sp² Carbon

Abstract

Virtually the only evidence for hydrogen bonding by alkenes has been obtained from their vibrational spectra. In their survey of C—H groups as acceptors in hydrogen bonding, Allerhand and Schleyer [7] observed the C—H stretching mode in the infrared spectrum of the molecules listed in Table 4.1 (see p. 116). The wavenumber of this mode (3060–3100 cm^-1) was found to decrease when azine or dimethyl sulphoxide was added to a CCl₄ solution of any of these compounds, a new peak or shoulder appearing; this is evidence that a complex forms between the solute and the donor species.