The low-temperature modification of n-propyl-ammonium chloride

Abstract

The room-temperature structure of n-propylammonium chloride, which shows rotation of the cations, goes over in a second-order transition into a low-temperature form with fixed positions of the cations. In this process, the crystal of the room-temperature form breaks up reversibly into many domains of the low-temperature form, the domains having differing orientations. The space group of the lowtemperature form is C~-C2/m. The transition is produced by the fixing of the positions of the cations in the (li0) planes of the room-temperature structure in a centrosymmetric arrangement, with the result that the angle between the a axes is contracted, and the c axis is tipped in the direction of the axis [110]. The amount of these distortions varies with the temperature. Approximate positions of the a~.oms in the low-temperature form are given.

Polymorphism in n-Alkylammonium Halides. A Wide Line Nuclear Magnetic Resonance Study of the Chlorides C11—C15

“…On the basis of this evidence it seems orobable tha: one of the thermal transitions involves a change from, at low temperature, a monoclinic or orthorhombic forin to a tetragonal structure at higher temperature. Such a transition has been observed for n-propylammonium chloride (9). The lowest temperature d.s.c.…”

“…The reported X-ray structural studies are limited almost entirely to room temperature measurements of the (001) long spacings (4)(5)(6)(7)(8), and only n-propyl-and npentylamnioniu~i~ chlorides (9,10) and t1-dodecylamrnoni~~m bromide (7) appear to have been s t~~d i e d in any greater detail. In general the chlorides are tetragonal up to a chain length of about 10 carbon atoms and either monoclinic (C,,,C,,,C,,,C,, ) or orthorhombic (C, ,,C,,) thcreafter.…”

Microstructural and Dynamical Heterogeneities in Ionic Liquids

“…For EAC polymorphs, the thermal expansion is small and anisotropic, which is attributed to EAC’s liquid organization characterized by an anisotropic framework consisting of apolar and polar domains, whereas an isotropic thermal expansion was observed for PAC attributing to striking intermolecular interactions between nitrogen atoms in PA cations and Cl anions. In addition, microscopic isostructurality was reported for other PA halides (Br and I) at room temperature …”

“…The temperature dependence of ethylammonium chloride (EAC) and propylammonium chloride (PAC) crystal structures was investigated by in situ X-ray powder diffraction spectroscopy. − A polymorphic transition, with a reconstructive character, was observed for PAC from a monoclinic phase formed at low temperatures to a tetragonal phase formed at high temperatures. For EAC polymorphs, the thermal expansion is small and anisotropic, which is attributed to EAC’s liquid organization characterized by an anisotropic framework consisting of apolar and polar domains, whereas an isotropic thermal expansion was observed for PAC attributing to striking intermolecular interactions between nitrogen atoms in PA cations and Cl anions.…”

“…In addition, microscopic isostructurality was reported for other PA halides (Br and I) at room temperature. 200 In contrast to alkylammonium ILs, imidazolium ILs show different crystal structures depending on anion structures and cation alkyl chain lengths. [C 2 MIM] ILs were extensively studied because they exhibit low melting points and high ion conductivities.…”