Organic chemistry

polymer

long chain molecule

monomer

small molecules used to form a polymer

viscous

thick sticky liquid

volatile

liquid that readily turns into a gas

flammable

substance that readily ignites

hydrocarbons

compounds that contain only carbon and hydrogen

fractions contain

mixtures of hydrocarbons with a similar number of carbons in their chains and therefore a similar boiling point

organic chemistry

study of compounds containing carbon

carbon facts

strong covalent bonds

4 electrons in the outer shell

up to 4 single covalent bonds

can have double or triple bonds

fossil fuels

crude oil, natural gas and coal

remains of organisms form millions of years ago

finite, non-renewable resources

obtained by drilling

formation of fossil fuels

dead plants/animals buried under sediment

high pressures and temps produced

anaerobic decay converts the organic matter to crude oil and natural gas

crude oil

complex mixture of hydrocarbons

crude oil cannot be used directly as a fuel

mixture of molecules of many diff chain lengths

diff physical and chemical properties which need to be separated

too viscous and does not burn

burning can cause pollution (sulphur impurities -> acid rain)

fractional distillation of crude oil method

1. Crude oil is first heated

2. Compounds evaporate and the vaporised crude oil enters the lower part of the fractionating tower

3. Fractionating tower is hot at the base and cooler at the top

4. Vapours rise until it condenses where its bp is lower than the temp of the column

5. Smaller the molecules, the lower the bp, the higher they rise

6. Fractions collect at diff heights

fractional distillation

process by which a mixture of miscible liquids is separated (heating) due to diff boiling points

evaporation + condensation

fractional distillation of crude oil

produces more long chain hydrocarbons which are commercially useless

petroleum or refinery gases

fuel for domestic heating and cooking

gasoline (petrol)

fuel for cars

kerosene (paraffin)

fuel for aircraft and domestic heating

diesel oil (gas oil)

fuel for larger vehicles e.g. lorries

fuel oil

fuel for ships

bitumen

pitch for roads and roofs

as molecules get larger, the fractions get

more viscous

less flammable

less volatile

darker in colour

burn with smokier flames

bp increases

problems with burning fossil fuels

Fossil fuels contain sulphides as impurities

Sulphides burn in air to form sulphur dioxide which leads to acid rain

Upsets the natural balance of carbon dioxide in the atmosphere, lead to global warming

acid rain

Caused by sulphur dioxide from coal-fired power station or nitrogen oxide from exhaust fumes of cars

pH of uncontaminated rain

6.5

pH of acid rain

2.5-5.5

acid rain harms

Marble statues and stone buildings dissolve away

Enhanced corrosion of metals

Water in lakes and rivers become acidic, pH too low for fish and they die

Acid rain damages trees and plants

preventions of acid rain

Calcium oxide sprayed into acid lakes

Low sulphur fuels used

Exhaust gases from factory chimneys are scrubbed with ammonia

Quantities of nitrogen monoxide from car exhausts can be reduced by using catalytic converters

molecular formula

tells you the actual number of atoms of each element e.g. C4H10

Empirical formula

simplest whole number ratio of the atoms of each element e.g. C2H5

General formula

chemical formula used to represent any member of a homologous series e.g. CnH2n+2

structural formula

tell you how atoms are joined together in a molecule e.g. CH3CH2CH2CH3

displayed formula

structural formula to show all the bonds present in a molecule

substitution

an atom or group of atoms in a molecule is replaced by another atom or group of atoms

e.g. ethane + bromine -> bromoethane + hydrogen bromide

(presence of UV light)

addition

one molecules combines with another to form one product

e.g. ethene + bromine -> 1,2-dibromoethane

combustion

molecule reacts with plentiful oxygen to form carbon dioxide and water (complete combustion)

incomplete combustion

inadequate oxygen to form carbon monoxide/carbon and water (incomplete combustion)

