Describe two different test tube reactions to identify the following organic compounds: propanal and benzoic acid.
There are several different answers one could make and an exam question would just require one for each.
1) Propanal - from the ending "al" this is an aldehyde.
- Add Tollens' reagent. Positive result: Silver mirror formed.
- Add Fehling's / Benedict Solution. Positive result: Red precipitate formed.
- Acidified potassium dichromate. Positive result: Orange to green (due to oxidation).
2) Benzoic acid - You probably have not come across this in the lab at school. Nevertheless from the name you can work out that it is a carboxylic acid.
- Add Sodium carbonate/ Sodium hydrogen carbonate. Positive result: Effervescence is observed.
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