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J Phys Chem A. 2009 Mar 5;113(9):1858-63. doi: 10.1021/jp809290j.

Theoretical study of the neutral hydrolysis of hydrogen isocyanate in aqueous solution via assisted-concerted mechanisms.

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1
Departamento de Quísica, Universidad de Extremadura, 06071 Badajoz. Spain. santi@unex.es

Abstract

A procedure is described for the theoretical study of chemical reactions in solution by means of molecular dynamics simulation, with solute-solvent interaction potentials derived from ab initio quantum calculations. We apply the procedure to the case of neutral hydrogen isocyanate hydrolysis, HNCO + 2 H(2)O --> H(2)NCOOH + H(2)O, in aqueous solution, via the assisted-concerted mechanisms and the two-water model. We used the solvent as a reaction coordinate and the free-energy curves for the calculation of the properties related to the reaction mechanisms, with a particular focus on the reaction and activation energies. The results showed that the mechanism with two water molecules attacking the C=N bond is preferred to the mechanism with three waters forming a ring of eight members. In addition, the aqueous medium significantly reduces the activation barrier (DeltaG(double dagger) = 13.9 kcal/mol) and makes the process more exothermic (DeltaG = -11.1 kcal/mol) relative to the gas-phase reaction, increasing the rate constant of the process to k = 4.25 x 10(5) s(-1).

PMID:
19209882
DOI:
10.1021/jp809290j
[Indexed for MEDLINE]
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