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We see that some substances are capable of adding oxygen to others.
                 These substances are known as oxidising agents.
                    Alkaline potassium permanganate or acidified potassium dichromate
                 are oxidising alcohols to acids, that is, adding oxygen to the starting
                 material. Hence they are known as oxidising agents.

                 4.3.3 Addition Reaction

                 Unsaturated hydrocarbons add hydrogen in the presence of catalysts
                 such as palladium or nickel to give saturated hydrocarbons. Catalysts
                 are substances that cause a reaction to occur or proceed at a different
                 rate without the reaction itself being affected. This reaction is commonly
                 used in the hydrogenation of vegetable oils using a nickel catalyst.
                 Vegetable oils generally have long unsaturated carbon chains while
                 animal fats have saturated carbon chains.






                    You must have seen advertisements stating that some vegetable oils
                 are ‘healthy’. Animal fats generally contain saturated fatty acids which
                 are said to be harmful for health. Oils containing unsaturated fatty acids
                 should be chosen for cooking.

                 4.3.4 Substitution Reaction

                 Saturated hydrocarbons are fairly unreactive and are inert in the presence
                 of most reagents. However, in the presence of sunlight, chlorine is added
                 to hydrocarbons in a very fast reaction. Chlorine can replace the hydrogen
                 atoms one by one. It is called a substitution reaction because one type
                 of atom or a group of atoms takes the place of another. A number of
                 products are usually formed with the higher homologues of alkanes.
                    CH  + Cl  → CH Cl + HCl (in the presence of sunlight)
                       4     2      3
                                    Q      U      E      S     T      I    O       N      S


                    1.   Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
                    2.   A mixture of oxygen and ethyne is burnt for welding. Can you tell why       ?
                         a mixture of ethyne and air is not used?


                 4.4 SOME IMPORTANT CARBON COMPOUNDS – ETHANOL
                      AND ETHANOIC ACID

                 Many carbon compounds are invaluable to us. But here we shall study
                 the properties of two commercially important compounds – ethanol and
                 ethanoic acid.


                 Carbon and its Compounds                                                                  71


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