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 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
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
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
Brtert-butyl bromide isobutane
3. Corey-House Synthesis
CH3 CH3 CH3
CH3CH-Br + Li CH3CH-Li + CuI (CH3CH)2-CuLiisopropyl 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 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
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 CH3
CH3CHCH2CHCH3 CH3CCH3
Br I2-bromo-4-methylpentane tert-butyl iodide
2-iodo-2-methylpropane 2o 3o
CH3
Cl-CHCH2CH3
sec-butyl chloride2-chlorobutane 2o
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 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
…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
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 CH3
CH3CCH3 + Cl2, heat CH3CCH2-Cl CH3 CH3
neopentane neopentyl chloride 2,2-dimethylpropane 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 Best with 1o or CH3!!!!!!
R-X + :Z- R-Z + :X-
2. Dehydrohalogenation
R-X + KOH(alc) alkene(s)
3. Preparation of Grignard Reagent
R-X + Mg RMgX
4. Reduction
R-X + Mg RMgX + H2O R-H
R-X + Sn, HCl 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-X + -:CCR´ R-CCR´ + :X- alkyne
R-X + :I- R-I + :X- iodide
R-X + :CN- R-CN + :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
2. dehydrohalogenation of alkyl halides
| | | |— C — C — + KOH(alc.) — C = C — + KX + H2O | | H X
a) RX: 3o > 2o > 1o b) no rearragement c) may yield mixtures d) Saytzeff orientatione) element effectf) isotope effectg) rate = k [RX] [KOH]h) Mechanism = E2
CH3CHCH3 + KOH(alc) CH3CH=CH2
Brisopropyl bromide propylene
CH3CH2CH2CH2-Br + KOH(alc) CH3CH2CH=CH2
n-butyl bromide 1-butene
CH3CH2CHCH3 + KOH(alc) CH3CH2CH=CH2
Br 1-butene 19% sec-butyl bromide +
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 CH3
CH3CHCH2CHCH3 CH3CCH3
OH OH4-methyl-2-pentanol tert-butyl alcohol
2-methyl-2-propanol 2o 3o
CH3
HO-CHCH2CH3 CH3CH2CH2-OH
sec-butyl alcohol n-propyl alcohol 2-butanol 1-propanol 2o 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 + HX R-X + H2O
a) HX: 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 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
2. With PX3
ROH + PX3 RX
a) PX3 = PCl3, PBr3, P + I2
b) No rearrangements
c) ROH: CH3 > 1o > 2o
CH3 CH3
CH3CCH2-OH + PBr3 CH3CCH2-Br CH3 CH3
neopentyl alcohol 2,2-dimethyl-1-bromopropane
3. Dehydration of alcohols
| | | |— C — C — acid, heat — C = C — + H2O | | H OH
a) ROH: 3o > 2o > 1o
b) acid is a catalystc) rearrangements are possible d) mixtures are possible e) Saytzefff) mechanism is E1
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
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 + HCl
CH3-OH + CH3SO2Cl CH3SO3CH3 + HCl
Esters are alkyl “salts” of acids.
6. 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
ketoneTeriary alcohols:
no reaction.
Primary alcohols ONLY can be oxidized to aldehydes:
CH3CH2CH2-OH + C5H5NHCrO3Cl CH3CH2CHO
pyridinium chlorochromate 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
CH3 CH3
CH3CH2-O-CH2CH3 CH3CH-O-CHCH3
diethyl ether diisopropyl ether
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!
