Cyclobutanol alkanone

Closer examination of the cyclobutanol t/c ratios from homologous and isomeric n-alkanones in the same zeolites reveals some interesting trends (Table 12). The t/c ratios from all of the alkanones in the Na-X and Na-Y zeolites are as expected from reaction in a large or flexible reaction cavity which is very polar (like that provided by an alcohol solution). The t/c ratios in the ZSM zeolites indicate that selectivity depends upon the total ketone length and the position of the odd electron centers of the BR along the chain. Ratios of 60 or more are reported from 4-alkanones with 9 or more carbon atoms the t/c ratios from 4-octanone in ZSM-5 and ZSM-11, 15 and 18 respectively, mark 8 carbon atom chains as being critical to a c-BR occupying... 

A laser flash study of the photoreactions of hexan-2-one and 5-methylhexan-2-one has provided evidence for the existence of the triplet 1,4-biradicals produced by the y-hydrogen abstraction typical of Norrish Type II reactivity. The photochemical behaviour of the alkanone, nonan-5-one, in urea inclusion compounds has been studied. In solution, irradiation of nonan-5-one yields hexan-2-one, propylene, and two cyclobutanols. In the clathrate, the fragmentation products were essentially the same but only one cyclobutanol was observed. The cyclization fragmentation ratio was established as 0.67, compared with 0.32 in methanol. The authors suggest that the CIS-cyclobutanol has less stringent rotational requirements and that it is this isomer (43) which is formed in the clathrate. 

The photolysis processes of alkanone guest molecules in urea inclusion compounds have also been studied and have been shown to involve Norrish Type 11 reactions. For 5-nonanonelurea and 6-imdecanone/urea, the reactions show an almost complete diastereoselective preference for the Z-cyclobutanol product. 

The photodecomposition of alkanones included within urea complexes has been reported by Casal et al. Urea, when crystallized in the hexagonal lattice, possesses long channels of approximately 5 A diameter into which guest molecules are incorporated. For 5-nonanone the possible reactions which may occur are shown in Scheme 6.15. In solution photodecomposition occurs principally via the Norrish Type n reaction, leading to 2-hexanone, propylene, and two isomeric cyclobutanols. The crystalline hexagonal urea complex gave, on the other hand, essentially only one cyclobutanol isomer — the cis. The formation of the cis isomer requires less stringent rotational requirements and is, therefore, the preferred product in the constrained channel environment. 

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