1. First Year Chemistry Theory (Organic) Starting date: 20 th October (Every Mon, Wed, Thu) Finishing Date: 17 th November Teacher: Prof. A. Basak Reference book: Clayden/T.W.G. Solomons Peter Sykes Topics to be covered: 1) Structure / stereochemistry 2) Ionic rxns– addition/ elimination/substitution/ rearrangements 3) Free radical reactions 4) Concerted reactions(Diels Alder/electrocyclic) 5) Amino acids /peptides/enzymes (chymotrypsin) 6) Carbohydrates/ nucleic acids

2. Lecture 1

3. Why read organic chemistry? Life is organic chemistry Organic chemistry is the chemistry of the compounds of carbon Deoxyribonucleic acids or DNA RNA Proteins Drug molecules:

5. Stereochemistry: Chemistry in space, as a function of molecular geometry. Constitution based chemistry: All these alcohols behave differently to certain reagents. That is due to their different modes of connectivity. x = functional group with same connectivity. However, reactivity of X may differ again certain reagents. Reactivity of the hydroxyl groups somewhat different.

6. Stereoisomerism Isomerism constitutionalstereo chain functional positional enantiomersdiastereomers Enantiomers:Stereoisomers that are mirror images of one another enantiomers If a molecule is nonsuperimposable with its mirror image, then it becomes optically active and is called a chiral molecule.

7. Chiral Centre (Asymmetric Centre): An atom, usually carbon attached to four different ligands (atoms or groups) Stereogenic Centre: An atom, again usually carbon, in which interchanging the position of two ligands gives rise to a stereoisomer. This includes the carbon atom attached to four different ligands as also the sp2 carbon which can show cis-trans isomerism

8. Representation in 2D: Projection Formula :Fischer, Newman…………. Fischer Projection : Suppose a molecule is drawn as : Rules: (1) Exchange in a group of three allowed

9. (2) 180 0 in plane rotation is allowed (3) 90 0 in plane rotation ? (4) 180 0 out of plane rotation ? Not Allowed

10. Absolute configuration : The R,S - notation (1)Assign priority sequence to the four groups attached to a stereogenic carbon following the sequence rule. (2) Observe the stereogenic centre from a direction opposite to the group of lowest priority. (3) Trace the path from 1 to 2 to 3 If clockwise R ( rectus, right) If anticlockwise S (sinister, left)

11. Sequence Rules: (1)If the four atoms directly attached to the stereogenic centre are different, higher atomic number takes precedence over lower. (2) If the atoms directly attached to the stereocentre are same, then work outward along the two chains atom by atom until a point of difference is reached. (3) Double and triple bonds are treated by assuming that each such bonded atom is duplicated or triplicated.

12. What are absolute configurations of the following compounds : More rules: R precedes S E precedes Z cis precedes trans Isotopic discrimination to be applied only when atomic no. fails