organic chem

structural isomers

have the same molecular formula but different structure formula

what are the types of structural isomers

chain, positional, functional group

what are chain isomers

have the same molecular formula but different arrangement of the carbon skeleton

positional isomers

they have the same molecular formula but different position of the functional group on the carbon skeleton

functional group isomers

have the same molecular formula but different functional group

stereoisomers

have the same structural formula but different arrangement of atoms in space - example E/Z isomerism

what shape is the C C double bond

planar - flat

what property do CC double bonds have

they are rigid so have restrictive movement about the double bond

what is E/Z isomerism

restricted rotation around the double bond - two different groups of atoms on the same carbon

What is an E isomer

same groups on opposite sides of double bond

what is an Z isomer

same groups on the same side of the double bond

CIP rules

1. use when we have 4 different groups around the double bond

2. we label them carbon one and carbon two

3. calculate atomic number of the first element directly bonded

4. the atomic number not the mass number with highest atomic number takes priority

fractional distillation

occurs when liquids of similar boiling points are separated

alkanes are found in…..

crude oil when there are a mixture of different length hydrocarbons

what is used to separate crude oil

fractional distillation is used

crude oil conditions

vapouried using a furnace to about 350 degrees

crude oil sections starting from top

1. gas

2. gasoline/petrol

3. kerosene

4. diesel oil

5. fuel oil

6. lubricating oil /bitumen

what happens to crude oil in a condenser

vaporised oil enter the column and rises through trays. Shortest vaporised first, longest dont vaporise they run down to the bottom

the column is a temperature gradient meaning

cooler at the top

gas uses

stove

petrol

used in cars

kerosine

used in jet fuel and heating

diesel oil

used in trains

fuel oil

used in ships / power stations

bitumen

used for roofing and tarmac - thick

cracking is when

long chain hydrocarbons are broken into short chain hydrocarbons

why do we crack materials

cracked to be more useful as long chain hydrocarbons are useless

types of cracking

catalyctic and thermal

thermal cracking conditions

high temperature of 1000 degrees and 70 atm of pressure

thermal cracking products

mainly alkenes used to make polymers

catalyctic cracking conditions

zeolite catalyst with a honeycomb structure, high temperature of 450 degrees and slight pressure

catalyctic cracking produces…

aromatic hydrocarbons useful in fuels for vehicles (6 carbons in a ring with delocalised electrons)

what is the zeolite catalyst in catalyctic cracking useful for?

makes it cheaper and speeds up the reaction cause we use a lower temperature and pressure

complete combustion of alkanes

burn completely in oxygen so produce large amounts of energy

what is combustion of alkanes used for

power vehicles and most of Britains electricity

in complete combustion

when something is burnt in a limited supply of oxygen produces carbon monoxide and and carbon (soot)

why is carbon monoxide poisonous

stops oxygen bonding and causes oxygen starvation

how can carbon monoxide be removed?

through a catalyctic converter

global warming

burning fossil fuels and green houses

what is the greenhouse gas effect

carbon dioxide and other greenhouse gases absorb infrared radiation from the sun but emit some of it back to the earth

photochemical smog

caused by ozone

how does photochemical smog exist

exists when sunlight, hydrocarbons and nitrogen dioxide mix to form ozone from cars and factories

how is photochemical smog made

when solid carbon particulates mix with ozone

how are oxides of nitrogen made

made when nitrogen and oxygen found in air combine under high pressure and temperature

what do catalyctic converters do

convert unburnt hydrocarbons and oxides of nitrogen to less harmful materials

acid rain cause

caused by burning fossil fuels that release sulfur dioxide when sulfur impurities react with oxygen

is sulfur dioxide acidic or alkali

acidic reacts with water to form sulfuric acid

how do we remove sulfur dioxide

wet scrubbing

what is wet scrubbing

dissolving calcium carbonate or oxide in water and spraying it on acidic sulfur dioxide gas

what is initiation

radicals are produced using UV light and the bond breaks forming two radicals

what is propagation

occurs when a radical reacts with a nonradical and new radicals and created causing a chain reaction

what is termination

final step in reaction when two radicals react and the chain reaction ends

what are halogenoalkanes

alkanes with 1 or more halogen attached to it

boiling point trends of halogenoalkanes

boiling point increases down the group for halogenoalkanes due to stonger intermolecular forces of attraction such as van der waals which increase as the size of the molecule increases

what type of bonds do halogenoalkanes have

have polar bonds due to delta positive hydrogen and delta negative halide

what are the most electronegative group

the halogens the most electronegative are oxygen, nitrogen and fluorine

how are polar bonds formed

by having two ions with opposite charges and therefore one element pulls electrons towards itself

polar bonds are attacked by ….

