2. According to the classical definition, a super acid is an acid with an acidity greater
than that of 100% pure sulfuric acid, which has Hammett acidity function of -12.
According to the modern definition, a super acid is a medium in which the
chemical potential of the proton is higher than in pure sulfuric acid.
3. More efficient proton donor than pure sulphuric acid.
Viscous, corrosive liquid.
1018 times more acidic than sulphuric acid.
Formed when powerful Lewis acid is dissolved in a powerful Bronsted acid.
4. HAMMETT ACIDITY FUNCTION:
Is a measure of acidity that is used for very concentrated solution of strong acid,
including super acid.
Proposed by the physical organic chemist
Louis Plack Hammett.
H0= pK BH + log [B]/[BH+]
5. EXAMPLES
1. Fluorosulphuric acid: (H0= -15.1)
Is a inorganic compound with chemical formula HSO3F
Strongest acid commercially available.
It is a tetrahedral molecule. Colourless liquid, although commercial
samples are yellow.
It is prepared by reaction of HF and sulfur trioxide.
SO3 + HF HSO3F
6. 2. Carborane: (H0< -18)
Chemical formula- H(CXB11Y5Z6) (X,Y,Z =H,Akl, F, Cl, Br, CF3)
These are a class of super acid, some of which are estimated to be
at least one million times stronger than pure sulphuric acid.
Strongest known Bronsted acid.
7. 3. Fluoroantimonic acid (H0 between -21 and -23)
Organic compound with chemical formula H2FSbF6.
It is extremely strong acid.
Prepared by treating hydrogen fluoride with antimony pentafluoride in a 2:1 ratio
This results in the formation of fluoronium ion.
2 HF + SbF5 SbF6
- + H2F
+
The extreme Acidity of fluoroantimonic acid is because of fluoroantimonic ion.
8. 4. Triflic acid (H0 = - 14.9)
Also known as trifluoromethanesulfonic acid.
Is a sulfonic acid With chemical formula CF3SO3H.
It is hygroscopic, colorless, slightly viscous liquid and soluble in polar solvents.
It is produced industrially by electrochemical fluorination of methane sulfonic
acid.
. CH3SO3H + 4HF CF3SO2F + H2O + 3H2
CF3SO2F is hydrolyzed.
It can also be produced by oxidation of trifluoromethylsulfenylchloride.
CF3SCl + 2Cl2 +3H2O CF3SO3H + 5HCl
It is mainly used in research as a catalyst in esterification.
9. 5. Magic acid (H0 = -19.2)
It consists a mixture of fluorosulpuric acid and antimony pentafluoride in 1:1
ratio.
It is conjugate Bronsted- Lewis super acid system developed by George Olah.
It has been used to stabilize carbonation and hypercoordinated carbonium ions
in liquid medium.
It can proton weak bases including methane, xenon, halogens and molecular
hydrogen.
10. APPLICATIONS:
In petrochemist, super acidic media are used as catalysts, especially
for alkylation.
Typical catalysts are sulfated oxides of titanium or zirconium
specially treated alumina or zeolite.
Solid acids are alkylation benzene with ethene and propene.
