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A
Alcohols
Acidity BasicityR CH 2 OH I R CHA F THE
pka HEEVery
weak
Thiols
R CHIS H I R CHEF Htt
pKa I 8 12 weakerbase
NoticeThis Nao Li Ko
2GHzOH t 2 Nao 2 CH EN t Itf
Useful way to make alkoxide
Alcohols Reactions depend on thenumber of alkyl grays bonded tocarbon
H Ito H cityH at It at
Methyl f 20 30
The OH is not a leaving groupbut several reactions involveconversion of the OH groupinto a good leaving group
The OH groupreacts as a
nucleophile or a bee is
strong acid This is how
the Qt is converted to a
leaving group
Alcohols + H-X
CH2 O H
Products
SN2
Summary:
Regiochemistry:
Stereochemistry:
Example:
HCl
OH
1° Alcohols: SN2
R
BrH Br
2°/3° Alcohols: SN1
C O HR
BrH
SN1Br
Products
R
R
CC
CC
C
H
H H
H H
H
RH
H
HH
CC
CC
C
H
H
H H
H
RH
H
HH
H
CC
CC
C
H
H H
H
RH
H
HH
H H
Under these acidic conditions, rearrangements are a particular problem with 2°carbocations
2° or 3° Alcohol Dehydration
E1
Summary:
Regiochemistry:
Stereochemistry:
Example:OH
2° or 3° Alcohols
(S)
HO H
OH
H2SO4
Products
H
OH S
O
O
OH
BirGoodtea
Ce Br I
N SmN intiAdda R CHEEi.fi R cHz i3r
r
proton 1544 H ItBreaks
AB.ir
bond
R H
F r c'toAdda p c o Breaks 1 aproton 1ps it bond R
Make a
Note the badacidicnature ofthis reaction R
J EI retizirR
Reachin of primary alcohols Sar2Reaction of secondary tertiary alcohols Sw1
Add a proton then carry out substitution ThsOlt is converted to a good leavinggroup HD
N Achiral tertiary alcohols give scrambledproducts SNL
eye NEniral
Products
Acid-catalyzed Hydration of an Alkene
S
O
O
OO
H
H H
O H
+
H
C
C
C
H
H
H
H
H
H
O HH
S
O
O
OO
H+
+
H
O HH
O HH
O HH
Summary:
Regiochemistry:
Stereochemistry:
Example:
H2O
H2SO4 (catalytic amount)
P alcohols EIreact via
E2 NOT a
MUnucleophile
Add a
proton
Break a
catchbond
It IED it
I vl H tH
H peek H E Hprotonaway
OHgroup protonated
in strong acidbreak a bond and with no nucleophile
eventually a proton will be takenaway to give an alkene
Zaitsev's RuleN A
a
9c
Wicked storyacidAdd a H H
proton morestable
H H H 20 m
cain acid
Eid IId gpnNucleophile
fit IE.EEIfI b A
strongH Take a
H Acid
protonaway
Protonadds to make a carbocation water attacks tomake a new bond take a proton away to make product alcohol
Markovnikov's RuleMixed time capsule
OHXL
animalOH on more substitutes
atom Markovnikov
Microscopic ReversibilityReaction mechanism involvethe same intermediatesin both directions
d II KateHyLe Chattier's PrincipleIf we add water we
get alcohol to predominate
If we do not add waterOR if we take water awayfrom the reaction as it is made
we get alkene
Alcohols + PBr3
O H
Products
SN2
Summary:
Regiochemistry:
Stereochemistry:
Example:
PBr3(S)
OH
H
1° or 2° Alcohols
BrP
Br
Br
Br
H
R'
R
112504CHZCHPH Eff HyceHz
vodka 123817sHP3590 9570 ethanol
pH pHtypically CHz CHL4090
EthyleneGlycol
Anti freeze
Chromic Acid Oxidation of Alcohols
C O H
Products
Summary:
Regiochemistry:
Stereochemistry:
Example:
H2CrO4(R)
1° Alcohols
R
H
Cr
O
O
OHHOH
OH H
OH H
Cr
O
O
OHHO
OH H
OH