Phenyl azide

Phenylazide is an organic compound with the formula C₆H₅N₃. It is one of the prototypical organic azides. It has a pungent odor. The structure consists of a linear azide substituent bound to a phenyl group. The C-N=N angle is approximately 120°.

Preparation

Phenyl azide is prepared by the diazotization of phenylhydrazine with nitrous acid:

Aryl iodides bearing electron-withdrawing substituents undergo metathesis with sodium azide in the presence of Cu(I), sodium ascorbate, and N,N'-dimethylethane-1,2-diamine (DMEA):

Chemical reactions

C₆H₅N₃ is used to make heterocycles via cycloaddition to alkenes and especially alkynes, particularly those bearing electronegative substituents. It reacts with triphenylphosphine to give the Staudinger reagent C₆H₅NP(C₆H₅)₃. Thermolysis induces loss of N₂ to give the highly reactive phenylnitrene C₆H₅N.

Phenyl azide and its analogues undergo the azide alkyne Huisgen cycloaddition, a classic example of click chemistry. For example, phenyl azide and phenylacetylene give diphenyl triazole.

Postherpetic neuralgia

Postherpetic neuralgia is a nerve pain due to damage caused by the varicella zoster virus. Typically, the neuralgia is confined to a dermatomic area of the skin, and follows an outbreak of herpes zoster (commonly known as shingles) in that same dermatomic area. The neuralgia typically begins when the herpes zoster vesicles have crusted over and begun to heal, but can begin in the absence of herpes zoster—a condition called zoster sine herpete (see Herpes zoster).

Treatment options for postherpetic neuralgia include antidepressants, anticonvulsants (such as gabapentin, pregabalin, or topiramate), gabapentin enacarbil (a prodrug of gabapentin) and topical agents such as lidocaine patches or capsaicin lotion. Opioid analgesics may also be appropriate in many situations. There are some sporadically successful experimental treatments, such as rhizotomy (severing or damaging the affected nerve to relieve pain) and TENS (a type of electrical pulse therapy).

Signs and symptoms