AQA AS Organic Chemistry

Define the term 'empirical formula'

A formula that gives the simplist whole number ration of atoms of each element in a compound

Define the term 'molecular formula'

A way of representing molecules that shows the actual number of atoms of each element in a molecule

Define the term 'General formula'

An algebraic formula that can describe any member of a family of compounds

Define the term 'Structural formula'

A way of representing molecules that shows the atoms carbon by carbon, with the attached hydrogens and functional groups

Define the term 'Displayed formula'

A way of representing a molecule that shows every atom and every bond

Define the term 'Skeletal formula'

A simplified organic formula which only shows the carbon skeleton and associated functional groups

How do you draw structures in 3D?

Wedges - Bonds coming out of the paper

Dotted lines - Bonds going into the paper

Normal lines - Bonds in the plane of the paper

Define the term 'Homologous series'

A family of organic compounds that have the same general formula and similar chemical properties

Define the term 'Structural isomer'

A molecule with the same molecular formula as, but different structural formula to another molecule

Define the term 'Stereoisomerism'

A molecule which has the same structural formula as another molecule, but has its atoms arranged differently in space

Define the term 'E-isomer'

A stereoisomer of an alkene that had the two highest priority groups on opposite sides of the carbon-carbon double bond

Define the term 'Z-isomer'

A stereoisomer of an alkene that has the two highest priority groups on the same side of the carbon-carbon double bond

(To help you remember it: Zee Zame Zide).

Define the term 'E/Z isomerism'

A type of stereoisomerism that is caused by the restricted rotation about a carbon-carbon double bond, each of he carbon atoms must have two different groups attached

Define the term 'Alkanes'

A saturated hydrocarbon with the general formula CnH2n+2

Define the term 'Petroleum'

A mixture consisting mainly of alkane hydrocarbons that can be separated into different fractions

Define the term 'Cracking'

Long chain hydrocarbons are broken down into shorter chain hydrocarbons. This produces a mixture of alkanes and alkenes

Describe thermal cracking. Include conditions in your answer.

Temperatures between 700k and 1200k

Pressure of up to 7000 KPa.

1) Carbon-carbon breaks to produce two free radicals.

2) Free radicals are highly reactive and react to produce many alkenes and some alkanes.

Why are long chain hydrocarbons not kept under high temperatures for long amounts of time?

At higher temperatures, these chains decompose. Given enough time, this will eventually result in products which are only hydrogen gas and solid carbon.

Describe catalytic cracking. Include conditions in your answer.

Zeolite catalyst.

720K.

Low pressure.

Hydrocarbons are mixed with a catalyst which has been ground into a fine powder.

Produces lots of branched alkanes and aromatic hydrocarbons

Describe a zeolite catalyst

A substance which has a honeycomb structure with an enormous surface area. They are usually acidic.

What type of products are usually formed from catalytic cracking?

Branched alkanes

Cycloalkanes (rings)

Aromatic compounds (e.g. benzene)

Define the term 'Halogenoalkanes'

An alkane with at least one halogen atom in place of a hydrogen atom

Define the term 'Ozone layer'

A layer of ozone (O3) found in the earth's upper atmosphere which protects the earth from ultra violet radiation

Define the term 'Alkenes'

An unsaturated hydrocarbon with the general formula CnH2n, containing at least one carbon-carbon double bond

How can we test for the presence of a C=C double bond?

Add bromine water (an orange solution) to the unknown solution. If a C=C double bond is present then the solution will decolourise (turn colourless).

What conditions are needed for an alcohol to be made from an alkene?

Steam

High temperature

High pressure

Acid catalyst

How many sigma and pi bonds are in a double bond?

1 sigma

1 pi

Why can double bonds not rotate?

Two p-orbitals have overlapped to make a pi orbital.

Why are alkenes more chemically reactive than alkanes?

The double bond is electron rich.

Why are the physical properties of alkenes similar to those of the alkanes?

Van der Waals forces are the only type of intermolecular forces that act between both alkanes and alkenes.

Why can single bonds rotate?

Two p-orbitals have not overlapped. There are no pi orbitals.

Define the term 'Bonding in alkenes'

Involves double covalent bonds, a centre of high electron density

Define the term 'Addition polymers'

A long chain molecule formed by an addition reaction. They are formed from monomers which have a carbon-carbon double bond.

Define the term 'monomer'.

An individual molecule that is repeated n times to make a polymer.

