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CHE-300 Review nomenclature syntheses reactions mechanisms

CHE-300 Review nomenclature syntheses reactions mechanisms. Alkanes Alkyl halides Alcohols Ethers Alkenes conjugated dienes Alkynes Alicyclics Epoxides. Alkanes Nomenclature Syntheses 1. reduction of alkene (addition of hydrogen) 2. reduction of an alkyl halide

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CHE-300 Review nomenclature syntheses reactions mechanisms

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  1. CHE-300 Review nomenclature syntheses reactions mechanisms

  2. Alkanes Alkyl halides Alcohols Ethers Alkenes conjugated dienes Alkynes Alicyclics Epoxides

  3. Alkanes Nomenclature Syntheses 1. reduction of alkene (addition of hydrogen) 2. reduction of an alkyl halide a) hydrolysis of a Grignard reagent b) with an active metal and acid 3. Corey-House Synthesis Reactions 1. halogenation 2. combustion (oxidation) 3. pyrolysis (cracking)

  4. Alkanes, nomenclature CH3 CH3CH2CH2CH2CH2CH3 CH3CHCH2CH2CH3 (n-hexane) (isohexane) n-hexane 2-methylpentane CH3 CH3 CH3CH2CHCH2CH3 CH3CCH2CH3 (no common name) CH3 3-methylpentane (neohexane) 2,2-dimethylbutane CH3 CH3CHCHCH3 CH3 (no common name) 2,3-dimethylbutane

  5. Alkanes, syntheses • 1. Addition of hydrogen (reduction). • | | | | • — C = C — + H2 + Ni, Pt, or Pd  — C — C — • | | • H H • Requires catalyst. • CH3CH=CHCH3 + H2, Ni  CH3CH2CH2CH3 • 2-butene n-butane

  6. Reduction of an alkyl halide • a) hydrolysis of a Grignard reagent (two steps) • i) R—X + Mg  RMgX (Grignard reagent) • ii) RMgX + H2O  RH + Mg(OH)X • SB SA WA WB • CH3CH2CH2-Br + Mg  CH3CH2CH2-MgBr • n-propyl bromide n-propyl magnesium bromide • CH3CH2CH2-MgBr + H2O  CH3CH2CH3 + Mg(OH)Br • propane

  7. with an active metal and an acid • R—X + metal/acid  RH • active metals = Sn, Zn, Fe, etc. • acid = HCl, etc. (H+) • CH3CH2CHCH3 + Sn/HCl  CH3CH2CH2CH3 + SnCl2 • Cl • sec-butyl chloride n-butane • CH3 CH3 • CH3CCH3 + Zn/H+  CH3CHCH3 + ZnBr2 • Br • tert-butyl bromide isobutane

  8. 3. Corey-House Synthesis CH3 CH3 CH3 CH3CH-Br + Li  CH3CH-Li + CuI  (CH3CH)2-CuLi isopropyl bromide CH3 CH3 (CH3CH)2-CuLi + CH3CH2CH2-Br  CH3CH-CH2CH2CH3 2-methylpentane (isohexane) mechanism = SN2 Note: the R´X should be a 1o or methyl halide for the best yields of the final product.

  9. Alkanes, reactions 1. Halogenation R-H + X2, heat or hv  R-X + HX a) heat or light required for reaction. b) X2: Cl2 > Br2 I2 c) yields mixtures d) H: 3o > 2o > 1o > CH4 e) bromine is more selective f) free radical substitution

  10. CH3CH2CH2CH3 + Br2, hv  CH3CH2CH2CH2-Br 2% n-butane n-butyl bromide + CH3CH2CHCH3 98% Br sec-butyl bromide CH3 CH3 CH3CHCH3 + Br2, hv  CH3CHCH2-Br <1% isobutane isobutyl bromide + CH3 CH3CCH3 99% Br tert-butyl bromide

  11. Alkyl halides nomenclature syntheses 1. from alcohols a) HX b) PX3 2. halogenation of certain alkanes 3. addition of hydrogen halides to alkenes 4. addition of halogens to alkenes 5. halide exchange for iodide reactions 1. nucleophilic substitution 2. dehydrohalogenation 3. formation of Grignard reagent 4. reduction

  12. Alkyl halides, nomenclature CH3 CH3 CH3CHCH2CHCH3 CH3CCH3 Br I 2-bromo-4-methylpentane tert-butyl iodide 2-iodo-2-methylpropane 2o 3o CH3 Cl-CHCH2CH3 sec-butyl chloride 2-chlorobutane 2o

