Alcohol

1. 1
Alcohol
Jully Tan
School of Engineering
This family of organic compounds is characterized by the hydroxyl
group: -OH. Note that when an R group (an alkyl group) replaces
one H in the water molecule, an alcohol results
O
R
O
H
EP101 / EG101
Alcohols
.
: :
C O-H
the alcohol
functional group
H
105o
water
H
109o
an alcohol
OH is the function group which is the center of the reactivity

2. 2
Alcohols are classified as primary, secondary or tertiary
according to the structure around the carbon to which the
hydroxyl group is attached
CH3
H
OH
CH3 OH
CH3
CH3 C
EP101 / EG101
Classification of Alcohols
.
ethyl alcohol
CH3CH2OH
H
CH3 C
H
OH
a 1o alcohol
isopropyl alcohol
(CH3)2CHOH
CH3 C
a 2o alcohol
tertiary-butyl alcohol
(CH3)3COH
a 3o alcohol
Aromatic (phenol): -OH is bonded to a benzene ring
OH
Nomenclature of Alcohols
parent
suffix
EP101 / EG101
In the IUPAC naming
system, there may be as
many as four components
to the name:
Locant indicates the position
of a substituent.
Prefix names the substituent group.
Parent is the parent alkane.
Suffix names a key function.
Examples
OH
CH3CH2CHCH3
CH3CHCH2CH2OH
CH3
2-butanol 3-methyl-1-butanol
suffix
locant parent
locant prefix locant

3. 3
IUPAC Rules for Naming Alcohols
(1) Select the longest continuous chain containing the
hydroxyl group as the parent. Drop the e in the alkane
name and add the suffix ol.
(2) Number the chain from the end that gives a lower
.
number to the position of the hydroxyl group
OH
EP101 / EG101
4 3 2 1
CH3CH2CHCH2OH
CH3
2-methyl-1-butanol
CH3CHCHCH3
CH3
3-methyl-2-butanol
OH
CH3
Note: The glycol name uses the common
name of the alkene that yields the diol
upon hydroxylation
EP101 / EG101
Common Names of Alcohols
Alkyl group names are approved by IUPAC for naming alcohols:
alkyl group + alcohol.
CH3CH2OH CH3CHCH3
CH3CCH2OH
CH3
ethyl alcohol isopropyl alcohol neopentyl alcohol
Glycol is a
common name for
compounds
containing two
hydroxyl groups.
In the IUPAC
system, they are
diols.
HOCH2CH2OH CH3CHCH2OH
OH
ethylene glycol
(1,2-ethanediol)
propylene glycol
(1,2-propanediol)
.

4. 4
OH
EP101 / EG101
Name these:
CH3
CH3 CH
CH2OH
CH3
CH3 C
OH
CH3
CH3 CH
CH2CH3
2-methyl-1-propanol
2-methyl-2-propanol
2-butanol
OH
Br CH3
3-bromo-3-methylcyclohexanol
EP101 / EG101
Unsaturated Alcohols
Hydroxyl group takes precedence over double and triple bonds.
Assign carbon with –OH the lowest number.
Use alkene or alkyne name.
pent-4-ene-2-ol or 4-penten-2-ol
OH
CH2 CHCH2CHCH3
HO OH 1,6-hexanediol
Glycols
1, 2 diols (vicinal diols) are called glycols.
Common names for glycols use the name of the alkene from which they were made.
CH2CH2
OH OH
1,2-ethanediol
ethylene glycol
CH2CH2CH3
OH OH
1,2-propanediol
propylene glycol

5. 5
EP101 / EG101
Naming Phenols
-OH group is assumed to be on carbon 1.
For common names of disubstituted phenols, use ortho- for 1,2; meta- for 1,3; and para-for
1,4.
Methyl phenols are cresols.
OH
Cl
3-chlorophenol
meta-chlorophenol
OH
H3C
4-methylphenol
para-cresol
Physical Properties of Alcohols: 1. Solubility
Solubility decreases as the size
of the alkyl group increases.
OH group is the hydrophilic part of alcohol (ROH)
which form H bond with water molecules.
Therefore, ROH is soluble in water. BUT when C
chain increased, the solubility in water decreased.
(increase the hydrophobicity)
Increase branching increased the ROH solubility.
WHY??? Because the C atom (hydrophobic part)
become more compact and smaller.
EP101 / EG101

