The Singular Gas-Phase Structure of 1-Aminocyclopropanecarboxylic Acid (Ac3c)

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• 作者：Ana I. Jim茅nez ; Vanesa Vaquero ; Carlos Cabezas ; Juan C. L贸pez ; Carlos Cativiela ; Jos茅 L. Alonso
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：July 13, 2011
• 年：2011
• 卷：133
• 期：27
• 页码：10621-10628
• 全文大小：861K
• 年卷期：v.133,no.27(July 13, 2011)
• ISSN：1520-5126

文摘

The natural nonproteinogenic 伪-amino acid 1-aminocyclopropanecarboxylic acid (Ac₃c) has been vaporized by laser ablation and studied in the gas phase by molecular-beam Fourier transform microwave spectroscopy. Comparison of the experimental rotational and ¹⁴N nuclear quadrupole coupling constants with the values predicted ab initio for these parameters has allowed the unambiguous identification of three Ac₃c conformers differing in the hydrogen bonding pattern. Two of them resemble those characterized before for the coded aliphatic 伪-amino acids. Remarkably, a third conformer predicted to be energetically accessible for all of these amino acids but never observed (the so-called 鈥渕issing conformer鈥? has been found for Ac₃c, close in energy to the global minimum. This is the first time that such a conformer, stabilized by an N鈥揌路路路O(H) hydrogen bond, is detected in the rotational spectrum of a gaseous 伪-amino acid with a nonpolar side chain. The conjugative interaction established between the cyclopropane ring and the adjacent carbonyl group seems to be responsible for the unique conformational properties exhibited by Ac₃c.