Define the term 'polymer backbone'

The longest series of covalently bonded atoms that together create the continuous chain of the molecule

Define the term 'repeating unit'

The smallest group of atoms that produce the polymer when repeated over and over

State one use for poly(chloroethene) or poly(vinyl chloride)

Aprons or drainpipes

Explain how you draw polymers from monomers

1) Change the double bond in the monomer to a single bond

(this is the repeating unit)

2) Add a long bond to each end of the repeating unit.

3) Draw square brackets over the long bonds

4) Add an 'n' outside of the square brackets in the bottom corner

What type of bonding holds different polymer chains together?

Intermolecular forces of attraction (e.g. Van der Waals)

Explain how plasticisers can be used to modify polymers

They are small molecules which get in-between the polymer chains and force them apart. This allows the layers to slide over each other (making it more flexible)

Explain why polymers are not biodegradeable

They polymer backbone is made up of strong, non-polar C-C and C-H bonds.

This makes them unreactive and unresponsive to attacks by enzymes or other molecules.

Compare the properties of high density polyethene (HDPE) and low density polyethene (LDPE)

HDPE:

There is less branching so the chains can pack together well. This results in:

1) High density

2) High melting point

3) Rigid structure

LDPE:

There is more branching so the chains cannot pack together well. This results in:

1) Low density

2) Low melting point

3) Flexible and ductile structure

Explain the steps behind the mechanical recycling of polymers

Step 1) Separate the different types of plastic

Step 2) Wash the plastics

Step 3) Grind the plastics into small pellets

Step 4) Melt and remould the plastics

Explain the steps behind the feedstock recycling of polymers

Step 1) Heat the plastics to room temperature

Step 2) Use the monomers that are made from step 1 to make new plastics

What are two problems with recycling plastics?

It can only be done a limited number of times because the polymer chains will become too short to use.

It doesn't always produce a high amount of monomer.

Define the term 'Alcohol'

A substance with the functional group -OH and a general formula of CnH2n+1OH

How do we name alcohols with:

a) 1 -OH group

b) 2 -OH groups

c) 3 -OH groups

a) -ol

b) -diol

c) -triol

What is the shape of the C-O-H bond angle? Why?

Bent.

There are two bonding pairs of electrons and two lone pairs of electrons on the oxygen atom. This reduces the normal tetrahedral bond angle of 109.5 degrees to 105 degrees

What is a primary alcohol?

An alcohol in which the carbon with the -OH group has only one R group attached to it.

What is a secondary alcohol?

An alcohol in which the carbon with the -OH group has only two R groups attached to it.

What is a tertiary alcohol?

An alcohol in which the carbon with the -OH group has three R groups attached to it.

What type of intermolecular forces can occur with alcohols? Explain your answer.

1) Van der Waals. These are between all molecules.

2) Hydrogen bonding. The lone pairs on the oxygen atom can bond to other molecules which contain hydrogen.

Explain why short chain alcohols are soluble in water but long chain alcohols are not.

The -OH group of alcohols can bond to water molecules but the non-polar hydrocarbon chain cannot.

As the length of hydrocarbon chain increases, more energy is needed to overcome the hydrogen bonds between the alcohol molecules. This is because the molecules are more tightly packed together as the size and matter increases.

Provide three uses of alcohols

1) Alcoholic drinks

2) Fuels

3) Solvents in chemical reactions

What is the name of the process that can be used to make ethanol from glucose?

Fermentation

What conditions are needed for fermentation?

Yeast (catalyst)

35 degrees

Absence of oxygen

Why must oxygen be kept out of the fermentation process?

To prevent ethanol being oxidised to ethanoic acid

In fermentation, why are compromise conditions used?

If the temperature is too high, the enzymes in yeast become ineffective.

If the temperature is too low, the reaction will be too slow.

What is the difference between methylated spirits and ethanol?

Methylated spirits is ethanol with a small percentage of poisonous methanol added to it.

Why should you not drink methylated spirits?

It is toxic.

Define the term 'dehydration'

When water is removed from a compound or a species.

State the conditions that are required for alcohols to be dehydrated.

Excess and concentrated sulphuric acid

Aluminium oxide catalyst

600 degrees

What is an oxidation reaction?

A chemical change in which electrons are lost, either by the addition of oxygen, the removal of hydrogen, or the removal of electrons.

What type of products are made from the dehydration of alcohols?

An alkene and water

What type of alcohols are oxidised to form aldehydes?

Primary

What type of alcohols are oxidised to form ketones?

Secondary

Why can tertiary alcohols not be oxidised easily?

