Organic chemistry

Question 1

homologous series

Answer 1

• Family of similar compounds
• similar chemical properties due to the same functional group.

Question 2

Functional group

Answer 2

• set of atoms which dictate the chemical properties of that compound.
• compounds that share same functional group, share similar chemical properties.

Question 3

Alkane

Answer 3

C - C

• ane

Question 4

Alkene

Answer 4

C = C

-ene

Question 5

Alcohol

Answer 5

C - O - H

-anol

Question 6

Carboxylic acid

Answer 6

C = O - O - H

-anoic acid

Question 7

Ester

Answer 7

C = O - O - C

-yl -anoate

Question 8

characteristics of a homologous series

Answer 8

All members of the series can be presented by the same general formula

Consecutive members of the series differ by CH2

They have similar chemical properties because they have the same functional group

Their physical properties change in a predictable way

Question 9

Alkane General formula

Answer 9

CnH2n+2

Question 10

Saturated Carbons

Answer 10

Alkanes are hydrocarbons (compounds that contain only carbon and hydrogen).

Since no more atoms can add onto the molecule they are described as saturated hydrocarbons.

They are generally unreactive except for combustion and substitution reaction.

Question 11

Alkane Combustion

Answer 11

The complete combustion of an alkane gives carbon dioxide and water

The incomplete combustion of an alkane gives carbon monoxide and water

Question 12

Alkane Substitution

Answer 12

Alkanes react with chlorine in bright light to give a mixture of chloroalkanes.

One hydrogen atom is substituted by one chlorine atom.

Cl- Chloroalkane
Cl2- dichloroalkane
Cl3 - trichloroalkane
Cl4 - tetrachloroalkane

Question 13

General formula Alkene

Answer 13

CnH2n

Question 14

Unsaturated hydrocarbons

Answer 14

Alkenes contain carbon double bonds (C=C). Unlike alkanes, alkenes can undergo addition reactions due to the C=C double bond, and are therefore called unsaturated hydrocarbons.

Question 15

Addition Reaction

Answer 15

The C=C double bond in alkenes can be broken to “add” molecules onto the compound. There will therefore two reactants but only one product formed.

Alkenes can undergo addition reactions with bromine, hydrogen, and steam.

Question 16

Test for Alkene

Answer 16

Aqueous bromine undergoes addition reactions with alkenes. As a result, the original brown colour of aqueous bromine will turn colourless in the presence of alkenes.

Dibromoethane

Question 17

Hydrogen

Answer 17

Hydrogen reacts with alkenes to produce alkanes.

The conditions required for this reaction are:
- Temperature 150 degrees
- Nickel catalyst

Question 18

Water (steam)

Answer 18

Water can react with alkenes to make alcohols. This type of reaction is called hydration.

The conditions required for this reaction are:
- Temperature 300 degrees
- Pressure 60 atmospheres
- Phosphoric acid catalyst

Question 19

Addition Polymerization

Answer 19

Polymerization is the formation of long chain molecules called polymers from a large number of monomer molecules.

Question 20

General formula Alcohols

Answer 20

CnH2n+1OH

Question 21

Ethanol manufacture

Answer 21

Ethanol can be manufactured by two methods:

• Catalytic hydration of ethene
• Fermentation

Question 22

Hydration of Ethene

Answer 22

Water can react with alkenes to make alcohols. This type of reaction is called hydration.

The conditions required for this reaction are:

Temperature 300 degrees
Pressure 60 atmospheres
Phosphoric acid catalyst

The advantages of hydration (for ethanol manufacture) are
- No waste products
-Produces ethanol continuously

The disadvantages are
- Use of crude oil which is non-renewable
- Requires a lot of energy for high heat and pressures

Question 23

Fermentation

Answer 23

Fermentation is the chemical breakdown of glucose by yeast (or other microorganisms). Carbon dioxide and ethanol is produced in the process and the reaction is catalysed by yeast enzymes.

             yeast Glucose ———> Ethanol + Carbon dioxide 

The advantages of fermentation
- Renewable (uses plants)
- Uses less energy (lower temperature & pressure)

The disadvantages are
- Slow, batch process i.e. needing new batch once yeast die
- Produces carbon dioxide as waste

Question 24

Properties & uses of ethanol

Answer 24

Ethanol burns with blue flame. Combustion of ethanol will produce carbon dioxide and water.

Ethanol can be used:
- As a fuel (i.e. combusted)
as a solvent in perfume and food industries
- To make other organic chemicals such as esters

Question 25

General formula carboxylic acids

Answer 25

CnH2n+1COOH

Question 26

Polymers

Answer 26

Polymers are large molecules built from small units (monomers). Different polymers are built from different monomers and have varying linkages between the monomers.

Question 27

Condensation polymerization

Answer 27

In a condensation reaction, two monomers react together and join. During the reaction a water molecule is lost in the process (therefore condensation).