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NMR Spectroscopic Study of the Aldoxane Formation in Aqueous Acetaldehyde Solutions
Crotonaldehyde
is an interesting intermediate in the chemical industry.
It is usually produced from aqueous acetaldehyde in a two step process
in which the first step is carried out under basic and the second
step under acidic conditions. It is commonly assumed that acetaldehyde
is converted in the first step to acetaldol and that acetaldol is
subsequently dehydrated in the second step to crotonaldehyde. We demonstrate
by <sup>1</sup>H and <sup>13</sup>C NMR spectroscopic studies that
acetaldol is hardly present in the reacting solutions at lower temperatures
and that the key intermediate is aldoxane (2,6-dimethyl-1,3-dioxane-4-ol).
For the first time, data on the chemical equilibrium of the aldoxane
formation in aqueous acetaldehyde solutions is provided. Furthermore,
preliminary information on the kinetics of that reaction is presented