It would require the C-C bond to break. This is very difficult and requires a lot of energy.

How can we stop a primary alcohol from being turned into a carboxylic acid?

Quench the reaction after an aldehyde is made. This can be done using distillation.

What is the shorthand way of writing oxidation?

[O]

Define the term 'Aldehyde'

A substance with the general formula CnH2nO

Define the term 'Biofuel'

A fuel made from biological material which has recently died

Define the term 'Carbocation'

An organic ion containing a positively charged carbon atom

Define the term 'Carbonyl compound'

A compound that contains a carbon oxygen double bond

Define the term 'Carboxylic acid'

A substance which has a COOH group attached to the end of a carbon chain

Define the term 'Chain isomer'

An organic molecule that contains the same atoms and functional groups as another molecule but has a different arrangement of the carbon skeleton

Define the term 'Crude oil'

A mixture consisting mainly of alkane hydrocarbons that can be separated into different fractions

These hydrocarbons are both branched and unbranched.

How is crude oil made?

Over millions of years, plant material and animal remains break down under high pressures and temperatures. This happens deep beneath the Earth's surface under many layers of rock and sediment.

Define the term 'Dehydration'

A reaction where water is eliminated

Explain the purpose of the dichromate(VI) ion. What would you observe when this is added to primary or secondary alcohols?

An oxidising agent, used to test for the presence of primary or secondary alcohols.

Orange dichromate(VI) ions turn to green chromium(III) ions in the presence of primary and secondary alcohols

What conditions are needed to turn a primary alcohol into an aldenhyde?

Dilute sulphuric acid

Small amounts of potassium dichromate(VI)

294K

What conditions are needed to turn a primary alcohol into a carboxylic acid?

Concentrated sulphuric acid

Lots of potassium dichromate(VI)

391K

Reflux

What is the name for the -C=O group?

Carbonyl

Where is the carbonyl group located in aldehydes?

At the end of the chain

Where is the carbonyl group located in ketones?

Within the body of the chain

Can secondary alcohols be oxidised past a ketone?

No

State the name of a test that can be used to distinguish between aldehydes and ketones. What would you observe?

Tollens' (silver mirror) test.

Colourless silver(I) complex ions are reduced to metallic silver when aldehydes are oxidised.

You would see a silver mirror on the inside of the test tube.

State the name of a test that can be used to distinguish between aldehydes and ketones. What would you observe?

Fehling's Test

Blue copper(II) complex ions are reduced to copper(I) and will oxidise aldehydes but not ketones.

You would see a brick red precipitate on the inside of the test tube.

State what fractional distillation is used for

A method of separating crude oil fractions using here boiling points

Explain how fractional distillation works

1) The crude oil is heated in a furnace

2) A mixture of liquid and vapours pass into a tower that is cooler at the top than at the bottom

3) The vapours travel up the tower until they reach their boiling point

4) When they reach their boiling point they condense into a liquid

5) Shorter chain hydrocarbons condense near the top of the tower and longer chain hydrocarbons condense at the bottom

State the order of fractions that are produced from the fractional distillation of crude oil (start at the top)

Refined gases

Petrol (naptha)

Kerosene or Paraffin

Diesel oil

Lubricating oil or waxes

Fuel oil

Tar or bitumen

State a use for each of the fractions that are produced from the fractional distillation of crude oil (start at the top)

Fuel

Cars

Jet fuel

Lorries

Engine oil

Power stations

Roads and roofing

State the order of the fractions produced by the fractional distillation of crude oil

Top: Gases

Petrol

Kerosene

Diesel oil

Lubricating oil and waxes

Fuel oil

Tar or bitumen

Define the term 'Functional group'

The group of atoms that is responsible for the characteristic reactions of a molecule

Define the term 'Functional group isomer'

An isomer with the same molecular formula as another molecule, but with the atom arranged into different functional groups

Define the term 'Ketone'

A substance with a general formula CnH2nO which has two alkyl groups attached to the carbonyl carbon atom

Define the term 'Position isomer'

A molecule with the same skeleton and molecular formula as another molecule but with the functional group attached to a different carbon

Explain how refluxing works (practical - Paper 3)

A method for heating a reaction so that you can increase the temperature of an organic reaction to boiling without losing volatile solvents, reactants or products.

Any vaporised compounds are cooled, condense and drip back into the reaction mixture

How many bonds does carbon form?

4

How many electrons are in a single bond?

2

How many electrons are in a double bond?

4