Organic chemistry

Question 1

What is a hydrocarbon?

Answer 1

A hydrocarbon is any compound that is formed from carbon and hydrogen atoms only.

Question 2

Describe an alkane:

Answer 2

• all have C-C bonds
• part of the homologous series
• saturated compounds, each carbon has made 4 bonds

Question 3

what is the mnemonic to remember the first four alkanes?

Answer 3

Monkeys - Methane
Eat - Ethane
Pealed - Propane
Bananas - Butane

Question 4

How do hydrocarbon properties change as the chain gets longer?

Answer 4

• it becomes more viscous (thicker)
• it becomes less volatile (higher boiling point)
• it becomes less flammable (harder to ignite)

Question 5

What is the word equation for complete combustion (oxygen is in excess)

Answer 5

hydrocarbon + oxygen –> carbon dioxide + water

Question 6

What is crude oil?

Answer 6

Crude oil is a fossil fuel. It is a finite resources so it will run out.

Question 7

What is fractional distillation?

Answer 7

1) The oil is heated until most of it has turned into gas. The gases enter a fractionating column (and the liquid is drained off)
2) In the column there is a temperature gradient (it is hot at the bottom and gets cooler as you move up)
3) The longer hydrocarbons have high boiling points. They condense back into liquids and drain of the column early on, near the bottom. The shorter hydrocarbons have lower boiling points so they condense and drain further up the column.
4) You end up with the oil separated into different fractions. Each fraction contains a mixture of hydrocarbons that all contain a similar number of carbon atoms (so similar boiling points)

Question 8

What is crude oil used for in modern life?

Answer 8

• fuel for most modern transport
• feedstock to make new compounds

Question 9

What is cracking?

Answer 9

Cracking is splitting up long-chain hydrocarbons, it is a thermal decomposition reaction:
1) heat long-chain hydrocarbons to vaporise them
2) then the vapour is passed over a hot powdered catalyst - aluminium oxide
3) the long-chain molecules split apart on the surface of the catalyst - catalytic cracking
4) you can also crack hydrocarbons if you vaporise them, mix with steam and heat them to a high temperature - steam cracking

Question 10

What are alkenes?

Answer 10

• alkenes are hydrocarbons with a double bond between two carbon atoms in the chain
• ## the C=C bond means they have two fewer hydrogens compared to alkanes - they are unsaturated

Question 11

what are the first four alkenes?

Answer 11

Ethene, propene, butene, pentene

Question 12

What is the general formula for alkenes?

Answer 12

CnH2n

Question 13

What is the general formula for alkanes?

Answer 13

CnH2n+2

Question 14

What is the word equation for incomplete combustion?

Answer 14

alkene + oxygen –> carbon + carbon monoxide + water

Question 15

How do alkenes react?

Answer 15

Alkenes react via addition reactions - the double bond means that it can be split, making it possible to add a new atom

Question 16

What is a functional group?

Answer 16

A group of atoms in a molecule that determine how that molecule typically reacts/

Question 17

What is hydrogenation?

Answer 17

• this is the addition of hydrogen
• hydrogen can react with the double bonded carbons to open the double bond and form a saturated alkane/ You need to have a catalyst

Question 18

How are alcohols formed?

Answer 18

• reacting steam with alkenes forms alcohols
• When alkenes react with steam, water is added across the double bond and an alcohol is formed

Question 19

How do halogens react with alkenes?

Answer 19

• Alkenes will also react in addition reactions with halogens like bromine, chlorine and iodine
• The molecules formed are saturated, with the C=C becoming bonded to a halogen atom

Question 20

what are polymers?

Answer 20

Polymers are long molecules formed when lots of small molecules (monomers) are joined together. This reaction is called polymerisation

Question 21

Explain addition polymers:

Answer 21

• the monomers that make up addition polymers have a double covalent bond
• lots of unsaturated monomer molecules (alkenes) can open up their double bonds and join together to form polymer chains; addition polymerisation
• When the monomers react in addition polymerisation reactions, the only product is the polymer, so an addition polymer contains the same type and number of atoms as the monomer that formed it

Question 22

How to draw the repeating unit of a polymer?

