Browsing by Author "Rochester, C. H."

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Infra-Red Study of the Reactions of Silicon, Titanium and Tin Tetrachlorides with Rutile
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (1), 1972) Pareitt, G. D.; Ramsbotham, J.; Rochester, C. H.
Hydroxy! groups on rutile react with silicon tetrachloride to form hydrogen chloride and TiOSi bonds. Nucleophilic attack of the silicon atom by oxide ions in the surface also occurs, and causes the displacement of chlorine atoms which adsorb on titanium ion sites. Unreaclcd chlorine atoms in the chemisorbed species are hydrolyzed by water to SiOH groups. The hydrogen chloride formed adsorbs on remaining exposed rutile surface. In the presence of adsorbed ammonia or pyridine the modified surface, after desorption of hydrogen chloride, exhibits Bronsted acidity which is enhanced by the addition of water. Bronsted acidity was also observed for a rutile surface treated with tin tetrachloride, hydrolyzed, and evacuated at 400 C to remove hydrogen chloride. The similar reactions of silica and rutile surfaces with titanium tetrachloride followed by hydrolysis and evacuation at 400 C conferred Bronsted acidity on silica but not on rutile. The modified silica surface also contained Lewis acid sites.
Polymerization of Ethylene on Chromium Oxide Catalysts: Part 4.—Infra-red Study of the Adsorption of Nitric Oxide and Ammonia on Active Catalyst
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (3), 1973) Eley, D. D.; Rochester, C. H.; Scurrell, M. S.
Nitric oxide adsorbs on reduced supported chromium(VI) oxide catalyst to give infra-red bands at 1740, ca. 1800, and ca. 1860 cm-1. The band at ca. 1800 cm1 has been assigned to nitric oxide molecules coordinatively chemisorbed on Cr4i ions in the surface. The band at 1740 cm-1 is considered to result from a combination of separate bands at 1743 and 1738 cm-1 due to nitric oxide covalently bound to Cr3+ and Cr5+ sites respectively. The band at ca. 1860 cm 1 is similarly assigned to nitric oxide chemisorbed on two types of site. The adsorption of ammonia gave infra-red bands due to coordinatively bound ammonia at 3400 and 3300 cm-1 which were insensitive to the extent of reduction of the catalyst. Correlations between the intensities of the bands due to adsorbed nitric oxide and the activities of catalyst samples for the polymerization of ethylene support the conclusion that Cr5i ions are the active sites in the polymerization process. The polymerization reaction was poisoned by the pre-adsorption of nitric oxide or ammonia.
Thermodynamics of Autoionization of Methanol+Water Mixtures
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (3), 1972) Parsons, G. H.; Rochester, C. H.
The enthalpies of ionization of methanol + water mixtures have been measured calorimetrically and arc used to calculate the entropies of autoionization. The enthalpies arc analyzed in terms of the separate contributions made by transfer of methanol, water, the proton, hydroxide ions and methoxide ions from water to the mixed solvents. Comparison of the relative acidities of water and methanol in the gas phase and in water shows that in water hydroxide ions are more strongly solvated than methoxide ions.