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A mechanistic investigation of ethylene oxide hydrolysis to ethanediol

Angelica Lundin ; Itai Panas (Institutionen för kemi- och bioteknik, Oorganisk miljökemi) ; Elisabet Ahlberg
JOURNAL OF PHYSICAL CHEMISTRY A (1089-5639 ). Vol. 111 (2007), 37, p. 9087-9092.
[Artikel, refereegranskad vetenskaplig]

The B3LYP/6-311 +G(d,p) description is employed to study the heterolytic ring opening mechanisms under microsolvation conditions for ethylene oxide in acidic, neutral, and alkaline environments. In acid and alkaline media, a concerted trans S(N)2 reaction is strongly favored as compared to the corresponding cis reaction. The importance of the nucleophile, water in acidic media and hydroxide ion in alkaline media, for lowering the activation enthalpy is emphasized and activation energies of similar to 80 and similar to 60 kJ mol(-1) are obtained under acid and alkaline conditions, respectively. Under neutral conditions, the trans SN2 mechanism becomes inaccessible because it invokes the formation of a transient HI and OH- pair across the 1,2-ethanediol molecule. Rather, epoxide ring opening is achieved by hydrolysis of a single water molecule. The latter mechanism displays significantly greater activation enthaply (205 kJ mol(-1)) than those in acid and alkaline environments. This is in agreement with experiment. Product distributions of simple olefins in neutral aqueous media, as well as the detrimental impact of acid/base conditions for the selectivity of epoxidation catalysts in aqueous media, are discussed.

Nyckelord: REACTIVE MOLECULES H2O; TITANIUM SILICALITE; HYDROGEN-PEROXIDE; FRAMEWORK TI(IV); TI-SILICALITE; EPOXIDATION; ZEOLITE; PROPYLENE; EPOXIDES; DENSITY



Denna post skapades 2007-10-22. Senast ändrad 2010-01-26.
CPL Pubid: 55848

 

Institutioner (Chalmers)

Institutionen för kemi (2001-2011)
Institutionen för kemi- och bioteknik, Oorganisk miljökemi (2005-2014)

Ämnesområden

Kvantkemi

Chalmers infrastruktur