Chapter 24- Alcohols and Carboxylic Acids

ALCOHOLS

• Alcohols are organic compounds with the hydroxyl functional group and the general formula CnH2n+2 .

• Alcohols are soluble in water but their solubility decreases as the chain of carbon atoms becomes longer.

• Alcohols are neutral in pH and can undergo combustion and oxidation.

• The first four alchols are liquids at room temperature and pressure.

  

• In presence of potassium manganate (VII) which is an oxidising agent, alkenes are oxidised to alcohols. Potassium Manganate (VII) changes colour from purple to colourless.

• Ethene is oxdised to ethanol which is one way to produce this alcohol.

• Another way to produce ethanol is by fermentation of yeast in presence of enzymes, 37 degrees celsius temperature and a neutral (7) pH. When yeast respires anaerobically, glucose is broken into carbon dioxide and ethanol.

• Ethanol is used as a solvent, in alcoholic drinks, and as a fuel.

CARBOXYLIC ACIDS

• Carboxylic acids are organic acids with the functional group -COOH, and the general formula CnH2n+1COOH.

• As the chain of carbon atoms increases, the melting and boiling points of carboxylic acids also increases.

  

• Carboxylic acids undergo the same reactions as normal acids, i.e. with alkalis/bases, carbonates and metals.

• They are usually weak acids with pH ranging from 3 to 5.

ESTERS

• A carboxylic acid reacts with an alcohol to form an organic compound called ester in a process called esterification.
• The first part of the name of the ester is the name of the alcohol with -yl at the end. The second part is the name of the carboxylic acid with -oate at the end. For e.g. ethyl methanoate is made from ethanol and methanoic acid.
• Esters are found in fats and waxes.
• They are used as solvents, in perfumes, and food flavourings.