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- 1. ROBOMATE LOGO CSIR NET JRF (AIR 52) UGC NET JRF (AIR 53) MH-SET-2016 QUALIFIED GATE QUALIFIED. BY VIKRAM PAWAR SIR
- 2. ROBOMATE LOGO Let us learn about …
- 3. ROBOMATE LOGO Introduction R – H R – X Haloalkane (alkyl halide) alkyl Alkane – H + X Ar – H Ar – X Haloarene (Aryl halide) Aryl – H + X Arene Ex: H3C – CH2 – X X Halo ethane Halo arene CH2X Benzyl halide H2C = CH – Cl Vinyl chloride
- 4. ROBOMATE LOGO (Based on No. of Halogen atoms) Haloalkanes Mono haloalkanes Poly haloalkanes Classification of Haloalkanes (10) alkyl halide (20) alkyl halide (30) alkyl halide Dihalo alkanes Trihalo alkanes Tetrahalo alkanes Geminal dihalide Vicinal dihalide
- 5. ROBOMATE LOGO H3C – CH2 – Cl H3C – C – CH3 Cl H H3C – C – CH3 Cl CH3 H3C – CH Cl2 H2C – CH2 Cl Cl CHCl3 CCl4 Tetra haloalkanes Tri haloalkanes Vicinal dihalide Gem. dihalide (30) alkyl halide (20) alkyl halide (10) alkyl halide Allylic halides H2C = CH – CH2 – Cl Benzyl Halides CH2 – Cl
- 6. ROBOMATE LOGO H3C–CH2–Br Ethyl bromide Bromoethane H3C – CH – CH3 Cl Iso propyl chloride 2–Chloropropane H3C – CH2 – CH2 – Cl n–propyl chloride 1–Chloropropane Sec–butyl bromide H3C – CH – CH2 – CH3 Br 2–Bromobutane Tert – butyl chloride H3C – C– Cl CH3 CH3 2 – Chloro – 2 – methylpropane Common Name IUPAC Name Compounds
- 7. ROBOMATE LOGO H2C = CH – Cl Vinyl chloride Chloroethene H2C = CH – CH2 – Br Allyl bromide 3–Bromoprop–1–ene o – chlorotoluene Cl CH3 2–Chlorotoluene Benzyl bromide CH2 – Br Bromophenylmethane H3C – CHCl2 Ethylidene dichloride 1,1 – Dichloroethane H2C – CH2 Cl Cl Ethylene dichloride 1,2 – Dichloroethane
- 8. ROBOMATE LOGO Some comparisons of bond length, bond enthalpies and dipole moment of different methyl halides are as follows: Bond Bond length (pm) C – X bond enthalpies (kJ/mol) Dipole moment (Debye) H3C – F 139 452 1.847 H3C – Br 193 293 1.830 178 351 1.860 H3C – Cl H3C – I 214 234 1.636
- 9. ROBOMATE LOGO Methods of preparation of Haloalkanes 1.From Alcohols: with HX ZnCl2 R – X + H2O Anhydrous Alcohols react with HX in presence of anhydrous ZnCl2 to give alkyl halides by dehydration. R-OH + H-X Conc. HCl + Anhydrous ZnCl2 = Lucas reagent Reactivity of HX HI > HBr > HCl >HF 30 > 2 0 > 10 > CH3OH Reactivity order of alcohols
- 10. ROBOMATE LOGO 2. From Alcohols: with SOCl2 R – OH + SOCl2 Reflux + SO2 R – Cl + HCl Pyridine DARZEN’S METHOD Darzen’s method is the best method to prepare R-Cl because the byproducts are removed in vapour state.
