The synergetic use of bonding evolution theory (BET) and noncovalent interaction (NCI) analysis allows to obtain new insight into the bond breaking/forming processes and electron redistribution along the reaction path to understand the molecular mechanism of a reaction and recognize regions of strong and weak electron pairing. This viewpoint has been considered for cheletropic extrusion of CO from unsaturated cyclic ketones cyclohepta-3,5-dien-1-one CHD, cyclopent-3-en-1-one CPE, and bicyclo[2.2.1]hept-2-en-7-one BCH by using hybrid functional MPWB1K in conjugation with aug-cc-pVTZ basis set. Decarbonylation of CHD, CPE, and BCH are nonpolar cyclo-elimination reactions that are characterized by the sequence of turning points (TPs) as CHD, 1-11-C[CC]CHTCSUPTAG & CHTCSUPTAG & ZFFF(TS)CHTCSUPTAG &(CHTCCHTCTAG &)-C-TAG &-0:HT + CO; CPE, 1-8-CC[(CHTCCHTCFHTCTAG &)-C-TAG &-F-TAG &]-[FF][FF]F-TS[C dagger C dagger]-0:BD + CO; and BCH, 1-8-CC[(CHTCCHTCTAG &)-C-TAG &]F[FF]F-TS[(CHTCCHTCTAG &)-C-TAG &]-0:CD + CO. Breaking of C-C bond between the terminal carbon atoms of diene/triene framework and carbon atom of CO fragment starts at a distance of ca. 1.9-2.0 A in the vicinity of the transition structure where the transition states are not reached yet. NCI analysis explains that the noncovalent interactions between two fragments appeared after the breaking of C-C bonds.