Irradiation of cyclononene (7b) and cycloundecene (7d) in pentane afforded cia-bicyclo [4.3. 0] nonane (lob) and cis-bicyclo [6.3. 0] undecane (loa), respectively. Small amounta of the Eragmentation produds 1-undecene (lad) and 1-undecyne (lM) were ale0 obtained from cycloundecene (7d). The photobehavior of the seriea of medium-and large-ring alkenes 7a- e is compared. Aside from E* 2 isomerization, the principal pathway in each case involves ...