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Azides

Azides can be obtained by nucleophilic substitution using sodium azide. This ion is a strong nucleophile but a weak base and therefore it easily leads to SN2 reactions, unless the reacting carbon is too crowded.

Substitution with sodium azide on 4-tert-butylcyclohexyl bromide, with inversion of configuration (SN2)
Opening of propylene oxide with NaN₃ at the less hindered carbon: 1-azido-2-propanol

If the azide attack is performed on an epoxide, the ring opening proceeds regioselectively by a quasi-SN2 mechanism at the less hindered position.

Click here to go to epoxide ring-opening reactions.

Reduction of an azide to a primary amine with LiAlH₄

Azides yield amines by reduction. Therefore, the combined reaction of azide substitution and reduction allows one to get amines very conveniently.

One can also get ACYL-azides by an addition-elimination mechanism from acyl chlorides:

Formation of an acyl azide from an acyl chloride and sodium azide

Click here to go to the addition-elimination mechanism.

ACYLAZIDES decompose by heating following the so-called Curtius rearrangement, a reaction closely related to the Hofmann rearrangement of amides:

Curtius rearrangement: the acyl azide loses N₂ on heating, a nitrene is formed and the R group migrates to nitrogen to give the isocyanate