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Msc-Chemistry.Pdf BHARATHIDASAN UNIVERSITY (Re-accredited with ‘A’ Grade by NAAC) CENTRE FOR DISTANCE EDUCATION PALKALAIPERUR, TIRUCHIRAPPALLI – 24 M.Sc., CHEMISTRY Major Paper -I Organic Chemistry - I I - Year Copy right reserved For Private Circulation only Lesson Writter Dr. T. Vimala, Associate Professor PG & Research Department of Chemistry Seethalakshmi Ramaswami College, Tiruchirappalli-620 002. 2 MAJOR PAPER I – ORGANIC CHEMISTRY UNIT – I Nomenclature, Reactive Intermediates, Methods of Determining Reaction Methods 1.1. Nomenclature of alicyclic, bicyclic and tricyclic compounds. Nomenclature of heterocycles having not more than two hetero atoms such as oxygen, nitrogen and sulphur. 1.2. Aromatic character: six-, five-, seven-, and eight-membered rings – Other systems with aromatic sextets Huckel’s theory of aromaticity, Concept of homoaromaticity and antiaromaticity, systems with 2,4,8 and 10 electrons, systems of more than 10 electrons, alternant and non-alternant hydrocarbons (azulene type). Bonding properties of systems with (4n + 2) electrons and 4n electrons, Heteraromatic molecules. Annulenes and sydnones and fullerenes. 1.3. Thermodynamic and kinetic aspects, Hammond’s postulate, isotope effects. Energy profile diagrams – Intermediate versus transition state, Product analysis and its importance, Crossover experiments, Kinetic methods, Stereochemical studies, Isotopic and substitutent effects. UNIT – II Stereochemistry 2.1 Fundamentals of Organic Stereochemistry: Principles of symmetry – Stereoisomerism – Optical isomerism – Definitions – Conventions used in stereochemistry: Newman, Sawhorse and Fischer notations and interconversions and representations. Nomenclature, correlation of configuration. Cahn – Ingold – Prelog rules for simple molecules. Optical activity and chirality – Types of molecules exhibiting optical activity – Fischer projection – Absolute configuration. Molecules with more than one chiral centre – Molecular chirality – Atropisomerism – Biphenyls, 3 allenes and spiranes. Methods of determining configuration. Enantiomerism of compounds containing chiral heteroatoms. 2.2 Geometrical Isomerism E & Z Nomenclature, Determination of configuration of geometrical isomers, Stereospecific and stereoselective synthesis – [Elementary examples]. 2.3 Basic concepts of conformational analysis – cyclohexane and decalins. UNIT-III Substitution Reactions 3.1 Aliphatic Nucleophilic substitution – Mechanisms – Effect of structure – Stereochemical factors – Neighbouring group participation, substitutions at allylic and vinylic carbons. Correlation of structure with reactivity – Solvent effects. 3.2 Aliphatic Electrophilic Substitution SE2, SEi and SE1 mechanisms, Diazonium coupling reactions. 3.3 Aromatic Nucleophilic substituion – SN1 SNAr, Benzyne mechanism – reactivity orientation. 3.4 Aromatic electrophilic substitution reaction – Orientaion, reactivity and mechanisms based on transition state theory with suitable reactions, - Origins of Hammett equation – Principles of Hammett correlation – Effect of structure ofn reaction mechanisms Hammett parameters; and , modified forms of Hammett equation. Taft Equation. UNIT-IV Addition and Elimination Reactions 4.1 Addition to carbon – carbon multiple bonds: Electrophilic, nucleophilic and free radical additions – Orientation of the addition – Stereochemical factors influencing the addition of bromine and hydrogen bromide, hydroxylation, hydroboration leading to formation of alcohols. Addition to carbonyl and conjugated carbonyl systems – Mechanism – Grignard 4 reagents – 1,2 and 1,4-additions (dimethyllithiumcuparate), Benzoin, Knovenagel, Stobbe and Darzen’sglycidic ester condensation and Reformatsky reactions. 4.2 Elimination Reactions: Mechanisms; E1, E2, E1cB – Stereochemistry of elimination, Hofmann and Saytzeff rules – Competition between elimination and substituion – Pyrolyticcis elimination, Chugaev reaction – Examples sucha as dehydration, dehydrohalogenatio, Hofmann degradation, Cope elimination – Bredt’s rule with examples. UNIT-V Organic Photochemistry & Pericyclic Reactions 5.1 Organic Photochemistry – Fundamental concepts – Jablonski diagram – Energy transfer, characteristics of photoreactions, photoreduction and photoxidation, photoreactions of ketones and enones, Norrish Type I and II reactions. Photochemistry of alkenes, dienes and aromatic compounds, Photoadditions – Barton reaction – ParternoBuchi reaction. 5.2 Concerted reactions – stereochemistry-orbital symmetry and concerted symmetry and correlation diagram – Frontier molecular orbital approach – Woodward and Hoffmann rules – Electrocylcic reactions – cycloaddition reactions – sigmatropic rearrangements – selection rules and examples with simple molecules – 1,3 and 1,5 hydrogent shifts – cope and Claisen rearrangements. Other molecular rearrangements References 1. J. March, Advanced Organic Chemistry: Reactions. Mechanisms and Structure, 5th ed., Wiley, 2000. 