1. Williamson Synthesis of Ethers
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 R-X + R´-X
CH3CH2-O-CH2CH3 + HBr, heat 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 CH3CH=CH2
C4H8 butylenes CH3CH2CH=CH2
α-butylene
1-butene
CH3
CH3CH=CHCH3 CH3C=CH2
β-butylene isobutylene
2-butene 2-methylpropene
C CH
H3C CH2CH3
CH3
C CH3C
H Br
Cl
*
* *
*
(Z)-3-methyl-2-pentene
(3-methyl-cis-2-pentene)
(E)-1-bromo-1-chloropropene
1. dehydrohalogenation of alkyl halides
| | | |— C — C — + KOH(alc.) — C = C — + KX + H2O | | H X
a) RX: 3o > 2o > 1o b) no rearragement c) may yield mixtures d) Saytzeff orientatione) element effectf) isotope effectg) rate = k [RX] [KOH]h) Mechanism = E2
CH3CHCH3 + KOH(alc) CH3CH=CH2
Brisopropyl bromide propylene
CH3CH2CH2CH2-Br + KOH(alc) CH3CH2CH=CH2
n-butyl bromide 1-butene
CH3CH2CHCH3 + KOH(alc) CH3CH2CH=CH2
Br 1-butene 19% sec-butyl bromide +
CH3CH=CHCH3
2-butene 81%
2. dehydration of alcohols:
| | | |— C — C — acid, heat — C = C — + H2O | | H OH
a) ROH: 3o > 2o > 1o
b) acid is a catalystc) rearrangements are possible d) mixtures are possible e) Saytzefff) mechanism is E1
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
3. 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.
CH3 H
\ /Na or Li C = C anti-
NH3(liq) / \ H CH3
trans-2-buteneCH3CCCH3
H H \ /
H2, Pd-C C = C syn- Lindlar catalyst / \ CH3 CH3
cis-2-butene
4. reduction of alkyne
Alkenes, reactions
1. Addition of hydrogen (reduction).
| | | |— C = C — + H2 + Ni, Pt, or Pd — C — C —
| | H Ha) Requires catalyst.b) #1 synthesis of alkanes
CH3CH=CHCH3 + H2, Ni CH3CH2CH2CH3
2-butene 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 + Br2/CCl4 CH3CH2CHCH2
Br Br 1-butene 1,2-dibromobutane
3. Addition of hydrogen halides. | | | |— C = C — + HX — C — C —
| | H Xa) HX = HI, HBr, HClb) Markovnikov orientation
CH3CH=CH2 + HI CH3CHCH3
I
CH3 CH3
CH2C=CH2 + HBr 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 OHa) requires acidb) Markovnikov orientationc) 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 — C — C — | | | | OR HgTFA 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
