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Direct Spectroscopic Evidence of Hyperconjugation Unveils the Conformational Landscape of Hydrazides

2014; Wiley; Volume: 126; Issue: 50 Linguagem: Inglês

10.1002/ange.201407801

1521-3757

Eric Gloaguen, Valérie Brenner, Mohammad Alauddin, B. Tardivel, Michel Mons, Anne Zehnacker, Valérie Declerck, David J. Aitken,

Molecular Spectroscopy and Structure

Abstract The stereochemistry of hydrazides makes them especially interesting as building blocks for molecular design. An exhaustive conformational analysis of three model hydrazides was conducted in a conformer‐selective approach by using a combination of high‐level quantum chemistry calculations and vibrational spectroscopy in the gas phase and in solution. The NH stretch frequency was found to be highly sensitive to hyperconjugation, thus making it an efficient probe of the conformation of the neighboring nitrogen atom. This property greatly assisted the identification of the isomers observed experimentally in the conformer pool. A rationalization of the hydrazide conformational landscape is proposed, therefore paving the way for a better characterization of secondary structures in larger systems.