The Phase Transition of 1,4-Dialkyl-1,4-diazoniabicyclo[2.2.2]octane Dibromides, C<i><sub>n</sub></i>–DABCO–C<sub><i>n</i>+2</sub>–Br
作者:Kengo Imamura、Jun Shimizu、Takashi Nogami
DOI:10.1246/bcsj.59.2699
日期:1986.9
The phase transition of 1,4-dialkyl-1,4-diazoniabicyclo[2.2.2]octane dibromide (diquaternary salt) in which the difference in the carbon numbers of the two alkyl groups is two, was studied by means of differential scanning calorimetry, infrared absorption spectroscopy, and a study of the bromide-anion conductivities. DSC measurements revealed the existence of the metastable phase. The conversion rate from the metastable phase to the stable phase was too slow to be followed. The phase transition could be explained by the free energy-temperature relation. The temperature-dependence of the infrared absorption spectra showed that the band progressions due to two different alkyl chains disappeared at the transition temperature. This shows that the trans-zigzag conformation in the low-temperature phase is destroyed by the conformational change of the alkyl chain at the transition temperature. The free energy-temperature relation was also confirmed by the IR spectra. Discontinuous increases in the bromide-anion conductivities were observed at the transition temperatures. The conductivity jump was explained by the voids caused by the conformational change in the alkyl chain.
研究了1,4-二烷基-1,4-二氮二环[2.2.2]癸烷二溴化物(双季铵盐)的相变,其中两个烷基团的碳原子数差为二,通过差示扫描量热法、红外吸收光谱法以及溴离子导电性研究进行了研究。DSC测量揭示了亚稳态的存在。从亚稳态转变为稳定态的转化速率太慢,无法跟踪。相变可以通过自由能-温度关系来解释。红外吸收光谱的温度依赖性表明,由于两种不同烷基链引起的光谱带在转变温度下消失。这表明在低温相中的反式锯齿构象在转变温度下因烷基链的构象变化而被破坏。自由能-温度关系也通过红外光谱得到了验证。在转变温度下观察到了溴离子导电性的非连续增加。导电性的跃升被解释为由于烷基链的构象变化造成的空隙。