Influence of fluorination on the conformational properties and hydrogen-bond acidity of benzyl alcohol derivatives

• Main Authors: Bogdan, Elena (Author), Compain, Guillaume (Author), Mtashobya, Lewis (Author), Le Questel, Jean-Yves (Author), Besseau, François (Author), Galland, Nicolas (Author), Linclau, Bruno (Author), Graton, Jérôme (Author)
• Format: Article
• Language: English
• Published: 2015-06-30.
• Subjects: Article
• Online Access: Get fulltext

 The effect of fluorination on the conformational and hydrogen-bond (HB)-donating properties of a series of benzyl alcohols has been investigated experimentally by IR spectroscopy and theoretically with quantum chemical methods (ab initio (MP2) and DFT (MPWB1K)). It was found that o-fluorination generally resulted in an increase in the HB acidity of the hydroxyl group, whereas a decrease was observed upon o,o?-difluorination. Computational analysis showed that the conformational landscapes of the title compounds are strongly influenced by the presence of o-fluorine atoms. Intramolecular interaction descriptors based on AIM, NCI and NBO analyses reveal that, in addition to an intramolecular OH???F interaction, secondary CH???F and/or CH???O interactions also occur, contributing to the stabilisation of the various conformations, and influencing the overall HB properties of the alcohol group. The benzyl alcohol HB-donating capacity trends are properly described by an electrostatic potential based descriptor calculated at the MPWB1K/6-31+G(d,p) level of theory, provided solvation effects are taken into account for these flexible HB donors.