6. 6
EP101 / EG101
2. Boiling Points
• ROH has bp higher than any HC of similar molecular mass.
•The large difference in bp is due to the intermolecular hydrogen bond in alcohol and
phenol.
• Presence of –OH group causes polarization in the molecule to form intermolecular
hydrogen bonds.
• van der waals hydrogen bonds ; the energy/strength increase for H bonds. So more
energy needed to break bonds.
• bp reduces by increased the branching of molecule due to smaller surface area and its
reduce the dipole inter-reaction between molecules and less energy needed to break bonds.
•
3. Acidity of Alcohol Phenol
R-OH + H2O R-O- + H3O+
+ - Smaller pKa=
= [ H O ][ RO
] 3 = -
K log
a a a whereby pK K
EP101 / EG101
ROH are weak acid
In aqueous, ROH donate proton to water to form alkoxide ion
If given disassociation constant, Ka, the smaller the Ka the more acidic the ROH
[ ROH
]
Delocalization of electron in the benzene ring makes phenoxide ion more acidic
stable in its form of as compared to alkoxide ion.
Presence of e withdrawing grp phenol acidity.
more acidic!!

7. 7
Molecular Structure and Acidity
C. Resonance delocalization of charge in A-
the more stable the anion, the farther the position of equilibrium is shifted to
EP101 / EG101
the right
ionization of the O-H bond of an alcohol gives an anion for which there is no
resonance stabilization
CH3CH2O-H H2O CH3CH2O - H3O+ +
An alcohol An alkoxide ion
+ pKa = 15.9
Molecular Structure and Acidity
D. Electron-withdrawing inductive effect
the polarization of electron density of a covalent bond due to the
electronegativity of an adjacent covalent bond
H
H
H
F
F
F
stabilization by the inductive effect falls off rapidly with increasing distance of
the electronegative atom from the site of negative charge
EP101 / EG101
C-CH2O-H
C-CH2O-H
Ethanol
pKa 15.9
2,2,2-Trifluoroethanol
pKa 12.4
CF3 -CH2 -OH CF3 -CH2 -CH2 -OH CF3 -CH2 -CH2 -CH2 -OH
2,2,2-Trifluoro-ethanol
(pKa 12.4)
3,3,3-Trifluoro-1-
propanol
(pKa 14.6)
4,4,4-Trifluoro-1-
butanol
(pKa 15.4)

8. 8
Simple alcohols are about as acidic as water.
Alkyl groups make an alcohol a weaker acid.
The more easily the alkoxide ion is solvated by water the more its formation is energetically
EP101 / EG101
favored.
Steric effects are important.
The presence of halogens in the alcohol increases the acidity of the alcohol due to
an inductive effect.
The electronegative halogen atom polarizes the X-C bond producing a partial
positive charge on the carbon atom. This charge is further transmitted through the
C-O s bond to the oxygen atom which is then better able to stabilize the negative
charge on the alkoxide oxygen.
Inductive effects increase with the number of electronegative groups and
decreases with the distance from the oygen.
EP101 / EG101

9. 9
EP101 / EG101
Acidity of Phenols
• Phenols and alcohols both contain hydroxyl groups however they are classified as separate functional
groups. Why?
Answer: Phenols have different properties than alcohols, most noteworthy is their acidity (pKa
difference of 106)
OH O
+ H2O + H3O+ pKa = 9.95
H3C
H2
C
OH + H2O H3C
H2
C
O
+ H3O+ pKa = 15.9
Solutions of alcohols in water are neutral, whereas a solution of 0.1 M phenol is slightly acidic
(pH 5.4).
• Why are phenols more acidic?
Resonance. The charge is delocalized around the ring.
O O O O
This gives a qualitative explanation as to why phenols are more acidic than alcohols but for
quantitative comparison, pKa’s must be determined experimentally.
• Ring substituents, especially halogens and nitro groups have marked effects on the acidity of
phenol by a combination or resonance and inductive effects. Both m-cresol and p-cresol are
weaker acids than phenol with pKa’s of 10.01 and 10.17 respectively.
EP101 / EG101
OH OH
CH3
CH3
m-cresol
p-cresol

