Aromaticity and Stereochemistry

Pre requisite: Nomenclature of benzene derivatives (mono and disubstituted), physical properties.

Introduction to aromatic compounds: Benzene, structure and stability, M.O concept, resonance and resonance energy; aromaticity and Huckel’s (4n+2) rule, magnetic criteria.

Aromatic electrophilic substitution – general pattern of the mechanism, s and p complexes, energy profile diagram, activating and deactivating effects of substituents, orientation, o/p ratio, halogenation, nitration, sulphonation and desulphonation, friedel crafts alkylation and acylation; side chain halogenation of alkyl benzenes (toluene, ethyl benzene), Birch reduction.

Self Study: Hydrogenation of benzene derivatives, industrial use of aromatic hydrocarbons.

Geometrical isomerism: concept of restricted rotation – cis-trans, syn-anti and E,Z system of nomenclature, geometrical isomerism in oximes, amides and alicyclic compounds. Optical isomerism: elements of symmetry, concept of asymmetry and chirality,  enantiomers and diastereomers, racemic mixture and meso isomers; molecular chirality – allenes, relative and absolute configuration, nomenclature of optical isomers – D,L nomenclature, sequence rule and the R,S system of nomenclature, resolution of enantiomers; elementary concepts of asymmetric synthesis (concept of diastereomeric induction).Elementary concept of chiral induction through chemical reaction (reaction of bromine to alkane and alkenes).

Self Study: Physical properties of enantiomers and diastereomers, optical activity, polarized light, optical activity of enantiomers.

Nomenclature, method of preparation, chemical reactions, theory of strainless rings, cyclopropane and its reactivity with halogens.

Newman, Fischer, Sawhorse and Flying-wedge formula; conformation of ethane, n-butane and cyclohexane – axial and equitorial bonds, conformational analysis of monosubstituted and disubstituted cyclohexane (dimethyl cylcohexane), concepts of conformational locking; chair conformation of α and β glucose and their stability.