2. D. Nasipuri, Stereochemistry of organic compounds-Principles and applications,New Age International, 2nd Edition, 2002. 3 I.L. Finar, Organic Chemistry, Vol. II, 5th ed., ELBS 1975. 5 4. J.M. Coxon, B. Halton, Organic Photochemistry, Camb. Uni. Press, 2nd edition, 1987. 5. G.R. Chatwal, Organic Phtochemistry, Himalaya Publicaions house, 1st edition, 1998. 6. P.S. Kalsi, Stereochemistry, Wiley eastern limited, New Delhi, 1990. 7. S.H. Pine, J.B. Hendrickson, D.. Cram and G.S. Hammond, Organic chemistry, McGraw Hill, 4th ed., 1980. 8. T.H. Lowry and K.S. Richardson, Mechanism and Theroy in Organic Chemistry, Harper and Row, 1976. 9. F.A. Carey and R.J. Sundberg, Advanced Organic Chemistry, Parts A & B, Plenum, 2002. 6 CONTENT UNIT TITLE PAGE NO I. Nomenclature, Reactive intermediates, Methods of 1 Determining reaction Methods II. Stereochemistry 49 III. Substitution Reactions 84 IV. Addition and Elimination Reactions 126 V. Organic Photochemistry & Pericyclic Reactions 167 Unit - I 1.1 Nomenclature Saturated and unsaturated monocyclic hydrocarbons are treated like their acyclic analogues but with the specifying prefix cyclo in front of the name. Monovalent substituent groups derived there from are again given the ending...yl, bivalent groups the ending...diyl (formerly...diyl) when different C atoms are involved and... ylidene or... 1,1-diyl when the free valences are at the same carbon atom. In numbering them, positions with free valences have precedence; only then are double and triple bonds together and thereafter double bonds given the lowest locants possible. The designations benzene, phenyl and ,m,p-phenylene are retained as trivial names. Monocyclic polyenes containing the maximum number of non-cumulative double bonds (for short called: mancude systems) and having the general composition CnHn or CnHn+1 (n > 6) can also be named as [n] annulenes. 1 Fused Polycyclic Hydrocarbons The nomenclature of these compounds in which at least two highly unsaturated rings are fused together through at least two common C-atoms is based on an extended series of trivial names. Systems comprising only benzene units and their substitution products are generally designated as arenes or, traditionally, aromatics. Fused hydrocarbon systems for which no trivial names are retained are systematically named as follows. That component that has the largest ring or/and that – if it is a trivial system according to Table-contains the largest number of rings is defined as parent (or base or primary or main) component. All other components are attached in the form of prefixes to the parent name by changing their ending... ene to ... eno. The following abbreviated prefix forms are retained. Acenaphtho from Naphtho From Acenaphthylene Naphthalene Antha from Anthracene Perylo from Perylene Benzo from Benzene Phenanthro from Phenanthrene With the exception of benzo, fusion prefixes for monocyclic systems are treated as exemplified for cyclopenta, cyclohepta etc. It should be noted here that for fused polycyclic systems the ending... ene always indicates the maximum number of non-cumulative double bonds, that is, a mancude system. 2 For the following compounds Chem. Abstr. Incomprehensibly uses the von Baeyer names bicyclo [4.2.0] octa-1,3,5,7-tetraene and 1H-bicyclo[4.1.0] hepta- 1.36-triene that totally disregard the aromatic character of these compounds. Bridged Polycyclic Hydrocarbons Von Baeyar System Saturated cyclic hydrocarbons containing two or more rings in which at least two rings have at least two common C-atoms are specified as bi-, tri-, tetra-, etc. –cycoalkanes. The total number of rings present evidently equals the number of C-C cleavages necessary to obtain an open chain compound. The names of such compounds are constructed stepwise in the following manner. a) the actual tridimensional structure is transformed into an appropriate planar representation, b) That ring is selected as main ring which includes as many skeletal atoms as possible, c) The largest possible carbon chain that connects two C-atoms of the main ring (consisting itself of tow branches) is defined as the main bridge. The corresponding points of connection are called bridge-heads, d) To assemble the full name the numbers of C atoms of both branches of the main ring, the main bridge and the secondary bridges, if present, are cited in descending order, separated by full stops, and placed in square brackets after the term cyclo. e) The numbering begins at the first bridgehead, tracing first the largest branch of the main ring up to the second bridgehead and then the next largest branch back to the
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