solubilization

Question 1

soubility definition

Answer 1

 DEFINITION: Solubility is rate and extent of solute to go into solvent to get homogenize until
equilibria.
 QUALITATIVE DEFINITION: The spontaneous interaction of two or more substances to form
a homogeneous molecular dispersion.
 QUANTITATIVE DEFINITION: The concentration of solute in a saturated solution at a certain
temperature.
 MOLAR SOLUBILITY: Molar solubility is defined as the no. of moles of the substances per one
liter of the solution.

Question 2

types of solution

Answer 2

 SATURATED SOLUTIONS are holding as much solute as possible at a given temperature. The
solution in which more amount of solute cannot be dissolved at room temperature is called saturated
solution.
 UNSATURATED SOLUTIONS will be able to dissolve more. The solution in which more amount

of solute can be dissolved at a certain temperature is called unsaturated solution. It is also called sub-
saturated solution.

 SUPERSATURATED SOLUTIONS are holding more than they should be able to at a given
temperature. When more amount of solute dissolved in saturated solution by increasing temperature,
then the resultant solution is called supersaturated solution.

Question 3

concepts of solubiity

Answer 3

 Like dissolves like
 Polar dissolves polar
 Nonpolar dissolves Nonpolar

Question 4

expressions for approximate solubiity

Answer 4

The solubility of different substances in solvents can be expressed in different ways. Basically the
solubility of substances is expressed as the no. of parts of solvent required for one part of solute. One the basis
of this statement the solubility of solute is classified into following types:
Very soluble Less than 1
Freely soluble From 1 – 10
Soluble From 10 – 30
Sparingly soluble From 30 – 100
Slightly soluble From 100 – 1000
Very slightly soluble From 1000 – 10,000
Practically insoluble More than 10,000

Question 5

biopharmaceutics classification system

Answer 5

Class Solubility Permeability Absorption Pattern Example
I High High Well absorbed Diltiazem

II Low High Variable Nifedepine

III High Low Variable Insulin

IV Low Low Poorly absorbed Taxol

Question 6

process of solubilitzation

Answer 6

The process of solubilization involves the breaking of inter-ionic or intermolecular bonds in the solute,
the separation of the molecules of the solvent to provide space in the solvent for the solute, interaction between
the solvent and the solute molecule or ion. Process is explained in three steps as follow:
STEP 1. Holes Open in the Solvent
STEP 2. Molecules of the solid breaks away from the bulk
STEP 3. The freed sold molecule is integrated into the hole in the solvent.

Question 7

mechanism perspective of solubilization for organic solute in water

Answer 7

1. Break up of solute-solute intermolecular bonds
2. Break up of solvent-solvent intermolecular bonds
3. Formation of cavity in solvent phase large enough to accommodate solute molecule
4. Vaporization of solute into cavity of solvent phase
5. Formation of solute-solvent intermolecular bonds
6. Reformation of solvent-solvent bonds with solvent restructuring

Question 8

factors influencing solubility- solubility of gases in liquid

Answer 8

The concentration of the dissolved gas, when it is in equilibrium with some of the pure gas above the
solution, is called solubility of a gas in liquid. The solubility of gases in liquids depends upon the following
important factors:
i. Pressure
ii. Temperature
iii. Presence of salt
iv. Chemical reaction

Question 9

effect of pressure gas

Answer 9

 The effect of pressure is observed only in the case of gases.
 An increase in pressure increases solubility of gas in liquid.
 At constant temperature, the solubility of a gas in a liquid is directly proportional to the applied
pressure by obeying Henry Law.
 For example, carbon dioxide is filled in cold drink bottles under pressure.

Question 10

effect of temperature

Answer 10

 Generally, with the increase in temperature the solubility of gases in liquids decreases.
 Because, when temperature is increased, the K.E of the molecules is increased which result in the
evolution of gas from the solution & in this way solubility is decreased.

Question 11

presence of salt

Answer 11

 By the addition of salt (Electrolyte) the solubility of gas in liquid is decreased. And this phenomenon
is called salting out process
 E.g. addition of NaCl in carbonated water. Because, due to the addition of NaCl, the attractiveness of
H2O towards dissociated from the solution.

