Organic Chemistry
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What happens to a hydrocarbon as the carbon chain becomes shorter?
It becomes less viscous, more volatile, more flammable.
What are the first 4 alkanes?
Methane, Ethane, Propane, Butane.
What is cracking?
The process of splitting up long-chain hydrocarbons into short-chain hydrocarbons.
Describe the process of catalytic cracking.
The long-chain hydrocarbons are heated and consequently vaporised (turned into gas). The vapour is then passed over a hot powdered aluminium oxide catalyst. The long-chain hydrocarbon molecules split apart on the surface of the specks of catalyst .
Describe the process of steam cracking.
The long-chain hydrocarbons are heated and consequently vaporised (turned into gas). The vapour is then mixed with steam and then heated to a very high temperature.
What is meant when describing an alkane as being ‘saturated’?
Containing the greatest possible number of hydrogen atoms, without carbon–carbon double or triple bonds.
Why do alkenes burn with a smoky flame?
There isn’t enough oxygen in the air for complete combustion with alkenes as alkenes need a large amount of oxygen to undergo complete combustion. Because of this, carbon monoxide is produced as well as carbon dioxide and water. Incomplete combustion results in a smoky yellow flame, and less energy being released compared to complete combustion of the same compound.
What is a functional group?
A group of atoms in a molecule that determines how that molecule typically reacts (e.g. C=C in alkenes).
How do alkenes usually react?
Via addition reactions, the carbon-carbon double bond will open up to leave a single bond and a new atom is added to each carbon.
How can a alkane be formed from an alkene?
By hydrogenation. The alkene is reacted with hydrogen in the presence of a catalyst to form an alkane.
How can a alcohol be formed from an alkene?
When alkenes react with steam, water is added across the double bond and an alcohol is formed.
Alkenes can react with halogens in addition reactions. TRUE or FALSE?
True
How can the addition of a halogen (bromine) to a double bond be used to test for alkenes.
If bromine water 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 is addition polymerisation?
The process in which unsaturated monomer molecules (alkenes) open up their double bonds and join together to form polymer chains.
How can alcohols form carboxylic acids?
Alcohols can be oxidised by reacting with oxygen to produce a carboxylic acid.
Why are alcohols used as solvents?
They can dissolve most things water can dissolve, but they can also dissolve substances that water can’t dissolve (e.g. hydrocarbons).
Why is ethanol used as a fuel?
It burns fairly cleanly and it’s non-smelly.
What method can be used to make ethanol?
Fermentation - an enzyme in yeast is used to convert sugars into ethanol. Carbon dioxide is also produced.
What are the best conditions for fermentation?
A temperature of about 37°C, in a slightly acidic solution and under anaerobic conditions (no oxygen). A reaction between an alkene and steam.
What is the functional group of the carboxylic acid homologous series of compounds?
-COOH
What are the first 4 carboxylic acids?
Methanoic, ethanoic, propanoic and butanoic acid.
What are the first 4 alkenes?
Ethene, propene, butene, pentene.
What are the first 4 alcohols?
Methanol, ethanol, propanol, butanol.
What can be formed using a carboxylic acid and an alcohol?
Esters are formed from an alcohol and a carboxylic acid in the presence of a acid catalyst.