Silicon-29 NMR studies of aqueous silicate solutions. 2. Transverse /sup 29/Si relaxation and the kinetics and mechanism of silicate polymerization

Journal Article · Wed Nov 16 04:00:00 EST 1988 · Inorg. Chem.; (United States)

DOI:https://doi.org/10.1021/ic00296a035· OSTI ID:5761884

Kinrade, S D; Swaddle, T W

For solutions of SiO/sub 2/ in aqueous MOH (M = Na, K, Rb) with M/sup +/:Si/sup IV/ = 1:1 (in which each Si carries one O/sup /minus// group), the temperature-dependent /sup 29/Si line broadening is almost entirely due to Si-Si chemical exchange, if contaminants are absent, and is uniform for most resonances. This implies involvement of a common vehicle of intermolecular Si exchange (polymerization)-evidently the neutral form of the monomer, Si(OH)/sub 4/. The temperature dependence of the inverse spin-site lifetime /tau//sup /minus/1/ is given by /Delta/H* = 50 kJ mol/sup /minus/1/ and /Delta/S* = /minus/69 J K/sup /minus/1/ mol/sup /minus/1/. Intramolecular cyclization processes are faster than intermolecular polymerization and results in greater line broadening for a few minor peaks. For solutions with M/sup +/:Si/sup IV/ > 1:1 (high pH), silicate species that have more than one O/sup /minus// per Si and that are relatively unreactive in Si-Si exchange form to varying degrees, leading to reduced and nonuniform temperature-dependent line broadening. When this is taken into account, Si-Si chemical exchange is seen to explain both /sup 29/Si line broadening and the results of selective inversion-recovery experiments. 26 refs., 10 figs., 2 tabs.

• Research Organization: Univ. of Calgary, Alberta (Canada)
• OSTI ID: 5761884
• Journal Information: Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 27:23; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
ALKALI METAL COMPOUNDS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
INFORMATION
ISOTOPES
KINETICS
LIGHT NUCLEI
MOLECULAR STRUCTURE
NMR SPECTRA
NUCLEI
NUMERICAL DATA
OXYGEN COMPOUNDS
POLYMERIZATION
POTASSIUM COMPOUNDS
REACTION KINETICS
RUBIDIUM COMPOUNDS
SILICATES
SILICON 29
SILICON COMPOUNDS
SILICON ISOTOPES
SODIUM COMPOUNDS
SPECTRA
STABLE ISOTOPES