Question 12

chemical reaction

Answer 12

If gases are reacted with water, they have greater solubility. For example, HCl gas reacts with water
& form HCl acid CO2 reacts with water form carbonic acid. So, by their chemical reactions, the solubility of
gases in liquid is increased.

Question 13

applications of gases in liquids

Answer 13

 Hydrochloric Acid
 Ammonia Water
 Effervescent preparations with CO2
 Aerosol products.

Question 14

solubilty of liquids in liquids

Answer 14

Factors affecting are:
1. Attractive forces an Raoult’s law
2. Temperature
3. Influence of foreign substances

Question 15

attractuve forces and raoults law

Answer 15

When two liquids are mixed, either Real or ideal solution is formed. If the adhesive forces are greater
than cohesive forces, then there will be negative deviation from Raoult’s Law, so the solubility (Miscibility)
is increased.
And if the cohesive forces are greater than adhesive forces then there will be positive deviation from
Raoult’s’ Law, leading to decreased solubility.

Question 16

temperature

Answer 16

The mutual solubility’s of partially miscible liquids are greatly affected by temperature. So by this we
can obtain following three types of graphs (solubility curves).
 TYPE 1: In binary liquid system such as phenol-water: the solubility’s of two phases increases with
increase in temperature until a temperature is obtained at which a homogenous mixture is formed. And
this temperature is called upper critical temperature or upper consulate temperature (UCT). The
temperature at which two phases merge into a single phase is called critical solution temperature.
 TYPE 2: The binary liquid systems such as trimethylamine-water & paraldehyde water is completely
miscible by decreasing the temperature. So they have lower consulate temperature (LCT). Above this
temperature they are partially miscible with each other.
 TYPE 3: Few binary mixtures such as nicotine-water shows both UCT & LCT, with an intermediate
temperature peg ion. Such mixtures are soluble in all proportion above UCT & below LCT, while b/w
UCT & LCT they are partially miscible with each other.

Question 17

influence of foreign substances

Answer 17

The addition of a foreign substance in a binary liquid system effect the critical solution temperature or
consulate temperature & in turn solubility. There will be two cases:
 Case 1: When the additional substance is soluble in one component, then the mutual solubility of
binary mixture is decreased. If binary mixture has UCT then it will be raised further & if mixture LCT
then the temperature will be further decreased.
 Case 2: If the third foreign substance is soluble in both the component, then it will increase the mutual
solubility’s by decreasing UCT & raising the LCT.

Question 18

solubility of solids in liquids

Answer 18

From the experimental evidences it is concluded that solubility of solids in liquids are influenced by
following factors:
1. Temperature
2. Surface area of solute
3. Molecular structure
4. Effect of particle size
5. Hydrophobicity of solute
6. Nature of solute and solvent

Question 19

effect of temp solid in liquid

Answer 19

Generally, in many cases solubility increases with the rise in temperature and decreases with the fall
of temperature but it is not necessary in all cases. However, we must follow tow behaviors:
 In endothermic process solubility increases with the increase in temperature and vice versa. E.g.
solubility of potassium nitrate increases with the increase in temperature.
 In exothermic process solubility decreases with the increase in temperature. E.g. solubility of calcium
oxide decreases with the increase in temperature.
 Gases are more soluble in cold solvent than in hot solvent.

Question 20

surface area of solute

Answer 20

 The size and shape of small particles (those in the micrometer range) also affect solubility.
 Solubility increases with the decreasing particle size and hence increasing the surface area of solute.

Question 21

molecular structure

Answer 21

The structure of solid has a great effect on solubility. For example:
a. Ephedrine is insoluble in water in its pure from but its salt ephedrine – HCL is soluble in water.
b. Same is the case of Phenobarbital converted into Phenobarbital Na.
c. Erythromycin is decomposed in gut, when it is in its pure from avoid this, it is converted into
erythromycin propionate.

