0

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