This document discusses acids and bases in non-aqueous media. It defines solvents and classifies them based on their polarity and ability to donate or accept protons. It describes how acids and bases are defined by Arrhenius and Brønsted-Lowry theories. Several non-aqueous solvents like liquid ammonia, sulfuric acid, sulfur dioxide and hydrogen fluoride are described in terms of their properties and how they influence acid-base behavior. Reactions like neutralization and autoionization in these solvents are also discussed. The document concludes by outlining some advantages of using non-aqueous solvents.

1. Aci
ds
and
Bas
Acid Base Equilibria in Non-
Aqueous Media

2. Aci
ds
and
Bas
Classification of
solvents
Solve
nt
• A substance that dissolves a solute
resulting in a solution
• Usually a liquid but can also be a
solid, gas or supercritical fluid
• Generally, the dielectric constant of
the solvent provides a rough
measure of a solvent’s polarity
• Solvents with dielectric constant
less than 15 are generally
considered to be non-polar
• Solvents with dielectric constant
greater than 15 are called polar
solvents (protic or aprotic)

3. Aci
ds
and
Bas
Hex Code
#2B463C
CMYK
100% 0%
45% 29%
RGB
0-180-99
Hex Code
#688F4E
CMYK 100%
44% 0% 4%
RGB
0-136-244
1.Protonic and non protonic
solvents
• The solvents from which
protons can be derived are
called protonic solvents e.g.
sulfuric acid, ammonia, HF etc.
• The solvents from which
protons can not be derived are
called non-protonic solvents
e.g. liquid sulfur dioxide,
benzene, chloroform etc.
Types of Non-Aqueous
solvents
2. Ionizing and Non-
Ionizing solvents
• The solvents which are capable of
undergoing self ionization (Auto
ionization) are called ionizing solvents
e.g. NH3, SO2 etc.
• The solvents which do not ionize at all
are called non-ionizing solvents e.g.
benzene, hydrocarbons etc.
These are non-polar in nature.

4. Aci
ds
and
Bas
Types of Non-Aqueous
solvents
• The solvents which have a tendency to
donate protons are acidic in nature and
are called acidic solvents e.g. acetic
acid, HF.
• The solvents which have strong
tendency to accept protons are basic in
nature and are called basic or
protophilic solvents e.g. liquid NH3
pyridine etc.
• The solvents which neither have
tendency to gain nor to lose protons
are called amphiprotic or amphoteric
solvents e.g. ethanol.
3. Acidic, Basic or
Amphiprotic solvents
4. Coordinating and Non-
Coordinating solvents
• The solvents which are capable
of coordinating with metal ions or
anions of solute are called
coordinating solvents e.g. NH3,
SO2 DMSO, DMF etc.
• The solvents which are not
capable of coordinating with
metal ions of solute are called
non-coordinating solvents e.g.
CCl4, saturated hydrocarbons etc.

5. Aci
ds
and
Bas
Definitions of acids and bases
• Arrhenius acids and bases
⮚Acid: Substance that, when dissolved in
water, increases the concentration of
hydrogen ions (protons, H+).
⮚Base: Substance that, when dissolved in
water, increases the concentration of
hydroxide ions.

6. Aci
ds
and
Bas
Definitions of acids and bases
• Brønsted–Lowry: must have both
1. an Acid: Proton donor
and
2. a Base: Proton acceptor

7. Aci
ds
and
Bas
The Brønsted-Lowry acid donates a proton,
while the Brønsted-Lowry base accepts it.
Brønsted-Lowry acids and bases are always paired.

8. Aci
ds
and
Bas
A Brønsted–Lowry acid…
…must have a removable (acidic) proton.
HCl, H2O, H2SO4, HSO4
-
A Brønsted–Lowry base…
…must have a pair of nonbonding electrons.
NH3, H2O, OH-

9. Aci
ds
and
Bas
Conjugate Acids and Bases:
• From the Latin word conjugare, meaning “to
join together.”
• Reactions between acids and bases always
yield their conjugate bases and acids.

