ORGANIC CHEM PAPER 1 - CHEMISTRY

introduction, crude oil, alkanes, alkenes, synthetic polymers

Define hydrocarbons

compounds that have only hydrogen and carbon

Define isomer

Molecules with the same molecular formula but different structures

Why are alkanes classified as hydrocarbons

They contain only hydrogen and carbon

what does empirical formula, molecular formula, general formula, structural formula and displayed formula mean?

empirical: simplest ratio
molecular: the actual number
general: formula that represents a homologous series
structural: written but shows how they are bonded
displayed: drawn out

what does functional group mean

a group of atoms bonded in a specific arrangement that influences the properties of the homologous series

what does homologous series mean

a series of organic compounds that have similar features and chemical properties due to them having the same functional group

what is the rule for naming compounds?

meth
eth
prop
but
pent
hex

what is a substitution organic reaction

a substitution reaction takes place when one functional group is replaced by another

what is an addition organic reaction

an addition reaction takes place when two or more molecules combine to form a larger molecule with no other products

what is a combustion organic reaction

when an organic substance reacts with oxygen to form co2 if complete, and co if incomplete and water

what is crude oil

crude oil is a mixture of different hydrocarbons

Describe the process of fractional distillation of crude oil

1. The oil is heated until most of turns into gas. The gas then enters a fractionating column

2. In the column there is a temperature gradient (hot at the bottom, cool at the top)

3. When the substances reach a part of the column where the temperature is lower than their boiling point they condense.

4. The longer hydrocarbons have high boiling point, and condense at the bottom

5. The shorter hydrocarbons have lower boiling points, so they condense at the top

6. The crude oil has now been split into its fractions

What is the order of fractions made from crude oil from top to bottom

Refinery gases, gasoline, kerosene, diesel, fuel oil, bitumen

What properties do hydrocarbons have as you go down the fractionating column

• their boiling points get higher

• Their length gets longer

• They get more viscous

• They get darker

Uses of refinery gases

Domestic heating and cooking

Uses of gasoline

Fuel in cars

Uses of kerosene

Fuel for planes

Uses of diesel

Fuel for trains and lorries

Uses of fuel oil

Fuel for large ships and power stations

Uses of bitumen

Surface roads and roofs

what happens when fuel is burnt

heat energy is released as its an exothermic reaction

what are the possible products of complete/incomplete combustion of hydrocarbons

• carbon dioxide

• carbon monoxide

• oxides of nitrogen

• oxides of sulfur

• water

why is carbon monoxide dangerous

• CO binds with haemoglobin

• oxygen cannot be transported to organs

how do oxides of nitrogen form

• when nitrogen and oxygen react in high pressure and temperature condition

• in car engines this condition is reached

how does combustion of hydrocarbons result in sulfur dioxide

• fossil fuels often are contaminated with small amounts of sulfur impurities

• when these are combusted, the sulfur gets oxidised to sulfur dioxide

how do oxides of nitrogen contribute to acid rain

• the nitrogen dioxide reacts with rain water to form nitric acids, which contribute to acid rain

• when the clouds rise, the temperature decreases and the droplets get larger

• when the droplets are heavy enough, they fall as acid rain

how does sulfur dioxide contribute to acid rain

• the sulfur dioxide produced from combustion gets dissolved in rainwater droplets to form sulfuric acid

• when the clouds rise, the temperature decreases and the droplets get larger

• when the droplets are heavy enough, they fall as acid rain

what is cracking

an industrial process used to break low demand, long chain hydrocarbon molecules into more useful, small chain hydrocarbons.

what are the conditions needed for cracking

• 600-700 degrees celsius

• catalyst of silica or alumina

• this causes thermal decomposition reactions

why is cracking necessary

• we have a greater supply of long chain hydrocarbons than short chain hydrocarbons

• cracking produces short chain hydrocarbons

• these short chain hydrocarbons are more in demand and more useful than long chain hydrocarbons

what is the general formula for alkanes

CnH2n+2

what are alkanes classified as and why

• saturated hydrocarbons

• they only have single c-c bonds and only contain carbon and hydrogen

what happens in the substitution reaction with alkanes

• only occurs with uv light and halogens

• one halogen atom gets swapped with one hydrogen → substitution reaction

what is the functional group for alkenes

C=C double bond

what is the general formula for alkenes

CnH2n

why are alkenes unsaturated hydrocarbons

they contain a double carbon bond and contain only hydrogens and carbons

how to name alkenes with but-x-ene

• the carbon atom with the C=C is the number

• count from left to right

what happens when alkenes react with bromine

• an addition reaction

• a dibromoalkane is formed

• the same process happens with any halogen and any alkene

• the C=C double bond is broken

how do you distinguish between an alkene and an alkane

• bromine water is an orange coloured solution

• add the substance to bromine water

• if it is an alkene, an addition reaction will take place, causing the solution to no longer contain bromine so it will decolorise

• if ti is an alkane, it will remain as an orange solution as the alkane will remain saturated

how are addition polymers formed

by joining up many small molecules and monomers. each monomer is a repeat unit connected by covalent bonds

what are polymers

large molecules of high relative molecular mass

why are addition polymers so hard to dispose

they are formed by joining many small molecules with strong c-c bonds. this makes them unreactive and chemically inert so they do not easily biodegrade.

why is putting addition polymers in landfill a problem

• addition polymers do not easily biodegrade, meaning decomposers cannot break them down

• this causes landfill sites to quickly fill up and take up valuable land

why is incinerating addition polymers a problem

• polymers release a lot of heat energy when they burn and produce co2

• polymers containing chlorine release toxic HCl gas when burned

• if incinerated by incomplete combustion, CO will be produced