Question 22

hydrophobicity of solute

Answer 22

 Hydrophobicity (from the Greek hydro, meaning water, and phobos, meaning fear) is the physical
property of a molecules (known as a hydrophobe) that is repelled from a mass of water.
 Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and non-polar
solvents. Hydrophobic molecules in water often cluster together, forming micelles.

Question 23

effect of particle size

Answer 23

graph

Question 24

nature of solute and solvent

Answer 24

 Solubility of a solute in a solvent purely depends on the nature of both solute and solvent.
 A polar solute dissolved in polar solvent.
 And a non-polar solute is freely soluble in a non-polar solvent.
 A polar solute has low solubility or insoluble in a non-polar solvent.

Question 25

techniques of solubility enhancemetn

Answer 25

a) Physical Modifications
a. Particle size reduction
i. Micronization
ii. Nanosuspension
b. Modification of the crystal habit
i. Polymorphs
ii. Pseudopolymorphs
c. Drug dispersion in carriers
i. Eutectic mixtures
ii. Solid dispersions
iii. Solid solutions
b) Chemical Modification
a. Change of the pH
b. Use of buffer
c) Other Methods
a. Cosolvency
b. Complexation

Question 26

distribution law

Answer 26

The distribution Law / Nernst Distribution Law / partition Law can be defined as: “If a solute X
distributes itself b/w immiscible solvents A and B at constant temperature and X is in the same molecular
condition in both solvents.”

K0 =
Concentration of X in A
Concentration of X in B

If C1 denotes the concentration of X in solvent A & C2 in solvent B, then the distribution law can be
expressed as:

K0 =
C1
C2

Where K0 is called Distribution coefficient / partition, coefficient / Distribution Ratio.

Question 27

application of distribution law

Answer 27

extraction
parition chromotography
adsorption of drug
preservation
preservation of emulsion and creams
release of drug

Question 28

extraction

Answer 28

This is the process used for the separations of active ingredients from the crude
substances, by using selective solvents & standard extractive procedure. So by the process of separation the
inert solvents are distilled off while leaving behind the active ingredients. This process is more efficient if the
solvent is used in a number of small portions than one whole lot.

Question 29

partition chromotography

Answer 29

This method is used to separate a mixture of small amount(s)
of active ingredients. This technique depends upon the difference in distribution coefficient b/w two
components.
1. The component with highest coefficient will first move down in the separating column while a
component with a lower distribution ratio comes down later.

Question 30

adsorption of drug

Answer 30

The passage and extent of drug absorption through cell membrane depends
upon the distribution coefficient. When the drug comes in contact with cell membrane, it is absorbed due to
its distribution coefficient and enters into the cell.

Question 31

preservation

Answer 31

The preservatives enter into the microorganisms due to distribution coefficient &
act on the DNA of the microorganism & so stop the growth of that microorganism. This process is called
preservation.

Question 32

preservation of emulsion and creams

Answer 32

In Emulsion & Creams, one component is
dispersed throughout the other. The preservation of such products (i.e. Emulsion & Cream) also follows the
distribution law.

Question 33

release of drug

Answer 33

DRUG: When drugs are made available at the site of action, the active ingredient is
selectively absorbed from the dosage from due to its distribution coefficient.

Question 34

solubiization

Answer 34

The process whereby water insoluble substances are brought into solution by incorporation into
micelles is termed as solubilization.

Question 35

factor affecting solubilization

Answer 35

-nature of surfactant
-nature of solubilizate
-effect of temperature

Question 36

nature of surfactant

Answer 36

o In homologous series of Ionic surfactant solubilizing power increases with increase of
hydrocarbon chain length.
o In non-ionic surfactants an increase in oxyethylene chain length decreases the solubilizing
power.

Question 37

nature of solubilizate

Answer 37

o No relation between the amount of solubilized and the physical properties of solubilized
molecule exists.
o An increase in alkylation Length of homologous series of solubilizate results into decrease in
solubility.
o Unsaturated compounds are relatively more soluble than their saturated counter parts
o Branching of solubilizate has no effect but cyclization generally increases the solubilization

Question 38

effect of temperature

Answer 38

o In most system the amount of solubilized increases with increase in temperature this is
particularly true in non-ionic surfactant as an increase in temperature gives / causes an increase
in micellar size.