CO

colourless, odourless, toxic gas

combines with haemoglobin in the red blood cells, reducing the ability of the blood to carry oxygen around the body, fatal

homologous series

Family of compounds which have common features

Successive members differ by a CH2 group

Same general formula but diff length carbon chains

Same functional group

Similar chemical properties

Similar bonding

Gradually changing physical properties e.g. mps, bps, viscosity

Alkanes

General formula - CnH2n+2

Hydrocarbons

Homologous series

saturated compounds

molecules held together by weak intermolecular forces

Monkeys Eat Peanut Butter

Greater number of carbon atoms (alkanes)

Greater chain length

Greater surface of contact between molecules

Greater attractions between molecules

More energy required to separate the molecules

Bp increases

Viscosity increases

Less volatile

Less flammable

substitution reaction (halogenation)

alkanes react with halogens in the presence of UV light

substitution reaction of halogenation to alkanes example

e.g. methane + bromine -> bromomethane + hydrogenbromide

orange bromine water turns colourless with alkanes in the presence of UV light

structural isomers

Compounds with the same molecular formula but different structural or displayed formula

branched - methyl, dimethyl

physical differences of structural isomers

Branched chain molecules have weaker intermolecular attractions

Less surface of contact between molecules

Less energy is required to separate molecules

Bp decreases

Alkenes

General formula - C2H2n

double bonds have an angle of 120 degrees

double bonds can change places

saturated compounds

contain only single c-c and c-h covalent bond, contain the maximum number of hydrogen atoms for a given number of carbons

unsaturated compounds

contain one c-c double bond, if this breaks then more atoms can be added on

Addition reactions of alkenes

2 molecules react to form one molecule

One of the c-c double bond breaks and a small molecule is added

Become saturated

Hydrogenation of alkenes example

e.g. ethane + hydrogen, nickel catalyst at 150 degrees

used to make margarine

Addition of Halogens to Alkenes example

e.g. bromine + ethene at room temp

addition with steam to form alcohols (alkenes) example

e.g. ethene + steam, 300 degrees, 60-70 atmospheric pressure, phosphoric acid (catalyst)

chemical test for c-c double bond

add orange bromine water, turns form orange to colourless

cracking

Breaking down of long chain molecules (useless) into small chain molecules (useful)

Produces mixtures of shorter chain alkenes and alkanes

anything less than or equal to 11 carbons is counted as a short chain

cracking example

thermal decomposition, 600-700 degrees, finely divided mixture of SiO2 (silica) / Al2O3 (alumina) catalyst

cracking used to

Provide commercially useful short-chain alkanes for use in petrol

Provide reactive alkenes, used to make polymers

polymers

Long chain molecule made up by joining many small molecules or monomers

natural polymers

silk, wool and cotton

synthetic polymers

polyethene, nylon

addition polymers

Made by addition polymerisation, formed by joining many small molecules (monomers)

Usually requires heat, pressure and an initiator

Polyethene

Used to make plastic bags, cling film, buckets, toys

poly propene

Used to make ropes, plastic, fishing nets

polychloroethene

Used to make window frames, drainpipes

polytetrafluoroethene

o Used to make non-stick coating on frying pans, burette taps

pros of plastics

Corrosion resistant

Good electrical and thermal insulators

Low density

Non toxic

Strong/durable

Cons of plastics

Inert and non-biodegradable, persist in environment

Some produce toxic gases when burnt

Starting materials come from a finite resource

Preventions of environmental problems

Recycling plastic

Reusing plastic

Biodegradable plastics

20-80 (fractional distillation of synthetic crude oil)

pale yellow

runny

burns very easily

clean flame

81-120 (fractional distillation of synthetic crude oil)

yellow

fairly runny

burns easily

yellow flame and smoke

121-170 (fractional distillation of synthetic crude oil)

dark yellow

fairly viscous

burns quite easily

quite smoky flame

171-240 (fractional distillation of synthetic crude oil)

brown

viscous

difficult to burn

smoky flame