A concerted reaction in organic chemistry is a chemical reaction where all bond making and breaking occur simultaneously in a single step, without any intermediates. It's a characteristic feature of pericyclic reactions, involving the cyclic rearrangement of electrons in a concerted manner.
A high-energy state during a chemical reaction where reactants are transformed into products; for concerted reactions, this state involves simultaneous bond formations and breakings.
A theory describing the electronic structure of molecules by considering electrons in molecular orbitals that cover the entire molecule, crucial for understanding pericyclic reactions