Acetaldehyde reaction with oxygen atoms

In studying the reaction of oxygen atoms with CH3CHO by using the photochemical method, at a pressure of 100 mm. Hg and with sensitization by mercury, Cvetanovi664 came to another conclusion, namely, that the reaction of oxygen atoms with acetaldehyde yielded mainly hydroxyl and the CH3CO radical. The hydroxyl formed reacted with an acetaldehyde molecule to form water, and acetyl yields diacetyl. The main reaction products were found to be water and biacetyl. 

First experiments on oxygen atom reactions with hydrocarbons, with the zone of discharge in water vapor, as well as in O2, used as a source of 0 atoms, have shown that the reaction products are formaldehyde, acetaldehyde, acids, alcohols, peroxides, i.e., products of lower degrees of conversion than that yielding H20, CO, and C02. 

Thus, CH20 and CO are obtained in equal amounts. Other reactions of a lower probability are the formation of alcohol by reaction 0 + C2H6 - C2H6OH, possibly depending on pressure, and the formation of acetaldehyde 0 + C2H6 - C2H 0 + H2. It will be noted that the formation of alcohol was observed by Murad and Noyes63 in the course of oxygen atom reactions with ethane. 

Great attention was paid to oxygen atom reactions with acetaldehyde. It will be mentioned that the study of this reaction encountered greater difficulties. 

The reaction of O atoms with acetaldehyde shows that the three possible types of oxygen atom reactions are scission of the C-C bond, the reaction yielding H20, and incorporation of the 0 atom at the C-H bond. 

A more complicated reaction scheme is proposed by the authors to include the formation of the by-products acetonitrile, acetaldehyde and ethylene. However, appropriate rate coefficients cannot be given as the reactions appear to be partially homogeneous gas phase reactions, implying that factors like the reactor geometry are also involved. Regarding the oxidation mechanism, the authors assume that two hydrogen atoms are first abstracted from propene, followed by reaction with surface oxygen or NH species. 

In the reaction of acetaldehyde with dichlorine (Equation 4.16), hydrogen atoms are substituted for chlorine atoms to give mono-, di-, and trichloroacetaldehyde (chloral) chlorine does not displace the oxygen atoms. 

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