Module 1:Hydrocarbons and Basic concepts

• General formula CnH2n+1(OH)
• Structural differences:

Chemical behaviour especially oxidation depends on the structural type

• Can be made by the hydration of steam
• Hydration of ethene C2H4 using steam in the presence of a phosphoric catalyst H3P04.
• Carried out at a high temperature and moderate pressure.
•  
• This reaction is reversible and so reaction of ethene is incomplete
• overall a 90% conversion is achieved

• Another method of manufacturing alcohol
• Carried out at low temperatures between 25 and 35. An enzyme called zymase is used.
• Fermentation of carbohydrates to ethanol is anaerobic. If air was present,ethanol would be oxidiesed to ethanal or ethanoic acid which would affect its flavour.
• Carbohydrates are converted into ethanol and carbon dioxide
• ethanol can be used in perfumes and is a solvent in methylated spirits and is being developed as an alternative fuel for cars.
• Spirits have a higher alcohol content as the fermented drink is distilled by slowly heating the alcohol-water mixture.
• The alcohol boils off faster than the water and is then allowed to condense

• Methylated spirits is undrinkable and tax exempt because it consists of ethanol mixed with small amounts of methanol and coloured die
• methanol can be used as a clean burning fuel
• used as an additive in high performance rating cars
• extremely toxic and can lead to death
• it is an important feedstock for the chemical industry and can be converted into methanal and ethanoic acid

• Hydrogen bonds formed between O-H affect properties

Melting and boiling points

• High melting and boiling points due to H bonds
• Have lower volatility than alkanes of a similar mass

Solubility

• Can dissolve in water as hydrogen bonds form between the polar O-H groups of the alcohol and water molecules
• as chain length increases, solubility decreases
• A large part of the alcohol molecule is the non-polar hydrocarbon chain
• This does not form hydrogen bonds with water molecules

Combustion

• in lots of oxygen alcohols burn completely to form carbon dioxode and water
• 

Oxidation of Alcohols

• primary and secondary alcohols can be oxidised using an oxidising agent eg (acidified) potassium dichromate ions
• during the reaction the potassium dichromate changes colour from orange to green

• Primary alcohols
• gently heated with pot. dichrom. oxidised to an aldehyde
• propan-1-ol is oxidised to propanal

• On stronger heating with excess acidified dichromate the alcohol will be completely oxidised going straight to a carboxylic acid
• In a lab the aldehyde needs to be distilled off as it is formed, to prevent it being oxidised to a carboxylic acid to make carboxylic acid,the reaction mixture is heated under reflux before distilling off the product.

Secondary alcohols

• Secondary alcohols are oxidised further by acidified dichromate ions to produce ketones.
• Ketomes cannot be oxidised further

• Tertiary alcohols cannot be oxidised, stays orange.

Esterification

• The reaction of an alcohol with a carboxylic acid to produce an ester and water,sulfuric acid is often used as the catalyst
• 
• O-H bond in alcohol is broken and water is formed.
• Esters-adhesives and solvents. Can produce different fruity smells

• in a boiling tube add 1cm of carboxylic acid to 1cm of the alcohol. Add a few drops of sulfuric acid.
• place boiling tube in hot water bath (80) for about 5 mins
• pour the product into a beaker of cold water
• see an oil floating on the surface of the water. This is the ester
• Dehydration of an alcohol
• alcohol is dehydrated to form an alkene (acid catalyst). Elimination reaction
• alcohol heated under reflux, in the presence of phosphoric acid for 40 mins