10. 10
Influence of substituents on the acidity of phenol:
Alkyl groups decrease the acidity of phenol where halogens increase the acidity of phenol through
inductive effects.
OH
Cl
m-chlorophenol
pKa = 8.85
OH
CH3
p-cresol
pKa = 10.17
EP101 / EG101
O
CH3
Electron donating alkyl group destabilizes
this resonance structure
OH
X
X = F, Cl, Br
X
O
Electron withdrawing halogen groups
stabilize the delocalized negative charge
Fluorine is most electronegative of the halogens, and therefore has the greatest influence on the
acidity of halophenols. This trend follows electronegativity: Chlorine has less of an effect than
fluorine and bromine an even smaller effect than chlorine.
Hydroboration-oxidation of alkene
EP101 / EG101
Synthesis of Alcohol
From Alkene
Hydration of alkene
Hydroxylation of alkene
Reduction of carbonyl
Catalytic hydrogenation if aldehyde ketone
Reduction of aldehyde ketone by hidride
Nucleophilic substitution of alkyl halide
Addition of grignard to carbonyl

11. 11
A. Synthesis From Alkene
Acid-Catalyzed Direct Hydration A1. of Alkenes
Alkenes react with water in the presence of acids to give alcohols
directly. Addition does not occur in the absence of acids
.
EP101 / EG101
H3C
H
H3C H
+ H2O
H+ OH
Mechanism of Direct Hydration of Alkenes
Step 1: electrophilic addition
OH2
Step 3: deprotonation
+ fast
EP101 / EG101
+
+ slow
H O
H
H + + H2O
Step 2: nucleophilic addition
:
+ + :
fast
O
H
H
+
tert-butyloxonium ion
:
+ :
OH2 H
O
H
OH +
+
H O
H
H
Note: Hydronium ion is reformed, so
the reaction is catalyzed by acid.

12. 12
Alcohols through Oxidation of Alkylboranes
Reaction of an alkylborane with hydrogen peroxide (H2O2)
and base (NaOH) leads to replacement of the borane group
with a hydroxyl group.
H2O2
The sequence of hydroboration-oxidation of an alkene yields
an alcohol with anti-Markovnikov orientation.
EP101 / EG101
an alkene
OH
anti-Markovnikov product
A2.
NaOH, H2O
BH2H
H
OH H
retention H
Oxidations of Alkenes--Syn Hydroxylation
The stereospecific formation of 1,2-diols (or glycols) from
alkenes may be carried out in two ways:
KMnO4, HO-cold
H2O HO OH
(i) OsO4, pyridine
(ii) Na2SO3/H2O or NaHSO3/H2O HO OH
EP101 / EG101
A3.

13. 13
B. Reduction of Carbonyl
Reduction of aldehyde yields 1º alcohol.
Reduction of ketone yields 2º alcohol.
2 Methods of reduction of carbonyl
Catalytic hydrogenation of aldehyde ketone, and
Reduction of aldehyde ketone by hydride.
EP101 / EG101
OH
EP101 / EG101
B1. Catalytic Hydrogenation
Add H2 with Raney nickel catalyst.
Also reduces any C= bonds.
Hydrogenation of Ketone yields 20 alcohol
Hydrogenation of Aldehyde yields 10 alcohol
H2, Ni
O
C
C
H

14. 14
B2. Reduction of aldehyde ketone by hydride.
H O
H O H
EP101 / EG101
Sodium Borohydride
Hydride ion, H-, attacks the carbonyl carbon, forming an alkoxide ion.
Then the alkoxide ion is protonated by dilute acid.
Only reacts with carbonyl of aldehyde or ketone, not with carbonyls of esters or carboxylic acids.
H
C
O
H
C
H
C
H
H3O+
Comparison of
Reducing Agents
LiAlH4 is stronger.
LiAlH4 reduces more stable compounds
which are resistant to reduction.
EP101 / EG101

