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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 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) Alkanes, nomenclature CH3CH2CH2CH2CH2CH3 (n-hexane) n-hexane CH3 CH3CH2CHCH2CH3 (no common name) 3-methylpentane CH3 CH3CHCHCH3 CH3 (no common name) 2,3-dimethylbutane CH3 CH3CHCH2CH2CH3 (isohexane) 2-methylpentane CH3 CH3CCH2CH3 CH3 (neohexane) 2,2-dimethylbutane Alkanes, syntheses 1. Addition of hydrogen (reduction). | | —C=C— + H2 + Ni, Pt, or Pd | | —C—C— | | H H Requires catalyst. CH3CH=CHCH3 2-butene + H2, Ni CH3CH2CH2CH3 n-butane 2. 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 b) 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 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. 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 CH3CH2CH2CH3 + Br2, hv CH3CH2CH2CH2-Br n-butane n-butyl bromide + CH3CH2CHCH3 Br sec-butyl bromide CH3 CH3 CH3CHCH3 + Br2, hv CH3CHCH2-Br isobutane 2% <1% isobutyl bromide + CH3 CH3CCH3 Br tert-butyl bromide 99% 98% 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 Alkyl halides, nomenclature CH3 CH3CHCH2CHCH3 Br 2-bromo-4-methylpentane 2o CH3 Cl-CHCH2CH3 sec-butyl chloride 2-chlorobutane 2o CH3 CH3CCH3 I tert-butyl iodide 2-iodo-2-methylpropane 3o Alkyl halides, syntheses 1. From alcohols a) 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 CH3CH2CH2CH2-OH + NaBr, H2SO4, heat n-butyl alcohol (HBr) n-butyl bromide 1-butanol CH3 CH3CCH3 OH CH3CH2CH2CH2-Br 1-bromobutane + HCl tert-butyl alcohol 2-methyl-2-propanol CH3-OH methyl alcohol methanol + CH3 CH3CCH3 Cl tert-butyl chloride 2-chloro-2-methylpropane HI, H+,heat CH3-I methyl iodide iodomethane …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 CH3CHCH2-OH isobutyl alcohol 2-methyl-1-propanol + PBr3 CH3 CH3CHCH2-Br isobutyl bromide 1-bromo-2-methylpropane 2. 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 CH3CCH3 CH3 + Cl2, heat neopentane 2,2-dimethylpropane CH3 CH3CCH2-Cl CH3 neopentyl chloride 1-chloro-2,2-dimethylpropane 5. 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 Reactions of alkyl halides: 1. Nucleophilic substitution R-X Best with 1o or CH3!!!!!! + :Z- R-Z + :X- 2. Dehydrohalogenation R-X + KOH(alc) alkene(s) 3. Preparation of Grignard Reagent R-X + Mg RMgX RMgX 4. Reduction R-X + Mg R-X + Sn, HCl R-H + H2O R-H 1. Nucleophilic substitution R-X + :OH- ROH + :X- alcohol R-X + H2O ROH + HX alcohol R-X + :OR´- R-O-R´ + :X- ether R-CCR´ + :X- alkyne R-X + :I- iodide R-X + :CN- R-CN + :X- nitrile R-X + :NH3 + HX primary amine R-X + -:CCR´ R-I R-NH2 + :X- R-X + :NH2R´ R-NHR´ + HX R-X + :SH- R-SH R-X + :SR´ + :X- R-SR´ + :X- Etc. Best when R-X is CH3 or 1o! SN2 secondary amine thiol thioether 2. dehydrohalogenation of alkyl halides | | — C — C — + KOH(alc.) | | H X a) b) c) d) e) f) g) h) RX: 3o > 2o > 1o no rearragement may yield mixtures Saytzeff orientation element effect isotope effect rate = k [RX] [KOH] Mechanism = E2 | | —C=C— + KX + H2O CH3CHCH3 Br + KOH(alc) CH3CH=CH2 isopropyl bromide propylene CH3CH2CH2CH2-Br + KOH(alc) n-butyl bromide CH3CH2CHCH3 Br sec-butyl bromide CH3CH2CH=CH2 1-butene + KOH(alc) CH3CH2CH=CH2 1-butene 19% + CH3CH=CHCH3 2-butene 81% 3. preparation of Grignard reagent CH3CH2CH2-Br + Mg CH3CH2CH2-MgBr n-propyl bromide n-propyl magnesium bromide 4. 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 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 Alcohols, nomenclature CH3 CH3CHCH2CHCH3 OH 4-methyl-2-pentanol 2o CH3 CH3CCH3 OH tert-butyl alcohol 2-methyl-2-propanol 3o CH3 HO-CHCH2CH3 CH3CH2CH2-OH sec-butyl alcohol 2-butanol 2o n-propyl alcohol 1-propanol 1o Alcohols, syntheses 1. oxymercuration-demercuration: a) Markovnikov orientation. b) 100% yields. c) no rearrangements CH3CH2CH=CH2 + H2O, Hg(OAc)2; then NaBH4 CH3CH2CHCH3 OH 2. hydroboration-oxidation: Anti-Markovnikov orientation. • 100% yields. • no rearrangements CH3CH2CH=CH2 + (BH3)2; then H2O2, NaOH CH3CH2CH2CH2-OH Reaction of alcohols 1. with HX: R-OH a) HX: + HX R-X + H2O HI > HBr > HCl b) ROH: 3o > 2o > CH3 > 1o SN1/SN2 c) May be acid catalyzed d) Rearrangements are possible except with most 1o alcohols. CH3CH2CH2CH2-OH + NaBr, H2SO4, heat n-butyl alcohol (HBr) n-butyl bromide 1-butanol CH3 CH3CCH3 OH CH3CH2CH2CH2-Br 1-bromobutane + HCl tert-butyl alcohol 2-methyl-2-propanol CH3-OH methyl alcohol methanol + CH3 CH3CCH3 Cl tert-butyl chloride 2-chloro-2-methylpropane HI, H+,heat CH3-I methyl iodide iodomethane 2. With PX3 ROH + PX3 RX a) PX3 = PCl3, PBr3, P + I2 b) No rearrangements c) ROH: CH3 > 1o > 2o CH3 CH3CCH2-OH CH3 neopentyl alcohol + PBr3 CH3 CH3CCH2-Br CH3 2,2-dimethyl-1-bromopropane 3. Dehydration of alcohols | | | | — C — C — acid, heat — C = C — + H2O | | H OH a) b) c) d) e) f) ROH: 3o > 2o > 1o acid is a catalyst rearrangements are possible mixtures are possible Saytzeff mechanism is E1 CH3CH2-OH CH3 CH3CCH3 OH + 95% H2SO4, 170oC CH2=CH2 + 20% H2SO4, 85-90oC CH3 CH3C=CH2 CH3CH2CHCH3 + 60% H2SO4, 100oC CH3CH=CHCH3 OH + CH3CH2CH=CH2 CH3CH2CH2CH2-OH + H+, 140oC rearrangement! CH3CH2CH=CH2 + CH3CH=CHCH3 4) As acids. a) With active metals: ROH + Na RONa + ½ H2 CH3CH2-OH + K CH3CH2-O-K+ + H2 b) With bases: CH4 < NH3 < ROH < H2O < HF ROH + NaOH NR! CH3CH2OH + CH3MgBr CH4 + Mg(Oet)Br 5. Ester formation. CH3CH2-OH + CH3CO2H, H+ CH3CO2CH2CH3 + H2O CH3CH2-OH + CH3COCl CH3CO2CH2CH3 + CH3-OH + CH3SO2Cl CH3SO3CH3 + HCl Esters are alkyl “salts” of acids. HCl 6. Oxidation Oxidizing agents: KMnO4, K2Cr2O7, CrO3, NaOCl, etc. Primary alcohols: CH3CH2CH2-OH + KMnO4, etc. CH3CH2CO2H carboxylic acid Secondary alcohols: OH CH3CH2CHCH3 O + K2Cr2O7, etc. CH3CH2CCH3 ketone Teriary alcohols: no reaction. Primary alcohols ONLY can be oxidized to aldehydes: CH3CH2CH2-OH + C5H5NHCrO3Cl pyridinium chlorochromate CH3CH2CHO aldehyde or CH3CH2CH2-OH + K2Cr2O7, special conditions Ethers nomenclature syntheses 1. Williamson Synthesis 2. alkoxymercuration-demercuration reactions 1. acid cleavage Ethers R-O-R or R-O-R´ Nomenclature: simple ethers are named: “alkyl alkyl ether” “dialkyl ether” if symmetric CH3CH2-O-CH2CH3 diethyl ether CH3 CH3 CH3CH-O-CHCH3 diisopropyl ether 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-OH + HBr CH3CH2CH2-Br CH3CH2CH2-O-CH(CH3)2 isopropyl n-propyl ether note: the alkyl halide is primary! 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! 2. alkoxymercuration-demercuration: a) Markovnikov orientation. b) 100% yields. c) no rearrangements CH3CH=CH2 + CH3CHCH3, Hg(TFA)2; then NaBH4 OH CH3 CH3 CH3CH-O-CHCH3 diisopropyl ether Avoids the elimination with 2o/3o RX in Williamson Synthesis. Reactions, ethers: 1. Acid cleavage. R-O-R´ + (conc) HX, heat CH3CH2-O-CH2CH3 + HBr, heat R-X + R´-X 2 CH3CH2-Br 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 Alkenes, nomenclature C3H6 propylene C4H8 butylenes CH3CH=CH2 CH3CH2CH=CH2 α-butylene 1-butene CH3CH=CHCH3 β-butylene 2-butene CH3 CH3C=CH2 isobutylene 2-methylpropene * * H3C CH2CH3 C C H CH3 (Z)-3-methyl-2-pentene (3-methyl-cis-2-pentene) * H3C Cl C C H Br * (E)-1-bromo-1-chloropropene 1. dehydrohalogenation of alkyl halides | | — C — C — + KOH(alc.) | | H X a) b) c) d) e) f) g) h) RX: 3o > 2o > 1o no rearragement may yield mixtures Saytzeff orientation element effect isotope effect rate = k [RX] [KOH] Mechanism = E2 | | —C=C— + KX + H2O CH3CHCH3 Br + KOH(alc) CH3CH=CH2 isopropyl bromide propylene CH3CH2CH2CH2-Br + KOH(alc) n-butyl bromide CH3CH2CHCH3 Br sec-butyl bromide CH3CH2CH=CH2 1-butene + KOH(alc) CH3CH2CH=CH2 1-butene 19% + CH3CH=CHCH3 2-butene 81% 2. dehydration of alcohols: | | | | — C — C — acid, heat — C = C — + H2O | | H OH a) b) c) d) e) f) ROH: 3o > 2o > 1o acid is a catalyst rearrangements are possible mixtures are possible Saytzeff mechanism is E1 CH3CH2-OH CH3 CH3CCH3 OH + 95% H2SO4, 