Primary amines — common mistakes

When naming the product of a reaction between an amine and an acyl chloride, remember it is an N-substituted amide. The 'N-' indicates that the substituent is attached to the nitrogen atom. For example, the reaction of ethylamine with propanoyl chloride gives N-ethylpropanamide.

The product, a diazonium salt ($ArN_2^+$), is unstable. At temperatures above 10 °C, it decomposes rapidly to form a phenol, nitrogen gas, and HCl. Keeping the reaction mixture cold allows the diazonium salt to persist in solution long enough to be used in subsequent reactions, such as azo coupling.

No, this is a common point of confusion. An amine has a nitrogen atom bonded to at least one alkyl or aryl group (e.g., $R-NH_2$). An amide has a nitrogen atom bonded directly to a carbonyl group ($C=O$), with the general structure $R-CO-NR'_2$. Their chemical properties are very different; for example, amides are neutral, not basic.

Lithium tetrahydridoaluminate ($LiAlH_4$) is an extremely powerful reducing agent that reacts violently and exothermically with water and other protic solvents (like alcohols). Dry ether is used as an inert (unreactive) solvent to prevent this dangerous side reaction and ensure the $LiAlH_4$ is available to reduce the intended functional group.