Unit 1: Aromaticity [9 h]Delocalised chemical bonding 1,3-butadiene, frontier orbitals. Criteria for aromaticity energy, structural and electronic criteria for aromaticity relationship among them. Aromatic, antiaromatic and homoaromatic compounds. Aromaticity in annulenes, polycyclic and nonbenzenoid compounds, charged rings – aromatic cations and anions. Heteroaromatic systems. Unit 2: Stereochemistry [9 h]Optical and geometrical isomerism Atropisomerism. Stereochemistry – symmetry and stereochemistry, chirality and symmetry, optical activity and chirality. Methods to determine configuration. Stereochemical descriptors, topicity relationships, molecules with more than one stereogenic centre. Asymmetric synthesis methods of resolution, optical purity. Stereoselectivity, stereospecificity and regioselectivity. Unit 3: Conformational Analysis and Linear Free Energy Relationship ?[12 h]Conformational analysis – acyclic and cyclic systems four, five and six-membered rings. Conformations of mono and di substituted of six membered rings. Conformational effects on the reactivity of acyclic and cyclic systems. Kinetically and thermodynamically favoured products. Chemoselectivity, regioselectivity, enantioselectivity, and stereoselectivity.Hammond postulate, Curtin-Hammett principle, microscopic reversibility. Baldwin rules. Isotope effects, substituent effects, linear free energy relationship (LFER), Hammet plots, steric and polar effects Taft parameters. Unit 4: Substitution Reactions [15 h]Aliphatic nucleophilic substitution – the SN1, SN2, borderline, SNi mechanisms and their stereochemistry. Factors affecting the rates of SN1, SN2 and SNi. Neighbouring group participation. Effect of substrate structure, nucleophile, leaving group and medium on reactivity. Ambident nucleophiles and substrates Substitution vs elimination reaction. Aromatic electrophilic and nucleophilic substitutions – mechanism factors influencing, ipso substitution and directive effect. Unit 5: Addition and Elimination Reactions [15 h]Hydrogenation of alkene – syn and anti-additions. Electrophilic addition to alkenes – Markovnikovs Rule HX, H2O, H2SO4, halogen, oxymercuration, hydroboration oxidation. Oxidation of alkenes to diols. Conjugate addition to alkenes. Nucleophilic addition-Nucleophilic addition reaction to carbonyl group – reactivity of aldehydes and ketones -molecular orbitals explanation. Addition of oxygen, nitrogen, sulfur and carbon based nucleophiles to carbonyls. Reactions with ylides. E1, E2, and E1cB reactions mechanisms factors influencing elimination – stereochemistry. Zaitsev and Hoffmann rule dehydrohalogenation, dehydration of alcohols, quaternary ammonium salts. Pyrolytic elimination.
