Question

How do you convert the following?
Ethanal to Propanone

Answer 1

Hint- Before providing the steps involved in the conversion of ethanol to propanone we will see what is ethanal and propanone. As ethanal is a two carbon aldehyde and propanone is a three carbon ketone.

Complete step by step solution:
The steps include in the preparation are-
> The first step is to make carbon carbon bond which is done by reacting the ethanal with Grignard reagent. The aldehyde ethanal has two carbon atoms and we need three carbon atoms which are added by Grignard reagent. After this process an intermediate magnesium salt is formed which is subjected to hydrolysis to give isopropyl alcohol.
$C{H_3}CH = O + C{H_3} - MgBr\xrightarrow{{}}\begin{array}{*{20}{c}}
  {}&{OMgBr}&{} \\
  {C{H_3}}&{ - \begin{array}{*{20}{c}}
  | \\
  C \\
  |
\end{array} - }&H \\
  {}&{C{H_3}}&{}
\end{array}\xrightarrow[{}]{{}}\begin{array}{*{20}{c}}
  {}&{OH}&{} \\
  {C{H_3}}&{ - \begin{array}{*{20}{c}}
  | \\
  C \\
  |
\end{array} - }&H \\
  {}&{C{H_3}}&{}
\end{array}$

> The alcohol formed is oxidized with the help of oxidizing agent acidified ${K_2}{Cr_2}{O_7}$ and the final product obtained is propanone.
$\begin{array}{*{20}{c}}
  {}&{OH}&{} \\
  {C{H_3}}&{ - \begin{array}{*{20}{c}}
  | \\
  C \\
  |
\end{array} - }&H \\
  {}&{C{H_3}}&{}
\end{array}\xrightarrow{{\left[ O \right]}}\begin{array}{*{20}{c}}
  {{H_3}C}&{\begin{array}{*{20}{c}}
  {\begin{array}{*{20}{c}}
  O \\
  {||}
\end{array}} \\
  { - C - } \\
  {}
\end{array}}&{C{H_3}}
\end{array}$

Additional Information-
Aldehydes are organic compounds containing-CHO radical, in which a carbon atom forms a solid bond with an oxygen atom and is also bonded with a hydrogen atom and another group denoted by R, which may be a second hydrogen atom, an alkyl group, or an aryl group. Methane (formaldehyde), HCOH and ethanal (acetaldehyde) are the most common and simple examples. (Aldehyde names end up on the suffix al in the systematic chemical nomenclature). Formaldehyde is used as a chemical intermediate, as an embalming solvent, and as a disinfectant, to manufacture synthetic resins via the reaction of phenols, urea and melamine. The processing of acetic acid is primarily carried out with acetaldehyde.

Note- In preparation of propanone, the oxidizing agent can be used are \[N{a_2}C{r_2}O_7, \;KMn{O_4}, \;PCC\] and many more can be used. The propanone can also be prepared by oxidation of ethanol and then the product formed is carboxylic acid which is further reacted with calcium hydroxide which on decarboxylation gives propanone.