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Ethanal's systemic name is acetylaldehyde and has the molecular formula C2H4O. It is the second shortest chain member of the aldehyde family hence the -al suffix and naming requires no numbering as the C=O bond in aldehydes is only at the end of the chain.


Chemical and Physical Properties

Due to ethanals short chain length and strong polar C=O bond it forms permanent dipole-dipole forces and can form hydrogen bonds so therefore water soluble. Unlike methanal it is a clear liquid at room temperature with a boiling point of 20.2 degrees Celcius and is also highly flammable.


Ethanal is quite reactive due to the electronegativity difference in the C=O bond and is susceptible to nucleophillic attack particularly addition reactions into alcohols (with OH-) and hydroxynitriles (with CN-.) Both these nucleophiles attack the delta positive carbon molecule and break the double bond saturating the carbon.

Ethanal can be easily oxidized to ethanoic acid in the presence of an acidified dichromate.

Ethanal is reduced to ethanol in the presence of H- nucleophile usuall in sodium borohydride.

Ethanal will provide a positive result in both Fehlings test and Silver mirror tests.

Role in ethanol metabolism

In alcohol metabolism, NAD+ oxidises ethanol in hepatocytes to ethanal; catalysed by alcohol dehydrogenase. Ethanal is an intermediate in this pathway which is further oxidized by NAD+ to acetic acid. This second step of oxidation mainly occurs in the mitochondria though a small amount may be fully oxidized in hepatocytes.

This process occurs rapidly as ethanal is toxic to cells.

Personal efficiency in ethanol metabolism is dependant on polymorphic gene interaction and how regularly ethanol is consumed[1][2].


  1. Lister T, Renshaw J. AQA chemistry. Oxford: Oxford University Press; 2015.
  2. Chemistry of a Hangover — Alcohol and its Consequences Part 2: ChemViews Magazine: ChemistryViews [Internet]. 2017 [cited 4 December 2017]. Available from:
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