Trimethyl phosphite adsorbed on silica: An NMR and infrared study
- Simon Fraser Univ., Burnaby, British Columbia (Canada)
- Univ. of Ottawa, Ontario (Canada)
Infrared spectroscopy and phosphorus-31 magic angle spinning nuclear magnetic resonance spectroscopy have been used to study the adsorption of trimethyl phosphite (TMP) on silica. At 23 C TMP reacts rapidly with surface silanol groups to give SiOCH{sub 3} as a chemisorbed product and liquid dimethyl phospite (DMP). However, formation of DMP ceases when about half of the SiOH groups have been consumed because DMP strongly hydrogen bonds to the remaining silanols thereby inhibiting further reaction between TMP and SiOH. TMP also undergoes isomerization to dimethyl methylphosphonate (DMMP) which is catalyzed by SiOH. As the number of initial silanol groups is decreased (by using higher temperatures of vacuum activation) the quantity of DMP produced decreases whereas that of DMMP increases. A mechanism for formation of DMP and DMMP has been suggested. At 100C isomerization does not occur, all SiOH groups are consumed, and the major product is DMP/SiOCH{sub 3} accompanied by a small quantity of a chemisorbed phosphorus-containing species having the proposed structure (SiO){sub 2}P-H({double bond}O). The latter is stable up to 400C. If TMP is heated with silica from 100 to 400C, in addition to SiOCH{sub 3}, the major new chemisorbed product of the reaction which can be identified by IR and NMR is (SiO){sub 2}P-Me({double bond}O) (Me = CH{sub 3}). The advantages of a combined IR-NMR approach is discussed.
- OSTI ID:
- 5234485
- Journal Information:
- Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:3; ISSN JPCHA; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ADSORPTION
CHALCOGENIDES
DATA
EXPERIMENTAL DATA
HYDROGEN COMPOUNDS
INFORMATION
INFRARED SPECTRA
INORGANIC ACIDS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MEDIUM TEMPERATURE
MINERALS
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHOSPHOROUS ACID
PHOSPHORUS 31
PHOSPHORUS ISOTOPES
RESONANCE
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SORPTIVE PROPERTIES
SPECTRA
STABLE ISOTOPES
SURFACE PROPERTIES