MESOPHASES OF ALKYLAMMONIUM SALTS .5. HEAT-CAPACITIES OF SYMMETRICAL HALIDES WITH ALKYL CHAINS LONGER THAN ETHYL

被引：18

作者：

XENOPOULOS, A ^{[1
]}

CHENG, JL ^{[1
]}

WUNDERLICH, B ^{[1
]}

机构：

[1] OAK RIDGE NATL LAB,DIV CHEM,OAK RIDGE,TN 37831

来源：

MOLECULAR CRYSTALS AND LIQUID CRYSTALS | 1993年 / 226卷

基金：

美国国家科学基金会;

关键词：

TETRA-N-ALKYLAMMONIUM BROMIDES AND IODIDES; DISORDER AND MOTION; MESOPHASES; THERMAL ANALYSIS; HEAT CAPACITY; ENTROPY;

D O I：

10.1080/10587259308028792

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

The heat capacities of tetra-n-alkylammonium bromides and iodides in the solid state have been measured from 130 K through their respective transitions and fitted at low temperatures to two THETA temperatures, using group vibrations computed from the vibrational spectra and the Tarasov analysis, as developed for linear macromolecules. The compounds analyzed were (C3H7)4NBr, (C4H9)4NBr, (C5H11)4NBr, (C6H13)4NBr, (C7H15)4NBr, (C8H17)4NBr, (C10H21)4NBr, (C12H25)4NBr, (C16H33)4NBr, (C18H37)4NBr, (C3H7)4NI, (C4H9)4NI, (C5H11)4NI, (C6H13)4NI, (C7H15)4NI, and (C12H25)4NI. The total vibrational contribution to the heat capacity is thus, derived and compared to the experimentally measured heat capacity over the whole temperature range. Positive deviations of the measured heat capacity from the calculation occur already below room temperature, implying the existence of large-amplitude, nonvibrational motion in the solid state, as suggested before by solid-state C-13 NMR analysis. Quantitative information on the entropy of disordering generated outside of the transition ranges is derived and agrees with the entropy deficits predicted by the analysis of the first-order transitions. An addition scheme is developed for the heat capacity of the methylene groups in these compounds, that is similar to the paraffins.

引用

页码：87 / 102

页数：16