170oC CH2=CH2 + 20% H2SO4, 85-90oC CH3 CH3C=CH2 CH3CH2CHCH3 + 60% H2SO4, 100oC CH3CH=CHCH3 OH + CH3CH2CH=CH2 CH3CH2CH2CH2-OH + H+, 140oC rearrangement! CH3CH2CH=CH2 + CH3CH=CHCH3 3. dehalogenation of vicinal dihalides | | —C—C— | | X X + Zn | | — C = C — + ZnX2 eg. CH3CH2CHCH2 + Zn Br Br CH3CH2CH=CH2 + ZnBr2 Not generally useful as vicinal dihalides are usually made from alkenes. May be used to “protect” a carbon-carbon double bond. 4. reduction of alkyne Na or Li NH3(liq) CH3 H \ / C=C / \ H CH3 anti- trans-2-butene CH3CCCH3 H2, Pd-C Lindlar catalyst H H \ / C=C / \ CH3 CH3 cis-2-butene syn- Alkenes, reactions 1. Addition of hydrogen (reduction). | | —C=C— + H2 + Ni, Pt, or Pd | | —C—C— | | H H a) Requires catalyst. b) #1 synthesis of alkanes CH3CH=CHCH3 2-butene + H2, Ni CH3CH2CH2CH3 n-butane 2. Addition of halogens. | | —C=C— + X2 | | —C—C— | | X X a) X2 = Br2 or Cl2 b) test for unsaturation with Br2 CH3CH2CH=CH2 1-butene + Br2/CCl4 CH3CH2CHCH2 Br Br 1,2-dibromobutane 3. Addition of hydrogen halides. | | | | — C = C — + HX — C — C — | | H X a) HX = HI, HBr, HCl b) Markovnikov orientation CH3CH=CH2 CH3 CH2C=CH2 + + HI HBr CH3CHCH3 I CH3 CH3CCH3 Br 4. Addition of sulfuric acid. | | —C=C— + H2SO4 | | —C—C— | | H OSO3H alkyl hydrogen sulfate Markovnikov orientation. CH3CH=CH2 + H2SO4 CH3CHCH3 O O-S-O OH 5. Addition of water. | | —C=C— + H2O, H+ | | —C—C— | | H OH a) requires acid b) Markovnikov orientation c) low yield CH3CH2CH=CH2 + H2O, H+ CH3CH2CHCH3 OH 6. Addition of halogens + water (halohydrin formation): | | | | — C = C — + X2, H2O — C — C — + HX | | OH X a) X2 = Br2, Cl2 b) Br2 = electrophile CH3CH=CH2 + Br2(aq.) CH3CHCH2 + HBr OH Br 7. oxymercuration-demercuration: a) Markovnikov orientation. b) 100% yields. c) no rearrangements CH3CH2CH=CH2 + H2O, Hg(OAc)2; then NaBH4 CH3CH2CHCH3 OH With alcohol instead of water: alkoxymercuration-demercuration: | | | | — C =C — + ROH, Hg(TFA)2 — C — C — | | OR HgTFA | | — C — C — + NaBH4 | | OR HgTFA | | —C—C— | | OR H ether 8. hydroboration-oxidation: a) #2 synthesis of alcohols. b) Anti-Markovnikov orientation. c) 100% yields. d) no rearrangements CH3CH2CH=CH2 + (BH3)2; then H2O2, NaOH CH3CH2CH2CH2-OH 9. Addition of free radicals. | | | | — C = C — + HBr, peroxides — C — C — | | H X a) anti-Markovnikov orientation. b) free radical addition CH3CH=CH2 + HBr, peroxides CH3CH2CH2-Br 10. Addition of carbenes. | | | | — C = C — + CH2CO or CH2N2 , hν — C — C — •CH2• | | —C=C— •CH2• CH2 “carbene” adds across the double bond H2C CHCH3 + CH2N2, hv H H2C C CH3 C H2 11. Epoxidation. | | C6H5CO3H — C = C — + (peroxybenzoic