Abstract
Analytical techniques for the detection of aldehydes often involve reaction with either a hydrazine or hydroxylamine derivative, resulting in the formation of a hydrazone or oxime, respectively. While there are various examples for the use of either type of derivatization reagent, there have been only few reports with data suitable to answer which of the two types of probes allows faster and more selective detection of aldehydes. Addressing this question, this work used 1H NMR spectroscopy to study the kinetics of the reactions of aromatic and aliphatic aldehydes with two derivatization probes, phenylhydrazine or O-phenylhydroxylamine, in tetrahydrofuran and in presence of an excess of acid catalyst. A fitting procedure was developed to determine the rate constants of these second order reactions while avoiding use of either aldehyde or probe in a large excess. Hydrazone formation was found to be on average 71 times faster than oxime formation. The rate constants for the reaction of aromatic aldehydes with the phenylhydrazine follow largely the trend predicted by Hammett substituent constants, with the notable exception of the hydrogen bond forming 2-hydroxybenzaldehyde. Unlike in studies with water as solvent, aliphatic aldehydes were not found to react faster than aromatic ones.
Original language | English (US) |
---|---|
Article number | 132852 |
Journal | Tetrahedron |
Volume | 119 |
DOIs | |
State | Published - Jul 30 2022 |
Bibliographical note
Funding Information:This project was funded partially through Boston Scientific and the Medical Device Center, University of Minnesota . J.V. thanks the American Chemical Society for Project SEED summer research support.
Funding Information:
The authors declare the following financial interests/personal relationships that may be considered as potential competing interests: Philippe Bühlmann reports financial support was provided by Boston Scientific Corp. John W. Vue reports financial support was provided by American Chemical Society. Philippe Bühlmann has patent pending to University of Minnesota. Blair Troudt has patent pending to University of Minnesota.
Publisher Copyright:
© 2022 Elsevier Ltd
Keywords
- Aliphatic aldehyde
- Aromatic aldehyde
- Hydrazone
- Oxime
- Rate constants