10. Aci
ds
and
Bas

11. Aci
ds
and
Bas
Ion-Product Constant
• This special equilibrium constant is
referred to as the ion-product constant
for water, Kw.
• At 25°C, Kw = 1.0 × 10-14
• Kw = [H+][OH-] = 1.0 x 10-14
• If [H+] goes up, [OH-] decreases
• Inverse relationship

12. Aci
ds
and
Bas
Physical properties of solvents
• Melting and boiling point
• Dielectric constant
• Viscosity
• Heat of fusion
• Heat of
vapourization

13. Aci
ds
and
Bas
Levelling Effect:
•The acidity of the weak acids can be enhanced using
basic solvents because the basic solvent has higher
affinity to take up protons from acid.
•So, acetic acid behaves as a strong acid in ammonia
solution.
• The basicity of the weak bases can be enhanced in
the presence of acidic solvent. This is called the levelling
effect of the solvent.

14. Aci
ds
and
Bas
Acid-Base behavior in non-
aqueous solvents
Differentiating
effect
Strengths of acids and bases
• If HCl is dissolved in
acetic acid, the extent
of ionization is far less
than in water and HCl
•In acetic acid the extent of
ionization of the three
hydrogen halides varies along
the series: HI˃HBr˃ HCl
•Thus, acetic acid exerts a
differentiating effect on the
acidic behavior of HCl, HBr
and HI, whereas water does
Due to leveling nitric, sulphuric, perchloric and hydrochloric
acids are all equally strong acids in dilute aq. solutions. So,
more strongly acidic solvents are necessary to differentiate
acidity.

15. Aci
ds
and
Bas
Autoionization of Water
We have seen, water is amphoteric.
In pure water, a few molecules act as bases
and a few act as acids.
This process is called autoionization.

16. Aci
ds
and
Bas
Acid-Base behavior in non-
aqueous solvents
Liquid dinitrogen tetraoxide, N2O4
undergoes self ionization as
N2O4 [NO]+ + [NO3]-

17. Aci
ds
and
Bas
Liquid Ammonia as
non-aqueous
solvent
Physical
Properties
Melting Point -77°C
Boiling point -33°C
Dielectric constant 22.0 at -33°C
Liquid range -77 to -33°C
Heat of fusion 0.018 KJ/mol
Heat of
Vapourization
-23.6 KJ/mol
• Acts as an associated
solvent
• Self Ionizable in nature
Why Ammonia acts as
a better solvent than
water
• Poor Conductor of
Electricity
• Specific heat of
ammonia is greater
than water
• Less viscous than
water
• High critical
temperature and
pressure
• Less associated than
water (due to lesser H-

18. Aci
ds
and
Bas
Liquid Ammonia as non-
aqueous solvent
Chemical
Reactions
• Acid Base reaction
• Precipitation reaction
• Redox reaction
• Solvation reaction
Acid Base
Reactions
•Liquid ammonia ionizes
as
Liquid ammonia is an ideal solvent for
reactions requiring a strong base, since the
amide ion is strongly basic.
2NH3 [NH4]+ +
[NH2]-

19. Aci
ds
and
Bas
Acid Base Neutralization
Reaction
Neutralization of an acid and base in liquid ammonia involves
combination of
NH4
+ ion (From Acid) and NH2
- ion (From Base):-
Reactions in Liquid
Ammonia
Thus, NH4Cl may be regarded as a strong acid and
KNH2 as strong base in liquid ammonia.
They are termed as “Ammono Acids” and “Ammono
Bases” (Neutralisation)

20. Aci
ds
and
Bas
• All acids that behave as strong acids in
water react completely with ammonia
(leveled) to form ammonium ions:
HClO4 + NH3 [NH4]+ + [ClO4]-
HNO3 + NH3 [NH4]+ + [NO3]-