acid) | | — C— C — O epoxide Free radical addition of oxygen diradical. | | —C=C— •O• PBA H2C CHCH3 H H2C C CH3 O 12. Hydroxylation. (mild oxidation) | | — C = C — + KMnO4 | | —C—C— | | OH OH syn OH | | | | — C = C — + HCO3H — C — C — anti peroxyformic acid | | OH glycol cis-2-butene + KMnO2 meso-2,3-dihydroxybutane mp 34o H3 C CH3 CH3 C C H H H OH H OH CH3 trans-2-butene + KMnO4 (S,S) & (R,R)-2,3-dihydroxybutane mp 19o CH3 H3 C H CH3 H OH HO H + HO H H OH C C H CH3 CH3 stereoselective and stereospecific CH3 13. Allylic halogenation. | | | | | | — C = C — C — + X2, heat — C = C — C — + HX | | H allyl X CH2=CHCH3 + Br2, 350oC CH2=CHCH2Br + HBr a) X2 = Cl2 or Br2 b) or N-bromosuccinimide (NBS) 14. Ozonolysis. | | | | — C = C — + O3; then Zn, H2O — C = O + O = C — used for identification of alkenes CH3 CH3CH2CH=CCH3 + O3; then Zn, H2O CH3CH2CH=O + CH3 O=CCH3 15. Vigorous oxidation. =CH2 + KMnO4, heat CO2 =CHR + KMnO4, heat RCOOH =CR2 + KMnO4, heat O=CR2 carboxylic acid ketone CH3CH2CH2CH=CH2 + KMnO4, heat CH3CH2CH2COOH + CO2 CH3 CH3 CH3C=CHCH3 + KMnO4, heat CH3C=O + HOOCCH3 Dienes nomenclature syntheses same as alkenes reactions same as alkenes special: conjugated dienes 1. more stable 2. preferred products of eliminations 3. give 1,2- & 1,4- addition products (cumulated dienes are not very stable and are rare) isolated dienes are as you would predict, undergo addition reactions with one or two moles… conjugated dienes are unusual in that they: 1) are more stable than predicted 2) are the preferred products of eliminations 3) give 1,2- plus 1,4-addition products nomenclature: CH2=CHCH=CH2 CH3CH=CHCH2CH=CHCH3 1,3-butadiene conjugated 2-methyl-1,3-butadiene (isoprene) conjugated 2,5-heptadiene isolated isolated dienes: (as expected) 1,5-hexadiene CH2=CHCH2CH2CH=CH2 + H2, Ni CH3CH2CH2CH2CH=CH2 CH2=CHCH2CH2CH=CH2 + 2 H2, Ni CH3CH2CH2CH2CH2CH3 CH2=CHCH2CH2CH=CH2 + Br2 CH2CHCH2CH2CH=CH2 Br Br CH2=CHCH2CH2CH=CH2 + HBr CH3CHCH2CH2CH=CH2 Br CH2=CHCH2CH2CH=CH2 + 2 HBr CH3CHCH2CH2CHCH3 Br Br conjugated dienes yield 1,2- plus 1,4-addition: CH2=CHCH=CH2 + H2, Ni CH3CH2CH=CH2 + CH3CH=CHCH3 CH2=CHCH=CH2 + 2 H2, Ni CH3CH2CH2CH3 CH2=CHCH=CH2 + Br2 CH2CHCH=CH2 + CH2CH=CHCH2 Br Br Br Br CH2=CHCH=CH2 + HBr CH3CHCH=CH2 + CH3CH=CHCH2 Br Br peroxides CH2=CHCH=CH2 + HBr CH2CH=CHCH3 + CH2CH2CH=CH2 Br Br Alkynes nomenclature syntheses 1. dehydrohalogenation of vicinal dihalides 2. coupling of metal acetylides with alkyl halides reactions 1. reduction 2. addition of halogens 3. addition of hydrogen halides 4. addition of water 5. as acids 6. with Ag+ 7. oxidation Alkynes, nomenclature