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The Influence of β‐Ammonium Substitution on the Reaction Kinetics of Aminooxy Condensations with Aldehydes and Ketones
Author(s) -
Ogunwale Mumiye A.,
Knipp Ralph J.,
Evrard Clint N.,
Thompson Lee M.,
Nantz Michael H.,
Fu XiaoAn
Publication year - 2019
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.201801143
Subject(s) - chemistry , kinetics , substitution (logic) , ammonium , substitution reaction , medicinal chemistry , photochemistry , organic chemistry , physics , computer science , programming language , quantum mechanics
The click‐chemistry capture of volatile aldehydes and ketones by ammonium aminooxy compounds has proven to be an efficient means of analyzing the carbonyl subset in complex mixtures, such as exhaled breath or environmental air. In this work, we examine the carbonyl condensation reaction kinetics of three aminooxy compounds with varying β‐ammonium ion substitution using Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR‐MS). We determined the activation energies for the reactions of the aminooxy compounds ATM, ADMH and AMAH with a panel of ketones and aldehydes that included acrolein and crotonaldehyde. The measurements indicate that the activation energies for the oximation reactions are quite low, less than 75 kJ mol −1 . ADMH is observed to react the fastest with the carbonyls studied. We postulate this result may be attributed to the ADMH ammonium proton effecting a Brønsted‐Lowry acid‐catalyzed elimination of water during the rate‐determining step of oxime ether formation. A theoretical study of oxime ether formation is presented to explain the enhanced reactivity of ADMH relative to the tetraalkylammonium analog ATM.