- 11. ROBOMATE LOGO 3.From Alcohols : R – OH + NaBr + H2SO4 R – Br + NaHSO4 + H2O Reaction of alcohol with NaBr & H2SO4
- 12. ROBOMATE LOGO 4. Reaction of alcohol With PCl3, PCl5 and SOCl2 H3 C – CH2 – OH Ethanol Chloroethane + PCl3 + H3PO3 H3C – CH2 – Cl Propan–1– ol 1- Chloropropane + + HCl + POCl3 PCl5 H3C–CH2–CH2–OH H3C–CH2–CH2–Cl H3C – CH2 – OH Chloroethane Ethanol + SOCl2 Pyridine reflux + + HCl SO2 H3C – CH2 – Cl
- 13. ROBOMATE LOGO 5. Halogenation of alkanes Ex: U.V. light HCl methyl chloride Chloromethane Methane H3C – H + i) + H3C – Cl Cl Cl | (Excess) Diffused sunlight/ H3C – Cl Cl2 – HCl CCl4 CHCl3 chloroform CH2Cl2 methylene dichloride Cl2 – HCl Cl2 – HCl carbon tetrachloride Reactivity of halogen is : Cl2 > Br2 > I2 (Excess) 1. Chlorination
- 14. ROBOMATE LOGO H3C – CH2 – CH3 Cl2 U.V. light H3C – CH2 – CH2 – Cl 1 – Chloropropane (45% ) H3C – CH – CH3 Cl 2 – Chloropropane (55% ) Propane
- 15. ROBOMATE LOGO 2) Bromination (Free radical substitution) R – H R – Br +Br2 + HBr R – H R – I To prevent reversibility, it is carried out with oxidizing agents like HgO, HIO3 or HNO3 etc. 3) Iodination (Reversible reaction) +I2 + HI
- 16. ROBOMATE LOGO H3C – CH = CH2 H+ Cl– Markownikoff’s Rule H3C – CH – CH3 | Cl iso / sec - propyl chloride (2 – Chloropropane) Propene The negative part of the unsymmetrical reagent goes to that Carbon atom containing less no. of Hydrogen atoms across the carbon carbon double bond. + Markownikoff’s Rule 6. Addition of Haloacids (HX) on Alkenes
- 17. ROBOMATE LOGO Action of HBr in the presence of peroxide on alkene H3C – CH = CH2 H+ Br– A.M.R. Peroxide 1 – Bromopropane H3C – CH2 – CH2 – Br Propene n - propyl bromide + Peroxide effect is only applicable to HBr. Markownikoff’s and AntiMarkownikoff’s rules are only applicable for unsymmetrical alkene.
- 18. ROBOMATE LOGO H—C C—H+ H+ — Cl– addition acetylene Vinyl chloride (Ethyne) From acetylene and HCl Preparation of Geminal dihalide H — C C—H — H — Cl = Ethylidene dichloride H — C — C — H — — H Cl H Cl — — addition M.R. H+ — Cl–
- 19. ROBOMATE LOGO 7. By Halogen exchange There are two halogen exchange methods to prepare haloalkanes. 1. Finkelstein reaction To prepare R – I R – X + Na I Dry Acetone R – I + NaX 2. Swarts reaction To prepare R – F R – Br + Ag F R – F + AgBr
- 20. ROBOMATE LOGO Methods of preparation of Haloarenes There are two types: Halogenation of Benzene (electrophilic substitution reaction) 1) From Benzene diazonium halide 2)
- 21. ROBOMATE LOGO Halogenation of Benzene (electrophilic substitution reaction) Cl2 , FeCl3 Br2 , FeBr3 I2 , HIO3 Cl (Chlorobenzene) (Bromobenzene) (Iodobenzene) Br I Benzene – HCl – HBr – HI
- 22. ROBOMATE LOGO From Benzene diazonium halide 1) sandmeyer’s reaction Cl N2 N N X – + Cu2Cl2 + HCl + HX Cl N2 N N X – + Cu & HCl + – HX 2) Gattermann reaction
- 23. ROBOMATE LOGO Chemical properties of Haloalkanes Dehydrohalogenation of R – X R – X + KOH + Alkene KX+ H2O alkyl halide (alc.) + KOH H2C= CH2+ KBr +H2O (alc.) Ethene H2C –CH2 H Br ethyl bromide (alkyl halide Alkene) 1. , -Elimination reaction
- 24. ROBOMATE LOGO + KOH = H2C C – CH3 CH3 (alc.) + + KBr H3C – C – CH3 CH3 Br tert – butyl bromide isobutylene H2O H3C – CH = CH – CH3 But – 2 – ene (Major product) , alc KOH + Saytzeff’s rule 2 – Chlorobutane KCl + H2O Cl H H3C – CH – CH – CH3 Saytzeff’s Product
