โ Scribed by P.J. Hendra; D.B. Powell
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The infra-red spectrum of piperazine has been measured over the range 4000-400 cm-L Observed infra-red bands and previously reported Raman bands have been assigned to fundamental skeletal modes of vibration.
ALTHOH~H a number of compounds analogous to 1:4 dioxan are known, e.g. 1:4 dithian, piperazine, etc., only the infra-red and Raman spectra of dioxan have been thoroughly investigated. A number of authors including RAMS~.Y [1],
]~HRKETT and BADGER [2], and I~ALHERB:E and BERI~STEII~ [3] have attempted assignments of observed absorption and Raman bands to fundamental modes of clioxan. It was therefore considered of interest to investigate the spectra of piperazine C4Hs(NH)2 more closely.
The configuration of heterocyclic compounds of this type has been investigated by a number of physical methods. MARSH [4] has concluded from X-ray diffraction data that dithian and diselenan are centrosymmetric, having the "chair" configuration whilst infra-red evidence for the structure of dioxan indicates a similar structure. Electron diffraction evidence for the structure of di-N-chloropiperazine [5] suggests that this compound is found in the symmetrical "chair" configuration whilst recently HASSEL and PEDERSElV [6] has confirmed this conclusion by electron diffraction experiments on piperazine and di-N-methyl piperazine.
The infra-red spectrum of piperazine was obtained both as a solid and as a solution in carbon tetrachloride and has been reported elsewhere [7].
The Raman spectrum has been determined by KAHOVEC and KOHLRAUSCH [8] and both this and the infra-red spectrum are given in Table 1. In the assignment which follows it is assumed that the molecule has a centrosymmetric "chair" configuration, at least in solution, and that the fundamental modes of dioxan as illustrated by RAMSAY could be assumed to apply to piperazine. It was anticipated that bands due to ~ N H would be found in similar regions to that of skeletal modes. It was decided therefore to solve the equations of RAMSAY for dioxan using suitable force constant and interatomic distance values in order to obtain a basis for the assignment.
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