Posted by Kelsey on .
what two tests can I use to determine if a comound is an alcohol or a short or long chained carboxylic acid. I have two substances a colourless liquid and a white solid.
I would try an aqueous solution with litmus paper. Alcohols are neutral and carboxylic acids are acidic. Second test is to add NaHCO3. Carboxylic acids evolve CO2 gas.
Comparing the boiling points could also be an option.
Carboxylic acid has a larger boiling point than alcohol.
Short chained carboxylic acid tend to have a lower boiling point than long chained carboxylic acid (more number of carbons).
I am not sure if you are looking for physical or chemical tests. Also is the expected alcohol primary, secondary or tertiary?
From experience the appearance of simple carboxylic acids are glassy solids, whereas alcohols are waxy solids. The latter tend to 'set' rather than crystalise.
Solubility in an alkaline solution would also be useful. Dissolve a small amount of each in a solvent and extract with 0.1 M NaOH. Separate the phases. Add 0.1 M HCl until the aqueous phase is acid. If the aqueous phase goes cloudy, then the sample was the acid. The alcohol sample might result in a slight haze with the HCl, but the acid sample should go very cloudy.