Organic Chemistry (Leaving Cert Chemistry)

hydrocarbon

compound consisting of carbon and hydrogen only

saturated hydrocarbon

a hydrocarbon with single bonds only.

alkane

a hydrocarbon containing only single bonds between carbon atoms

general formula for alkanes

CnH2n+2

structural isomers

compounds with the same molecular formula but different structural formula

alkene

a hydrocarbon containing double bonds between carbon atoms

general formula for alkenes

CnH2n

chemical formula for prep of ethene

ethanol + aluminium oxide = ethene + water // C2H5OH + Al2O3 = C2H4 + H2O

alkyne

a hydrocarbon containing triple bonds between carbon atoms

general formula for alkynes

CnH2n-2

chemical formula for prep of ethyne

calcium carbide + water = calcium hydroxide + ethyne // CaC2 + 2H2O = Ca(OH)2 + C2H2

aliphatic compound

organic compound consisting of open chains of carbon atoms and closed ring structures

aromatic compound

organic compound containing a benzene ring

octane number

the ability of a fuel to resist auto-ignition (knocking)

what hydrocarbon has an octane number of 0?

heptane

what hydrocarbon has an octane number of 100?

2, 2, 4 trimethylpentane

what factors affect octane number?

chain length, degree of branching, cyclical compounds (more of all these increase octane number)

what processes increase octane number?

isomerisation, catalytic cracking, dehydrocyclisation, adding oxygenates

isomerisation and result

turns long straight chain hydrocarbons into their isomers // shorter chains, more branches

catalytic cracking and result

breaks long chain hydrocarbons into shorter chain hydrocarbons using a catalyst // shorter chain hydrocarbons, one being unsaturated

dehydrocyclisation

converts hydrocarbons into ring compounds

adding oxygenates and results

adding oxygen containing compounds to the fuel // cleaner fuel with higher octane number

MTBE

methyl tertiary butyl ether

fractional distillation

process that separates crude oil into its component hydrocarbons according to their boiling points

organic chemistry

the study of compounds of carbon

unsaturated hydrocarbon

molecule containing double bonds between carbon atoms

homologous series

families of hydrocarbons / series of compounds with similar chemical properties, graduations of physical properties, general formula and methobof prep, consecutive members differ by CH2

auto-ignition (knocking)

premature ignition of the petrol-air mixture before normal ignition of the mixture by a spark takes place

steam reforming

a reaction used for the manufacture of hydrogen, by reducing steam with natural gas at high temperature

electrolysis

use of electricity to bring about a chemical reaction in an electrolyte

hess's law

if a chemical reaction takes place in a number of stages, the sum of the heat changes in the separate stages is equal to the heat change if the reaction is carried out in one stage

law of conservation of energy

energy can neither be created or destroyed but can only be converted from one form of energy into another

what are the three homologous series?

alkanes, alkenes, alyknes

what is at the top of the fractionating column?

refinery gas, 20 degrees, used as fuel

what is at the bottom of the fractionating column?

fuel oil, 350 degrees, fuel for ships and factories // residue used in asphalt