2350-76-7Relevant academic research and scientific papers
Solvent effects on methyl transfer reactions. 1. The Menshutkin Reaction
Castejon, Henry,Wiberg, Kenneth B.
, p. 2139 - 2146 (1999)
A full quantum mechanical description of the Menshutkin Reaction has been obtained for gas phase and solution by using density functional theory (DFT) and the self-consistent isodensity polarizable continuum model (SCI-PCM). Ammonia and pyridine are compared as nucleophiles, and methyl chloride and bromide are used as methyl transfer reagents. In the gas phase, all of the reactions proceed via an initial dipole complex, followed by a transition state leading to an ion pair. Methyl bromide shifts the position of the transition state to an earlier position than that found with methyl chloride. In the reaction with methyl chloride, replacing ammonia with pyridine stabilizes the transition state by 3 kcal/mol and stabilizes the ion pair by 17 kcal/mol. In the SCIPCM solvent effect calculations, the dipole complex disappears in both cyclohexane and DMSO. The transition state is shifted to an earlier stage of the reaction and is stabilized with respect to the gas phase. The ion pair product is strongly stabilized, and in DMSO it is calculated to dissociate into free ions. The reactions also were studied using Monte Carlo free energy perturbation. The results were in good agreement with the reaction field calculations. The rates of reaction between pyridine and methyl bromide were determined at 25°C in cyclohexane, di-n-butyl ether, and acetonitrile and compared with the computational results. Activation free energies calculated using the SCRF-SCIPCM model agree remarkably well with the experimental values.
Does alkyl chain length really matter? Structure-property relationships in thermochemistry of ionic liquids
Verevkin, Sergey P.,Zaitsau, Dzmitry H.,Emel'Yanenko, Vladimir N.,Ralys, Ricardas V.,Yermalayeu, Andrei V.,Schick, Christoph
, p. 84 - 95 (2013/07/28)
DSC was used for determination of reaction enthalpies of synthesis of ionic liquids [Cnmim][Cl]. A combination of DSC with quantum chemical calculations presents an indirect way to study thermodynamics of ionic liquids. The indirect procedure for vaporization enthalpy was validated with the direct experimental measurements by using thermogravimetry. First-principles calculations of the enthalpy of formation in the gaseous phase have been performed for the ionic species using the CBS-QB3 and G3 (MP2) theory. Experimental DSC data for homologous series of alkyl substituted imidazolium, pyridinium, and pyrrolidinium based ionic liquids with anions [Cl] and [Br] were collected from the literature. We have shown that enthalpies of formation, enthalpies of vaporization, and lattice potential energies are linearly dependant on the alkyl chain length. The thermochemical properties of ILs generally obey the group additivity rules and the values of the additivity parameters for enthalpies of formation and vaporization seem to be very close to those for molecular compounds.
