chemistry topic 7 organic chemistry

what are the first four alkanes

methane, ethane, propane, butane

what are the waste products of combustion?

Carbon dioxide and water vapour

what happens during combustion?

the carbon and hydrogen in the fuels are oxidised.

what are fossil fuels made from?

its formed from the remainder of plants and animals and mainly plankton that dried out millions of years ago and were buried in mud. over millions of years with high temperature and pressure the remains form crude oil which can be drilled up from the rocks where its found

What is crude oil formed from?

crude oil is a mixture of lots of different hydrocarbons, most of which are alkanes.

How does fractional distillation work?

oil is heated until most of it is turned into gas, then the gases enter a fractionating column. in the column theres a temperature gradient. longer hydrocarbons have higher boiling points. they condense and drain out into different fractions (hotter ones at the bottom cooler at the top)

what is crude oil used for?

fuel for modern transport

what does the petrochemical industry use crude oil for?

as a feedstock to make new compounds for use in things like polymers, solvents, lubricants and detergents

What is cracking?

Long chain hydrocarbons being split into shorter chain hydrocarbons

why are products from fractional distillation split up?

because longer hydrocarbons form long black liquids that aren't that useful like tar whereas shorter chain hydrocarbons are flammable so make good fuels

What does cracking produce?

Alkanes and alkenes

How is cracking carried out?

cracking is a thermal decomposition reaction
the first step is to heat long chain hydrocarbons to vaporise them.
the vapour is passed over a hot powdered aluminium oxide catalyst
the long chain molecules split apart on the surface of the specks of the catalyst - catalystic cracking

What is steam cracking?

you can crack hydrocarbons by vaporising them, mixing them with steam and then heat them to a very high temperature

what are alkenes

unsaturated hydrocarbons

what bonds do alkenes form?

double CC bonds

what are the first four alkenes?

Ethene
Propene
Butene
Pentene

if theres a large amount of oxygen what do alkenes combust to produce?

they combust completely to form carbon dioxide and water

if alkenes dont combust completely what do they produce

carbon + carbon monoxide + carbon dioxide + water

what is a functional group?

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

Most of the time, how do alkenes react?

addition reactions

what is the addition of hydrogen known as?

hydrogenation

what happens to an alkene that reacts with hydrogen

the double-bonded carbons open up to form the equivalent, saturated alkane

what happens when steam reacts with hydrogen?

water is added across the double bond bond and an alcohol is formed

what happens when halogens react with alkenes?

they react in addition reactions and the molecules that form are saturated with the C=C carbons each becoming bonded to a halogen atom

what happens when orange bromine water is added to a saturated compound?

when orange bromine water is added to a saturated compound like an alkane no reaction will happen and it'll stay bright orange

what happens when bromine is added to an alkene?

the bromine will add across the double bond making a colourless dibromo-compound so the bromine water is decolourised

What are polymers?

long chains of monomers

what is the reaction when polymers called?

polymerisation

What are plastics made from?

polymers which are usually carbon based

what are the properties of the first four alcohols?

-flammable
-soluble in water
-react with sodium
-can be oxidised
-different alcohols form different carboxylic acids

how can ethanol be made?

by fermentation

How does fermentation work?

fermentation uses an enzyme in yeast to convert sugars into ethanol. carbon dioxide is also produced. the reaction occurs in solution so the ethanol produced is aqueous

whats the equation for fermentation

sugar -yeast-> ethanol + carbon dioxide

what conditions does fermentation happen best at?

it happens fastest at a temperature of around 37°C in a slightly acidic solution under anaerobic conditions

what happens if the condition for fermentation aren't as good?

if there is a too high or low temperature or ph the enzyme could be denatured or could work at a much slower rate

what is the functional group of carboxylic acids

-COOH

How do carboxylic acids react with carbonates?

Produce salt, water and carbon dioxide

what happens when carboxylic acids dissolve in water?

when they dissolve they ionise and release H+ ions resulting in an acidic solution. But, because they dont ionise completely they just form weak acidic solutions. this means they have a higher pH than aqueous solutions of strong acids with the same concentration.

what can be made from carboxylic acids?

esters

What are esters formed from?

alcohol and carboxylic acid

what happens during condensation polymerisation?

monomers react together and bonds form between them making polymer chains. for each new bond that forms a small molecule is lost.

what functional group is an amino acid in?

they have an amino group and carboxyl group

what are proteins made of?

polymers of amino acids

what do amino acids form?

polymers known as polypeptides via condensation polymerisation.

what jobs do enzymes do in the body?

they work as catalysts, haemoglobin transports oxygen, antibodies form part of the immune system, and the majority of the body tissue is made up from proteins

what is DNA made up of?

nucleotides which contain a molecule known as a base