[oCh3m_nub]

A bottle contained an unknown which may be an amine, a carboxylic acid, an ester or an aldehyde. Describe how will identify the content of the bottle. Say exactly what you will do and what you will see.

Here is my answers so far.

To identify the unknown contents of the bottle. I can conduct a solubility test. Most organic compounds are not soluble in water, except for low molecular-weight amines and oxygen-containing compounds. Low molecular-weight compounds are generally limited to those with fewer than five carbon atoms.

Testing for:
Carboxylic acid with fewer that five carbon atoms are soluble in water and form solutions that given and acidic response (pH<7) when tested with litmus paper. When test with red litmus paper will turn blue?

Amine with fewer that five carbons are also soluble in water and their solutions give a basic response (pH>7) when tested with litmus paper. When test with red litmus paper will turn blue?

Aldehyde with fewer that five carbon atoms are soluble in water and form neutral solution (pH=7)...

Ester can not be tested for pH balance or physical change. Perhaps I can test it for its odor... a synthesizing ester?

[horsebox]

Is there a limit to what chemicals you can use? If not the silver mirror test can tell you which one the aldehyde is. The only acid there is the carboxylic acid and the only base is the amine so your approaches for those work. As for the ester you could do an acid base titration using something that will hydrolyse the ester back into a carboxylic acid. For example adding NaOH will raise the pH of everything accept the ester because NaOH will hydrolyse the ester into a carboxylic acid so the acid will lower the pH. There is probably a way easier way to identify esters than that though.

[Cherriyan]

If the unknown substance in the bottle has fruity and pleasant odour, then it's an ester. Litmus test can be done to check for the carboxylic acid. Fehling's and Tollen's test can be done to figure out if the unknown substance is an aldehyde or not! If all the above tests are negative, then the substance will be amine.