Alcohols

• The general formula: CnH(2n+1)OH
• The OH group is the hydroxyl group
• The C-O-H angle is 105 degrees.
• Classification of alcohols:

Primary- OH group at the end of a carbon chain (surrounded by1 R group and 2 H atoms)

Secondary- OH group in the body of a chain (surrounded by2 R groups and 1 H atom)

Tertiary- OH group at a branch in the chain (surrounded by 3 R groups)

• Physical properties: High melting point due to hydrogen bonding between molecules. Shorter chain alcohols are soluble in water because of H-bonds between OH groups and water.

• First, crude oil is cracked, producing ethene.
• Ethene is then hydrated, which means that water is added to the double bond
• Conditions: 

Catalyst- Phosphoric acid absorbed on silica.

Temperature- 570K

Pressure- 6500 kPa

• This gies a conversion of ethanol of only 5%, but the excess ethene is separated and used gain until 95% of the reaction mixture is obtained,
• The reaction is exothermic.
• Advantages: fast process, continuous flow process and produces pure ethanol
• Disadvantages: requires fairly high technology, uses lots of energy and uses non-renewable raw materials (crude oil)

• Sugar (glucose) is broken down into ethanol by enzymes present in yeast.
• Carbon dioxide is also another product.
• This is a process called anaerobic respiration.
• Conditions:

Temperature: 37 degrees

Absence of air to prevent oxidation of ethanol to ethanoic acid

Yeast enzymes

• Once the fermenting solution contains about 15% of ethanol the enzymes are unable to function and the fermentation stops.
• Advantages: low technology process, does not use much energy, uses renewable raw materials (sugar cane)
• Disadvantages: Batch process, relatively slow process and produces impure ethanol

• alcoholic drinks
• cosmetics
• drugs
• detergents
• inks
• motor fuel

Carbon neutrality

• Carbon dioxide released when something is burnt is balanced by the carbon dioxide absorbed by the plant from which it is originally obtained.
• Ethanol made from fermentation is renewable!!

Combustion

• Produces carbon dioxide and water on complete combustion.

Oxidation

• Primary alcohols are oxidised to aldehydes, secondary alcohols are oxidised to ketones. Aldehydes can further be oxidised to carboxylic acids.
• Tertiary alcohols are not easily oxidised. This is because a C-C bond needs to break, rather than a C-H bond.
• Solution of acidified potassium dichromate is the oxidising agent. Orange dichromate ions turn to green chromium ions.

• Use dilute acid and less potassium dichromate..
• Heat the mixture under reflux