• The reactions of organic compounds can be classified into?substitution,?addition?and?combustion

Substitution

• A?substitution?reaction takes place when one functional?group is replaced by another
  • Example:?Methane reacts with bromine under ultraviolet light

   

CH₄? ? +? ? Br₂?????? →????????????CH₃Br? ?+? ? HBr

? ? Methane + Bromine ??→ ??Bromomethane + Hydrogen Bromide

Addition

• An?addition?reaction takes place when two or more molecules combine to form a larger molecule with no other products
  • Example:?Bromine will react with ethene and the bromine molecule will react and add across the double bond of the ethene

   

C₂H₄?????+???????Br₂?? ? ? ??→?????????C₂H₄Br₂

Ethene ??+ ??Bromine ??→ ??Dibromoethane

Combustion

• This is the scientific term for burning. In a?combustion?reaction, an organic substance reacts with oxygen to form carbon dioxide (or carbon monoxide if incomplete combustion) and water.
  • Example:?Alkenes burn when heated in air of oxygen
  • If there is an unlimited supply of air / oxygen, the products are carbon dioxide and water:

   

CH₄???+ ??2O₂???→ ??CO₂???+ ??2H₂O

C₃H₈???+ ??5O₂???→ ??3CO₂???+ ??4H₂O

• This is termed complete combustion
  • If there is a limited supply of air / oxygen, the products are carbon monoxide and water:

   

CH₄???+ ???O₂???→ ??CO ??+ ??2H₂O

• This is termed incomplete combustion

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