Title 06. HYDROCARBONS.pdf ✅

6. HYDROCARBON – ALKANE
Reactivity of alkane towards free radical halogenation is ∝ stability of free radical C6H5 − CH3 > CH2 = CH − CH3 > (CH3 )3CH > CH3 − CH2 − CH3 > CH3 − CH3 > CH4 Reactivity of halogen towards free radical substitution F2 > Cl2 > Br2 > I2 Knocking tendency of petroleum as fuel decrease with increase in side chain. Straight chain > Branched chain HYDROCARBON - ALKENE CH3 − CH2 − Cl CH3 − CH2 − X CH CH3 − CH2 − Br 3 − CH2 − I R − SO R − NO2 3H CH3 − CH2 − Cl CH2 = CH2 + CH4 CH3 − CHO CH3 − CH2 − OH CH3 − COOH C(s) + 2H2O(l) CO2 + H2O X2/ hν Cl2/ hν I2/ hν Br2/ hν HIO3/HNO3 HNO3 H2SO4 + SO3 SO2Cl2 + hν 573/O2 Cu tube Pyrolysis + 773 K Mo2O3/O2 (CH3COO)2Mn/O2 Incomplete Combustion 3n + 1 2 O2 Combustion Oxidation at 3°H KMnO4 Aromatization Cr2O3/Al2O3 773 K Cr2O3/Al2O3 773 K, 10 − 20 atm Isomerization Anhy. AlCl3
H2SO4/∆ or R – C ≡ C – R R – C ≡ C – R H3PO4/∆ or Al2O3/∆ Alc. KOH −HX Zn dust Δ Zn dust For higher alkene H2/Pd − CaCO3 give cis Alkene Lindlar catalyst Na/Liq. NH3 Birch redeuction give trans alkene Pyrolysis Δ Δ Kolbe electrolysis (X:Cl, Br, I) → Saytzeff′s rule CH2 = CH2 CH3– CH = CH2 R– CH = CH2 R– CH = CH–R Elimination Reaction (E1 & E2) H3C – CH = CH – CH3 H3C – CH2 – CH = CH2 more substituted alkeneis major product less substituted alkene is major product
• Order of reactivity of olefins for hydrogenation CH2 = CH2 > R– CH = CH2 (Reverse of stability) • Order of reactivity of alkene towards hydration • > CH3– CH = CH2 > CH2 = CH2 Anti addition of Br2 cis ⟶ d,l dibromide Markownikoff Rule (M.R. ) Br2 Br − CCl4 H − O − H Dry NaCl KI Cold Conc. H2SO4 (EAR) H − X HBr, HCl, HI(EAR) H+/H2O OsO4/NaHSO3 or dil (Markownikov′s rule) HBr Peroxide (Anti − Markownikov′s rule) CH3COOH + CO2 CO2 + H2O Br − CH2 − CH = CH2 Cl − CH2 − CH = CH2 Br − CH2 − CH − CH3 H + or O−H ൬ 3n 2 ൰ O2 combustion NBS HBr + R2O2 (Anti − Markownikov′s rule) Cl2/500°C