The gas-phase alcoholysis of protonated homoleptic alkoxysilanes


Autoria(s): RAINONE, Raquel; MALASPINA, Thaciana; XAVIER, Luciano A.; RIVEROS, Jose M.
Contribuinte(s)

UNIVERSIDADE DE SÃO PAULO

Data(s)

20/10/2012

20/10/2012

2010

Resumo

Tetra-alkoxysilanes are common and useful reagents in sol-gel processes and understanding their reactivity is important in the design of new materials. The mechanism of gas-phase reactions that mimic alcoholyis of Si(OMe)(4) (usually known as TMOS) under acidic conditions have been studied by Fourier transform ion cyclotron resonance techniques and density functional calculations at the B3LYP/6-311+G(d,p) level. The proton affinity of TMOS has been estimated at 836.4 kJ mol(-1) and protonation of TMOS gives rise to an ionic species that is best represented as trimethoxysilyl cations associated with a methanol molecule. Protonated TMOS undergoes rapid and sequential substitution of the methoxy groups in the gas-phase upon reaction with alcohols. The calculated energy profile of the reaction indicates that the substitution reaction through an S(N)2 type mechanism may be more favorable than frontal attack at silicon. Furthermore, the sequential substitution reactions are promoted by a mechanism that involves proton shuttle from the most favorable protonation site to the oxygen of the departing group mediated by the neutral reagent molecule.

Identificador

EUROPEAN JOURNAL OF MASS SPECTROMETRY, v.16, n.3, Special Issue, p.379-388, 2010

1469-0667

http://producao.usp.br/handle/BDPI/31490

10.1255/ejms.1077

http://dx.doi.org/10.1255/ejms.1077

Idioma(s)

eng

Publicador

IM PUBLICATIONS

Relação

European Journal of Mass Spectrometry

Direitos

closedAccess

Copyright IM PUBLICATIONS

Palavras-Chave #tetra-alkoxysilanes #proton affinity #ion/molecule reactions #catalyzed proton-shuttle #SOL-GEL KINETICS #MASS-SPECTROMETRY #METAL-ALKOXIDES #ELECTROSPRAY-IONIZATION #NUCLEOPHILIC REACTIONS #TRANSPORT CATALYSIS #SILICON ALKOXIDES #HYDROLYSIS #CONDENSATION #POLYCONDENSATION #Physics, Atomic, Molecular & Chemical #Spectroscopy
Tipo

article

proceedings paper

publishedVersion