Gas Phase UV Irradiation of 2-Pentanone

Introduction:
2-Pentanone is a ketone compound with the molecular formula C5H10O. It is also known as methyl propyl ketone. When 2-pentanone is exposed to gas phase UV irradiation, it undergoes a photochemical reaction to form different products.

Products:
The major product(s) produced by gas phase UV irradiation of 2-pentanone is (are) acetone and ethene. The reaction proceeds as follows:

2-pentanone + hv → acetone + ethene

Explanation:
The gas phase UV irradiation of 2-pentanone involves the breaking of carbon-carbon bonds and carbon-oxygen bonds in the molecule. The UV radiation provides the energy required to break these bonds and initiate the reaction.

The first step in the reaction is the abstraction of a hydrogen atom from the methyl group of 2-pentanone by a photon of UV radiation. This generates a methyl radical and a carbonyl oxide intermediate.

The carbonyl oxide intermediate then undergoes a ring opening reaction to form an acyl radical. This acyl radical can undergo further reactions to form different products depending on the reaction conditions.

Under gas phase UV irradiation, the acyl radical undergoes a β-scission reaction to form acetone and ethene. The β-scission reaction involves the breaking of a carbon-carbon bond adjacent to the carbonyl group in the acyl radical.

Conclusion:
In conclusion, gas phase UV irradiation of 2-pentanone results in the formation of acetone and ethene as the major products. This is due to the β-scission reaction of the acyl radical intermediate formed during the photochemical reaction.