ALCOHOLS AND ETHERS Introduction to Alcohols

• Compounds in which the hydroxyl group is bonded to an alkyl

group are called alcohols. They are known as alkyl derivative of water.

• R – H H – OH R – OH

alkane water alcohol

1. Classification of Alcohols A. According to The number of –OH Groups 1. Monohydric Alcohols

CH3OH CH3CH2OH CH3CH2CH2OH

methyl alcohol ethyl alcohol propyl alcohol

2. Polyhydric Alcohols

B. According to The Carbon Atom Having The –OH Group 1. Primary (1

o)Alcohols

2. Secondary (2

o)Alcohols

3. Tertiary (3o)Alcohols

Example 1

Which of the following is an alcohol?

Example 2

Which of the following is not an alcohol?

Example 3

Which of the following is a monohydric alcohol?

Example 4

Which of the following is a polyhydric alcohol?

Example 5

Which of the followings are tertiary alcohols?

2. Nomenclature of Alcohols

• Common names are used for simpler alcohols. Common names are

derived by naming the alkyl group attached to the –OH group and

then the word “alcohol” is added.

According to IUPAC system;

• Change last letter “–e” with “–ol” in the alkane name of longest

carbon atom chain in which hydroxyl group is bonded.

• Number the carbon atoms in the chain starting from nearer to the

hydroxyl group. Indicate the position of the hydroxyl group by using

number.

• If there are more than one –OH group, use “di, tri, tetra…” before

–ol .

4-methyl 2-pentanol 4-bromo-3-methyl 2-butanol

3-cyclopentyl 1-propanol 3-amino 2-butanol

2, 4-dimethyl 1, 4-pentanediol 5-chloro-2-methyl 1,3,4-hexanetriol

Example 6

Name the following structures according to IUPAC system.

Example 7

Which of the following structures is named wrongly?

Example 8

What is the correct name for the following structure?

A. 1-bromo-2-methyl 3-cyclopentanol

B. 1-bromo-2-methyl 3-pentanol

C. 2-methyl-3-bromo 1-cyclopentanol

D. 3-bromo-2-methyl 1-cyclopentanol

Example 9 Which of the following is 2, 3, 4-trimethyl 1-hexanol?

Example 10

Which of the following is the isomer of 2, 3-dimethyl 2-butanol?

3. Physical Properties of Alcohols

• Alcohols have both polar and non polar parts in their structures.

• C1 to C11 are colorless and have characteristic smell.

• Water soluble, solubility decreases with increasing chain length.

But increases with branching.

• Boiling points of alcohols increase with increasing molecular

weight and the number of hydroxyl group in the molecule.

4. Chemical Properties of Alcohols

• In the first group of reactions alcohols may serve as acids (proton

donors) and they dissociate in manner similar to water.

Salt formation: Alcohols form salts with active metals such as Na, K,..

etc.

Ester formation: In the presence of an acid catalyst, alcohols react with acids to form esters.

H3C OH

Methyl Alcohol

• Inorganic acids also form esters with alcohols. Such as the

esterification of glycerol with HNO3 forms glyceryl trinitrate, is an

explosive ingredient in dynamite.

• In the second group of reactions hydroxyl group is replaced. First

type is conversion of alcohols to alkyl halides.

• Second type is dehydration.

• Third type is oxidation of alcohols. KMnO4 and K2Cr2O7 oxidize 1o

and 2o alcohols, 3

o alcohols cannot be oxidized.

Example 11

Arrange the following compounds in order of increasing

solubilities.

Example 12

Which of the following has the highest boiling point?

Example 13

Which of the following alcohol has the highest melting point?

Example 14

How many liters of hydrogen gas is produced at STP, when

2.3 g of sodium is put into excess ethanol?

A. 1.12 B. 2.24 C. 4.48 D. 8.96

Example 15

Predict the result of following reactions.

Example 16

What are the result of following oxidation reactions.

Example 17

Write the equations for each of the following.

A. n-propyl alcohol to propene

B. n-butyl alcohol to butanoic acid

C. 2-pentanol to diethyl ketone

D. t-butyl alcohol to t-butyl bromide

E. Isobutyl alcohol to methyl ethyl ketone

Example 18

How many liters of ethylene at STP can be prepared from

40 g of 92% ethyl alcohol by 70% yield?

