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Issue 14, 2005
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Spectroscopic and theoretical studies on intramolecular OH–π hydrogen bonding in 4-substituted 2-allylphenols

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Abstract

2-Allylphenol (1) constitutes a mixture of conformers, in which an OH–π hydrogen bonded closed (1a) and open form (1b) can be distinguished. 4-Substituted 2-allyphenols (2–9) have been synthesised and investigated by theoretical and spectroscopic methods. In 1–9, the energy and the structure of the hydrogen bonds show distinct variation with substituents. In the PE spectra of most compounds, two ionisations can be distinguished which are related to the allylic π(C[double bond, length as m-dash]C) orbitals of the two conformers a and b and differ in energy by ΔIP(C[double bond, length as m-dash]C). Alternatively, ΔIP(C[double bond, length as m-dash]C) can be determined indirectly from comparison of the PE spectra of the respective phenols and anisoles with the same substituents. ΔIP(C[double bond, length as m-dash]C) values between 0.3 and 1.1 eV were found. Frequency shifts Δν(OH) of the O–H vibration in CHCl3 solution were measured by IR spectroscopy. By means of correlation analysis of the relationship between the strength of the intramolecular hydrogen bond, ΔIP(C[double bond, length as m-dash]C), Δν(OH) values and substituent constants it is established how substituents in 4-position affect the intramolecular OH–π hydrogen bond. The investigations demonstrate that the ΔIP(C[double bond, length as m-dash]C) data can be used as descriptors for this intramolecular interaction.

Graphical abstract: Spectroscopic and theoretical studies on intramolecular OH–π hydrogen bonding in 4-substituted 2-allylphenols

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Publication details

The article was received on 06 Apr 2005, accepted on 12 May 2005 and first published on 13 Jun 2005


Article type: Paper
DOI: 10.1039/B504765J
Org. Biomol. Chem., 2005,3, 2620-2625

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    Spectroscopic and theoretical studies on intramolecular OH–π hydrogen bonding in 4-substituted 2-allylphenols

    P. Rademacher, L. Khelashvili and K. Kowski, Org. Biomol. Chem., 2005, 3, 2620
    DOI: 10.1039/B504765J

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