Содержание
- 2. ALKANES (a “family” of hydrocarbons) CnH2n+2 CH4 C2H6 C3H8 C4H10 etc. C2H6 ethane H H H—C—C—H
- 3. sp3, bond angles = 109.5o σ-bonds (sigma) rotation about C--C (conformations) representation: “andiron” or “sawhorse”
- 4. “staggered” “eclipsed” torsional strain: deviation from staggered. Newman projections:
- 5. The barrier to rotation about the carbon-carbon bond in ethane is 3 Kcal/mole. The rotation is
- 9. Two isomers of butane C4H10: CH3CH2CH2CH3 n-butane bp 0 oC mp –138 oC d 0.622 g/cc
- 11. conformations about C2-C3 in n-butane:
- 13. Alkane name isomers CH4 methane 1 C2H6 ethane 1 C3H8 propane 1 C4H10 butanes 2 C5H12
- 14. hexanes C6H14 common names CH3 CH3CH2CH2CH2CH2CH3 CH3CHCH2CH2CH3 n-hexane isohexane CH3 CH3 CH3CH2CHCH2CH3 CH3CCH2CH3 ????? CH3 neohexane
- 15. IUPAC nomenclature (Geneva, 1920) names of radicals (alkyl groups): CH3- “methyl” CH3Cl methyl chloride CH3OH methyl
- 16. CH3CH2CH2CH2- “n-butyl” CH3 CH3CH2CHCH3 or CH3CH2CH- “sec-butyl” | CH3 CH3CHCH2- “isobutyl” CH3 CH3CCH3 “tert-butyl” |
- 20. Web problems to help with naming and recognizing organic radicals: Click here or copy and paste
- 21. IUPAC rules for naming alkanes: parent chain = longest continuous carbon chain ? “alkane”. branches on
- 22. hexanes C6H14 IUPAC names CH3 CH3CH2CH2CH2CH2CH3 CH3CHCH2CH2CH3 (n-hexane) (isohexane) n-hexane 2-methylpentane CH3 CH3 CH3CH2CHCH2CH3 CH3CCH2CH3 (no
- 23. CH3CH2 CH2CHCH2CHCH3 CH3 CH3 2,4-dimethylheptane CH3 CH3 CH CH3CH2CH2CHCH2 CH3 CH2CH2CCH3 CH3 6-isopropyl-2,2-dimethylnonane
- 24. “classes of carbons” primary carbon (1o) – a carbon bonded to one carbon secondary carbon (2o)
- 25. classification of hydrogens, halides – hydrogens or halides are classified by the carbon to which they
- 26. alkanes, physical properties non-polar or only weakly polar, cannot hydrogen bond ? relatively weak intermolecular forces
- 27. alkane mp oC bp oC methane -183 -162 ethane -172 -89 propane -187 -42 n-butane -138
- 28. fossil fuels: natural gas petroleum coal petroleum is a complex mixture of hydrocarbons 1. solvents 2.
- 29. products from fractional distillation of petroleum: fraction b. range carbons natural gas below 20o C1 –
- 30. syntheses Industrial Laboratory large amounts (tons) small amounts (grams) lowest cost non-profit mixtures often okay pure
- 31. Alkanes, syntheses: (to be covered later) Reduction of an alkyl halide a) hydrolysis of a Grignard
- 32. Reduction of an alkyl halide a) hydrolysis of a Grignard reagent (two steps) i) R—X +
- 33. CH3 CH3 CH3CH-Br + Mg ? CH3CH-MgBr isopropyl bromide isopropyl magnesium bromide CH3 CH3CH-MgBr + H2O
- 34. with an active metal and an acid R—X + metal/acid ? RH active metals = Sn,
- 35. Corey-House synthesis R-X + Li ? R-Li + CuI ? R2CuLi R2CuLi + R´-X ? R—R´
- 36. note: the previous equations are not balanced: R-X + 2 Li ? R-Li + LiX 2
- 37. CH3 CH3 CH3 CH3CH-Br + Li ? CH3CH-Li + CuI ? (CH3CH)2-CuLi isopropyl bromide CH3 CH3
- 38. Alkanes, syntheses: (to be covered later) Reduction of an alkyl halide a) hydrolysis of a Grignard
- 39. ALKANES ALKYL HALIDES Mg H2O Sn,HCl Li CuI R’X
- 40. Reactions of alkanes: alkane + H2SO4 ? no reaction (NR) alkane + NaOH ? NR alkane
- 41. Alkane, reactions: Halogenation 2. Combustion (oxidation) 3. Pyrolysis (cracking)
- 42. Combustion CnH2n+2 + (xs) O2, flame ? n CO2 + (n+1) H2O + heat gasoline, diesel,
- 43. Halogenation R-H + X2, heat or hv ? R-X + HX a) heat or light required
- 44. CH3CH3 + Cl2, hv ? CH3CH2-Cl + HCl ethane ethyl chloride CH3CH2CH3 + Cl2, hv ?
- 45. CH3CH2CH2CH3 + Cl2, hv ? CH3CH2CH2CH2-Cl 28% n-butane n-butyl chloride + CH3CH2CHCH3 72% Cl sec-butyl chloride
- 46. CH3CH3 + Br2, hv ? CH3CH2-Br + HBr ethane ethyl bromide CH3CH2CH3 + Br2, hv ?
- 47. CH3CH2CH2CH3 + Br2, hv ? CH3CH2CH2CH2-Br 2% n-butane n-butyl bromide + CH3CH2CHCH3 98% Br sec-butyl bromide
- 48. In the reaction of alkanes with halogens, bromine is less reactive but more selective. Why? How?
- 49. chlorination of propane, mechanism: Cl—Cl ? 2 Cl• abstraction of 1o hydrogen: Cl• + CH3CH2CH3 ?
- 50. 2) abstraction of 1o hydrogen: Cl• + CH3CH2CH3 ? CH3CH2CH2• + HCl or abstraction of 2o
- 51. The number of hydrogens (probability factor) may also be important. CH3CH2CH2CH3 + Cl2, hv ? CH3CH2CH2CH2-Cl
- 52. CH3 CH3 CH3 CH3CHCH3 + Cl2, hv ? CH3CHCH2-Cl + CH3CCH3 isobutane Cl isobutyl chloride =
- 53. Relative reactivity in bromination: 3o : 2o : 1o = 1600 : 82 : 1 In
- 54. Why is relative reactivity of H: 3o > 2o > 1o ? CH3—H ? CH3• +
- 55. Relative reactivity in halogenation: Stability of free radicals: Ease of formation of free radicals: Ease of
- 56. Halogenation R-H + X2, heat or hv ? R-X + HX a) heat or light required
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