2. Bases Properties and Examples

Base Strenght

“Strong Base” is one which hydrolyzes completely, deprotonating acids in an acid-base reaction, hence, raising the pH of the solution towards 14. Compounds with a pH of more than about 13 are called strong bases. Strong bases, like strong acids, attack living tissue and cause serious burns. They react differently to skin than acids do so while strong acids are corrosive, we say that strong bases are caustic. Common examples of strong bases are the hydroxides of alkali metals and alkaline earth metals like NaOH and Ca(OH)2. Very strong bases are even able to deprotonate very weakly acidic C-H groups in the absence of water. Superbases are a class of especially basic compounds and harpoon bases are a special class of strong bases with poor nucleophilicity.

Examples of Strong Bases (Hydroxide compounds) in descending strenght:

  • Potassium hydroxide (KOH)
  • Barium hydroxide (Ba(OH)2)
  • Cesium hydroxide (CsOH)
  • Sodium hydroxide (NaOH)
  • Strontium hydroxide (Sr(OH)2)
  • Calcium hydroxide (Ca(OH)2)
  • Lithium hydroxide (LiOH)
  • Rubidium hydroxide (RbOH)

The cations of these strong bases appear in groups 1 and 2 of the periodic table (alkali and alkaline earth metals).

Even stronger bases are:

  • Sodium hydride (NaH)
  • Lithium diisopropylamide (LDA) (C6H14LiN)
  • Sodium amide (NaNH2)

“Weak Base” is one that does not fully ionize in solution. When a base ionizes, it takes up a hydrogen ion from the water around it, leaving an OH- ion behind. Weak bases have a higher H+ concentration than strong bases. Weak bases exist in chemical equilibrium in the same way weak acids do. The Base Ionization Constant Kb indicates the strength of the base. Large Kbs belong to stronger bases. The pH of a base is greater than 7 (where 7 is the neutral number; below 7 is an acid), normally up to 14. Common example of a weak base is ammonia, which is used for cleaning.

Examples of Weak Bases:

  • Alanine (C3H5O2NH2)
  • Ammonia (water) (NH3 (NH4OH))
  • Dimethylamine ((CH3)2NH)
  • Ethylamine (C2H5NH2)
  • Glycine (C2H3O2NH2)
  • Hydrazine (N2H4)
  • Methylamine (CH3NH2)
  • Trimethylamine ((CH3)3N)

Leave a Reply

Your email address will not be published. Required fields are marked *