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The structural evolution pathways leading to the conversion of some α-chlorinated carboxylic acids (Cl n H 3-n CCOOH, n = 0, 1, 2, 3) to their respective acid chlorides by thionyl chloride are investigated via density functional theoretical (DFT) modelling. For all compounds where n = 0–3, acid chloride formation occurs via two competing pathways, consisting of three activation barriers in both cases, all of which are enthalpy-controlled and moderate (ΔGǂ < 190 kJ mol−1). Though both pathways are not limited by the same step, they are both composed of only cyclic activated complexes. Rapid intra-molecular small molecule transfer (HCl) allows one pathway to be slight more productive than the other. Whereas all acids evolve via both competing pathways, the evolution of formic acid occurs exclusively via that which involves intramolecular HCl transfer where all the constituent transition states are formed quasi-synchronously. Results for both pathways are summarized in a detail kinetic model which, of-course, is based on the thermodynamic profiles. [Display omitted] • Chlorination of α-chlorinated carboxylic acids proceed via two competing pathways of near equal probabilities. • Chlorination of carboxylic acids occurs fastest via two-step process. • The chlorination rates for carboxylic acids are controlled by a combination steric and electronic factors. • All activated complexes in the transformation if carboxylic acids to acids chlorides are cyclic. • The mechanistic steps for the conversion of carboxylic acids to acid chlorides are enthalpy controlled. [ABSTRACT FROM AUTHOR]

When dpktch was reacted with ZnCl2 in refluxing acetonitrile in air [ZnCl2(η3-dpktch)] was isolated in good yield. Infrared spectra suggest weaker binding of dpktch in [ZnCl2(η3-dpktch)] than in [CdCl2(η3-dpktch)]. 1H-NMR studies in non-aqueous media show that [ZnCl2(η3-dpktch)] is sensitive to changes in its environment and exchanges its amide proton. Electronic absorption spectral measurements confirmed the sensitivity of [ZnCl2(η3-dpktch)] to changes in its surroundings and show inter-conversion between two intra-ligand-charge-transfer transitions (ILCT) at 330 ± 2 nm and 404 ± 2 associated with [ZnCl2(η3-dpktch)] and its conjugate base. Thermo-optical measurements in non-aqueous dmf and dmso show facile inter-conversion between [ZnCl2(η3-dpktch)] and its conjugate base, respectively. Also, it is shown that protonation of dmf by [ZnCl2(η3-dpktch)] is exothermic (standard enthalpy of protonation ΔHθ = -40.7 ± 1.8 kJ mol-1), but endothermic for dmso (ΔHθ = +8.3 ± 1.5 kJ mol-1). Chemical stimuli in concentrations as low as 5.0 × 10-7 M can be detected and determined using [ZnCl2(η3-dpktch)] in non-aqueous media. X-ray crystallographic studies on a monoclinic, P21/n single crystal of [ZnCl2(η3-dpktch)] confirmed the N,N,O-coordination of dpktch and revealed interdigitated units of [ZnCl2(η3-dpktch)] connected via a web of hydrogen bonds. [ABSTRACT FROM AUTHOR]