Comparative study of the electron impact decomposition of 5,5,9-trimethyl-1-oxaspiro[4.5]decan-2-one and 5,5,9-trimethyl-1-oxabicyclo[4.4]decan-2-one

1.	The -lactone is more stable than the -lactone both relative to electron impact and upon chemical ionization.
2.	The major pathways for fragmentation upon electron impact for the -lactone are related to decomposition of the cyclohexane ring, while, in the case of -lactone, fragmentation of the oxygen-containing part of the molecule also occurs in addition to these processes.

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 969–971, April, 1989.