15. 15
C. Nucleophilic Substitution of Alkyl Halide
A nucleophile has an unshared pair of electrons available
for bonding to a positive center
.
Nucleophiles may be negatively charged:
- - - -
:: : : : :
HO , CH3O , I , NH2
:
: :
d+
EP101 / EG101
: :
: :
: :
or neutral:
: :
H2O , H3N, CH3OH
Nucleophiles attack
electropositive center.
Halide ion
is the leaving
group.
C X
d-
The polarity of the
carbon-halogen bond
determines the
reactivity pattern:
Reaction of t-Butyl Chloride with Hydroxide:
The reaction of t-butyl chloride with sodium hydroxide in a mixture of
water and acetone (to help dissolve the RCl) shows the following rate
expression
CH3
CH3
CH3-C-Cl + Cl-
The reaction rate depends on the concentration of t-butyl chloride, but
shows no dependence on the concentration of hydroxide ion
EP101 / EG101
:
+ HO-acetone
CH3
CH3
H2O
CH3-C-OH
.
A r e a c tion r a te th a t d ep e n d s on
th e c o n c en tr a tion o f on ly on e
r e a c ta n t (to th e fir s t p ow e r ) is
c a lled fir s t-o rd e r o r u n im o le cu la r .

16. 16
A Proposed Mechanism with a Carbocation Intermediate
bond heterolysis:
CH3
CH3
:
O-H
H
CH3
CH3
CH3
CH3
EP101 / EG101
CH3
CH3
nucleophilic addition:
CH3
CH3
(2) + + :
:
nucleophile
fast +:
t-butyloxonium ion
CH3-C
O-H
H
CH3-C
O-H
H
proton exchange:
(3) +:
+ :
base
fast
CH3
CH3
O-H
H
CH3-C CH3-C
+
O-H H3O+
(1) slow step + +
t-butyl carbocation
a high energy intermediate
CH3-C-Cl
CH3-C
Cl-
C OH
H
H
H3C
+ Cl
C O
H
H
H3C
+ Cl
H
H
C OH
H3C
EP101 / EG101
Examples
H
(1) - HO
+
nucleophile substrate
C Cl
H
H3C
product leaving group
O
(2) +
C Cl
H
H
H3C
H
H
nucleophile substrate
ethyloxonium ion leaving group
product
H
H
+ H3O
H2O

17. 17
R MgBr + C
R O MgBr
EP101 / EG101
Reaction with Carbonyl
R- attacks the partially positive carbon in the carbonyl.
The intermediate is an alkoxide ion.
Addition of water or dilute acid protonates the alkoxide to produce an alcohol.
R C O R C O
HOH
R C OH
OH
D. Addition of Grignard to Carbonyl
C H3
C
R
O
CH3
R
HOH
C H3
R C
OH
R
MgCl
EP101 / EG101
Some Grignard Reagents
Br
+ Mg
ether MgBr
Cl
CH3CHCH2CH3
ether
+ Mg CH3CHCH2CH3
CH3C C H2
Br + Mg
ether
C H3C CH2
MgB r

18. 18
CH3
H
CH3
H
CH3
CH3
H
H3C
C O
CH3
CH3
EP101 / EG101
D1-Synthesis of 1° Alcohols
Grignard + formaldehyde yields a primary alcohol with one additional carbon.
HOH
H
H
CH3 CH
CH2 CH2 C
H
O H
C O
CH3
H3C C
CH2 C MgBr
H
H H
CH3 CH
CH2 CH2 C
H
O MgBr
D2- Synthesis of 2º Alcohols
Grignard + aldehyde yields a secondary alcohol.
CH3 CH CH2 CH2 C
MgBr
H
CH3
H3C CH2 C MgBr
H H
C O
H
CH3 CH
CH2 CH2 C
H
O H
HOH
CH3
CH3
H
H3C
C O
CH3
O H
EP101 / EG101
D3- Synthesis of 3º Alcohols
Grignard + ketone yields a tertiary alcohol.
CH3 CH CH2 CH2 C
MgBr
CH3
CH3
H3C CH2 C MgBr
H H
C O
H3C
CH3
CH3 CH
CH2 CH2 C
CH3
HOH

