The photodimerisation of the chloro-, methoxy- and nitro-derivatives of trans-cinnamic acid: a study of single crystals by vibrational microspectroscopy

The techniques of infrared and Raman microscopy have been used to monitor the photochemical dimerisation reactions of β-2-chloro-trans-cinnamic acid, β-3-chloro-trans-cinnamic acid, β-4-chloro-trans-cinnamic acid, α-2-methoxy-trans-cinnamic acid, β-2-nitro-trans-cinnamic acid, β-3-nitro-trans-cinnamic acid and β-4-nitro-trans-cinnamic acid. In this way the topotactic nature of the reactions has been confirmed. These reactive derivatives have been compared with the unreactive γ-forms of these and related compounds.