A SEMINAR ON Markownikoff’s AND ANTI Markownikoff’s RULE Rayat Shikshan Sanstha's S.M. JOSHI COLLEGE, HADAPSAR, PUNE-28 A SEMINAR ON Markownikoff’s AND ANTI Markownikoff’s RULE Prof. MADHURI TUPE (Assistant Professor) Department of Chemistry

Markownikoff’s Rule “When a hydrogen halide reacts with an unsymmetrical alkene the hydrogen of the hydrogen halide attaches itself to the carbon of the alkene bearing the larger number of hydrogens and smaller number of carbons"

Addition reactions of unsymmetrical alkenes Addition of HBr to propene CH3CH=CH2: H–Br can add in two different ways Two products are possible: Contains more H atoms CH3CH=CH2 CH3CH=CH2 H–Br Br–H CH3CH2–CH2Br CH3CHBr–CH3 Minor product Major product

It’s all controlled by carbocations Secondary carbocation Two C joined to C+ Primary carbocation One C joined to C+ Major product Minor product

Types of carbocation Least stable Primary carbocation One carbon chains attached to C+ Secondary carbocation: Two carbon chains attached to C+ Tertiary carbocation: Three carbon chains attached to C+ Most stable

Reasons for carbocation stability Least stable Electron-donating ability of alkyl groups. Each alkyl group pushes electrons towards C+ charge of carbocation. Positive charge is spread over alkyl groups The more alkyl groups attached to the C+ The more the positive charge is spread out The greater the stability of the carbocation Primary Secondary Most stable Tertiary

Markovnikov’s Rule With unsymmetrical alkene In the addition of an acid to an alkene the hydrogen will go to the vinyl carbon that already has the greater number of hydrogens.

Anti Markovnikov’s Rule In the addition of an acid to an alkene the hydrogen will go to the vinyl carbon that already has the lowest number of hydrogens.

4- Addition of Sulfuric acid (H-OSO3H) heat Addition of Sulfuric acid to alkenes also follows Markovnikov’s rule, as the example Propene Isopropyl hydrogen sulfate H2O heat 2-Propanol

5- Addition of Water : Hydration Addition of HOH across the double bond is in accordance with Markovnikov’s rule, as the example

6- Addition of HOX : Halohydrin Formation The addition of the chloronium ion, Cl+ or bromonium ion, Br+ and the hydroxide ion, OH-, follows the Markovnikov’s rule, as the example.

7- Oxidation of alkenes syn hydroxylation 1) Oxidation of alkenes with Permanganate (Baeyer test) syn hydroxylation Examples:

trans-1,2-cyclohexanediol 2) Oxidation of alkenes with peroxy acid Epoxide anti hydroxylation Examples: 2,3-butanediol trans-1,2-cyclohexanediol

8- Ozonolysis Oxidation of alkenes by ozone O3 The ozonolysis reaction can be summarized by the following equation:

Examples:

9- Polymerization A) B)