  13. Alkyl halides, syntheses • 1. From alcohols • With HX • R-OH + HX  R-X + H2O • i) HX = HCl, HBr, HI • ii) may be acid catalyzed (H+) • iii) ROH: 3o > 2o > CH3 > 1o (3o/2o – SN1; CH3/1o – SN2) • iv) rearrangements are possible except with most 1o ROH

  14. CH3CH2CH2CH2-OH + NaBr, H2SO4, heat  CH3CH2CH2CH2-Br n-butyl alcohol (HBr) n-butyl bromide 1-butanol 1-bromobutane CH3 CH3 CH3CCH3 + HCl  CH3CCH3 OH Cl tert-butyl alcohol tert-butyl chloride 2-methyl-2-propanol 2-chloro-2-methylpropane CH3-OH + HI, H+,heat  CH3-I methyl alcohol methyl iodide methanol iodomethane

  15. …from alcohols: b) PX3 i) PX3 = PCl3, PBr3, P + I2 ii) ROH: CH3 > 1o > 2o iii) no rearragements CH3CH2-OH + P, I2 CH3CH2-I ethyl alcohol ethyl iodide ethanol iodoethane CH3 CH3 CH3CHCH2-OH + PBr3  CH3CHCH2-Br isobutyl alcohol isobutyl bromide 2-methyl-1-propanol 1-bromo-2-methylpropane

  16. Halogenation of certain hydrocarbons. • R-H + X2, Δ or hν  R-X + HX • (requires Δ or hν; Cl2 > Br2 (I2 NR); 3o>2o>1o) • yields mixtures!  In syntheses, limited to those hydrocarbons that yield only one monohalogenated product. • CH3 CH3 • CH3CCH3 + Cl2, heat  CH3CCH2-Cl • CH3 CH3 • neopentane neopentyl chloride • 2,2-dimethylpropane 1-chloro-2,2-dimethylpropane

  17. Halide exchange for iodide. • R-X + NaI, acetone  R-I + NaX  • i) R-X = R-Cl or R-Br • ii) NaI is soluble in acetone, NaCl/NaBr are insoluble. • CH3CH2CH2-Br + NaI, acetone  CH3CH2CH2-I • n-propyl bromide n-propyl idodide • 1-bromopropane 1-idodopropane • iii) SN2 R-X should be 1o or CH3

  18. Reactions of alkyl halides: • Nucleophilic substitutionBest with 1o or CH3!!!!!! • R-X + :Z- R-Z + :X- • Dehydrohalogenation • R-X + KOH(alc)  alkene(s) • Preparation of Grignard Reagent • R-X + Mg  RMgX • Reduction • R-X + Mg  RMgX + H2O  R-H • R-X + Sn, HCl  R-H

  19. 1. Nucleophilic substitution R-X + :OH- ROH + :X- alcohol R-X + H2O  ROH + HX alcohol R-X + :OR´-  R-O-R´ + :X- ether R-X + -:CCR´  R-CCR´ + :X- alkyne R-X + :I- R-I + :X- iodide R-X + :CN-  R-CN + :X- nitrile R-X + :NH3 R-NH2 + HX primary amine R-X + :NH2R´  R-NHR´ + HX secondary amine R-X + :SH-  R-SH + :X- thiol R-X + :SR´  R-SR´ + :X- thioether Etc. Best when R-X is CH3 or 1o! SN2

  20. 2. dehydrohalogenation of alkyl halides • | | | | • — C — C — + KOH(alc.)  — C = C — + KX + H2O • | | • H X • RX: 3o > 2o > 1o • no rearragement  • may yield mixtures  • Saytzeff orientation • element effect • isotope effect • rate = k [RX] [KOH] • Mechanism = E2

  21. CH3CHCH3 + KOH(alc)  CH3CH=CH2 Br isopropyl bromide propylene CH3CH2CH2CH2-Br + KOH(alc)  CH3CH2CH=CH2 n-butyl bromide 1-butene CH3CH2CHCH3 + KOH(alc)  CH3CH2CH=CH2 Br 1-butene19% sec-butyl bromide + CH3CH=CHCH3 2-butene81%

  22. 3. preparation of Grignard reagent • CH3CH2CH2-Br + Mg  CH3CH2CH2-MgBr • n-propyl bromide n-propyl magnesium bromide • reduction • CH3CH2CH2-Br + Mg  CH3CH2CH2-MgBr • CH3CH2CH2-MgBr + H2O  CH3CH2CH3 + Mg(OH)Br • propane • CH3CH2CHCH3 + Sn/HCl  CH3CH2CH2CH3 + SnCl2 • Cl • sec-butyl chloride n-butane

  23. Alcohols nomenclature syntheses 1. oxymercuration-demercuration 2. hydroboration-oxidation 3. 4. hydrolysis of some alkyl halides reactions 1. HX 2. PX3 3. dehydration 4. as acids 5. ester formation 6. oxidation

