alcohols

• primary alcohols

  An alcohol in which the hydroxyl (-OH) group is attached to a carbon that is in turn attached to one other carbons.
• secondary alcohol

  An alcohol in which the hydroxyl (-OH) group is attached a carbon that is attached to two other carbons.
• tertiary alcohol

  An alcohol in which the hydroxyl (-OH) group is attached to a carbon that is in turn attached to three other carbons.
• oxidation of alcohols

  -primary --[O]--> aldehydes --[O]--> carboxylic acids

  -secondary --[O]--> ketones
• oxidising agents - K2Cr2O7

  -acidified potassium dichromate K2Cr2O7 which is orange

  -when alcohols are oxidised the orange dichromate ions (Cr2O7 2-) are reduced to green Cr3+ ions
• oxidising agents - KMnO4

  -acidified potassium manganate KMnO4 is purple

  -when alcohols are oxidised the manganate ions (MnO4-) are reduced to colourless Mn 2+ ions
• Fehling's solution

  -alkaline soln containing Cu 2+ ions - oxidising agent

  -when warmed with aldehyde, aldehyde is oxidised to carb. acid and Cu 2+ reduced to Cu+

  -clear blue will turn opaque red due to copper(I) oxide ppt

  -ketones cannot be oxidised and therefore give a -ve test
• Tollens' reagaent

  -aqueous alkaline soln of silver nitrate in XS ammonia

  -aka ammoniacal silver nitrate solution

  -when warmed with aldehyde, aldehyde oxidised to carb acid and Ag+ reduced to Ag atoms

  -Ag forms a silver mirror on the inside of the tube

  -ketones cannot be oxidised and give -ve test
• combustion of alcohol

  -undergo complete combustion

  alcohol + oxygen ---> carbon dioxide + water

  -lower alcohols burn with almost invisible flame and make good fuels

  -ethanol produced sustainably as fuel by fermentation of sugars

  -energy density for ethanol is lower than gasoline so either ethanol cars have large fuel tank or must be filled more often

  -blending ethanol and gasoline increases energy density also makes it safer as you can see flame in case of fire

  -socio-economic concerns about using large quantities of farm land to produce crops for fermentation