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

Publication date: Available online 20 March 2018 Source:Computational and Theoretical Chemistry Author(s): Arezu Nouri, Ehsan Zahedi, Morteza Ehsani, Azita Nouri, Ebrahim Balali 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† TS FC†FC†C-0 by the following chemical events: (a) change of topological signature of N2–N3 bond; (b) increasing the number of non-bonding monosynaptic attractor on N1 atom; (c) breaking of N1–N2 bond and extrusion of nitrogen molecule; (d) decreasing the number of non-bonding monosynaptic attractors on N1 atom; (e) breaking of C4–C5 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 N1–C5 bond; and (h) formation of N1–C4 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 asynchrono...

Source: Computational and Theoretical Chemistry - March 21, 2018 Category: Chemistry Source Type: research