  24. Alcohols, nomenclature CH3 CH3 CH3CHCH2CHCH3 CH3CCH3 OH OH 4-methyl-2-pentanol tert-butyl alcohol 2-methyl-2-propanol 2o 3o CH3 HO-CHCH2CH3 CH3CH2CH2-OH sec-butyl alcohol n-propyl alcohol 2-butanol1-propanol 2o 1o

  25. Alcohols, syntheses • 1. oxymercuration-demercuration: • Markovnikov orientation. • 100% yields.  • no rearrangements  • CH3CH2CH=CH2 + H2O, Hg(OAc)2; then NaBH4 • CH3CH2CHCH3 • OH

  26. 2. hydroboration-oxidation: • Anti-Markovnikov orientation.  • 100% yields.  • no rearrangements  • CH3CH2CH=CH2 + (BH3)2; then H2O2, NaOH  • CH3CH2CH2CH2-OH

  27. Reaction of alcohols 1. with HX: R-OH + HX  R-X + H2O a) HX: HI > HBr > HCl b) ROH: 3o > 2o > CH3 > 1oSN1/SN2 c) May be acid catalyzed d) Rearrangements are possible except with most 1o alcohols.

  28. CH3CH2CH2CH2-OH + NaBr, H2SO4, heat  CH3CH2CH2CH2-Br n-butyl alcohol (HBr) n-butyl bromide 1-butanol 1-bromobutane CH3 CH3 CH3CCH3 + HCl  CH3CCH3 OH Cl tert-butyl alcohol tert-butyl chloride 2-methyl-2-propanol 2-chloro-2-methylpropane CH3-OH + HI, H+,heat  CH3-I methyl alcohol methyl iodide methanol iodomethane

  29. With PX3 • ROH + PX3 RX • PX3 = PCl3, PBr3, P + I2 • No rearrangements • ROH: CH3 > 1o > 2o • CH3 CH3 • CH3CCH2-OH + PBr3 CH3CCH2-Br • CH3 CH3 • neopentyl alcohol 2,2-dimethyl-1-bromopropane 

  30. Dehydration of alcohols • | ||| • — C — C — acid, heat  — C = C — + H2O • | | • H OH • ROH: 3o > 2o > 1o • acid is a catalyst • rearrangements are possible  • mixtures are possible  • Saytzeff • mechanism is E1

  31. CH3CH2-OH + 95% H2SO4, 170oC  CH2=CH2 CH3 CH3 CH3CCH3 + 20% H2SO4, 85-90oC  CH3C=CH2 OH CH3CH2CHCH3 + 60% H2SO4, 100oC  CH3CH=CHCH3 OH + CH3CH2CH=CH2 CH3CH2CH2CH2-OH + H+, 140oC  CH3CH2CH=CH2 rearrangement!  + CH3CH=CHCH3

  32. As acids. • With active metals: • ROH + Na  RONa + ½ H2 • CH3CH2-OH + K  CH3CH2-O-K+ + H2 • With bases: • CH4 < NH3 < ROH < H2O < HF • ROH + NaOH  NR! • CH3CH2OH + CH3MgBr  CH4 + Mg(Oet)Br

  33. Ester formation. • CH3CH2-OH + CH3CO2H, H+ CH3CO2CH2CH3 + H2O • CH3CH2-OH + CH3COCl  CH3CO2CH2CH3 + HCl • CH3-OH + CH3SO2Cl  CH3SO3CH3 + HCl • Esters are alkyl “salts” of acids.

  34. Oxidation • Oxidizing agents: KMnO4, K2Cr2O7, CrO3, NaOCl, etc. • Primary alcohols: • CH3CH2CH2-OH + KMnO4, etc.  CH3CH2CO2H • carboxylic acid • Secondary alcohols: • OH O • CH3CH2CHCH3 + K2Cr2O7, etc.  CH3CH2CCH3 • ketone • Teriary alcohols: • no reaction.

  35. Primary alcohols ONLY can be oxidized to aldehydes: CH3CH2CH2-OH + C5H5NHCrO3Cl CH3CH2CHO pyridinium chlorochromatealdehyde or CH3CH2CH2-OH + K2Cr2O7,special conditions

  36. Ethers nomenclature syntheses 1. Williamson Synthesis 2. alkoxymercuration-demercuration reactions 1. acid cleavage

  37. Ethers R-O-R or R-O-R´ Nomenclature: simple ethers are named: “alkyl alkyl ether” “dialkyl ether” if symmetric CH3 CH3 CH3CH2-O-CH2CH3 CH3CH-O-CHCH3 diethyl ether diisopropyl ether

  38. 1. Williamson Synthesis of Ethers R-OH + Na  R-O-Na+  R-O-R´ R´-OH + HX  R´-X (CH3)2CH-OH + Na  (CH3)2CH-O-Na+ +  CH3CH2CH2-O-CH(CH3)2 CH3CH2CH2-OH + HBr  CH3CH2CH2-Br isopropyl n-propyl ether note: the alkyl halide is primary! 

