What bases are the strongest?

Answer 1

In chemistry, a superbase is an extremely strong base. There is no commonly accepted definition for what qualifies as a superbase. In general, there are three main classes of superbases: organic, organometallic, and inorganic.

In organic synthesis, the Schlosser base (or Lochmann-Schlosser base), i.e. the combination of tert-butyllithium and potassium tert-butoxide, is a commonly used superbase. tert-Butyllithium undergoes a cation exchange with potassium tert-butoxide giving tert-butyl potassium and lithium tert-butoxide, an exchange driven by lithium's affinity for the alkoxide oxygen. Replacement of the lithium cation with potassium causes the tert-butyl anion to acquire greater ionic character and thus greater basicity.

Organometallic compounds of reactive metals are usually superbases, for example organolithium and organomagnesiums (Grignard reagents). Another type of organic superbase has a reactive metal exchanged for a hydrogen on a heteroatom, such as oxygen (unstabilized alkoxides) or nitrogen (lithium diisopropylamide).

Inorganic superbases are typically salts with highly charged, small negative ions, e.g. lithium nitride, which has extreme negative charge density and so is highly attracted to acids, like the aqueous hydronium ion. Alkali and earth alkali metal hydrides (sodium hydride, calcium hydride) are superbases.

Answer 2

In terms of strength, guanine-cytosine (GC) base pairs are stronger than adenine-thymine (AT) base pairs, as GC base pairs form three hydrogen bonds compared to the two hydrogen bonds in AT base pairs. This results in a more stable structure and higher melting temperature for DNA strands with a higher GC content.