McAllister, M. I., Boulho, C., Brennan, C., Sidebottom, P. J. and Lennon, D. (2020) Isotopic substitution experiments in the hydrogenation of mandelonitrile over a carbon supported Pd catalyst: a nuclear magnetic resonance study. Molecular Catalysis, 484, 110720. (doi: 10.1016/j.mcat.2019.110720)
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Abstract
A mechanistic exploration of the liquid phase hydrogenation of the aromatic cyanohydrin mandelonitrile (C6H5CH(OH)CH2CN) over a carbon supported Pd catalyst to produce the primary amine, phenethylamine (C6H5CH2CH2NH2) is conducted. Prior examination showed the reaction to involve the production of the ketone intermediate 2-aminoacetophenone (C6H5C(O)CH2NH2), formed as a consequence of the presence of an acid catalysed tautomeric side reaction. The corresponding deuteration reaction, reported here and analysed by multinuclear NMR spectroscopy and mass spectrometry, is employed to further investigate accessible pathways. Examination of the resultant product distribution of the deuteration, and the location of deuterium incorporation establishes the role of a hydroxy-imine species as a key reaction intermediate. In addition, the acid catalysed tautomerism to the ketone is shown to be a reversible side reaction, but also a contributor to desired product formation. Moreover, an order for the three critical hydrogen consuming steps in phenethylamine formation is established. Hydrogenation of the nitrile functionality to afford the hydroxy-imine precedes hydrogenolysis of the hydroxyl group, with the final step being hydrogenation of the imine to form the target product, phenethylamine.
| Item Type: | Articles |
|---|---|
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Boulho, Dr Cedric and McAllister, Mairi and Lennon, Professor David |
| Creator Roles: | McAllister, M. I.Conceptualization, Methodology, Investigation, Validation, Writing – original draft Boulho, C.Methodology, Investigation Lennon, D.Conceptualization, Methodology, Investigation, Writing – review and editing, Supervision, Project administration |
| Authors: | McAllister, M. I., Boulho, C., Brennan, C., Sidebottom, P. J., and Lennon, D. |
| College/School: | College of Science and Engineering > School of Chemistry |
| Journal Name: | Molecular Catalysis |
| Publisher: | Elsevier |
| ISSN: | 2468-8274 |
| ISSN (Online): | 2468-8231 |
| Published Online: | 23 November 2019 |
| Copyright Holders: | Copyright © 2019 The Authors |
| First Published: | First published in Molecular Catalysis 484:110720 |
| Publisher Policy: | Reproduced under a Creative Commons License |
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