RI 2025 Nitrogen Compounds

-1- Raffles Institution Year 6 H2 Chemistry 2025 Lecture Notes 20 Nitrogen Compounds – Amines, Amides, Amino Acids & Proteins Content Amines (exemplified by ethylamine and phenylamine) (i) their formation (ii) salt formation (iii) other reactions of phenylamine Amides (exemplified by ethanamide) (i) formation from acyl chlorides (ii) neutrality of amides (ii) hydrolysis (under acidic and basic conditions) Amino acids (exemplified by aminoethanoic acid) (i) their acid and base properties (ii) zwitterion formation Proteins (i) formation of proteins (ii) hydrolysis of proteins Condensation Polymers (i) polyamides and polyesters Learning outcomes Candidates should be able to: (a) describe the formation of amines as exemplified by ethylamine (through amide and nitrile reduction) and by phenylamine (through the reduction of nitrobenzene) (b) describe the reaction of amines in the formation of salts (c) describe and explain the basicity of primary, secondary and tertiary amines in the gaseous phase (interpret as Lewis bases) (d) explain the relative basicities of ammonia, ethylamine and phenylamine, in aqueous medium, in terms of their structures (e) describe the reaction of phenylamine with aqueous bromine (f) describe the formation of amides from the condensation reaction between RNH2 and R'COCl (g) explain why an amide is neutral in terms of delocalisation of the lone pair of electrons on nitrogen (h) describe the chemistry of amides, exemplified by the following reactions: (i) hydrolysis on treatment with aqueous alkali or acid (ii) reduction to amines with lithium aluminium hydride (i) describe the acid/base properties of amino acids and the formation of zwitterions [knowledge of isoelectric points is not required] (j) describe the formation of peptide (amide) bonds between -amino acids, and hence explain protein formation (k) describe the hydrolysis of proteins

-2- Amines RNH2 1 – Introduction 1.1 What are amines?  Amines are derivatives of ammonia in which one or more hydrogen atoms of the ammonia molecule have been substituted by alkyl or aryl groups.  Amines are classified as primary, secondary or tertiary amines depending on the number of alkyl or aryl groups attached to the nitrogen atom. Type of amine Ammonia (not amine) Primary (1°) Secondary (2°) Tertiary (3°) Structure Number of R groups attached to N 0 1 2 3 1.2 Nomenclature  In the common names of amines, the names of the alkyl/aryl groups bonded to nitrogen are given first, followed by the suffix -amine. primary (1o) amine secondary (2o) amine tertiary (3 o) amine Aliphatic amines CH3–NH2 methylamine CH3CH2–NH2 ethylamine CH3CH2CH2–NH2 propylamine N-methylethylamine (ethylmethylamine) N,N-dimethylethylamine (ethyldimethylamine) H2N–CH2CH2–NH2 ethane-1,2-diamine (phenylmethyl)amine N H diethylamine N N-methyldiethylamine (diethylmethylamine) Aromatic amines 