Alcohol and Aldehyde Watch

Fuenciado
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#1
Report Thread starter 4 years ago
#1
Which test should be used to distinguish between a primary alcohol and an aldehyde?
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Swtmess
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#2
Report 4 years ago
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Oxidation of primary alcohol will turn into aldehyde then into carboxylic acid where the oxidation of aldehyde will result in the formation of carboxylic acid only.
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Protoxylic
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You could use Tollen's or Fehling's solution, a positive result would confirm the presence of an aldehyde. However, in some cases these reagents can oxidise the alcohol and therefore give a false positive. In this case, you could perform an oxidation under distillation of both the aldehyde and alcohol. The distillation product can then be tested with the Tollen's or Fehling's. A positive result, red ppt with Fehlings, silver mirror/black ppt with Tollen's, confirms the presence of an aldehyde and therefore you can deduce that this product was the alcohol. A negative result would be the oxidation product of the aldehyde which would be the respective carboxylic acid and therefore was the original aldehyde.
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