- 25. ROBOMATE LOGO Formation of higher alkanes alkyl halide Wurtz reaction R – X+ 2Na + X – R Dry ether R – R+ 2NaX Sodium Alkane (– X –R) H3C – Br +2Na + Br – CH3 H3C– CH3 + 2NaBr Ethane Dry ether methyl bromide Bromoethane H5C2 – Br + 2Na + Br – C2H5 + 2NaBr n – Butane Dry ether H5C2 – C2H5
- 26. ROBOMATE LOGO 3 H3C–Br + 6Na + 3Br –C2H5 Dry ether H3C –CH3 + H5C2 –C2H5 + 6NaBr (Major) (Minor) (Major) H5C2–CH3 +
- 27. ROBOMATE LOGO 3. Nucleophilic substitution reaction R – X + Nu– R – Nu + X – There are total 7 reactions 1. with aq. KOH/NaOH 2. with moist silver Oxide (Ag2O) 3. with NH3 (Hoffmann’s Ammonolysis) 4. with sodium alkoxide (R—ONa) 5. with alc. KCN 6. with alc. AgCN 7. with silver carboxylate (RCOO — Ag)(Preparation of Ester)
- 28. ROBOMATE LOGO 1. with aq. KOH/NaOH R X R OH (alkyl halide) (Alcohol) KOH(aq) + KX + R X R OH (alkyl halide) (Alcohol) Ag2O(aq) + 2AgX + 2. with moist silver Oxide (Ag2O) [ Ag2O + H2O → 2AgOH R – X +AgOH → R – OH +AgX↓ ] Make a note 2R X + dry Ag2O R-O-R(Ether)
- 29. ROBOMATE LOGO 3. with NH3 (Hoffmann’s Ammonolysis) RX + alc.NH3 R NH2 (Excess) 10 Amine 4. with sodium alkoxide ( R ONa) (Williamson’s synthesis) (Preparation of Ethers) CH3 Cl C2H5ONa C2H5 O CH3
- 30. ROBOMATE LOGO 5. with alc. KCN : 6. with alc. AgCN : KBr H3C – CN Acetonitrile (or) H3C – Br Bromomethane +K – CN (alc.) H3C – NC methyl isocyanide Ag – CN H3C – Cl (Chloromethane) AgCl ( Methyl carbylamine ) +
- 31. ROBOMATE LOGO 7. with silver carboxylate (RCOO Ag) Br2 R Br + RCOO-Ag+ + Ag Br Preparation of ester 1) silver formate ethyl bromide H – COOC2H5 ethyl formate alc. Br – C2H5 (Ethyl Methanoate) AgBr + H – C – O Ag O +
- 32. ROBOMATE LOGO H5C2 – NH2 H5C2 – Br – HBr + (C2H5)2 NH (diethylamine) – HBr H5C2 – Br H5C2 – Br (C2H5)3N (triethylamine) (tetraethyl ammonium bromide) (C2H5)4NBr – + (Excess) This reaction is also known as alkylation of ammonia.
- 33. ROBOMATE LOGO Williamson’s Synthesis (Preparation of ethers) H5C2 – O – Na H5C2 – O – CH3 alc. (sodium ethoxide) (Iodomethane) (ethyl methyl ether) + NaI + I – CH3 (Methoxy ethane) + NaOH OH (Phenol) ONa sodium phenoxide H3C – I O – CH3 Anisole + NaI – H2O , Alc.
- 34. ROBOMATE LOGO Limitation + H3C – C – Br CH3 CH3 tert – butyl bromide (30) H5C2 – O – Na Elimination (isobutylene) + H5C2 – OH H3C – C CH2 CH3 + NaBr Only 10 alkyl halide is used in this method, because 20 and 30 alkyl halide give alkene on elimination.
- 35. ROBOMATE LOGO H3C – C – ONa CH3 CH3 + CH3I H3C 𝟑C O CH3 + NaI
- 36. ROBOMATE LOGO SN2 Reaction : H3C – Br H3C – OH + KBr (methyl bromide) (aq.) (Methanol) Boil Hydrolysis +K OH Rate of reaction [H3C – Br] [OH–] Towards SN2 Mechanism : H3C – X 10 20 30
- 37. ROBOMATE LOGO Boil, Hydrolysis Non – polar solvent Slow (R.D.S.) H – C – Br H H + – : OH Br– HO– C+ H H H Transition state (Unstable) Fast HO – C – H H H (Methanol) (100% Inversion of configuration) + Br– (R.D.S. = Rate determining step)
- 38. ROBOMATE LOGO H3C – Br+ OH– (Reactants) H HO – CH3 + 𝑩𝒓− – (Products) Reaction coordinate (Progress of Reaction with time) Potential energy E Br– HO– C+ H H H Transition state (Unstable) E Energy of activation H Heat of reaction (H is –ve since the reaction is exothermic) E is the difference between energies of transition state and reactants H is the difference between energies of products and reactants.
