HALOALKANES AND HALOARENES CHAPTER 1 ORGANIC CHEMISTRY CLASS 12

HALOALKANES AND HALOARENES is the first organic topic discussed in 12th grade . the presentation includes the full chapter discussion including , preparation, reactions etc.

1. HALOALKANES AND HALOARENES

2. The replacement of hydrogen atom(s) in a hydrocarbon, aliphatic or aromatic, by halogen atom(s) results in the formation of alkyl halide (haloalkane) and aryl halide (haloarene), respectively These are are compounds containing halogen atoms attached to alkyl or aryl group General representation Haloalkanes R-X Haloarenes Ar -X X – F, Cl, Br, I

3. NOMENCLATURE Based on original alkane with a prefix indicating halogens and position . CH 3 CH 2 CH 2 Cl 1-chloropropane CH 3 CHClCH 3 2-chloropropane CH 2 ClCHClCH 3 1,2-dichloropropane CH 3 CBr(CH 3 )CH 3 2-bromo-2-methylpropane

4. STRUCTURAL DIFFERENCE Halogenoalkanes are classified according to the environment of the halogen PRIMARY 1° SECONDARY 2° TERTIARY 3° C-C-X -C-X C-C-X

5. SP 3

6. Nature of C-X bond

7. ALKANE 02 RH ALCOHOL 01 R -OH ALKENE 03 HALOALKANE 04 METHODS OF PREPARATION OF HALOALKANES

8. FROM ALCOHOL R-OH

9. CH 3 OH + HCl CH 3 Cl ZnCl2 CH 3 OH + PCl 3 CH 3 Cl + H 3 PO 3 3 3 PCl 5 CH 3 OH + + CH 3 Cl HCl + + + + POCl 3 CH 3 OH SOCl 2 CH 3 Cl HCl SO 2 CH 3 OH CH 3 Cl X2/Red P

10. ALKANE 02 RH

11. HALOALKANE 04 Halogen exchange reaction Finkelstein Reaction Alkyl iodides are often prepared by the reaction of alkyl chlorides/ bromides with NaI in dry acetone. This reaction is known as Finkelstein reaction. NaCl or NaBr thus formed is precipitated in dry acetone. It facilitates the forward reaction according to Le Chatelier’s Principle. Dry acetone

12. Swarts reaction The synthesis of alkyl fluorides is best accomplished by heating an alkyl chloride/bromide in the presence of a metallic fluoride AgF , Hg 2 F 2 , CoF 2 or SbF 3 . The reaction is termed as Swarts reaction

13. ANILINE 02 TOULENE 01 METHODS OF PREPARATION OF HALOARENES

14. CH 3 TOULENE 01 CH 3 CH 3 The ortho and para isomers can be easily separated due to large difference in their melting points. Reactions with iodine are reversible in nature and require the presence of an oxidising agent (HNO3 , HIO4 ) to oxidise the HI formed during iodination. Fluoro compounds are not prepared by this method due to high reactivity of fluorine.

15. ANILINE 02 NH 2

16. Why is sulphuric acid not used during the reaction of alcohols with KI? Write structures of different dihalogen derivatives of propane. Among the isomeric alkanes of molecular formula C5H12, identify the one that on photochemical chlorination yields A single monochloride. (ii) Three isomeric monochlorides. (iii) Four isomeric monochlorides. 4 Draw the structures of major monohalo products in each of the following

17. NUCLEOPHILIC SUBSTITUTION REACTION