Trichloroacetaldehyde catalyst

The photocatalysis of TCE on the TiO2-coated optical microfibers in the presence of oxygen was further investigated by in situ C MAS NMR spectroscopy 191 ). The major products are phosgene and carbon dioxide, with small quantities of DCAA and trichloroacetaldehyde remaining on the catalyst at the end of the reaction. Solid-state NMR spectroscopy has also been applied successfully for the investigation of the photocatalytic degradation of dichloromethane (192,193). 

Furukawa et al. [274] and Natta cl al. [275,276] succeeded independently in the preparation of crystalline polyacetaldehyde by using some organometallic compounds, such as diethylzinc or triethylaluminium, for the low-temperature polymerisation of acetaldehyde. Metal alkyls and metal alkoxides, e.g. aluminium isopropoxide, zinc ethoxide or ethyl orthotitanate, have also polymerised other aldehydes such as propionaldehyde and trichloroacetaldehyde to give crystalline polymers (Table 9.3) [270,275,277], A highly crystalline isotactic polymer has been obtained from the polymerisation of w-butyraldehyde with triethylaluminium or titanium tetrachloride-triethylaluminium (1 3) catalysts. Combinations of metal alkyl, e.g. diethylzinc, with water [278] or amine [279] appeared to give very efficient catalysts for aldehyde polymerisations. 

Chloral (trichloroacetaldehyde) with no catalyst gives a 60% ASE at 30% weight gain (94). After 15 weeks at 70% relative humidity, however, all weight gain was lost as well as the ASE. This shows a very unstable, perhaps reversible, bond formation. 

Chlorination of Ethanol. Ethyl alcohol either absolute or containing water is chlorinated to form the hemiacetal of trichloroacetaldehyde from which chloral is liberated by treatment with concentrated sulfuric acid. Ferric chloride may be employed as a chlorination catalyst, but its use does not appear necessary. Five moles of hydrogen chloride is liberated for each mole of chloral produced, and the other by-products include ethyl chloride, ethylene dichloride, and ethyl ether. 

Chloral (trichloroacetaldehyde) cyclizes to metachloral in the presence of chlorosulfonic acid (0.5-5%) as catalyst at —20 to 50 °C. The cyclization was performed in an airtight polyethylene reactor the mixture solidified after 3 hours and the reaction was complete after 80 hours giving a yield of 97.9%, which was much better than that obtained by the conventional method using sulfuric acid. ... 

In recent years there has been a flurry of activity on enantioselective transformations involving the use of ketenes in combination with chiral amine catalysts. Any discussion in this area must begin with the work of Wynberg [123]. In pioneering studies, Wynberg demonstrated that quinidine (176) is an effective catalyst for the enantioselective cycloaddition of ketene (161) and trichloroacetaldehyde (175, Equation 14) [124]. This process furnished... 

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