The Shape of -Alanine
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- 作者：M. Eugenia Sanz ; Alberto Lesarri ; M. Isabel Peñ ; a ; Vanesa Vaquero ; Vanessa Cortijo ; Juan C. Ló ; pez ; and José ; L. Alonso
- 刊名：Journal of the American Chemical Society
- 出版年：2006
- 出版时间：March 22, 2006
- 年：2006
- 卷：128
- 期：11
- 页码：3812 - 3817
- 全文大小：210K
- 年卷期：v.128,no.11(March 22, 2006)
- ISSN：1520-5126
文摘
The combination of Fourier transform microwave spectroscopy in a pulsed supersonic jet withlaser ablation has made 
-alanine amenable to a structural study in the gas phase. Two new conformersof -alanine have been identified together with the two previously observed by McGlone and Godfrey [J.Am. Chem. Soc. 1995, 117, 1043]. The comparison between the experimental rotational and 14N nuclearquadrupole coupling constants and those calculated ab initio provide a definitive test for molecular structuresand confirm unambiguously the identification of all conformers. For the two most abundant conformers, anintramolecular hydrogen bond between the amino group and carbonyl oxygen (N-H···O=C) is established,and the COOH adopts a cis-COOH configuration. The next conformer in order of abundance presents anO-H···N intramolecular hydrogen bond with a trans configuration for the COOH group. The high sensitivityof the experiment has allowed us to detect for the first time a conformer uniquely stabilized by an n-
*hyperconjugative interaction between the nucleophile N: of the amino group and the * orbital at the carbonylgroup. Partial conformational relaxation has been observed in the supersonic expansion.
-alanine amenable to a structural study in the gas phase. Two new conformersof -alanine have been identified together with the two previously observed by McGlone and Godfrey [J.Am. Chem. Soc. 1995, 117, 1043]. The comparison between the experimental rotational and 14N nuclearquadrupole coupling constants and those calculated ab initio provide a definitive test for molecular structuresand confirm unambiguously the identification of all conformers. For the two most abundant conformers, anintramolecular hydrogen bond between the amino group and carbonyl oxygen (N-H···O=C) is established,and the COOH adopts a cis-COOH configuration. The next conformer in order of abundance presents anO-H···N intramolecular hydrogen bond with a trans configuration for the COOH group. The high sensitivityof the experiment has allowed us to detect for the first time a conformer uniquely stabilized by an n-*hyperconjugative interaction between the nucleophile N: of the amino group and the * orbital at the carbonylgroup. Partial conformational relaxation has been observed in the supersonic expansion.