Mechanism of Organic Reactions and Stereochemistry

Aromatic character of arenes, Huckel’s rule,  cyclic carbocations/carbanions and heterocyclic compounds,annulenes & kekulene as examples, elementary idea of aromatic,antiaromatic and homoaromatic compounds. Pseudoasymmetry. Electrophilic aromatic substitution: halogenation, nitration, sulphonation and Friedel-Craft’s alkylation/acylation with their mechanisms. Directing effects of the groups.

Electrophilic aromatic substitution: Mechanisms, orientation , directive influence and reactivity. Reactions: nitration, nitrosation, sulfonation, halogenation, Friedel-Crafts reactions, one carbon electrophiles (reactions: chloromethylation, Gatterman-Koch, Gatterman, Hoesch, Vilsmeier-Haack reaction, Reimer-Tiemann, Kolbe-Schmidt)

Aryl halides: Preparation, including preparation from diazonium salts. nucleophilic aromatic substitution; Benzyne mechanism, relative reactivity of alkyl, allyl/benzyl, vinyl and aryl halides towards nucleophilic substitution reactions.

Fischer Projection, Newmann and Sawhorse Projection formulae and their interconversions;

Geometrical isomerism: cis–trans and, syn-anti isomerism E/Z notations with C.I.P rules. Optical Isomerism: Symmetry elements & optical activity, specific rotation, chirality/asymmetry, enantiomers, molecules with two or more chiral-centres, Distereoisomers, meso structures, racemic mixture and resolution , relative and absolute configuration: D/L and R/S designations,prochirality,ligand & facial selectivity.

Sustitution at sp³ centre - Mechanism: SN¹, SN² ,SNⁱ mechanisms with stereochemical aspects, effect of solvent, substrate structure, leaving group, nucleophiles including ambident nucleophiles (cyanide & nitrite) substitution involving NGP, classical & non-classical carbocations, relative rates & stereochemical features [systems: alkyl halides, allyl halides, alcohols, ethers, epoxides].

[Self study: General preparation and reactions of alkyl halides]