28 terms

IGCSE Chemistry: Organic chemistry

http://www.diegcse.com/chemistry-section-3
STUDY
PLAY

Terms in this set (...)

Homologous series
A series of organic compounds that have the same general formula, similar chemical reactions and where each member differs from the next by a -CH₂- group
Hydrocarbon
A compound containing only the elements hydrogen and carbon
Saturated
An organic compound in which all the bonds are single bonds
Unsaturated
An organic compound that contains a carbon-carbon double bond
General formula
A formula that states the ratio of atoms of each element in the formula of every compound in a particular homologous series
Isomerism
Compounds that have the same molecular formula but different displayed formulae are said to exhibit this
Alkanes
A homologous series of compounds that have the general formula CnH2n+2
CH₄
Molecular formula for methane
C₂H₆
Molecular formula for ethane
C₃H₈
Molecular formula for propane
C₄H₁₀
Molecular formula for butane
C₅H₁₂
Molecular formula for pentane
Combustion
When oxygen combines with another compound to form water and carbon dioxide. These reactions are exothermic, meaning they produce heat.
Incomplete combustion
When a lack of oxygen combines with another compound to form water and carbon monoxide. Carbon monoxide is poisonous - it reduces the capacity of the blood to carry oxygen.
Substitution reaction
When one atom is replaced by another atom in a reaction.
CH₄ + Br₂ → CH₃Br + HBr
Methane and bromine react together in the presence of ultraviolet light to form bromomethane.
Alkenes
A homologous series of compounds that have the general formula CnH2n. They are all unsaturated.
C₂H₄
Molecular formula for ethene
C₃H₆
Molecular formula for propene
C₄H₈
Molecular formula for butene
C₅H₁₀
Molecular formula for pentene
Addition reactions
When an unsaturated compound becomes saturated. The double bond breaks and two new atoms/groups are added to each of the previously double bonded carbon.
Decolorization of bromine
1,2-dibromomethane is colorless, so when bromine or bromine water is shaken with ethene the bromine will be decolorized. This can be used to test for the presence of unsaturation in a molecule.
Fermentation
When sugar or starch is dissolved in water and yeast is added, before being fermented for several days in the absence of air at room temperature. The excess yeast is filtered off to obtain a dilute solution of ethanol.
Direct hydration of ethene
When a mixture of ethene and steam is passed over a phosphoric acid catalyst at a temperature of 300°C and 60-70 atmospheres of pressure. Ethanol is produced and condensed as a liquid.
Fermentation
This ethanol production method uses renewable resources but is very slow and produces a solution that requires further processing if pure ethanol is required.
Direct hydration of ethene
This ethanol production method uses non-renewable resources but is continuous, fast and produces pure ethanol. However, high temperatures and pressures are required, increasing the cost.
Dehydration of ethanol to ethene
Ethanol can be dehydrated by passing ethanol vapor over a hot aluminum oxide catalyst. This can be used to manufacture ethene for the production of poly(ethene).