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Conformational effect on gas‐phase protonation and NH 4 + clustering of 1,2‐diols
Author(s) -
Bouchoux Guy,
Jezequel Sylvie,
PenaudBerruyer Florence
Publication year - 1993
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210280426
Subject(s) - protonation , chemistry , proton affinity , conformational isomerism , dihedral angle , ab initio , adduct , crystallography , diol , proton , cyclopentane , ab initio quantum chemistry methods , ion , molecule , stereochemistry , hydrogen bond , organic chemistry , physics , quantum mechanics
Ab initio molecular orbital calculations at the MP2/6–31G*//3–21G level are reported on conformers of neutral ethane‐1,2‐diol (ethylene glycol; 1), its protonated from 1H + and the ammonium adduct [1NH 4 ] + for an OCCO dihedral angle (θ) of 0–180°. The proton affinity ( PA ) of 1 was determined in ion cyclotron resonance bracketing experiments to be 820 ± 3 kJ mol −1 . An adduct stabilization energy of 134 kJ mol −1 was calculated for [1NH 4 ] + . Total optimization at the 3–21G level of cis ‐ and trans ‐cyclopentane‐1,2‐diol (2 and 3) and their protonated forms 2H + and 3H + showed distorted envelope structures with θ values of 47.2°, 73.4°, 33.0° and 58.0°, respectively. The calculation predicts PA (2) = 845 kJ mol −1 and PA (3) = 815 kJ mol −1 .