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Castro EA, Arellano D, Pavez P, et al. Kinetic study of the phenolysis of O-methyl and O-phenyl O-2,4-dinitrophenyl thiocarbonates and O-ethyl 2,4-dinitrophenyl dithiocarbonate. J Org Chem. 2003;68(16):6192-6doi: 10.1021/jo034538+.
Castro, E. A., Arellano, D., Pavez, P., & Santos, J. G. (2003). Kinetic study of the phenolysis of O-methyl and O-phenyl O-2,4-dinitrophenyl thiocarbonates and O-ethyl 2,4-dinitrophenyl dithiocarbonate. The Journal of organic chemistry, 68(16), 6192-6. https://doi.org/10.1021/jo034538+
Castro, Enrique A, et al. "Kinetic study of the phenolysis of O-methyl and O-phenyl O-2,4-dinitrophenyl thiocarbonates and O-ethyl 2,4-dinitrophenyl dithiocarbonate." The Journal of organic chemistry vol. 68,16 (2003): 6192-6. doi: https://doi.org/10.1021/jo034538+
Castro EA, Arellano D, Pavez P, Santos JG. Kinetic study of the phenolysis of O-methyl and O-phenyl O-2,4-dinitrophenyl thiocarbonates and O-ethyl 2,4-dinitrophenyl dithiocarbonate. J Org Chem. 2003 Aug 08;68(16):6192-6. doi: 10.1021/jo034538+. PMID: 12895049.
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J Org Chem. 2003 Aug 08;68(16):6192-6. doi: 10.1021/jo034538+.

Kinetic study of the phenolysis of O-methyl and O-phenyl O-2,4-dinitrophenyl thiocarbonates and O-ethyl 2,4-dinitrophenyl dithiocarbonate.

The Journal of organic chemistry

Enrique A Castro, David Arellano, Paulina Pavez, José G Santos

Affiliations

  1. Facultad de Química, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile. [email protected]

PMID: 12895049 DOI: 10.1021/jo034538+

Abstract

The reactions of a series of phenols with O-methyl O-2,4-dinitrophenyl thiocarbonate (MDNPTOC), O-phenyl O-2,4-dinitrophenyl thiocarbonate (PDNPTOC), and O-ethyl 2,4-dinitrophenyl dithiocarbonate (EDNPDTC) are studied kinetically in water, at 25.0 degrees C and an ionic strength of 0.2 M (KCl). All reactions show pseudo-first-order kinetics under an excess of phenol over the substrate, and are first order in phenoxide anion. The reactions of EDNPDTC show a linear Brønsted-type plot of slope beta = 0.67, suggesting a concerted mechanism. On the other hand, the phenolyses of MDNPTOC and PDNPTOC exhibit linear Brønsted-type plots of slopes beta = 0.27 and 0.28, respectively, consistent with stepwise mechanisms where the formation of an anionic tetrahedral intermediate (T(-)) is rate determining. By comparison of the kinetics and mechanisms of the reactions under investigation with similar reactions, the following conclusions arise: (i). Substitution of S(-) by O(-) in the intermediate T(-) destabilizes this species. (ii). The change of DNPO in T(-) to DNPS also destabilizes this intermediate. (iii). Substitution of MeO by PhO as the nonleaving group of the substrate does not affect the kinetics, probably by a compensation of electronic and steric effects. (iv). The change of an amino group in a tetrahedral intermediate to a phenoxy group destabilizes the intermediate.

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