What do you mean by:
(i) Elimination reactions
(ii) Rearrangement reactions?
(i) Elimination reactions: An elimination reaction is one which involves the loss of two atoms or groups either from the same or adjacent atoms of a substance leading to the formation of multiple bond i.e. double or triple bond. In such reactions at least two σ; bonds are lost and one 
; bond is created. These are two types:
(a) β-elimination reaction. Here loss of two atoms or groups takes place from the adjacent carbon atoms in the molecule. For example,
(i) Dehydrohalogenation of alkyl halides with an alcoholic solution of KOH.
(ii) Dehydration of alcohols in the presence of concentrated H2SO4 upon heating:
(iii) 
-Elimination reactions. In such reactions, there is loss or elimination of two atoms or groups from the same carbon atom in the molecule. For example.
(b) Dehydrohalogenation of chloroform with NaOH
(ii) Dehydrogenation of primary or secondary alcohols with reduced copper at 573K.
(iii) Rearrangement reactions Reactions involving the shift or migration of an atom or a group from one atom to another within the same molecule are called rearrangement reactions for example.
(i) n-Butane rearranges to form 2-methyl propane when heated in a sealed tube in the presence of AlCl3/HCl.
(ii) Ammonium cyanate upon heating rearranges to form urea.