Question 39

pharmaceutical application of solubilization

Answer 39

 Phenobic Compounds (Cersol, Chlorocersol, Chlorokylenol, Thymol etc.) are solubilizing in water
exploiting the principle of solubilization. e.g. Dettol
 Solubilization of Iodine in Non-Ionic Surfactant - Such preparation is known as iodophores.
Iodophores are less corrosive when used for surgical sterilization than Iodide-Iodine System.
 Steroids for ophthalmic Preparation - Optical Clarity Requirement limits the use of oily solution so
non-ionic surfactants (polysorbate or polyethylene sorbitian, esters of fatty acids are used to prepare
solution of steroids in water.
 Essential / Volatile Oils are solubilized using the principle of solubilization.
 Water insoluble vitamins (A, D, E and K) - Fat soluble vitamins are made water soluble e.g.
multivitamin syrups / drops
 Problem of ‘Cloud Point’ is always there because it is decrease with added substances. Sucrose esters
are used though increase hemolytic properties.
 Many other drugs like:
o Analgesics
o Sedatives
o Sulfonamide
o Antibiotics etc.
These drugs are also solubilized using the solubilizing technique.

Question 40

surfactants

Answer 40

 Surfactants are wetting agents that lower the surface tension of a liquid, allowing easier spreading, and
lower the interfacial tension between two liquids.
 A surfactant or surface active agent is a substance that, when dissolved in water, gives a product, the
ability to remove dirt from surfaces such as the human skin, textiles, and other solids.
 Each surfactant molecule has a hydrophilic (water-loving) head that is attracted to water molecules
and a hydrophobic (water-hating) tail that repels water and simultaneously attaches itself to oil and
grease in dirt.
 Surfactants are also referred to as wetting agents and foamers. Surfactants lower the surface tension of
the medium in which it is dissolved. By lowering this interfacial tension between two media or
interfaces (e.g. air/water, water/stain, stain/fabric)

Question 41

natural and synthetic origin surfactants

Answer 41

They can be either. Surfactants from natural origin (vegetable or animal) are known as oleo-chemicals

and are derived from sources such as palm oil or tallow. Surfactants from synthetic origin are known as petro-
chemicals and are derived from petroleum.

Question 42

classification of surfactants

Answer 42

1. Ionic surfactant
   a. Anionic
   b. Cationic
   c. Zwitterionic (amphoteric)
2. Non-ionic surfactants

Question 43

anionic

Answer 43

 In aqueous solution these ionizes into a large anion, responsible for emulsifying ability, and a small
cation.
 In solution, the head is negatively charged. This is the most widely used type of surfactant for
laundering, dishwashing liquids and shampoos because of its excellent cleaning properties and high
(based on sulfate, sulfonate or carboxylate anions)
 An example: Sodium dodecyl sulfate (SDS)

 The most commonly used anionic surfactants are alkyl sulphates, alkyl ethoxylate sulphates and soaps.

Question 44

anionic surfactants ave 5 subgroups

Answer 44

 ALKALI METALS AND AMMONIUM SOAPS: These are Na, K or NH4 slats of long chain fatty
acids, such as olive, stearic and recinoleic. They usually produce O/W which are stable at pH above
10. They are sensitive to even weak acids. These are incompatible with polyvalent such as Al+3, Ca+2
,
Mg+2, Zn+2 which causes phase inversion. They are not suitable for internal consumption or for broken
skin due to high pH.
 SOAPS OF DIVALENT AND TRIVALENT METALS: Ca+2, Mg+2, Zn+2 salts of fatty acids of
these elements produce W/O emulsions. They are also not used internally but are less sensitive to acids.
 AMINE SOAPS: A number of amines form salts with fatty acids. Most important is triethanolamine
(N(CH2.CH2OH)3).

