Nitrilimine

Nitrilimines or nitrile amides are a class of organic compounds sharing a common functional group with the general structure Template:Chem2 corresponding to the conjugate base of an amine bonded to the N-terminus of a nitrile. The dominant structure for the parent compound nitrilimine is that of the propargyl-like Template:EquationNote in scheme 1 with a C–N triple bond and with a formal positive charge on nitrogen and two lone pairs and a formal negative charge on the terminal nitrogen. Other structures such as hypervalent Template:EquationNote, allene-like Template:EquationNote, allylic Template:EquationNote and carbene Template:EquationNote are of lesser relevance.

$H-\equiv N+-N--H$ Template:EquationRef

Template:Pad

$\mathrm{H}-\equiv \mathrm{N}=\mathrm{N}-\mathrm{H}$ Template:EquationRef

Template:Pad

$H-C-=N+=N-H$ Template:EquationRef

Template:Pad

$H-C+=N-N--H$ Template:EquationRef

Template:Pad

$\mathrm{H}-\mathrm{C}\text{:}-\mathrm{N}=\mathrm{N}-\mathrm{H}$ Template:EquationRef

Nitrilimines were first observed in the thermal decomposition of 2-tetrazoles releasing nitrogen:

One alternative synthesis technique is an elimination reaction of hydrazoyl halides.

Nitrilimines are linear 1,3-dipoles represented by structures Template:EquationNote and Template:EquationNote. A major use is in heterocyclic synthesis. E.g. with alkynes they generate pyrazoles in a 1,3-dipolar cycloaddition. Due to their high energy, they are usually generated in situ as a reactive intermediate.