Understanding Organic Reactions: Addition, Elimination, Substitution, and Oxidation

1. Organic Reactions - II Chapter 1

2. Four Types • Addition Reactions • Elimination Reactions • Substitution Reactions • Oxidation • AESO………………………

3. Substitution Reactions • An H atom or a functional group is replaced by a different atom or functional group | | — C — X + AY → — C — Y + AX | |

4. Substitution Reaction of Alkanes • Halogenation: Reaction with Halogen, X2 • Produces RX + HX; additional halides may be produced • heat or UV light and a catalyst is required

5. Practice it Now!! • Write the structural formula of the product(s) formed • when propane reacts with excess of bromine in the presence of UV light. • When cyclohexane reacts with bromine in the presence of UV light.

6. Substitution Reaction of Aromatic compounds • Reaction with Halogen, X2 : Halogenation forming Ø – X + HX (iron (III) bromide, FeBr3, catalyst) • Ø – represents the aryl group • Reaction with Nitric acid, HNO3 : Nitration forming Ø – NO2 (nitro) + HOH • Reaction with Alkyl halide, RX : Alkylation forming Ø – R + HX

7. Aromatic Substitution Reactions • Halogenation: substitution of H with a halogen (X = Cl, Br, I, F) • Nitration: substitution of H with a –NO2 (nitro group)

8. Aromatic Substitution Reactions • Alkylation: substitution of H with an Alkyl group (C-chain) Let’s Practice it Now!! Complete Q# 4 (a) and (b) on page 30 of your textbook.

9. Oxidation Reaction • A reaction in which a carbon atom forms more bonds to oxygen, O, or less bonds to hydrogen, H. • An oxidizing agent (O) removes two H atoms from a carbon (one from an –OH group) resulting in the formation of double C=O bonds. • Generally, more carbon-oxygen bonds are formed during an oxidation. • Alcohols and aldehydes show this type of reaction.

10. Oxidation Reactions • Alcohols undergo oxidation to form aldehydes and ketones • oxidizing agent, such as H2O2, Cr2O7-2, KMnO4 in H2SO4 are required

11. Oxidation Reactions • Aldehydes undergo oxidation to form carboxylic acids (RCOOH) and HOH • oxidizing agent, such as H2O2, Cr2O7-2, KMnO4 in H2SO4 are required • Ketones are not oxidized under these conditions as they lack the critical H for the elimination to occur

12. Practice it Now . Draw structural diagrams to illustrate the following reactions. • oxidation of 1- propanol • Oxidation of 2- butanol • Oxidation of 2-butanal

13. Special Reactions • Condensation Reaction • Hydrolysis Reactions • Polymerization Reactions • Condensation reaction: • Two molecules combine to form a single organic molecule. • A small molecule, usually water, is also produced. • Is considered as an elimination reaction.

14. Condensation Reaction- also called as dehydration synthesis | | | | — C — OH + HO — C — → — C — O — C — + HOH | | | | | | | | | — C — OH + H2N — C — → — C — N — C — + HOH | | | • Alcohols react with other alcohols to form ether + HOH • sulphuric acid, H2SO4, is used as a catalyst • Can be considered as an elimination reaction

15. Condensation Reaction- also called as dehydration synthesis • Carboxylic Acids react with alcohols to form ester (R-COO-R ) and water • Reaction is called Esterification • sulphuric acid, H2SO4, is required as catalyst • Is biologically very significant

16. Condensation Reaction- also called as dehydration synthesis • Carboxylic acids also react with amines (R-NH2) to form amide (R-CONH-R) and HOH • sulphuric acid, H2SO4, is used as a catalyst • Biologically very important

17. Hydrolysis Reactions • Water is added to a bond to split a large organic molecule apart. • This reaction is the reverse of a condensation reaction • Biologically significant - digestion

18. Hydrolysis Reactions- Saponification • Esters react with NaOH to form sodium salt of a carboxylic acid (Na+R-COO- )and an alcohol (R-OH) • Used for making soap