- 39. ROBOMATE LOGO SN1 Reaction : Boil, Hydrolysis polar solvent H3C – C – Br CH3 CH3 (tert – butyl alcohol) H3C – C – OH CH3 CH3 + (tert–butyl bromide) Br– + – OH Kinetic expression : Rate of reaction [substrate] Rate of reaction [(CH3)3C – Br] K [(CH3)3C – Br] Where, K = Rate constant =
- 40. ROBOMATE LOGO slow R.D.S. H3C – C – Br CH3 CH3 (Polar solvent) H3C – C+ Br– CH3 CH3 1200 C CH3 H3C CH3 : Br – (tert – butyl carbocation) (sp2 hybridised) Transition state – I + Mechanism : It is two steps reaction: Formation of tert–butyl carbocation. Step I :
- 41. ROBOMATE LOGO Step II : Formation of Product: H3C – C+ OH– CH3 CH3 : –OH C CH3 H3C CH3 Transition state – II + attack attack Front side Back side H3C – C – OH CH3 CH3 (50% retention) CH3 HO –C – CH3 CH3 (50% Inversion) Fast
- 42. ROBOMATE LOGO SN1 Substitution nucleophilic first order The order for substitution nucleophilic first order 30>20>10 for alkyl halides. SN1 is favoured in polar solvents. SN1 involves carbonium ion mechanism.
- 43. ROBOMATE LOGO E Energy of activation H Heat of reaction (H is –ve since the reaction is exothermic) (CH3) 3 C – Br+ OH– (Reactants) H (CH3) 3 C – OH+ Br① Reaction coordinate (Progress of Reaction with time) Potential energy (Products) E1 E2 (CH3) 3 C+ Transition state – II Transition state – I Energy profile diagram
- 44. ROBOMATE LOGO Chemical properties of Haloarenes : a) Dow’s Process Cl (Chlorobenzene) + 2 NaOH 623 K 300 atm (6 – 8%) ONa sodium phenoxide + NaCl + H2O (phenate) ONa + HCl (Dil.) OH Phenol + NaCl (carbolic acid) 1. Nucleophilic substitution reaction and its mechanism.
- 45. ROBOMATE LOGO b) With substituted Haloarenes Cl NO2 i) NaOH,443K ii) H+ OH + NaCl (4–Nitrochlorobenzene) or NO2 (4 – Nitrophenol ) or (p– nitrochlorobenzene) (p – nitrophenol)
- 47. ROBOMATE LOGO 2. Electrophilic substitution reaction Halogenation (X+ is substituted) Nitration (NO2 + is substituted) Sulphonation (SO3 is substituted) Friedel – Craft’s reaction Friedel – Craft’s alkylation reaction (R+ is substituted) Friedel – Craft’s acylation reaction (RCO+ is substituted)
- 48. ROBOMATE LOGO Chlorobenzene 2Cl2 + 1,4–Dichloro benzene (Major) 1,2–Dichloro benzene (Minor) + 1–Chloro–4–nitro benzene (Major) 1–Chloro – 2–nitro benzene (Minor) 2HO–NO2 Conc. H2SO4 Anhydrous FeCl3 Cl Cl + Cl Cl Cl NO2 Cl 2 Cl NO2 + 2H2O Conc. 2HCl
- 49. ROBOMATE LOGO Sulphonation 2Conc. H2SO4 , 4–Chlorobenzene sulphonic acid (Major ) + 2–Chlorobenzene sulphonic acid (Minor) Cl SO3H Cl SO3H + Chlorobenzene Cl 2 2H2O
- 50. ROBOMATE LOGO Chlorobenzene 2 CH3Cl Anhydrous AlCl3 Cl CH3 1–Chloro–4–methyl benzene (Major ) 1–Chloro–2– methylbenzene (Minor) + Anhydrous AlCl3 Friedel– Craft’s Cl CH3 + 2HCl Cl 2 2 H3C – C - Cl O (Minor) (Major ) + Cl C – CH3 O Cl C – CH3 O
- 51. ROBOMATE LOGO 3. Reaction with metals Wurtz fitting reaction + 2Na+ RX Dry ether X R + 2NaX alkyl benzene Fitting reaction + 2Na Dry ether + 2NaX (Diphenyl) X 2