Cubic Mesophase in an Unsymmetrical Alkyl Ammonium Salt. Synthesis and Structural Model

Abstract

N,N,N-butylethylpentylpropylammonium iodide 4 and related molecules have been selectively synthesised from commercially available aldehydes, amines and alkyl iodides using a reductive alkylation procedure. The crystalline texture of 4 obtained on cooling is optically isotropic between crossed polarisers, indicating a cubic structure. Differential scanning calorimetry (DSC, +10 K min-1) reveals a glass phase transition at -59 degrees C and a melting point at 192 degrees C. The melting entropy (23.9 J mol-1 K-1) indicates a first-order transition between a highly disordered mesophase and the isotropic liquid. Powder X-ray diffraction patterns were indexed in the cubic system (a = 14.08A; Pm3n space group). In this cell, the molecular packing with Z = 6 corresponds to a rather low compactness of 65%. Iodine and tetraalkylammonium ions occupy positions with a 4m2 site symmetry. These highly symmetrical states may be generated by stepwise rotation of the ammonium cation. The same structural model for orientationally disordered crystal (ODIC) phases can be applied to a series of tetraalkylammonium bromides and iodides.

Enantiomerically pure quaternary ammonium salts with a chiral alkyl chain N(CH3)(n‐C3H7)2(sec‐C4H9)I: Synthesis and physical studies

“…The reductive alkylation reactions can be performed with various aldehydes. 3,18 On the contrary, the quaternization failed when other iodoalkanes are used because the bulky trialkylamine favors elimination reactions. Nevertheless, this synthetic strategy appears as a general one to obtain a wide variety of enantiomerically pure ammonium salts of both configurations.…”

“…1 Such species can be used for studying the influence of controlled chirality on the formation of mesophases 3 as well as organic reactions using asymmetric ionic liquids 1 or asymmetric phase transfer reagents. 2 In the latter cases, working with either enantiomer of the ammonium cation allows to obtain either enantiomer of the target compound.…”

“…Compound 1 was synthesized starting from the primary (R)-(1-methylpropyl)amine, by adapting a three-step procedure already reported in the literature, 3 as follows. Synthesis of the secondary amine NH(n-C 3 H 7 )((R)-sec-C 4 H 9 ).…”

“…1,2 The ability of tetraalkylammonium salts with four different alkyl chains to form mesophases has also been studied. 3 Our interest in such cations is part of a general strategy to synthesize optically active hybrid molecular magnets. 4 The ultimate goal of this approach is to measure magnetochiral dichroism [5][6][7][8] in a ferromagnetically ordered material.…”

Temperature‐dependent Raman spectroscopy of anilinium chloride near phase transition

“…The existence of various solid phases of the organic ammonium salts has long been established, but mainly alkyl ammonium halides appear to have been studied in any details [8][9][10][11][12][13]. It is found that in such ionic compounds hydrogen bonding helps in undergoing a series of phase transitions.…”