Organic Chemistry Definitions

Question 1

What are hydrocarbons?

Answer 1

Molecules made up of hydrogen and carbon atoms only

Question 2

What is a homologous series?

Answer 2

A group of organic compounds with similar chemical properties due to them having the same functional group.

Question 3

What are alkanes?

Answer 3

Hydrocarbons with only single bonds between carbon and hydrogen atoms. They are saturated as all carbon-carbon bonds are single covalent bonds so no atoms can be added.

Question 4

What is the general formula for alkanes?

Answer 4

CnH2n+2

Question 5

What does it mean if a molecule is saturated?

Answer 5

No atoms can be added to the molecule

Question 6

What changes in properties are there as alkane chain-length increases?

Answer 6

-Melting and boiling point increases (short-chain gaseous RT)
-Volatility decreases (short-chain more volatile so evaporate more easily)
-Viscosity increases (short-chain less viscous)
-Flammability decreases (short-chain more flammable)

Question 7

What is the general reaction for complete combustion of a hydrocarbon?

Answer 7

hydrocarbon + oxygen –> carbon dioxide + water
-Also releases a lot of energy so is an exothermic reaction

Question 8

What is crude oil?

Answer 8

-A fossil fuel that is a mixture of a very large number of compounds, namely hydrocarbons
-It is a finite, non-renewable resource

Question 9

How is crude oil formed?

Answer 9

It is formed from plants and animals (mainly plankton) that have decayed over millions of years buried in mud under high pressures and temperatures

Question 10

What is feedstock?

Answer 10

A raw material used to provide reactants for an industrial reaction. The products of fractional distillation can be used as raw materials to make solvents, detergents, lubricants, polymers etc.

Question 11

What is a petrochemical?

Answer 11

A substance made from crude oil via chemical reactions

Question 12

What are kerosene, petrol and diesel used for?

Answer 12

Kerosene- aircraft fuel
Petrol- car fuel
Diesel- lorry or train fuel

Question 13

What is cracking?

Answer 13

A thermal decomposition reaction in which longer chained alkanes are broken down into shorter chained alkanes and an alkene

Question 14

What are the steps of catalytic cracking?

Answer 14

-Long chained hydrocarbons heated and vaporised
-Hydrocarbon vapour passed over hot powdered aluminium oxide (catalyst)
-As the hydrocarbons come into contact with the catalyst, they split into smaller alkane and an alkene

Question 15

What are the steps of steam cracking?

Answer 15

-Long chained hydrocarbons heated and vaporised
-Hydrocarbon vapour mixed with steam and heated to very high temperature, causing long chained alkane to split apart into short chained alkane and an alkene

Question 16

What are alkenes?

Answer 16

Hydrocarbons with carbon-carbon double bond. They are unsaturated because there is a double bond which can open up to form two new bonds.
They can be added together to form polymers as the double bond can break to form two new bonds

Question 17

What is the test for alkenes?

Answer 17

Bromine water test. Bromine water added to alkene solution, bromine reacts with alkenes which decolourises the bromine water, changing it from orange to colourless.

Question 18

What are the differences between alkanes and alkenes?

Answer 18

-Alkanes saturated while alkenes are unsaturated due to their carbon-carbon double bond.
-Alkenes are more reactive due to the C=C bond and can be added together to form polymers
-Alkenes can undergo addition reactions in which atoms are ‘added’ to the alkene across the C=C bond

Question 19

What is a hydrogenation reaction?

Answer 19

-When alkenes react with hydrogen (addition reaction) to form an alkane
-Conditions: 60°C, nickel catalyst
-The C=C bond breaks apart, so two hydrogen atoms are added to the alkene to make an alkane

Question 20

What is the addition reaction with steam?

Answer 20

• alkene + water –> alcohol
  -Conditions: catalyst, high pressure and temperature
  -Ethanol, unreacted ethene and water vapour are cooled so ethene condenses, ethanol and water separated using fractional distillation (used in industry for alc. bev.)

