7/27/2019 Alcohol 13

1/19

1

Chapter 5

Alcohol

Organic Chemistry

7/27/2019 Alcohol 13

2/19

2

Candidates should be able to:

1. Write the general formula for hydroxyl compounds;2. Name hydroxyl compounds according to the IUPAC nomenclature;

3. Classify alcohols into primary, secondary and tertiary alcohol;

4. State the physical properties of hydroxyl compounds.

5. Classify the reactions of alcohols

i) ROH bond is broken: the formation of an alkoxide with sodium,

esterification, acylation, oxidation to carbonyl compounds and

carboxylic acids;

ii) ROH is broken and OH is replaced by other groups: the

formation of haloalkanes and the dehydration to alkenes and ethers;

7/27/2019 Alcohol 13

3/19

3

1. Introduction

i. General formula CnH2n+1OH

ii. Functional group hydroxyliii. Divided into 2 group- i) aliphatic ii) aromatic

2. IUPAC nomenclature

i. Aliphatic alcohol compound are named byreplacinge of corresponding alkane by suffix ol.

ii. The longest carbon chain

iii. Number the carbon atom with OH group with thelowest number possible

iv. If there are 2 hydroxyl groups diol,

3 hydroxyl groups - triol

7/27/2019 Alcohol 13

4/19

4

7/27/2019 Alcohol 13

5/19

1. When an OH group is bonded to a ring, the ring is numberedbeginning with the OH group.

2. Because the functional group is at C1, the 1 is usually omitted

from the name.

3. The ring is then numbered in a clockwise or counterclockwise

fashion to give the next substituent the lowest number.

Examples: Naming cyclic alcohols

Nomenclature of cyclic Alcohols:

5

7/27/2019 Alcohol 13

6/19

6

Activity 1

Name the compounds according to the IUPAC

nomenclature :-

a. CH3OH

b. CH3CH2OHc. CH3CHOHCH3

d. COHCH3CH3CH3

e. CH2OHCH2OHf. CH2OHCHOHCH2OH

7/27/2019 Alcohol 13

7/19

7

Alcohols contain a hydroxy group (OH) bonded to ansp3 hybridized carbon and may be 1o, 2o or 3o.

3. Classification

7/27/2019 Alcohol 13

8/19

8

1. Boiling point of alcohols is higher than corresponding RMM.

????

4. Physical Properties:

Stearic factors affect hydrogen bonding.

7/27/2019 Alcohol 13

9/19

9

ii. Lower members of alcohol, the higher solubility of that alcohol

Solubility decreases

7/27/2019 Alcohol 13

10/19

10

5. Reaction of alcohol

7/27/2019 Alcohol 13

11/19

11

a) bond fusion between O and H ( RO-H)

i) formation of an alkoxide with sodium

General eq: RO-H + Na RONa + H2

Example :

C2H5OH + Na C2H5ONa + H2

Observation : .

7/27/2019 Alcohol 13

12/19

7/27/2019 Alcohol 13

13/19

13

iii) Oxidation

Reagent:

Condition :.

Observation :.

7/27/2019 Alcohol 13

14/19

14

Example

7/27/2019 Alcohol 13

15/19

15

Activity 2 - worksheet

7/27/2019 Alcohol 13

16/19

b) Fusion of R-OH bond

i) Dehydration

Reagent

excess H2SO4/ 170C

R-OH

R=R ROR

CH3CH2OH

CH2=CH2 CH3CH2-O-CH2CH3

ETHERALKENES

7/27/2019 Alcohol 13

17/19

ii) Halogenations

R-OH HX R-X

ZnCl2,heated

iii) With PCl3 /PCl5/ SOCl2

R-OH R-X + HClPCl3 /PCl5/ SOCl2r.t

iv) Combustion - CO2 + H2O

7/27/2019 Alcohol 13

18/19

18

Activity 3- worksheet

Take a break

7/27/2019 Alcohol 13

19/19

Lucas test / Lucas reagentR-OH HX R-X

ZnCl2,heated

Observation :

1-cloudy after more than 5 min

2-cloudy about 5 min

3- immediately

Iodoform Test identify the presence of alcohol and

carbonyl

Reagent aqueous iodine and aqueous NaOH

Observation

yellow crystals

H

CH3 C R

OH

CH3C=O

R @H