Answer 22

1) draw the two alkene carbons, replacing the double bond with a single bond and add an extra single bond to each of the carbons
2) then fill in the rest of the groups in the same way that they surrounded the double bond in the monomer
3) draw brackets around the repeating part (make sure the sticks go through the bracket), and put an “n” after it

Question 23

How to get the displayed formula of a polymer?

Answer 23

1) draw out the repeating part of the polymer, and get rid of the two bonds going out through brackets. put a double bond between carbons
2) The name of the polymer is the alkene with “poly” written before it

Question 24

Describe the alcohol group:

Answer 24

• functional group “-OH”
  -the name will end in “-ol”
• the general formula is: CnH2n+1-OH
• they all have similar properties

Question 25

Describe the alcohol group properties:

Answer 25

- flammable - they undergo complete combustion - the first four are all soluble in water, their solutions have a neutral pH - they react with sodium - alcohols can be oxidised by reacting with oxygen - different alcohols form different carboxylic acids

Question 26

What are alcohols used for?

Answer 26

- they are used as solvents as they can dissolve most of what water can dissolve, as well as things water cannot dissolve - the first four are used as fuels as they burn fairly cleanly and non-smelly

Question 27

how is ethanol made through fermentation?

Answer 27

__________yeast_____________________________ sugar ------------> ethanol + carbon dioxide

Question 28

Describe the carboxylic acids:

Answer 28

- functional group "-COOH" - they are part of the homologous series - their names end in "-anoic acid"

Question 29

Describe the carboxylic acids properties?

Answer 29

- they react like all other acids, with carbonates to produce a salt, water and carbon dioxides - the salts formed in these reactions and end in "-aoate" - carboxylic acids can dissolve in water. When they dissolve, they ionise and release H+ ions, resulting in an acidic solution

Question 30

How are esters made from carboxylic acids?

Answer 30

- esters have the functional group "-COO-" - esters are formed from an alcohol and a carboxylic acid - an acid catalyst is often used (like sulfuric acid) - the formula is: alcohol + carboxylic acid ------> ester + water

Question 31

What is condensation polymerisation?

Answer 31

- it involves monomers which contain different functional groups - the monomers react together and bonds form between them, making polymer chains - for each new bond that forms, a small molecule is lost. This is why its called condensation polymerisation - The simplest types of condensation polymers contain 2 different types of monomer, with two of the same functional group

Question 32

describe addition polymerisation VS condensation polymerisation:

Answer 32

*Number of type of monomers:* A - only one monomer type containing C=C C - two monomer types each containing two of the same functional groups OR one monomer type with 2 different functional groups *number of products:* A - only one product formed C - two types of product - the polymer and a small molecule *functional groups involved in polymerisation:* A - carbon-carbon double bond in monomer C - two reactive groups on each monomer

Question 33

How are amino acids naturally occurring polymers?

Answer 33

- they have an amino group (NH2) and an acidic carboxyl group (COOH)

Question 34

Why are proteins polymers of amino acids?

Answer 34

- amino acids can form polymers known as polypeptides via condensation polymerisation - the amino group can react with the acid group to form a chain. For every new bond that is formed a molecule of water is lost - One or more long-chains of polypeptides make proteins.

Question 35

How is DNA molecules made from nucleotide polymers?

Answer 35

- DNA is made of 2 polymer chains of monomers - nucleotides. the nucleotides each contain a small molecule known as a "base" - There are 4 bases (A,C,G,T) - The bases on the different polymer chains pair up with each other and form cross links keeping the two strands of nucleotides together and giving the double helix structure - the order of the bases acts as a code for an organism's genes

Question 36

How do simple sugars form polymers?

Answer 36

Sugars are small molecules that contain; carbon, oxygen, hydrogen. Sugars can react together through polymerisation reactions to form larger carbohydrate polymers, which living things use to store energy, and cellulose, which is found in plant cell walls