Infrarot‐Spektren der Cyclane und Cyclanone VI. CH‐stretching‐ und CH2‐bending‐Schwingungen von Cyclanonen

The vibrational spectra of the cyclanones with 5 ≤ n ≤ 15 have been studied in CCl4‐solution, in the CH‐stretching and CH2‐bending regions, using LiF‐ and CaF2‐resolution respectively. Band shapes are found to be complex but fit fairly well with the generally accepted values assigned to CH2‐stretching an ‐bending vibrations. By comparison with some α,α,α′,α′‐tetradeutero‐cyclanones an assignment of the stretching bands of the α‐CH2‐groups is suggested. These groups seem to absorb at about 20 cm−1 higher than the normal CH2‐ groups. Possible interpretations for this shift are discussed. The width of the strong absorption regions of the asymmetric and the symmetric stretching vibrations as well as that of the δ(CH2)‐ bendings show pronounced correlation with ring size, exhibiting maximum width for the medium size rings with n = 9, 10, 11.