5. Preparation of Alcohols

A. Hydration of Alkenes

B. Hydrolysis of Alkyl Halides

Example 19

Perform the following transformations.

A. ……… 1-propanol

B. ……… isobutanol

C. ……… ter-butanol

Example 20

What is the result of following reaction?

Chloro cyclobutane + NaOH ……………

Example 21

Which alcohol and how many grams are produced by the

hydration of 9.6 g of 2-butene?

6. Some Important Alcohols

1. Methyl Alcohol

It is colorless, flammable, and has characteristic odor.

It is highly toxic, can cause blindness, large quantities

cause death. To prevent poisoning pyridine is added.

It can be used as antifreeze in radiators.

It is soluble in water and organic solvents, and can also

dissolve fats and resins.

It is the most acidic member of monohydric alcohols.

It can easily burn with a bluish flame.

It can be easily oxidized to formaldehyde and CO2.

It is also called wood alcohol. Because it is first obtained from the

distillation of wood.

In industry it is produced from water gas (CO + H2) under high pressure

and temperature in the presence of catalyst.

About 40% of methanol production is converted to formaldehyde, and

from there into products as diverse as plastics, plywood, paints,

explosives, and permanent press textiles.

2. Ethyl Alcohol

It is colorless, soluble in water and has a characteristic smell, affecting

the central nervous system.

95% of its solution is called ethyl alcohol, used in laboratories.

100% pure ethyl alcohol is named as absolute alcohol.

It is a important organic solvent, used in the preparation of

tincture of iodine, paints, essence, perfumes and cosmetics.

In medicine it is used as disinfectant.

It is commonly prepared from grape juice by fermentation.

Preparation of Ethyl Alcohol

3. Glycol

Alcohols containing two –OH groups are called gylcols. The most

common glycol is ethylene glycol, C2H4(OH)2.

It is colorless, odorless, syrupy liquid, completely miscible in water.

Since it has low melting point it is used as antifreeze in radiators.

It is also used in hydraulic brake fluid in cars, as a liquid, oil, ink and

resin solvent.

4. Glycerin or Glycerol

The simplest trihydric alcohol, C3H5(OH)3.

It is colorless, odorless, syrupy liquid, soluble in water, methanol and

ethanol. It absorbs moisture well.

It is used in the production of dynamite, invented by Alfred Nobel, a

Swedish scientist.

It is also used in tobacco, shaving and toilet soaps, cosmetics, lotions,

ointments, antifreeze, cellophane, printing-press ink.

It is produced from fats and oils in basic medium.

7. Introduction to Ethers

Ethers are alcohol derivatives resulting from the condensation of

alcohols.

General formula is CnH2n+2O

8. Nomenclature of Ethers

First name the groups attached to oxygen atom in alphabetical order,

and then read the word “ether”.

If the groups are symmetric, use –di before the name of the group.

Example 22

9. Physical Properties of Ethers

Bond angle is not equal to 180o in R-O-R, they have a limited polarity.

They are more volatile than their corresponding alcohols.

Boiling point increases by the increasing molecular weight. Branching

lowers the boiling point.

Since ethers are polar they are soluble in many polar and non polar

substances very well.

10. Physical Properties of Ethers

Chemically ethers resemble alkanes rather than alcohols or water.

When ethers are heated with concentrated strong acid halides they

undergo decomposition reactions.

R-O-R + H-X → R-O-H + R-X

Example 22

C2H5-O-C2H5 + H-Cl → C2H5-OH + C2H5-Cl

11. Preparation of Ethers

1. Dehydration of Alcohols

2. The Williamson Synthesis of Ethers

Example 23

2C2H5-OH → C2H5 -O- C2H5 + H2O

C2H5-Cl + C2H5-ONa → C2H5 -O- C2H5 + NaCl

12. Diethyl Ethers

The most commonly known ether. Colorless, volatile, flammable liquid

with characteristic odor.

Causes fainting when inhaled, used in medicine as an anesthetic.

Good solvent for organic substances.