 ALKYL SULPHATES: These are esters of fatty alcohols and H2SO4. The most important are Na-
Lauryl sulphate and Nacetostearyl sulphate. They alone produce O/W emulsions of low stability. But

produce stable emulsion in conjunction with fatty alcohols.
 ALKYL PHOSPHATES: These are similar to alkyl sulphates but the alcohols are phosphated instead
of sulphated. They are also used in combination with fatty alcohols.

Question 45

cationic

Answer 45

 The quaternary ammonium compounds comprise the most important group of cationic surfactants.
 They have disinfectant and preservative qualities as well as emulsifying properties.
 In solution, the head is positively charged. (based on quaternary ammonium cations)
 An example: Benzethonium chloride (BZT)

Question 46

zwitterionic (amphoteric)

Answer 46

These surfactants are very mild, making them particularly suited for use in personal care and household
cleaning products. They can be:
1. Anionic (negatively charged),
2. Cationic (positively charged) or
3. Non-ionic (no charge) in solution,
depending on the acidity or pH of the water.
An example of an amphoteric / zwitterionic surfactant is alkyl betaine.

Question 47

non-ionic surfactants

Answer 47

 These surfactants do not have an electrical charge, which makes them resistant to water hardness
deactivation.
 They are excellent grease removers that are used in laundry products, household cleaners and hand
dishwashing liquids.
 All soluble surface active agents have:
o A hydrophobic group i.e. a long chain of hydrocarbon
o A hydorphilic group i.e. carboxy, hydroxy, amino group.

Question 48

types of non-ionic surfactancs

Answer 48

1. Glyco and Glycerol Esters
2. Sorbitan Esters
3. Macrogol Esters (Polyethylene or Polyoxyethylene glycol esters)
4. Macrogol Ethers
5. Poly-sorbates
6. Poloxalkols
7. Polyvinyl alcohols
8. Higher fatty alcohols
   The most commonly used non-ionic surfactants are ethers of fatty alcohols e.g. Cocamide MEA

Question 49

properties of surfactants

Answer 49

1. On microorganisms: Surfactants such as quaternary ammonium compounds have useful anti-
   bacterial properties and so used as disinfectants for the instruments and skin, anti-bacterial creams and

throat lozenges. They undergo adsorption at the cell surface followed by changes in cellular
permeability leading to the death due to loss of essential substances from the cell.
2. On removal of bronchial mucus from the respiratory treat. In various infections such as asthma,
bronchitis and tuberculosis bronchial mucus becomes viscous. So surfactants are used in the treatment
of such conditions b/c they promote wetting, so mucus becomes soft and its removal is facilitated.
Surfactants are given in the form of aerosols.
3. On human skin: The repeated contact b/w the skin and certain detergents may cause mild irritation
and dry skin leading to blisters and pustules. This lead to onset of infection.

Question 50

mechanism of surfactan

Answer 50

1. ROLL-UP MECHANISM: The surfactant lowers the oil/solution and fabric/solution interfacial
   tensions and in this way lifts the stain of the fabric.
2. EMULSIFICATION: The surfactant lowers the oil-solution interfacial tension and makes easy
   emulsification of the oily soils possible.
3. SOLUBILIZATION: Through interaction with the micelles of a surfactant in a solvent (water), a
   substance spontaneously dissolves to form a stable and clear solution.

