The application of zoelites as catalysts for a number of organic, liquid-phase, acid-promoted reactions is discussed with reference to zeolite acidity and structure on product yield and selectivity. The zeolites described are predominantly high silica materials including Nu-2, ZSM-5, Nu-10 and EU-1 structures. Examination of the Claisen rearrangement of allyl phenyl ether has shown that it is promoted by zeolites relative to the thermal reaction and that the extent of conversion increases with zeolite acidity. In addition to the expected products, 2-allylphenol and the cyclic 2-methyldihydrobenzofuran, small quantities of the <i>para</i>-product, 4-allylphenol are detected over H-Nu-2 and (Cu(II),H)-Y zeolites. 4-Allylphenol is not detected in the thermal rearrangement and its formation in the present work is attributed to an intermolecular mechanism <i>via</i> ether cleavage. Also examined is the Fries rearrangement of phenyl acetate and phenyl benzoate. The product selectivity is compared with that over Nafion-H, an acidic, non-porous, perfluorinated ion-exchange resin. Both rearrangements are more <i>para</i>-selective when performed in the presence of zeolites. In the rearrangement of phenyl acetate a number of by-products in addition to the expected 2- and 4-hydroxyacetophenones are observed. The aldol self-condensation of acetophenone to yield β-methylchalcone and of acetophenone and benzaldehyde to yield chalcone is promoted by H-Nu-2 zeolite. The ring closure of 2-benzoylbenzoic acid to anthraquinone takes place quantitatively over H-Nu-2. The cyclisation is monitored by i.r. to completion and the product isolated by extraction or sublimation. Of those zeolites examined, H-Nu-2 is likely to be most widely applicable as a catalyst in organic synthesis because of its relatively large pore dimensions, high silica content (thermal stability) and high acidity.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:653381 |
| Date | January 1990 |
| Creators | Kibby, Sarah A. M. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/10989 |
Page generated in 0.0017 seconds