19. 19
EP101 / EG101
Synthesis Phenol
Sulfonation Fused Alkylation
EP101 / EG101

20. 20
EP101 / EG101
Reaction of Alcohol
Oxidation of ROH
Reduction of ROH
Breaking of Carbon–OH bond
ROHRX
ROHC=C
ROH ROR
Breaking of O-H
Formation of esther
EP101 / EG101
A. Oxidation of Alcohol
-ROH is main source of C=O (carbonyl)
-Oxidation of primary and secondary alcohol will give aldehyde and ketone respectively.
+ Cr3+ (green)
Cu or
CrO3/pyridine(C5H5N)
Chromic acid
H2CrO4

21. 21
1o 2o Alcohol Oxidations
EP101 / EG101
Primary alcohols aldehydes
PCC/CH2Cl2 (pyridinium chlorochromate, C5H5NH+ClCrO3
-)
CrVI in one form or another (H2CrO4 or K2Cr2O7)
MnVII (KMnO4/NaOH/H2O/heat)
Color of reagents can be useful.
CrVI is yellow; CrIII is blue
Cu or
CrO3/pyridine(C5H5N)
Chromic acid
H2CrO4
EP101 / EG101
3o Alcohol Oxidations
Tertiary alcohols cannot be oxidized under
normal conditions.
Heat them too much in the presence of
strong oxidizers; start cleaving C-C bonds.
Why?
When an alcohol is oxidized, a hydrogen is removed from the carbon. If that hydrogen is
not present, no oxidation can occur.
H
OH
O
[O]
OH
NRX

22. 22
OTs
CH3CH2CH3
EP101 / EG101
B. Reduction of Alcohol
OH
CH3CHCH3
alcohol
TsCl
CH3CHCH3
LiAlH4
alkane
tosylate
C. Breaking of Carbon-Hydroxyl Carbon
EP101 / EG101

23. 23
EP101 / EG101
Reaction with HCl
Chloride is a weaker nucleophile than bromide.
Add ZnCl2, which bonds strongly with
-OH, to promote the reaction.
The chloride product is insoluble.
Lucas test: ZnCl2 in conc. HCl
1° alcohols react slowly or not at all.
2° alcohols react in 1-5 minutes.
3° alcohols react in less than 1 minute.
Limitations of HX Reactions
HI does not react
Poor yields of 1° and 2° chlorides
May get alkene instead of alkyl halide
Carbocation intermediate may rearrange.
C2.2. Reaction with tionyl chloride, SOCl2
EP101 / EG101
Produces alkyl chloride, SO2, HCl
S bonds to -OH, Cl- leaves
Cl- abstracts H+ from OH
C-O bond breaks as Cl- transferred to C

24. 24
C2.3. Reaction with Phosphorus halogen, PX3
P bonds to -OH as Br- leaves
EP101 / EG101
Br- attacks backside
HOPBr2 leaves
Dehydration of Alcohols
Alkenes are also generally prepared by the dehydration of
alcohols in the presence of a strong acid.
EP101 / EG101
H+
heat
C
H
C
OH
+ H2O
C3.

25. 25
CH3
O
CH3
EP101 / EG101
D1. Esterification
Fischer: alcohol + carboxylic acid
Tosylate esters
Sulfate esters
Nitrate esters
Phosphate esters
Acid + Alcohol yields Ester + Water
Sulfuric acid is a catalyst.
Each step is reversible.
O
CH3 C OH
+ H O
CH2CH2CHCH3
H+
CH3C
OCH2CH2CHCH3
+ HOH
ketone aldehyde RCOOH
alkene
ROH
RX
EP101 / EG101
ROR
alkyne
RH
Alcohols are central
to organic syntheses