Storing crotonaldehyde in refrigerator for few weeks produces traces of crotonic acid which poison the catalyst used for the reaction. I filtered through basic alumina but could not help. Aqueous treatment is not suitable for my further reaction.
You can use freshly distilled crotonaldehyde to get rid of crotonic acid
From DD Perrin:
Aldehyde has a bp of 104-105, easy to distile. The acid is a solid til 72 degrees
As mentioned above, fractional distillation is the method to use here, discard the first and last ~5%.
Crotonaldehyde is a fairly sensitive compound, you may want to look at your storage conditions as distilling a compound every time you need it becomes tiresome. Reagent bottles are pretty terrible for storing sensitive chemicals as the seals have limited lifetimes even if used correctly.
I would recommend freshly distilling the crotonaldehyde under nitrogen into a schlenk flask, then doing a freeze pump thaw process before filling it with argon. Seal the stopper with parafilm, wrap the flask in tin foil then put it in the fridge. Use flame dried glassware.
If it is large amount, wash with bicarbonate solution, dry on anh. sodium sulfate and then distill. For small amount, a careful fractional distillation is needed. In any case, keep the product under nitrogen blanket all the time.
By the way, in order to remove the respective carbonic acid and to recieve reliable and reproducible experimental results, e. g., in organic synthesis and in particular in catalyst development and screening experiments, prior to use a liquide aldehyde starting material should be - always - distilled in vacuo (in case of your aldehyde to avoid polymerization) using a Vigreux column. Solid aldehydes should be freshly recrystallized. These are routine purification procedures desribed, e . g., by Armarego and Perrin in the book "Purification of Laboratory Chemicals", Publisher: Butterworth and Heinemann, 2000.
Just go for bicarbonate washing before experiment to get rid of acid.
To remove traces of crotonic acid present in the crotonaldehyde give washing treatment with sodium bicarbonate to dissolve acid and then extract with ether & remove ether under vacuum to get pure crotonaldehyde