15.6 Reactions of Alcohols: A Review and a Preview
description
Transcript of 15.6 Reactions of Alcohols: A Review and a Preview
15.6Reactions of Alcohols:
A Review and a Preview
Table 15.2 Table 15.2 Review of Reactions of AlcoholsReview of Reactions of Alcohols
reaction with hydrogen halides reaction with hydrogen halides
reaction with thionyl chloridereaction with thionyl chloride
reaction with phosphorous tribromidereaction with phosphorous tribromide
acid-catalyzed dehydrationacid-catalyzed dehydration
conversion to conversion to pp-toluenesulfonate esters-toluenesulfonate esters
New Reactions of Alcohols in This ChapterNew Reactions of Alcohols in This Chapter
conversion to ethersconversion to ethers
esterificationesterification
esters of inorganic acidsesters of inorganic acids
oxidationoxidation
cleavage of vicinal diolscleavage of vicinal diols
15.7Conversion of Alcohols to Ethers
RCHRCH22OO
HH
CHCH22RR
OHOH
HH++
RCHRCH22OO CHCH22RR HH OHOH++
Conversion of Alcohols to EthersConversion of Alcohols to Ethers
acid-catalyzedacid-catalyzedreferred to as a "condensation"referred to as a "condensation"equilibrium; most favorable for primary alcoholsequilibrium; most favorable for primary alcohols
ExampleExample
2CH2CH33CHCH22CHCH22CHCH22OHOH
HH22SOSO44, 130°C, 130°C
CHCH33CHCH22CHCH22CHCH22OCHOCH22CHCH22CHCH22CHCH33
(60%)(60%)
Figure 15.2 Mechanism of Formation of Diethyl EtherFigure 15.2 Mechanism of Formation of Diethyl Ether
Step 1:Step 1:
CHCH33CHCH22OO•••• ••••
HH
HH OSOOSO22OHOH
CHCH33CHCH22OO ••••
HH
OSOOSO22OHOHHH
++ ––++
Figure 15.2 Mechanism of Formation of Diethyl EtherFigure 15.2 Mechanism of Formation of Diethyl Ether
Step 2:Step 2:
CHCH33CHCH22••••
HH
HH
++OO
CHCH33CHCH22OO•••• ••••
HH
++++
CHCH33CHCH22
CHCH33CHCH22OO ••••
HH
••••
HH
HH
OO••••
Figure 15.2 Mechanism of Formation of Diethyl EtherFigure 15.2 Mechanism of Formation of Diethyl Ether
Step 3:Step 3:
++++
CHCH33CHCH22
CHCH33CHCH22OO ••••
HHOSOOSO22OHOH
–– ••••••••••••
HH OSOOSO22OHOH••••••••
CHCH33CHCH22
CHCH33CHCH22OO ••••••••
reaction normally works wellreaction normally works wellonly for 5- and 6-memberedonly for 5- and 6-memberedringsrings
Intramolecular AnalogIntramolecular Analog
HOCHHOCH22CHCH22CHCH22CHCH22CHCH22OHOH
HH22SOSO44 130°130°
OO
(76%)(76%)
Intramolecular AnalogIntramolecular Analog
HOCHHOCH22CHCH22CHCH22CHCH22CHCH22OHOH
HH22SOSO44 130°130°
OO
(76%)(76%)
via:via:
OO
HH
++OO
HH
HH
••••
••••
••••
15.8Esterification
condensationcondensation
Fischer esterificationFischer esterification
acid catalyzedacid catalyzed
reversiblereversible
EsterificationEsterification
ROROHH HH22OO++HH++
++R'COHR'COH
OO
R'CR'COROR
OO
Example of Fischer EsterificationExample of Fischer Esterification
HH22OO++
CHCH33OHOH++COHCOH
OO
COCHCOCH33
OO
HH22SOSO44
0.1 mol0.1 mol 0.6 mol0.6 mol
70% yield based on benzoic acid70% yield based on benzoic acid
high yieldshigh yields
not reversible when carried outnot reversible when carried outin presence of pyridinein presence of pyridine
Reaction of Alcohols with Acyl ChloridesReaction of Alcohols with Acyl Chlorides
ROROHH HClHCl++ ++R'CClR'CCl
OO
R'CR'COROR
OO
pyridinepyridine
++ CClCClOO22NN
OOCHCH33CHCH22
CHCH33
OOHH
(63%)(63%)
NONO22
CHCH33CHCH22
CHCH33
OOCC
OO
ExampleExample
analogous to reaction with acyl chloridesanalogous to reaction with acyl chlorides
Reaction of Alcohols with Acid AnhydridesReaction of Alcohols with Acid Anhydrides
ROROHH ++ ++R'CR'COROR
OOOO
R'COCR'R'COCR'
OO
R'COHR'COH
