybridization and Hyperconjugation
碩士 === 國立成功大學 === 化學系專班 === 94 === Weinhold and co-workers suggested the X-H bond length in X-H…Y hydrogen bonded complexes is controlled by a balance of two main factors acting in opposite directions. One is n(Y)→σ*(X-H) hyperconjugative interaction leading to X-H bond lengthening, and the other is...
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ndltd-TW-094NCKU50650492016-05-30T04:22:00Z http://ndltd.ncl.edu.tw/handle/56238806511274981470 Re-examination of the two factors affecting H-bonding:Rehybridization and Hyperconjugation 驗証影響氫鍵的兩個因素:重新混成與負超共軛 Fang-Chun Chen 陳芳君 碩士 國立成功大學 化學系專班 94 Weinhold and co-workers suggested the X-H bond length in X-H…Y hydrogen bonded complexes is controlled by a balance of two main factors acting in opposite directions. One is n(Y)→σ*(X-H) hyperconjugative interaction leading to X-H bond lengthening, and the other is rehybridization leading to X-H bond shortening. We concentrate on the C-H bond length of methane substituted by halogens. All computations are performed using Gaussian98 program, and all discussions in this paper are based on B3LYP/6-31+G* calculations. Without hydrogen bond acceptors, the C-H bond length is mainly affected by s-character of C atom. When hydrogen bond acceptor is present, at larger distance, the C-H bond length shortening is due to the increase in the s-character of the C-H bond, and at shorter distance, the C-H bond length lengthening is due to n(Y)→σ*(X-H) hyperconjugative interaction. If we change with different hydrogen bond acceptors(Y), the C-H bond length is mainly affected by hyperconjugative interaction. The C-H bond length even has linear relation with E(2). If we use the same hydrogen bond acceptor(Y), the C-H bond length keeps the same in spite of different substitutions on C atom of methane. If we change the central atom, the C-H bond length still has linear relation with E(2), but the slope is different. The larger electronegativity of the central atom is, the smaller the slope is. Shao-Pin Wang 王小萍 2006 學位論文 ; thesis 79 zh-TW |
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碩士 === 國立成功大學 === 化學系專班 === 94 === Weinhold and co-workers suggested the X-H bond length in X-H…Y hydrogen bonded complexes is controlled by a balance of two main factors acting in opposite directions. One is n(Y)→σ*(X-H) hyperconjugative interaction leading to X-H bond lengthening, and the other is rehybridization leading to X-H bond shortening. We concentrate on the C-H bond length of methane substituted by halogens. All computations are performed using Gaussian98 program, and all discussions in this paper are based on B3LYP/6-31+G* calculations.
Without hydrogen bond acceptors, the C-H bond length is mainly affected by s-character of C atom. When hydrogen bond acceptor is present, at larger distance, the C-H bond length shortening is due to the increase in the s-character of the C-H bond, and at shorter distance, the C-H bond length lengthening is due to n(Y)→σ*(X-H) hyperconjugative interaction. If we change with different hydrogen bond acceptors(Y), the C-H bond length is mainly affected by hyperconjugative interaction. The C-H bond length even has linear relation with E(2). If we use the same hydrogen bond acceptor(Y), the C-H bond length keeps the same in spite of different substitutions on C atom of methane. If we change the central atom, the C-H bond length still has linear relation with E(2), but the slope is different. The larger electronegativity of the central atom is, the smaller the slope is.
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Shao-Pin Wang |
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Shao-Pin Wang Fang-Chun Chen 陳芳君 |
author |
Fang-Chun Chen 陳芳君 |
spellingShingle |
Fang-Chun Chen 陳芳君 Re-examination of the two factors affecting H-bonding:Rehybridization and Hyperconjugation |
author_sort |
Fang-Chun Chen |
title |
Re-examination of the two factors affecting H-bonding:Rehybridization and Hyperconjugation |
title_short |
Re-examination of the two factors affecting H-bonding:Rehybridization and Hyperconjugation |
title_full |
Re-examination of the two factors affecting H-bonding:Rehybridization and Hyperconjugation |
title_fullStr |
Re-examination of the two factors affecting H-bonding:Rehybridization and Hyperconjugation |
title_full_unstemmed |
Re-examination of the two factors affecting H-bonding:Rehybridization and Hyperconjugation |
title_sort |
re-examination of the two factors affecting h-bonding:rehybridization and hyperconjugation |
publishDate |
2006 |
url |
http://ndltd.ncl.edu.tw/handle/56238806511274981470 |
work_keys_str_mv |
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