Diazirine, absorption spectrum

The ultraviolet absorption spectrum has an intense band with a maximum below 200 mg and a finely structured long-wavelength band from about 280 to 330 mg (e 308.5 mg = 176 liter/mole cm.). The long wavelength band remains diffuse under high resolution. The shape of this band is unusual, but appears to be a common feature of all the diazirines so far reported (see later) and is reminiscent of the absorption spectrum of 2,3-diazabicyclo[2,2,l]-2-heptene, another molecule containing a strained nitrogen double bond. ... 

The photolysis of diazirine °° at 3130 A yields ethylene and nitrogen methylene is probably formed in the primary process. The long wavelength absorption ( max = 3200 A) had been identified as the allowed (a, n ) transition and semi-empirical Huckel calculations indicate that the methylene produced must be (Ai) or (Bi). There is evidence that methylene produced from the photolysis of diazirine is more selective than methylene from diazomethane, owing to decreased excess translational energy. At low pressures 5-30 torr, diazomethane was identified as an intermediate by its absorption spectrum and the question arises, is methylene formed directly, or does it arise from decomposition of diazomethane The quantum yield of disappearance of diazirine is 2.0+0.5 and the quantum yield of diazomethane formation is about 0.2. The intermediate diazomethane is... 

In contrast to the aliphatic diazo compounds, which are invariably colored, all the diazirines so far prepared are colorless. The UV absorption of diazirines corresponds approximately to that of the aliphatic azo compounds. Diazirine shows in methanol an absorption maximum at 321 mja. The IR spectrum of the diazirines shows a band at ca. 1580 cm". ... 

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