We then discovered that this compound can be prepared at room temperature, where it is stable. Irradiation at> 320 nm in isopentane/methylcyclohexane (5: 1) gave the unknown together with products formed by attack on the solvent, whether the reaction was run at room temperature or 77 K. The contamination problem was not solved by working in the gas phase, for long-wavelength irradiation of 1 in a Pyrex bulb gave ketene 4 and its isomer ...