HCCH ethyne acetylene CH3CH2CCH 1-butyne ethylacetylene CH3 HCCCHCH2CH3 3-methyl-1-pentyne sec-butylacetylene Synthesis, alkynes: 1. dehydrohalogenation of vicinal dihalides H H | | —C—C— | | X X H | + KOH — C = C — | X H | —C=C— | X + NaNH2 — C C — + NaX + NH3 + KX + H2O Synthesis of propyne from propane Br2, heat CH3CH2CH3 CH3CH2CH2-Br + CH3CHCH3 Br KOH(alc) CH3CHCH2 Br Br Br2 CH3CH=CH2 KOH NaNH2 CH3CH CH Br CH3C CH 2. coupling of metal acetylides with 1o/CH3 alkyl halides R-CC-Na+ + R´X R-CC-R´ + NaX a) SN2 b) R´X must be 1o or CH3X CH3CC-Li+ + CH3CH2-Br CH3CCCH2CH3 Alkyne, reactions 1. Addition of hydrogen (reduction) HCCH + 2 H2, Pt CH3CH3 [ HCCH + one mole H2, Pt CH3CH3 + CH2=CH2 + HCCH ] Na or Li NH3(liq) —CC— H2, Pd-C Lindlar catalyst H \ / C=C / \ H \ / C=C / \ H H anti- syn- Na or Li NH3(liq) CH3 H \ / C=C / \ H CH3 anti- trans-2-butene CH3CCCH3 H2, Pd-C Lindlar catalyst H H \ / C=C / \ CH3 CH3 cis-2-butene syn- 2. Addition of X2 X X X | | | — C C— + X2 — C = C — + X2 — C — C — | | | X X X CH3CCH + Br2 Br Br Br CH3C=CH + Br2 CH3-C-CH Br Br Br 3. Addition of hydrogen halides: H H X | | | — C C— + HX — C = C — + HX — C — C — | | | X H X a) HX = HI, HBr, HCl b) Markovnikov orientation CH3CCH + HCl CH3C=CH2 Cl Cl + HCl CH3CCH3 Cl 4. Addition of water. Hydration. O — C C — + H2O, H+, HgO — CH2 — C— H OH —C=C— “enol” Markovnikov orientation. keto-enol tautomerism CH3CH2CCH + H2O, H2SO4, HgO 1-butyne O CH3CH2CCH3 2-butanone 5. As acids. terminal alkynes only! a) with active metals CH3CCH + Na CH3CC-Na+ + ½ H2 b) with bases CH4 < NH3 < HCCH < ROH < H2O < HF CH3CCH + CH3MgBr CH4 + CH3C CMgBr SA SB WA WB 6. Ag+ terminal alkynes only! CH3CH2CCH + AgNO3 CH3CH2CC-Ag+ CH3CCCH3 + AgNO3 NR (not terminal) formation of a precipitate is a test for terminal alkynes. 7. Oxidation CH3CH2CCCH3 + KMnO4 CH3CH2COOH + HOOCCH3 CH3CCH + hot KMnO4 CH3COOH + CO2 CH3CCCH3 + O3; then Zn, H2O 2 CH3COOH Alicyclics nomenclature syntheses like alkanes, alkenes, alcohols, etc. reactions as expected exceptions: cyclopropane/cyclobutane CH3 H3C CH3 methylcyclopentane 1,1-dimethylcyclobutane Br Br Br Br Br trans-1,2-dibromocyclohexane Br 3 4 2 5 1 6 cyclopentene 3-methylcyclohexene 1,3-cyclobutadiene Cycloalkanes, syntheses A. Modification of a cyclic compound: H2, Ni Br Sn, HCl Br Mg; then H2O Cycloalkanes, reactions: 1. halogenation Cl2, heat Cl + HCl 2. combustion 3. cracking 4. exceptions exceptions: H2, Ni, 80o CH3CH2CH3 Cl2, FeCl3 Cl-CH2CH2CH2-Cl H2O, H+ CH3CH2CH2-OH conc. H2SO4 CH3CH2CH2-OSO3H HI CH3CH2CH2-I exceptions (cont.) + H2, Ni, 200o CH3CH2CH2CH3 Cycloalkenes, syntheses Cl OH KOH(alc) H+, Δ cyclohexene Br Br Zn Cycloalkenes, reactions: 1. addition of H2 8. hydroboration-oxid. 2. addition of X2 9. addition of free radicals 3. addition of HX 10. addition of carbenes 4. addition of H2SO4 11. epoxidation 5. addition of H2O,H+ 12. hydroxylation 6. addition of X2 + H2O 13. allylic halogenation 7. oxymerc-demerc. 