Strong Bases

Strong bases are bases which completely dissociate in water into the cation and OH^- (hydroxide ion). The hydroxides of the Group I (alkali metals) and Group II (alkaline earth) metals usually are considered to be strong bases. These are classic Arrhenius bases. Here is a list of the most common strong bases.

• LiOH - lithium hydroxide
• NaOH - sodium hydroxide
• KOH - potassium hydroxide
• RbOH - rubidium hydroxide
• CsOH - cesium hydroxide
• *Ca(OH)₂ - calcium hydroxide
• *Sr(OH)₂ - strontium hydroxide
• *Ba(OH)₂ - barium hydroxide

* These bases completely dissociate in solutions of 0.01 M or less. The other bases make solutions of 1.0 M and are 100% dissociated at that concentration. There are other strong bases than those listed, but they are not often encountered.

Properties of the Strong Bases

The strong bases are excellent proton (hydrogen ion) acceptors and electron donors. The strong bases can deprotonate weak acids. Aqueous solutions of strong bases are slippery and soapy. However, it's never a good idea to touch a solution to test it because these bases tend to be caustic. Concentrated solutions can produce chemical burns.

Superbases

In addition to the strong Arrhenius bases, there are also superbases. Superbases are Lewis bases that are Group 1 salts of carbanions, such as hydrides and amides. Lewis bases tend to be even stronger than the strong Arrhenius bases because their conjugate acids are so weak. While Arrhenius bases are used as aqueous solutions, the superbases deprotonate water, reacting with it completely. In water, none of the original anion of a superbase remains in solution. The superbases are most often used in organic chemistry as reagents.

Examples of the superbases include:

• Ethoxide ion
• Butyl lithium (n-BuLi)
• Lithium diisopropylamide (LDA) (C₆H₁₄LiN)
• Lithium diethylamide (LDEA)
• Sodium amide (NaNH₂)
• Sodium hydride (NaH)
• Lithium bis(trimethylsilyl)amide, ((CH₃)₃Si)₂NLi