•CH2• “carbene” adds across the double bond | |— C = C — •CH2•
H2C CHCH3 + CH2N2, hvHCH2C
CH2
CH3
11. Epoxidation.
| | C6H5CO3H | |
— C = C — + (peroxybenzoic acid) — C— C —
O epoxideFree radical addition of oxygen diradical. | |— C = C — •O•
H2C CHCH3
HCH2C
OCH3
PBA
12. Hydroxylation. (mild oxidation)
| | | |— C = C — + KMnO4 — C — C — syn | | OH OH
OH | | | |— C = C — + HCO3H — C — C — anti peroxyformic acid | | OH
glycol
cis-2-butene + KMnO2 meso-2,3-dihydroxybutane mp 34o
CH3
H OH
H OH
CH3
trans-2-butene + KMnO4 (S,S) & (R,R)-2,3-dihydroxybutane mp 19o
CH3 CH3
H OH + HO H
HO H H OH
CH3 CH3
stereoselective and stereospecific
C CH
H3C CH3
H
C CH
H3C H
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
CH3
CH3CH2CH=O + O=CCH3
15. Vigorous oxidation.
=CH2 + KMnO4, heat CO2
=CHR + KMnO4, heat RCOOH carboxylic acid
=CR2 + KMnO4, heat O=CR2 ketone
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 2,5-heptadiene
conjugated isolated
2-methyl-1,3-butadiene (isoprene)
conjugated
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
peroxidesCH2=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
CH3
CH3CH2CCH HCCCHCH2CH3
1-butyne 3-methyl-1-pentyne
ethylacetylene sec-butylacetylene
Synthesis, alkynes:
1. dehydrohalogenation of vicinal dihalides
H H H | | |— C — C — + KOH — C = C — + KX + H2O | | | X X X
H | — C = C — + NaNH2 — C C — + NaX + NH3
| X
Synthesis of propyne from propane
CH3CH2CH3
Br2, heatCH3CH2CH2-Br + CH3CHCH3
Br
KOH(alc)
CH3CH=CH2Br2
CH3CHCH2
Br Br
KOH
CH3CH CH
Br
NaNH2CH3C 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
HCCH + 2 H2, Pt CH3CH3
[ HCCH + one mole H2, Pt CH3CH3 + CH2=CH2 + HCCH ]
H \ /
Na or Li C = C anti- NH3(liq) / \
H— C C —
\ / H2, Pd-C C = C syn-
Lindlar catalyst / \ H H
Alkyne, reactions
1. Addition of hydrogen (reduction)
CH3 H
\ /Na or Li C = C anti-
NH3(liq) / \ H CH3
trans-2-buteneCH3CCCH3
H H \ /
H2, Pd-C C = C syn- Lindlar catalyst / \ CH3 CH3
cis-2-butene
2. Addition of X2
X X X | | |— C C— + X2 — C = C — + X2 — C — C
— | | | X X X
Br Br BrCH3CCH + Br2 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, HClb) Markovnikov orientation
ClCH3CCH + HCl CH3C=CH2 + HCl CH3CCH3
Cl Cl
4. Addition of water. Hydration.
O
— C C — + H2O, H+, HgO — CH2 — C—
H OH
— C = C —
“enol” keto-enol tautomerism
Markovnikov orientation.
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.
CH3CH2CCCH3 + KMnO4
CH3CCH + hot KMnO4
CH3CCCH3 + O3; then Zn, H2O
CH3CH2COOH + HOOCCH3
CH3COOH + CO2
2 CH3COOH
7. Oxidation
Alicyclics
nomenclature
syntheses
like alkanes, alkenes, alcohols, etc.
reactions
as expected
exceptions: cyclopropane/cyclobutane
CH3
BrBr Br Br
CH3
H3C
methylcyclopentane 1,1-dimethylcyclobutane
trans-1,2-dibromocyclohexane
Br
Br
exceptions:
H2, Ni, 80o
CH3CH2CH3
Cl2, FeCl3
Cl-CH2CH2CH2-Cl
H2O, H+
CH3CH2CH2-OH
conc. H2SO4
CH3CH2CH2-OSO3H
HI CH3CH2CH2-I
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
Br
Br
Br
OSO3H
OH
OH
Br
+
H2, Pt
Br2, CCl4
HBr
H2SO4
H2O, H+
Br2 (aq.)
dimerization
trans-1,2-dibromocyclohexane
Markovnikov
n
OH
OH
Br
+
O
HF
H2O,Hg(OAc)2 NaBH4
(BH3)2 H2O2, NaOH
HBr, perox.
polymer.
CH2CO,hv
PBA
Markovnikov
anti-Markovnikov
anti-Markovinikov
OH
OH
OH
OH
Br
KMnO4
HCO3H
Br2, heat
O3 Zn, H2O
KMnO4, heat
O=CHCH2CH2CH2CH2CH=O
HO2CCH2CH2CH2CH2CO2H
cis-1,2-cylohexanediol
trans-1,2-cyclohexanediol
Epoxides
nomenclature
syntheses
1. epoxidation of alkenes
reactions
1. addition of acids
2. addition of bases
Epoxides, nomenclature
CH2H2CO
HCH2C
OCH3 O
O
ethylene oxide propylene oxide cyclopentene oxide
(oxirane) (methyloxirane)
C6H5CO3H
Synthesis:
β-butylene oxidecis-2-butene
epoxides, reactions:
1) acid catalyzed addition
CH2H2CO
CH2H2CO
CH2H2CO
H2O, H+
CH3CH2OH, H+
HBr
OHCH2CH2
OH
OHCH3CH2-O-CH2CH2
OHCH2CH2
Br
CH2H2CO
CH2H2CO
CH2H2CO
CH2H2CO
NaOH, H2O
NaOCH2CH3
CH3CH2OH
NH3
1. CH3CH2MgBr
2. H2O
OHCH2CH2
OH
CH3CH2-O-CH2CH2-OH
H2N-CH2CH2-OH
CH3CH2CH2CH2-OH
2. Base catalyzed addition
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, unimolecular (SN1)
3o > 2o > 1o > CH3
C WRDS
C + :W
C + :Z C Z
carbocation
1)
2)
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.
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