Understanding the kinetics and molecular mechanism of the Curtius rearrangement of 3-oxocyclobutane-1-carbonyl azide

• Published in: Computational and theoretical chemistry Vol. 1130; pp. 121 - 129
• Main Authors: Nouri, Arezu, Zahedi, Ehsan, Ehsani, Morteza, Nouri, Azita, Balali, Ebrahim
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.04.2018
• Subjects: BET; Catastrophe theory; Curtius rearrangement; ELF; Molecular mechanism; BET; Curtius rearrangement; Catastrophe theory; Molecular mechanism; ELF
• ISSN: 2210-271X
• DOI: 10.1016/j.comptc.2018.03.019

[Display omitted] •Kinetics and molecular mechanism of thermal Curtius rearrangement of 3-oxocyclobutane-1-carbonyl azide have been studied.•The concerted pathway is 104–105 times faster than stepwise path.•The reaction via concerted pathway can be described with catastrophe sequence 9-CF†C†TSFC†FC†C-0.•Electron flow redistribution along the reaction is asynchronous. The approach presented here is an unprecedented insight into the understanding of kinetics and molecular mechanism of thermal Curtius rearrangement of 3-oxocyclobutane-1-carbonyl azide. Curtius rearrangement can proceed via concerted and stepwise mechanisms. The CBS-QB3 and CBS-APNO composite methods indicated that concerted pathway is dominant and 104–105 times faster than stepwise path. The bonding evolution theory analysis at the B3LYP/6-311G(d,p) revealed that the reaction via concerted pathway can be described with catastrophe sequence 9-CF†C†TSFC†FC†C-0 by the following chemical events: (a) change of topological signature of N2N3 bond; (b) increasing the number of non-bonding monosynaptic attractor on N1 atom; (c) breaking of N1N2 bond and extrusion of nitrogen molecule; (d) decreasing the number of non-bonding monosynaptic attractors on N1 atom; (e) breaking of C4C5 bond and formation of pseudoradical centers on the C4 and C5 atoms; (f) annihilation of pseudoradical center on the C5 atom; (g) change of topological signature of N1C5 bond; and (h) formation of N1C4 bond. Along the reaction course electron flow redistribution is asynchronous and bond breaking/forming do not takes place simultaneously demonstrating that the reaction is concerted yet highly asynchronous process.