  39. CH3CH2CH2-OH + Na  CH3CH2CH2-ONa +  CH3CH2CH2-O-CH(CH3)2 (CH3)2CH-OH + HBr  (CH3)2CH-Br 2o The product of this attempted Williamson Synthesis using a secondary alkyl halide results not in the desired ether but in an alkene! The alkyl halide in a Williamson Synthesis must beCH3 or 1o! 

  40. 2. alkoxymercuration-demercuration: • Markovnikov orientation. • 100% yields.  • no rearrangements  • CH3CH=CH2 + CH3CHCH3, Hg(TFA)2; then NaBH4 • OH • CH3CH3 • CH3CH-O-CHCH3 • diisopropyl ether • Avoids the elimination with 2o/3o RX in Williamson Synthesis.

  41. Reactions, ethers: • Acid cleavage. • R-O-R´ + (conc) HX, heat  R-X + R´-X • CH3CH2-O-CH2CH3 + HBr, heat  2 CH3CH2-Br

  42. Alkenes nomenclature syntheses 1. dehydrohalogenation of an alkyl halide 2. dehydration of an alcohol 3. dehalogenation of a vicinal dihalide 4. reduction of an alkyne reactions 1. addition of hydrogen 8. hydroboration-oxidation 2. addition of halogens 9. addition of free radicals 3. addition of hydrogen halides 10. addition of carbenes 4. addition of sulfuric acid 11. epoxidation 5. addition of water 12. hydroxylation 6. halohydrin formation 13. allylic halogenation 7. oxymercuration-demercuration 14. ozonolysis 15. vigorous oxidation

  43. Alkenes, nomenclature C3H6 propylene CH3CH=CH2 C4H8 butylenes CH3CH2CH=CH2 α-butylene 1-butene CH3 CH3CH=CHCH3 CH3C=CH2 β-butylene isobutylene 2-butene 2-methylpropene

  44. * * (Z)-3-methyl-2-pentene (3-methyl-cis-2-pentene) * (E)-1-bromo-1-chloropropene *

  45. 1. dehydrohalogenation of alkyl halides • | | | | • — C — C — + KOH(alc.)  — C = C — + KX + H2O • | | • H X • RX: 3o > 2o > 1o • no rearragement  • may yield mixtures  • Saytzeff orientation • element effect • isotope effect • rate = k [RX] [KOH] • Mechanism = E2

  46. CH3CHCH3 + KOH(alc)  CH3CH=CH2 Br isopropyl bromide propylene CH3CH2CH2CH2-Br + KOH(alc)  CH3CH2CH=CH2 n-butyl bromide 1-butene CH3CH2CHCH3 + KOH(alc)  CH3CH2CH=CH2 Br 1-butene19% sec-butyl bromide + CH3CH=CHCH3 2-butene81%

  47. dehydration of alcohols: • | ||| • — C — C — acid, heat  — C = C — + H2O • | | • H OH • ROH: 3o > 2o > 1o • acid is a catalyst • rearrangements are possible  • mixtures are possible  • Saytzeff • mechanism is E1

  48. CH3CH2-OH + 95% H2SO4, 170oC  CH2=CH2 CH3 CH3 CH3CCH3 + 20% H2SO4, 85-90oC  CH3C=CH2 OH CH3CH2CHCH3 + 60% H2SO4, 100oC  CH3CH=CHCH3 OH + CH3CH2CH=CH2 CH3CH2CH2CH2-OH + H+, 140oC  CH3CH2CH=CH2 rearrangement!  + CH3CH=CHCH3

  49. dehalogenation of vicinal dihalides • | | | | • — C — C — + Zn  — C = C — + ZnX2 • || • X X • eg. • CH3CH2CHCH2 + Zn  CH3CH2CH=CH2 + ZnBr2 • Br Br • Not generally useful as vicinal dihalides are usually made from alkenes. May be used to “protect” a carbon-carbon double bond.

  50. 4. reduction of alkyne CH3 H \ / Na or Li C = C anti- NH3(liq) / \ H CH3 trans-2-butene CH3CCCH3 H H \ / H2, Pd-C C = C syn- Lindlar catalyst / \ CH3 CH3 cis-2-butene

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