Pyrolysed depth

A plethora of products is obtained when either elemol (273), in the presence of p-nitrobenzoic acid (or benzoic acid), or elemyl-p-nitrobenzoate is pyrolysed at about 200 °C. These include the elemenes (274)—(276) together with the selinenes (277)—(281). The sequence of formation and the factors affecting the thermolyses are discussed in depth, together with the data for the thermolysis of dihydro-geijerene (282). This latter compound has been synthesized from germacrone (227) by a Cope rearrangement to j3-elemenone (283) followed by a retro-aldoliza-tion to (284) and subsequent Wolff-Kishner reduction. 

Membranes were deposited by dip-coating on commercial Membralox supports (pore diameter 4 nm) and were dried and calcined in air at temperatures in the range 150-550°C for about 1 h. During this heat treatment the methyl ligands pyrolyse, creating a continuous network of micropores. The film thickness varies between 37.5 and 110 nm from one region to another, probably due to non-uniform thickness of the y-alumina support. EDS measurements indicate that silica penetrates the support to a depth of about 2 pm. 

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