Question 21

What is a halogenation reaction?

Answer 21

-alkene + halogen –> halogenoalkane
(eg ethene + bromine –> dibromoethane)
-When alkenes react with halogens (eg bromine) in which the halogen atoms are added across the C=C bond
-Does not require catalyst but shake solution

Question 22

How do alkenes react with oxygen?

Answer 22

-Alkenes react with oxygen in combustion reacts like other hydrocarbons but often burn in air with smoky flames due to incomplete combustion

Question 23

What is addition polymerisation?

Answer 23

-A reaction in which alkenes can be used to make polymers. -Many small monomers (alkenes) join together to form very large molecules (polymers) such as poly(ethene)
-Conditions: catalyst and high pressure

Question 24

What are alcohols?

Answer 24

A homologous series with the -OH functional group

Question 25

What is the general formula for alcohols?

Answer 25

CnH2n+1 OH

Question 26

What are properties of the first four alcohols?

Answer 26

-Methanol, ethanol, propanol, butanol
-Flammable, soluble and can be oxidised to form carboxylic acids

Question 27

What happens when alcohols are combusted?

Answer 27

Undergo complete combustion, react with O2 to form carbon dioxide and water

Question 28

What happens when alcohols are added to water?

Answer 28

Dissolve in water forming a solution with a neutral pH

Question 29

What happens when alcohols are oxidised?

Answer 29

Form a carboxylic acid with a -COOH functional group

Question 30

What are the uses of alcohols?

Answer 30

-Used as fuels (release lots of energy when burned as fuel)
-Used as solvents in industry (can dissolve things which water cannot)
-Used in alcoholic beverages

Question 31

What are the uses of ethanol?

Answer 31

-As a chemical feedstock to produce other organic compounds.
-As a biofuel (ethanol can be burned like petrol).
-Used in alcoholics drinks such as beer, wine, and spirits.

Question 32

What are the adv. and disadv. of production of ethanol using ethene and steam?

Answer 32

-Adv: ethene cheap and reaction is cheap and efficient
-Disadv: ethene is made from crude oil which is a non-renewable resource, so if it starts to run out it will become expensive

Question 33

What are the conditions of production of ethanol using fermentation?

Answer 33

-Fermentation tanks, requires yeast cells with enzymes to catalyse the reaction.
-30-40°C (optimum temp. for enzyme). Must be anaerobic respiration so ethanol doesn’t oxidise to ethanoic acid

Question 34

What are adv. and disadv. of production of ethanol using fermentation?

Answer 34

-Adv: glucose is renewable resource, yeast easy to grow
-Disadv: slow process. Ethanol produced not pure so must be distilled

Question 35

What are carboxylic acids?

Answer 35

A homologous series of organic compounds with the functional group -COOH

Question 36

What happens when carboxylic acids react with a metal carbonate?

Answer 36

carboxylic acid + metal carbonate –> salt + carbon dioxide + water

Question 37

What is the general formula for carboxylic acids?

Answer 37

CnH2n+1 COOH

Question 38

What happens when carboxylic acids react with alcohols?

Answer 38

-carboxylic acid + alcohol –> ester + water
eg ethanoic acid + ethanol –> ethyl ethanoate
-Use an acid catalyst

Question 39

What is a condensation polymerisation reaction?

Answer 39

-A reaction that involves at least two different monomers with two functional groups.
-When these types of monomers react they join together,they usually lose small molecules such as water.
-Formation of polyester involves dicarboxylic acid monomers (2 COOH groups) and diol monomers (2 OH groups)

Question 40

What functional groups do amino acids have?

Answer 40

-Amino acids have one amino group (NH2) and one carboxyl group (COOH)
-They react by condensation polymerisation to produce
polypeptides

Question 41

What monomers are starch and cellulose made of?

Answer 41

-Starch is made up of glucose
-Cellulose is made up glucose