14. ozonolysis 15. vigorous oxidation H2, Pt Br2, CCl4 Br trans-1,2-dibromocyclohexane Br HBr H2SO4 H2O, H+ Br2 (aq.) Br OSO3H Markovnikov OH OH Br dimerization + HF + H2O,Hg(OAc)2 (BH3)2 NaBH4 OH H2O2, NaOH Markovnikov anti-Markovnikov OH HBr, perox. anti-Markovinikov Br polymer. n CH2CO,hv PBA O OH KMnO4 cis-1,2-cylohexanediol OH OH HCO3H OH trans-1,2-cyclohexanediol Br Br2, heat O3 Zn, H2O KMnO4, heat O=CHCH2CH2CH2CH2CH=O HO2CCH2CH2CH2CH2CO2H Epoxides nomenclature syntheses 1. epoxidation of alkenes reactions 1. addition of acids 2. addition of bases Epoxides, nomenclature H2C CH2 O H H2C C CH3 O ethylene oxide propylene oxide (oxirane) (methyloxirane) O cyclopentene oxide Synthesis: C6H5CO3H O cis-2-butene β-butylene oxide epoxides, reactions: 1) acid catalyzed addition H2C CH2 O H2C CH2 O H2C CH2 O H2O, H+ CH3CH2OH, H+ HBr OH CH2CH2 OH OH CH3CH2-O-CH2CH2 OH CH2CH2 Br 2. Base catalyzed addition H2C CH2 O OH CH2CH2 OH NaOH, H2O H2C CH2 NaOCH2CH3 O CH3CH2OH H2C CH2 O H2C CH2 O NH3 CH3CH2-O-CH2CH2-OH H2N-CH2CH2-OH 1. CH3CH2MgBr 2. H2O CH3CH2CH2CH2-OH Mechanisms: Free radical substitution SN2 SN1 E2 E1 ionic electrophilic addition free radical electrophilic addition Memorize (all steps, curved arrow formalism, RDS) and know which reactions go by these mechanisms! Free Radical Substitution Mechanism initiating step: 1) X—X 2 X• propagating steps: 2) X• + R—H H—X + R• 3) R• + X—X R—X + X• 2), 3), 2), 3)… terminating steps: 4) 2 X• X—X 5) R• + X• R—X 6) 2 R• R—R Substitution, nucleophilic, bimolecular (SN2) SN2 RDS Z: + CH3 > 1o > 2o > 3o C W Z C + :W Substitution, nucleophilic, unimolecular (SN1) 1) RDS C W C + :W carbocation 2) C + 3o > 2o > 1o > CH3 :Z C Z Mechanism = elimination, bimolecular E2 W RDS C C H base: 3o > 2o > 1o C C + H:base + :W Elimination, unimolecular 1) 2) C C H W C C H 3o > 2 o > 1 o RDS -H E1 C C H C C + :W Ionic electrophilic addition mechanism 1) 2) C C C C Y + YZ + Z RDS C C Y C C Z Y + Z Free radical electrophilic addition of HBr: Initiating steps: 1) peroxide 2 radical• 2) radical• + HBr radical:H + Br• (Br• electrophile) Propagating steps: 3) Br• + CH3CH=CH2 CH3CHCH2-Br (2o free radical) • 4) CH3CHCH2-Br + HBr CH3CH2CH2-Br + Br• • 3), 4), 3), 4)… Terminating steps: 5) Br• + Br• Br2 Etc.