Chapter 22: Some Families of Organic Compounds

Question 1

Chloroalkane

Answer 1

A chloroalkane is a compound in which one or more of the hydrogen atoms in an alkane molecule have been replaced by chlorine atoms.

Question 2

Functional group

Answer 2

is an atom or group of atoms which is responsible for the characteristic properties of an organic compound or a series of organic compounds.

Question 3

Primary alcohol

Answer 3

A primary alcohol is one where the carbon atom joined to the -OH group is attached to only one other carbon atom. EG ethanol.

Question 4

Secondary alcohol

Answer 4

A secondary alcohol is one where the carbon atom joined to the -OH group is attached to two other carbon atoms. EG propan-2-ol.

Question 5

Tertiary alcohol

Answer 5

A tertiary alcohol is one where the carbon atom joined to the -OH group is attached to three other carbon atoms. EG 2-methylpropan-2-ol

Question 6

Uses of ethanol

Answer 6

1. Fuel
2. Solvent
3. Alcoholic drinks

Question 7

Uses of chloroalkanes

Answer 7

As a solvent; for removing oil and grease from machinery and the dry cleaning of clothes.

Question 8

Physical properties of chloroalkanes

Answer 8

1. They readily dissolve in non-polar solvents such as cyclohexane and methylbenzene.
2. Liquids at room temp.

Question 9

Functional group in alcohols

Answer 9

-OH group (hydroxyl group)

Question 10

General formula of alcohols

Answer 10

Cn H2n+1 OH

Question 11

Physical properties of alcohols

Answer 11

1. Boiling point; Alcohols have higher boiling points that the corresponding alkanes. The higher boiling points are due to the fact that the highly polar -OH group gives rise to hydrogen bonding between the alcohol molecules. Because of this hydrogen bonding, extra energy must be supplied to break these bonds.
2. Solubility in water; Methanol, ethanol and propan-1-ol are infinitely soluble in water because of hydrogen bonding between the alcohol molecule and water molecules.

Question 12

Why are chloroalkanes liquid at room temperature but the corresponding alkanes are gases?

Answer 12

The polarity of the carbon-chlorine bond gives rise to intermolecular forces.

Question 13

Fermentation

Answer 13

• Ethanol for alcoholic drinks is produced by fermentation.
• Fruits such as grapes contain glucose.
• When yeast is added glucose forms a solution of ethanol and carbon dioxide.
  C6H12O6——-} 2C2H5OH + 2CO2

Question 14

Why is methanol added to industrial alcohol ?

Answer 14

Methanol is added as a denaturing agent. It prevents people from drinking it. Mixture is then called methylated spirits.

Question 15

Planar carbon compounds

Answer 15

1. Aldehydes
2. Ketones
3. Carboxylic acids
4. Esters

Question 16

General formula for aldehydes

Answer 16

Cn H2n+1 CHO

Question 17

Properties of aldehydes

Answer 17

1. Boiling points of aldehydes are higher than those of the corresponding alkanes due to the existence o dipole-dipole forces but are lower than those of the corresponding alcohols due to absence of H bonding.
2. Lower members of aldehydes very soluble in water due to H bonding between O atom in carbonyl group and H atom of a water molecule.

Question 18

Why does solubility in water of alcohols and aldehydes decrease with the length of the carbon chain.

Answer 18

Due to the increasing influence of the insoluble alkyl portion of the molecule

Question 19

Comment on the boiling point of ketones

Answer 19

• Ketones have higher boing points than the corresponding alkanes due to the existence of dipole-dipole forces between the molecules. However ketones have lower boiling points than the corresponding alcohols due to the absence of H bonding.

Question 20

Comment on the solubility of ketones

Answer 20

• The lower members of ketones are very soluble in water due to the polarity of the carbonyl group. H bonding occurs between the O atom in the carbonyl group and the H atom in the water molecules.

Question 21

Aromatic compounds

Answer 21

Aromatic compounds are compounds that contain a benzene ring structure in their molecules.

Question 22

The principle of steam distillation

Answer 22

The principle of steam distillation is that a mixture of two immiscible liquids boils at a temperature that is lower than the boiling points of each of the individual liquids. The hot mixture of water vapour and oil is passed through a condenser and the distillate collected contains a mixture of water and oil.

Question 23

What is an emulsion

Answer 23

An emulsion is a dispersion of small droplets of one liquid in another liquid in which it is not soluble.

Question 24

Comment on the boiling points of carboxylic acids

Answer 24

Carboxylic acids are liquid at room temperature.
The boiling points of carboxylic acids are higher than those of alcohols because of the greater amount of H bonding in carboxylic acids.

Question 25

Comment on the solubility of carboxylic acids

Answer 25

Carboxylic acids are completely soluble in water due to their ability to form H bonds with water molecules.

Question 26

General formula of carboxylic acids

Answer 26

Cn H2n + 1 COOH

Question 27

General formula for esters

Answer 27

RCOOR'

Question 28

Condensation reaction

Answer 28

A condensation reaction is a chemical reaction in which two molecules combine to form a larger molecule with the release of a smaller molecule such as water.

Question 29

Physical properties of esters

Answer 29

1. Lower members of the ester family are volatile liquids with pleasant fruity smells.