Conformation of non‐aromatic ring compounds XXXI: Infrared and Raman Spectra of some trans‐1,2‐dihalogenocyclopentanes

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Abstract
The infrared and Raman spectra of trans‐1,2‐dichloro‐(I), trans‐1‐bromo‐2‐chloro(II), trans‐1,2‐dibromo‐(III) and trans‐1,2‐dibromo‐1‐methylcyclo‐pentane(IV) were measured in carbon disulfide and in the neat liquid. From the properties of the bands assigned to the carbon‐halogen stretching frequencies it is concluded that the diaxial conformations predominate in solution, the halogen atoms occupying the most buckled part of the ring. The absorption bands of I are broader than those of III and IV. This seems to indicate that the ring geometry of I is less defined and that in compound I twisting of the ring in a pseudolibration movement occurs to a larger extent. From a comparison with the carbon‐halogen stretching frequencies in the analogous cyclohexanes several common features emerge.