nucleophiles

what are nucleophiles

electron pair donors , they have a long pair of electrons that are donated to an electron deficient area

examples of nucleophiles

hydroxide ions, cyanide ions, ammonia

halogenoalkanes react with hydroxide ions using…

nucleophillic substitution alcohols are formed

conditions for halogenoalkanes reaction with hydroxide ions

warm aqueous sodium hydroxide carried out under reflux

halogenoalkanes reaction with cyanide ions using….

nucleophilic substitution to make nitriles

conditions for halogenoalkanes reaction with cynanide ions to make nitriles

warm ethanolic potassium cyanide carried under reflux

halogenoalkanes react with ammonia using

nucleophilic substitution to form amines

conditions for halogenoalkanes reaction with ammonia

heat with ethanolic ammonia and it must be in excess

why do we need excess ammonia in the process of the reaction between halogenoalkanes and ammonia

we need an excess as another molecule of NH3 acts as a base by reacting with hydrogen

what smell does an amine have

fishy smell

what is produced when a halogenoalkane reacts ammonia

an amine

halogenoalkane reactivity

become more reactive as we go down the group - bond enthalpy and bond strength determines this

what is the other way that halogenoalkanes can react with hydroxide ions

can react via elimination using warm ethanolic sodium hydroxide carried out under reflux to produce an alkene

what do hydroxide ions act as in the elimination reaction with halogenoalkanes

act as a base (proton acceptor)

how do hydroxide ions attack in the elimination reaction between hydroxide ions and halogenoalkanes

they attack the hydrogen on the carbon adjacent to the carbon with the halogen on it

what do you get when halogenoalkanes react in an elimination reaction with hydroxide ions

you get an alkene, water and the halide ion

what plays a part in determining whether a mechanism is elimination or substitution when using hydroxide ions

if the solvent used is ethanol an alkene is made and it is an elimination reaction however if the solvent used is water to make an alcohol then it is a substitution reaction

CFCs

chlorofluoroccarbons they are used to break down ozone in the atmosphere they have had all hydrogens replaced by chlorine and fluorine

how are CFCs broken down

they are broken down by UV in the atmosphere radicals are formed and catalyse the breakdown of ozone

initiation step for the breakdown of CFCs using ozone equation

CCl3F + hv —> CCl2F + Cl

propagation step for the breakdown of CFCs using ozone equation

Cl + O3 —> O2 + ClO

ClO + O3 —> 2O2 + Cl

termination step for the breakdown of CFCs using ozone equation

radicals react to form a non radical

what does Cl act as in the breakdown of ozone

catalyst

properties of CFCs

stable, unreactive, non toxic chemicals

alternative for CFCs

HFCs and hydrocarbons

alkenes are..

hydrocarbons that are unsaturated and have at least one double bond

are alkenes reactive

they are reactive due to them having a high charge density meaning that they lone electron pairs

cycloalkenes exception

have two fewer hydrogens than the chain version

electrophile

a radical that accepts a pair of electrons from the carbon double bond that have a high charge density arrow is draw from double bond to electrophile as electron deficienr

electrophiles examples

polar molecules - hydrogen bromide and concentrated sulfuric acid )

electrophile that have positive charges

H+ ion and NO2+ ion

why does an alkene decolorise when it is added to bromine water

it forms a dibromoalkane which is colorless and Bromine is polarised as electrons in the double bond repels electrons in Bromine - so temporary dipole is created then the delta negative bromine attracts the electron pair and forms a bond breaking Br2 in the process

what happens when you react hydrogen halides with unsymmetrical alkenes?

you form two products a minor product and a major product

what is the amount of product formed by an unsymmetrical alkene dependent on?

stability and carbocation intermediate the more alkyl groups bonded to the carbocation the more stable the intermediate

why is it that having more alkyl groups produces a more stable intermediate

this is because alkyl groups push electrons towards the positive carbocation stabilising it

primary carbocation has…

one alkyl group bonded to it that donates electrons causing a positive inductive effect

what carbocation is the most stable

tertiary carbocation

major product

most stable product

minor product

least stable product

addition of sulfuric acid to alkenes conditions and products

cold concentrated H2SO4 and to form alkyl hydrogen sulfates then is hydrated by cold water through hydrolysis to give an alcohol

what is H2SO4 in the process of making alcohols from an alkene

a catalyst meaning it is also reformed