OO
pyridinepyridine
(83%)(83%)
++CC66HH55CHCH22CHCH22OHOH
OO
FF33CCOCCFCCOCCF33
OO
CC66HH55CHCH22CHCH22OCCFOCCF33
OO
ExampleExample
15.9Esters of Inorganic Acids
Esters of Inorganic AcidsEsters of Inorganic Acids
ROH + HOEWGROH + HOEWG ROEWG + HROEWG + H22OO
EWG is an electron-withdrawing groupEWG is an electron-withdrawing group
HONOHONO22 (HO)(HO)22SOSO22 (HO)(HO)33PP OO++ ––
Esters of Inorganic AcidsEsters of Inorganic Acids
ROH + HOEWGROH + HOEWG ROEWG + HROEWG + H22OO
EWG is an electron-withdrawing groupEWG is an electron-withdrawing group
HONOHONO22 (HO)(HO)22SOSO22 (HO)(HO)33PP OO++ ––
CHCH33OH + HONOOH + HONO22 CHCH33ONOONO22 + H + H22OO
(66-80%)(66-80%)
15.10Oxidation of Alcohols
Primary alcoholsPrimary alcohols
Secondary alcoholsSecondary alcoholsfrom Hfrom H22OO
Oxidation of AlcoholsOxidation of Alcohols
RCHRCH22OHOH
OO
RCHRCH
OO
RCOHRCOH
OO
RCR'RCR'RCHR'RCHR'
OHOH
Aqueous solutionAqueous solution
Mn(VII) Mn(VII) Cr(VI)Cr(VI)
KMnOKMnO44 HH22CrOCrO44
HH22CrCr22OO77
Typical Oxidizing AgentsTypical Oxidizing Agents
Aqueous Cr(VI)Aqueous Cr(VI)
FCHFCH22CHCH22CHCH22CHCH22OHOH
KK22CrCr22OO77
HH22SOSO44
HH22OO
FCHFCH22CHCH22CHCH22COHCOH
(74%)(74%)
OO
Aqueous Cr(VI)Aqueous Cr(VI)
FCHFCH22CHCH22CHCH22CHCH22OHOH
KK22CrCr22OO77
HH22SOSO44
HH22OO
FCHFCH22CHCH22CHCH22COHCOH
(74%)(74%)
OO
NaNa22CrCr22OO77
HH22SOSO44
HH22OO
(85%)(85%)
HH
OHOH
OO
All are used in CHAll are used in CH22ClCl22
Pyridinium dichromate (PDC)Pyridinium dichromate (PDC)
(C(C55HH55NHNH++))2 2 CrCr22OO77
2–2–
Pyridinium chlorochromate (PCC)Pyridinium chlorochromate (PCC)
CC55HH55NHNH++ ClCrO ClCrO33––
Nonaqueous Sources of Cr(VI)Nonaqueous Sources of Cr(VI)
Example: Oxidation of Example: Oxidation of a primary alcohol with a primary alcohol with PCCPCC
CHCH33(CH(CH22))55CHCH22OHOHPCCPCC
CHCH22ClCl22
OO
CHCH33(CH(CH22))55CHCH
(78%)(78%)
ClCrOClCrO33––
NN
HH
++
PDCPDC CHCH22ClCl22
OO
(94%)(94%)
CHCH22OHOH(CH(CH33))33CC
CHCH(CH(CH33))33CC
Example: Oxidation of Example: Oxidation of a primary alcohol with a primary alcohol with PDCPDC
MechanismMechanism
involves formation involves formation and elimination of and elimination of a chromate estera chromate ester
CC
OOHH
HOHOCrOHCrOH
OO
OO
CC
OO
HH HHOO
OO
CrOHCrOH
MechanismMechanism
involves formation involves formation and elimination of and elimination of a chromate estera chromate ester
CC
OOHH
HOHOCrOHCrOH
OO
OO
CC
OO
HH HHOO
OO
CrOHCrOH
OO••••
••••
CC OO
15.11Biological Oxidation of Alcohols
alcohol alcohol dehydrogenasedehydrogenase
Enzyme-catalyzedEnzyme-catalyzed
CHCH33CCHH22OOHH ++ NADNAD++
++ ++ ++HHNADNAD HHCHCH33CCHH OO
nicotinamide adenine dinucleotide (oxidized form)nicotinamide adenine dinucleotide (oxidized form)
HOHO
HOHO
OOOO
NNNN
NHNH22
PPOO
PPOO
OO
HOHOOHOH
HH
CC
OO
NHNH22NN
OO OO OO OO
++
____
Figure 15.3 Structure of NADFigure 15.3 Structure of NAD++
Enzyme-catalyzedEnzyme-catalyzed
CHCH33CCHH22OOHH ++
NN
HH
CNHCNH22
OO
++
RR
++HH++
Enzyme-catalyzedEnzyme-catalyzed
NN
HH
CNHCNH22
OO
RR
CHCH33CCHH
OOHH
••••
15.1215.12Oxidative Cleavage of Vicinal DiolsOxidative Cleavage of Vicinal Diols
Cleavage of Vicinal Diols by Periodic AcidCleavage of Vicinal Diols by Periodic Acid
CCCC
HOHO OHOH
HIOHIO44 CC OO OO CC++
Cleavage of Vicinal Diols by Periodic AcidCleavage of Vicinal Diols by Periodic Acid
HIOHIO44
CHCH CCHCCH33
CHCH33
OHOHHOHO
CHCH33CCHCCH33
OO
CHCH
OO
++
(83%)(83%)
Cyclic Diols are CleavedCyclic Diols are Cleaved
HIOHIO44
OHOH
OHOH
OO
HCCHHCCH22CHCH22CHCH22CHCH
OO