21. Aci
ds
and
Bas
Reactions in Liquid
Ammonia
• Certain compounds like urea which are incapable of donating protons to water can
readily donate proton to ammonia in liquid ammonia.
• In addition, some acids that behave as weak acids in water react completely with
ammonia and hence are strong acids in this solvent:
HC2H3O2 + NH3 [NH4]+ + [C2H3O2]-

22. Aci
ds
and
Bas
Sulphuric acid as non-
aqueous solvent
Chemical
Reactions
Melting Point 10.37°C
Boiling point 300°C
Dielectric constant 110 at 20°C
Density 1.83 g/cm3
Specific
Conductance
1.04×10-2 Ω-1 cm -1
Viscosity 24.54 g cm -1 s-1
Physical
Properties
Autoionization of sulphuric
acids results in:
Species that are basic in
water are also basic in
sulphuric acid
Likewise, water behaves as a
base in sulphuric acid
2H2SO4 H3SO4
+ +
HSO4
-
OH- + 2H2SO4 H3O+ +
2HSO4
-
NH3
+ H2SO4 NH4
+ +
HSO4
-
H2O + H2SO4 H3O+ +
HSO4
-

23. Aci
ds
and
Bas
Reactions in
Sulphuric acid
Amides, such as urea, which are non electrolyte in water and acids in ammonia
accept protons from sulphuric acid:
Acetic acid is a weak acid in aqueous solution and nitric acid as a strong acid, but
both behave as bases in sulphuric acid:
Sulphuric acid is a very acidic medium, so almost all
chemical species which react upon solution are bases.
Due to the extreme tendency of the sulphuric acid to donate
protons, molecules exhibiting basic tendencies will be leveled
to HSO4-

24. Aci
ds
and
Bas
Reactions in
Sulphuric acid
Perchloric acid is one of the strongest acids known, but in
sulphuric acid it is practically a non electrolyte, behaving as
a very weak acid :
Disulphuric acid (Pyrosulphuric acid) behaves as acid in
sulphuric acid :
HClO4 + H2SO4 H3SO4
+ + ClO4
-

25. Aci
ds
and
Bas
Liquid Sulphur Dioxide
as non-aqueous solvent
Physical
Properties
Melting Point -75.46°C
Boiling point -10.02°C
Dielectric
constant
17.40
• Non-protonic/ aprotic solvent
• One of the important non aqueous
solvent widely used in industry
Reactions in
Liquid SO2
Acid Base
Reactions
• Liquid SO2 undergoes
auto ionization as
• Acid Base or Neutralization
reaction in liquid SO2 may be
given as

26. Aci
ds
and
Bas
Neutralisation Reactions: In sulphur dioxide
• Neutrilisation Reactions: In sulphur dioxide, the
process of neutralisation is observed similar to found
in case of aqueous solution.
• The process of neutralisation in liquid sulphur dioxide
involves combination of SO2+ And SO32- ions to form
un-ionised SO2.
• Thus, all compounds containing or making available
SO32- ions in liquid sulphur dioxide are termed as
Bases and those compounds containing or making
SO2 + ions are termed as Acids.
• E.g. (i) Reaction of thionyl chloride and cesium
sulphate gives a neutralisation reaction

27. Aci
ds
and
Bas
Liquid Hydrogen Fluoride
(HF)
as non-aqueous solvent
Reactions in
Liquid HF
Melting Point -83°C
Boiling point -20°C
Heat of
vapourization
7.493 KJ/mol
Physical
Properties
• Liquid HF
ionizes as

28. Aci
ds
and
Bas
Supera
cids
• Extremely potent acids, capable of protonating even hydrocarbons,
are termed as superacids and include mixture of HF and SbF5
• And HSO3F and SbF5 is called magic acid (one of the strongest acids
known)
• In superacidic media, hydrocarbons
act as bases

29. Aci
ds
and
Bas
Advantages of using non-
aqueous solvents

30. Aci
ds
and
Bas
Advantages of using non-
aqueous solvents

31. Aci
ds
and
Bas
Advantages of using non-
aqueous solvents

32. Aci
ds
and
Bas