Photochemical behaviour of crotonaldehyde

The photochemical polymerization of crotonaldehyde is slow as compared to that of acrolein . The quantum yield was estimated to be 0.02 at 3660 A. 

The main reaction products are CO, CjHg, CH4 and trace amounts of H2 were also formed. McDowell and Sifniades identified some 1,5-hexadiene and 3-butene-l-al around 30 °C in the wavelength region 2450-4000 A. The latter has recently been confirmed , and a quantum yield, ch2=chch2Cho = 0-1 was determined at 3130 A and 48 °C. The products of the mercury-sensitized reaction are CO, CjHg and a compound of mass number 40, as well as some C2H2 (ref. 83). 

The occurrence of free radicals in the photolysis at 2537 A was proved by the Paneth technique. A radical of mass number 41, assumed to be either the allyl-radical or the isomer propenyl radical, was detected in the mercury-sensitized reaction. By adding methyl radicals to the system, the crotonyl radical could also be identified. 

The following primary processes have been suggested 

CH3CH-CH-I-CHO CH3CH-CH2-I-CO CH2=CHCH2CH0 CH3+CH-CHCHO CH3CH-CHCO + H 

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