A theoretical and experimental 1H NMR spectroscopy study of the stereoelectronic interactions that rule the conformational energies of alanine and valine methyl ester. (30th July 2013)

• Record Type: Journal Article
• Authors: Cormanich, Rodrigo A.; Ducati, Lucas C.; Tormena, Cláudio F.; Rittner, Roberto
• Is Part Of: Journal of physical organic chemistry. Volume 26:Number 10(2013:Oct.)
• Page Start: 849
• Page End: 857
• Publication Date: 2013-07-30
• Subjects: Chemistry, Physical organic -- Periodicals; 547.1
• DOI: 10.1002/poc.3180
• Languages: English
• ISSNs: 0894-3230

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p> <named-content id="d294e410" content-type="chemicalTechnology" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink">Amino acids</named-content> exhibit a bipolar zwitterionic structure (⁺H₃N‐CHR‐COO⁻) in solution; hence, conformational studies of these compounds have been limited to the gas phase. The conformational preferences of <named-content id="d294e422" content-type="chemicalTechnology" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink">amino acids</named-content> have been widely attributed to <named-content id="d294e425" content-type="reactionType" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink">intramolecular</named-content> hydrogen bonding, despite steric and hyperconjugative effects. In this work, we propose the conformational study of alanine and valine methyl esters, which do not show zwitterionic structures in solution, by¹H NMR and theoretical calculations. The ³<italic>J</italic>_HH spin–spin coupling constants and theoretical calculations were found to be in agreement, showing that the interplay between steric hindrance and hyperconjugation is the forces that are responsible for determining the conformational preferences of alanine and valine methyl esters. Copyright © 2013 John Wiley &amp; Sons, Ltd.</p> </abstract>