Organic Compounds with Oxygen and Nitrogen Functional Groups
Organic Compounds with Oxygen and Nitrogen Functional Groups tests alcohols, phenols, ethers, aldehydes, ketones, carboxylic acids, amines, and diazonium salts, with emphasis on distinguishing tests and reaction products.
Core rules
- Alcohols are neutral and less acidic than water; phenols are more acidic because the phenoxide ion is resonance-stabilized.
- Aldehydes are oxidized by Tollens reagent to carboxylate and by Fehling's solution to Cu2O; ketones resist these mild oxidants.
- Carboxylic acids are stronger acids than phenols and alcohols; electron-withdrawing groups increase acidity.
- Amines are basic because of the lone pair on nitrogen; in water, solubility and solvation affect the observed base strength.
- Diazonium salts undergo coupling and substitution reactions, making them useful synthetic intermediates.
Worked example
Distinguish propanal from propanone using Tollens reagent. Propanal is an aldehyde: it reduces Ag+ in ammoniacal AgNO3 to metallic silver, giving a silver mirror, and is oxidized to propanoate. Propanone is a ketone and has no aldehydic hydrogen, so no silver mirror forms under the same mild conditions. Fehling's test also distinguishes aliphatic aldehydes from ketones.
Traps
Do not call phenol an alcohol; its acidity and reactions differ. Do not expect Fehling's solution to give a positive test with aromatic aldehydes such as benzaldehyde. Do not confuse Tollens with Fehling in product identity. Do not assume all amines are equally basic; substituent and solvent effects matter.