Hydroxyl compounds
A. Classification:
1. alkanol: primary alcohol (1 alkanol)
butan-1-ol
OH
OH
secondary alcohol (2 alkanol)
tertiary alcohol (3 alkanol)
butan-2-ol
2-methylbutan-2-ol
OH
OH
2. phenol
Classify by number of hydoxyl groups per molecule:
1. monohydric alkanol
H
H
H
ethanol
H
H
O
H
O
2. polyhydric alkanol
H
H
ethane-1,2-diol
O H
HH H
B. IUPAC name:
Br
OH
OH
pent-4-en-2-ol
3-bromocyclohexanol
OH
but-3-yn-1-ol
OH
OH
OH
HO
OH
hex-2-ene-1,6-diol
2-methylphenol
o-methylphenol
1,4-dihydroxybenzene
p-dihydroxybenzene
C. Preparation:
Industrial process:
1. Fermentation of carbohydrates:
yeast
C6 H12O6 (aq) 
 2CO2 ( g )  2CH 3CH 2OH (aq)
2. Hydration of alkene:
Hydroxyl groups / page 1
H
H
H
H
+
H
O
HgSO 4
H
O
H
H SO
2 4
O H
H
H
H
H
3. Formation of methanol:
_ pressure, 400 C , Cr2 O3  ZnO
CO( g )  2 H 2 ( g ) high

 CH3OH
o
Laboratory method:
1. Nucleophilic substitution:
+
OH
+
Br
-
HO
Br
2. Reduction of carbonyl compounds
a. By lithium tetrahydrioaluminate LiAlH4:
Li AlH4 in ether is a strong reducing agent which can reduce acid, ester, carbonyl group
(containing O atom) but not alkene and alkyne.
1. LiAlH /ether
4
+
2. H
OH
O
b. By hydrogenation:
Hydrogenation can also be used to convert alkene and alkyne to alkane.
Pt
+
H
O
2
OH
3. Oxidation of alkenes:
Oxidize alkene by strong oxidizing agent, acidified potassium permanganate.
OH
+
H
O
H
+
(O)
KM nO /H
4
+
OH
Phenol:
1. Sulphonation
O
S
SO
OH
ONa
NaOH
O
3
H
OH
+
o
400 C
H SO
2 4
2. Diazo salt
O
N
HNO
3
O
H SO
2 4
H
O
H
Zn
HCl
NH2
+
N
N
NaNO3
HCl
OH
3. Physical properties of alkanol:
Hydroxyl groups / page 2
a. Intermolecular H-bond
b. High boiling point, melting point and solubility in water
4. Chemical properties of alkanol:
Principle of reaction:
ROH
Breakage of OH bond to form RO ion
favor 1alkanol or R with electron withdrawing group
Breakage of CO bond to form C+ ion
Favour stable carbonium ion
a. Intramolecular dehydration (Elimination, alkene formation)
By dehrating agent:
Condition: high temperature 180C, Conc. sulphuric acid, mole ratio of alkanol:acid = 1:1
H 2 SO
OH
4
+
H
180 o C
O
H
By catalyst:
Condition: Aluminium oxide as catalyst, 350C
Al O 3
2
OH
+
o
H
O
H
350 C
b. Intermolecular dehydration
Condition: high temperature 140C, Conc. sulphuric acid, mole ratio of alkanol:acid = 2:1
H 2 SO 4
+
OH
H
+
140o C
HO
O
O
H
c. Halogenation
Lucas Test:
R
H
O
H Cl
+
H Cl
ZnCl
R
Cl
+
H
O
H
2
Reagent: zinc chloride + Conc. HCl
Procedure: Mix the Lucas reagent with alkanol; observe the rate of the appearance of the
turbidity. (Chloroalkane oil droplets are insoluble in aqueous phase.)
Result: Turbidity forms immediately.
Turbidity forms slowly (5 minutes).
3 alkanol
2 alkanol
Turbidity does not form.
Other reagents for halogenation:
PX3, PX5, SOCl2
1 alkanol
PX 3  3ROH 
 3RX  H 3 PO3
PX 5  ROH 
 RX  POX 3  HX
white fumes
SOCl2  ROH 
 RCl  SO2  HCl
d. React with sodium
Hydroxyl groups / page 3
2CH 3OH  2 Na 
 2 NaOCH 3  H 2
sodium methoxide, a strong organic alkali
Application of sodium alkoxide:
Formation of ether:
+
Na O
+
NaBr
NaBr
+
O
Br
Formation of alkene:
Br
+
Na O
+
OH
e. Esterification (Condensation)
O
O
conc. H SO 4
2
+
OH
+
O
H
O
H
HO
ethyl ethanoate
f. Oxidation
Oxidizing agents: KMnO4/H+/neutral/OH
Mild oxidizing agent: CuO
+
KMnO4 /H
+
O
+
(O)
H
O
H
OH
aldehyde
Strong oxidizing agent: KMnO4/H+
+
KMnO /H
4
O
O
(O)
+
OH
acid
Different alkanols are refluxed with acidified potassium permanganate:
Primary alkanol:
O
+
KMnO / H
4
OH
+
OH
+
2 (O)
H
O
H
Secondary alkanol:
+
OH
(O)
+
KMnO / H
4
+ HOH
O
ketone
Tertiary alkanol:
Hydroxyl groups / page 4
KM nO / H
4
+
no change
(O)
+
OH
g. Haloform reaction (Iodoform test)
O
I
+
I
+ NaOH
2
2
CHI
NaOH
OH
3
- +
O Na
+
O
iodoform, yellow solid
5. Physical properties of phenol:
Colouless solid (slightly pink) at room temperature, high vapour pressure at room temperature,
slightly soluble in water, highly toxic, high melting point and boiling point due to intermolecular
hydrogen bonding
6. Chemical properties of phenol:
a. Acidic
O
OH
H
+
+
phenoxide ion
Reasons:
O in phenol becomes slightly electron deficient
+
O
OH
+
O
H
+
O
H
H
-
-
Phenoxide ion is stabilized by resonance effect
O
-
-
O
O
-
O
-
React with NaOH:
- +
O Na
OH
+
NaOH
+
NaHCO
+
H
O
H
OH
no change
3
b. Act as nucleophile in nucleophilic substitution
Hydroxyl groups / page 5
O
Cl
O Na
+
+
NaCl
+
NaCl
O
O Na
O
+
O
Cl
O
O
O Na
+
O
+
Na O
O
O
O
c. Electrophilic substitution
Phenol is an activating group,
o,p-directing,
explain by resonance effect
Nitration:
OH
OH
OH
dil. HNO
3
+
H SO
2 4
O
O
N
N
O
O
major
O
O
N
OH conc. HNO
OH
3
O
H SO
2 4
O
N
N
O
O
2,4,6-trinitrophenol (a kind of explosive)
Halogenation:
Br
OH
OH
Br
Br
Br
Br
a product in the experiment involving rate order
Sulphonation:
OH
co nc. H2 SO4
SO
OH
O
3
S
OH
O
benzenesulphonic acid
d. Complex formation
React with iron (III) ion to form a blue/violet coloration.
Hydroxyl groups / page 6
OH
OH
Fe
3+
+
n
Fe (
)
3+
n
Hydroxyl groups / page 7