The N 2 gas is released to the atmosphere from diazo to carbene transformation (Scheme 1). Thus, if the activation energy barrier for breaking the carbon-nitrogen bond in a diazo compound is crossed, the reaction becomes irreversible. In other words, regardless of whether the reaction is thermodynamically exothermic or endothermic, it is governed by kinetics. The kinetics of a reaction can be affected by molecular engineering, either at the backbone or at the function group level. There is, however, one important point to remember: not all the reactions lead to stable carbene intermediates because of intramolecular rearrangements . Scheme1: The schematic representation of N 2 release from a diazo compound and generation of carbene.