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Targeting the Rich Conformational Landscape of N ‐Allylmethylamine Using Rotational Spectroscopy and Quantum Mechanical Calculations
Author(s) -
Silva Weslley G. D. P.,
Poonia Tamanna,
Wijngaarden Jennifer
Publication year - 2020
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.202000757
Subject(s) - conformational isomerism , chemistry , rotational spectroscopy , spectroscopy , hyperfine structure , steric effects , molecular physics , computational chemistry , crystallography , atomic physics , stereochemistry , physics , molecule , quantum mechanics , organic chemistry
The highly variable conformational landscape of N ‐allylmethylamine (AMA) was investigated using Fourier transform microwave spectroscopy aided by high‐level theoretical calculations to understand the energy relationship governing the interconversion between nine stable conformers. Spectroscopically, transitions belonging to four low energy conformers were identified and their hyperfine patterns owing to the 14 N quadrupolar nucleus were unambiguously resolved. The rotational spectrum of the global minimum geometry, conformer I, shows an additional splitting associated with a tunneling motion through an energy barrier interconnecting its enantiomeric forms. A two‐step tunneling trajectory is proposed by finding transition state structures corresponding to the allyl torsion and NH inversion. Natural bond orbital and non‐covalent interaction analyses reveal that an interplay between steric and hyperconjugative effects rules the conformational preferences of AMA.