Everything from the 4 lessons of this topic on a few pages: the key idea of each lesson, the diagram to remember, the points to learn and the traps examiners set. Read it, cover it, test yourself.
An amine is ammonia with one or more H atoms replaced by alkyl or aryl groups: a primary amine is RNH2, a secondary amine is R2NH. Primary alkyl amines are made by heating a halogenoalkane with excess ammonia in ethanol in a sealed tube, by reducing an amide with LiAlH4 or by reducing a nitrile with LiAlH4 or H2/Ni. Because the amine product is itself a nucleophile, it can react with more halogenoalkane to give a secondary amine. The lone pair on nitrogen accepts H+, so amines are bases: ethylamine is stronger than ammonia because the electron-donating alkyl group makes the lone pair more available, while phenylamine is much weaker because its lone pair is delocalised into the benzene ring.
Basicity is about how available the lone pair on N is to accept H+, not about how many H atoms there are. Alkyl groups push electron density onto N (stronger base); a benzene ring pulls the lone pair into its delocalised system (weaker base). In the halogenoalkane route, forgetting the excess ammonia means a mixture of primary, secondary and tertiary amines and quaternary salts.
Phenylamine, C6H5NH2, is made by reducing nitrobenzene with tin and concentrated HCl, heated under reflux, then adding NaOH to release the free amine from its salt. Its N lone pair is partly delocalised into the ring, which makes it a weak base but activates the ring: with aqueous bromine at room temperature it gives a white precipitate of 2,4,6-tribromophenylamine. With nitrous acid (NaNO2 + HCl) below 10 °C it forms benzenediazonium chloride, which couples with phenol in alkaline solution to give an azo dye containing –N=N–. The azo link joins two benzene rings into one extended delocalised system, which absorbs visible light, so azo compounds are used as dyes and indicators.
The reducing agent for nitrobenzene is tin and concentrated HCl, followed by NaOH; do not write NaBH4 or LiAlH4. Diazotisation must be kept below 10 °C (but not frozen), otherwise phenol and N2 form. Coupling with phenol needs alkaline conditions. Phenylamine with bromine water needs no catalyst and gives three Br atoms on the ring.
An amide contains the –CONH– group. Amides are made by reacting an acyl chloride with ammonia (giving RCONH2) or with a primary amine (giving an N-substituted amide, RCONHR′); the reaction is fast at room temperature and gives steamy HCl, which reacts with more base. Amides are hydrolysed by heating under reflux: with aqueous acid the products are the carboxylic acid and an ammonium salt, with aqueous alkali they are the carboxylate salt and ammonia or the amine. Amides are much weaker bases than amines, effectively neutral, because the N lone pair is delocalised over the C=O group. LiAlH4 reduces an amide to an amine.
Learn the hydrolysis products by condition: acid gives the free carboxylic acid and the nitrogen as an ammonium ion; alkali gives the carboxylate salt and the free ammonia or amine. Amides are not basic like amines: their N lone pair is delocalised onto the C=O. Reduction needs LiAlH4; NaBH4 does not reduce amides.
An α-amino acid has the general formula RCH(NH2)COOH. In the solid and in neutral solution the COOH group donates H+ to the NH2 group, forming a zwitterion, H3N+CH(R)COO−: the strong ionic attractions between zwitterions give amino acids high melting points and solubility in water. The pH at which the amino acid has no overall charge is its isoelectric point. In acid the COO− is protonated, giving the positive ion H3N+CH(R)COOH; in alkali the NH3+ loses H+, giving the negative ion H2NCH(R)COO−. Amino acids join by condensation, losing water, to form peptide (amide) bonds, –CONH–; peptides are hydrolysed back to amino acids by heating with acid or alkali. In electrophoresis, ions move in an electric field at a set pH: the direction depends on the sign of the charge, and the speed on the size of the charge and of the ion.
In acid, an amino acid is positive (NH3+, COOH) and moves to the cathode; in alkali it is negative (NH2, COO−) and moves to the anode. The peptide bond is an amide link made by condensation, not addition. Two different amino acids give two dipeptides, not one, because the order matters.