A Combined Theoretical and Experimental Study of Solid Octyl and Decylammonium Chlorides and of Their Aqueous Solutions

Abstract

The analysis of the thermal behavior of octyl- (OAC) and decylammonium chloride (DAC) has provided relevant new information. OAC shows a polymorphic phase transition that starts at 308 K and is completed at 313 K, between a monoclinic and a tetragonal structure, which belongs to a space group different from what was observed for other alkylammonium chlorides. At the melting temperature (463 K), the growing of a strong first sharp diffraction peak (FSDP) occurring at a d-spacing of ca. 21.0 Å was observed. DAC is characterized by two phase transitions at 318 (T(d1)) and 323 K (T(d2)). At T(d1), the LT polymorph coexists with a new-formed phase. At T(d2) the LT polymorph is replaced by a further polymorphic modification of DAC that becomes the only one at 328 K. This second phase transition signals the occurrence of a phase, closely related to the LT polymorph of HeAC, that crystallizes in the tetragonal crystal system a = ca. 5.00 Å and c = ca. 28.5 Å, P4/nmm space group. DAC melting starts at 458 K and is accompanied, as in the case of OAC, by the growing of a strong FSDP at a d-spacing of ca. 24.8 Å. A parallel DSC study confirmed the above-mentioned transitions. In addition, the structural properties of OAC/water and DAC/water mixtures were studied using an integrated approach, which combines X-ray diffraction and molecular dynamics (MD) techniques. A very good agreement between theoretical and experimental diffraction patterns has been obtained for both investigated mixtures. A thorough analysis of the MD trajectories shows that strong anion-water interactions are present in the mixtures, where Cl(-) forms a rather unstructured first hydration shell of water molecules bound to the anion in a linear Cl···H-O configuration. Moreover, cations and anions were found to interact with each other, and to form "solvent-shared ion pairs", in which one or more water molecules are shared between Cl(-) and the alkylammonium cation.

New Experimental Evidences Regarding Conformational Equilibrium in Ammonium−Bis(trifluoromethanesulfonyl)imide Ionic Liquids

“…Comprehensive derivation of all the Equations is described elsewhere. This methodology has been successfully applied to the study of molecular [30][31][32] and ionic liquids, [33][34][35][36][37][38] as well as solutions. This methodology has been successfully applied to the study of molecular [30][31][32] and ionic liquids, [33][34][35][36][37][38] as well as solutions.…”

“…[28,29] Summarizing, the analysis of both reciprocal space (QI(Q)M(Q)) and distance space (Diff(r)) functions is used to compare X-Ray experimental data and simulations. [38,40] [38,40] …”

“…[28,29] Summarizing, the analysis of both reciprocal space (QI(Q)M(Q)) and distance space (Diff(r)) functions is used to compare X-Ray experimental data and simulations. This methodology has been successfully applied to the study of molecular [30][31][32] and ionic liquids, [33][34][35][36][37][38] as well as solutions. [38,40]…”

“…This methodology has been successfully applied to the study of molecular [30][31][32] and ionic liquids, [33][34][35][36][37][38] as well as solutions. [38,40]…”

Assessing the Quality of Milk Using a Multicomponent Analytical Platform MicroNIR/Chemometric

“…Spectroscopic techniques are widely recognized as solvent-free, fast, and easy-to-use tools to perform the chemical investigation of different matrices without destroying samples (Oliveri et al, 2011 ; Materazzi et al, 2017a , b ; Véstia et al, 2019 ). In particular, NIR spectroscopy associated with chemometric analysis proved its high potential in multicomponent analyses, at low costs and without requiring the supervision of specialized personnel (Kurdziel et al, 2003 ; Migliorati et al, 2013 ; Kordi et al, 2017 ; Materazzi et al, 2017c ; Mees et al, 2018 ). NIR spectroscopy has been largely proposed for the investigation of milk with the aim of providing innovative and rapid methods for the detection of lactose, proteins, carotenoids, and fatty acid contents (Jankovskà and Šustovà, 2003 ; Numthuam et al, 2017 ; Risoluti et al, 2017 ; Wang et al, 2019 ; Soulat et al, 2020 ).…”