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Mechanism of Organic Reactions
Course Objectives :
The course aims to provide students with an in-depth knowledge of different types of reaction mechanisms i.e. substitution, elimination and addition reactions of aliphatic and aromatic organic compounds.
Course Outcomes (COs):
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COURSE |
Learning outcomes (at course level) |
Learning and teaching strategies |
Assessment Strategies |
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Paper Code |
Paper Title |
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CHY 222 |
Mechanism of Organic Reactions |
The students will be able to- CO51-learn the mechanistic and stereochemical aspects of the substitution, elimination and addition reaction of aliphatic and aromatic organic compounds. CO52- account for the formation of specific products in an organic reaction CO53-differentiate kinetically and thermodynamically controlled reaction. CO54-demonstrate basic knowledge of frontier molecular orbital theory in organic reactions and of the HSAB principle. CO55-illustrate the mechanistic concepts to specific name reactions CO56-apply the basic principles involved in C-C and C-hetero multiple bond formation and be able to illustrate specific name reactions using these principles |
Interactive lectures
Discussion
Tutorials
Assignments
Power Point presentation |
Written Test
Quiz
Assignment
Tutorial
Group Activity
Semester end examination
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Aliphatic Nucleophilic Substitution: SN1, SN2, mixed SN1 and SN2, ion pair and SN1 mechanism, SNi mechanism, neighbouring group participation; Substitution at allylic and vinylic carbon atoms, ambident nucleophiles, effect of substrate structure, nucleophile, leaving group, reaction medium on the reactivity. Regioselectivity.
Elimination Reactions: E2, E1, E1CB and E2C (syn elimination) mechanisms, E1 – E2 – E1CB spectrum, orientation of the double bond, effect of substrate structure, attacking base, leaving group and reaction medium on reactivity. Mechanism and orientation in pyrolytic elimination.
(a) Aromatic Nucleophilic Substitution: SNAr, benzyne and SRN1 mechanism, effect of substrate structure, leaving group and attacking nucleophiles on reactivity. Typical reactions– Bucherer reaction, Rosenmund-von Braun reaction, von-Richter, Sommelet-Hauser and Smiles rearrangement.
(b)Aromatic Electrophilic Substitution: Arenium ion mechanism, orientation and reactivity, energy profile diagrams. Directive influence and its explanation in different substitutions. o/p ratio, ipso attack, substitution reactions involving diazonium ions, Vilsmeir-Haack reaction., Friedel-Craft reaction: Alkylation, arylation (Scholl reaction), acylation (ring closer, Haworth reaction, Hoesch reaction).
Aliphatic Electrophilic Substitution: Bimolecular mechanism– SE2 and SEi, the SE1 mechanism, substitution accompanied by double bond shifts, halogenation, sulphonation, aliphatic diazonium coupling, direct amination, metalation with organometallic compounds, trans metalation with metal and metal halides, insertion by nitrenes, insertion by carbenes, acylation at an aliphatic carbon. Effect of substrates, leaving group and solvent polarity on the reactivity.
Free radical substitution mechanisms, mechanism at an aromatic substrate, neighbouring group participation and free radical rearrangements, reactivity for aliphatic and aromatic substrates, reactivity at bridgehead, reactivity of the attacking radical and effect of solvent on reactivity.
Important reactions involving free radicals: Sandmeyer and Gattermann reaction, Hunsdiecker reaction, Gomberg-Bachmann reaction, coupling of alkynes.
Addition to C-C multiple bond: Mechanistic and stereochemical aspects of addition reaction involving electrophiles, nucleophiles and free radical, regio and chemo selectivity, orientation and reactivity, addition to cyclopropane ring, hydrogenation of aromatic rings.
Addition to C-Hetero Multiple Bonds: Mechanism of metal hydride reduction of saturated and unsaturated carbonyl compounds, acids, esters and nitriles, addition of Grignard reagents, organozinc, organocopper and organolithium reagents to carbonyl and unsaturated carbonyl systems.
Formation of enolates, kinetic and thermodynamic control, 1,2 vs 1,4 addition, HSAB principle, reactions of enolate anions with electrophiles: O and C alkylation. Enolate condensation reactions: Synthetic applications of inter and intramolecular Aldol condensations, Claisen, Dieckmann, Knoevenagel, Stobbe’s condensations. Stereoselective enolate reactions: Diastereoselection, Zimmermann-Traxler model, Evans mode. Baylis-Hillmann reaction, Robinson annulation
- Advanced Organic Chemistry: Reactions, Mechanisms and Structure; Seventh Edition; J. March; John Wiley and Sons Asia Private Limited, New Delhi, 2015.
- Advanced Organic Chemistry Part A & B; Fifth Edition; F. A. Carey and R. J. Sundberg; Springer, US, 2007.
- Principles of Organic Synthesis; Third Edition; R.O.C. Norman and J.M. Coxon; Chapman and Hall Ltd., London, 2003.
- A Guidebook to Mechanism in Organic Chemistry; Sixth Edition; P. Sykes; Pearson Education, Delhi, 2011.
- Supplement for Basic Principles of Organic Chemistry; First Edition; J. D. Roberts and M. C. Caserio; W. A. Benzamin Inc., New York, 1965.
- Organic Chemistry: Vol. I and II; Singh, Mukherjee, Kapoor; Second Edition; New Age International Private Limited, New Delhi, 2018.