Question 51

applications of surfactant

Answer 51

 DETERGENT: Detergent is a compound, or a mixture of compounds, intended to assist cleaning.
The term is often used to differentiate between soap and other chemical surfactants used for cleaning
purposes.
 FABRIC SOFTENER: Fabric softenr (also called Fabric Conditioner) is used to prevent static cling
and makes the fabric softer.
 EMULSIFIER: Emulsifier (also known as an emulgent or surfactant) is a substance which stabilizes
an emulsion.
 ADHESIVE: Adhesive is a compound that adheres or bonds two items together.
 INK: Ink is a liquid containing various pigments and / or dyes used for colouring a surface to render
an image or text. Ink is used for drawing or writing with a pen or brush.
 AS FLOCCULATING AGENTS: A controlled amount of the flocculation is often desirable in the
formulation of suspension in order to obtain the required rheological properties and optimum stability.
 LAXATIVE: Laxative is a preparation used for encouraging defecation, or the expulsion of feces.
Laxatives are most often taken to treat constipation.
 AS WETTING AGENTS: Hydrophobic powdered are difficult to wet and either float on the water
surface or form large floccules. So viscosity of the preparation is increased up to such an extent that it
is difficult to pour or with drawl of the correct dose from an inject able suspension is not possible so
surfactants are added which reduce the inter particle attractive forces and increase adsorption at the
solid / liquid interface.
 AS SOLUBILIZING AGENTS: Chloroxylenol, a phenolic compound is used as anti-septic agent.
Due to presence of surfactants Chloroxylenol is made solubilized. Similarly surfactants have been used
to increase water solubility of phenobarbitone, volatile oils, chloroform, iodine hormones, dyes and
sulphonamides.
 They are used as additives to ointment and suppository bases.
 OTHER APPLICATION OF SURFACTANTS:
o Wetting
o Ski Wax
o Snowboard Wax
o Foaming
o Defoaming
o Quantum dot coating
o Biocides (Sanitizers)
o Hair Conditioners (after shampoo)
o Spermicide (Nonoxynol 9)

Question 52

miccile

Answer 52

 A micelle (rarely micella, plural micellae) is an aggregate of surfactant molecules dispersed in a liquid
colloid.
 A typical micelle in aqueous solution forms a roughly spherical or globular aggregate with the
hydrophilic “head” regions in contact with surrounding solvent, sequestering the hydrophobic tail
regions in the micelle center.

 At concentration of surfactants in bulk, phase become saturated. The surfactants molecules will begin
to aggregate known as micelles.
 As the concentration of monomer is increased, aggregation occurs over a narrow concentration range.
 These aggregates which may contain 50 or more monomers are called micelles. A micelles lie within
the size range of colloidal system.

Question 53

IUPAC definition

Answer 53

 Micelle: Particles of colloidal dimensions that exists in equilibrium with the molecules or ions in
solution from which is formed.
 Micelle (polymers): Organized auto-assembly formed in a liquid and composed of amphiphilic
macromolecules, in general amphiphilic di- or tri- block copolymers made of solvophilic and
solvophobic blocks.
Note: During formation of micelles, free energy of system is reduced.

Question 54

CMC

Answer 54

 The concentration of monomer at which micelles form is termed as the critical micelle concentration.

Question 55

micellization

Answer 55

 The process of micelle formation is known as micellization
 Compounds forming micelles are called surfactant, surface active agent or amphiphiles
 There are drugs which also from micelles and are known as micellar drugs e.g. cholorquine,
diphenhydramine, orphenadrine, chlorphenoramine etc.
Note: Since the diameter of each micelle is of order of 50 Å, micelle lie within the size range to be a colloid.

Question 56

types of micelles

Answer 56

According to MC Bains there are two types:
1. A small, spherical changed micelle which exist in all concentrations i.e. above and below CMC and is
responsible for electrical conductivity.
2. A large, lamellar, un-dissociated micelle and is responsible for low osmotic properties.

Question 57

micelle shape as per types of surfactant

Answer 57

Simple surfactants with single chains and relatively
large head groups

Spherical or ellipsoidal micelles

Simple surfactants with relatively small head groups,
or ionic surfactants in the presence of large amounts
of electrolyte

Relatively large cylindrical or rod-shaped micelles

Double-chain surfactants with large head groups and
flexible chains

Vesicles and flexible bilayer structures

Double-chain surfactants with small head groups or
rigid, immobile chains

Planar extended bilayer structures

Double-chain surfactants with small head groups,
very large, bulky hydrophobic groups

Reversed or inverted micelles

Question 58

determination of CMC

Answer 58

Below the CMC the concentration of amphiphiles undergoing adsorption at the air-water interface
increases as the total concentration of amphiphiles is raised. Eventually a point is reached at which both the
interface and the bulk phase become saturate with monomers. This is called CMC. Any further amphiphiles
added in excess of this concentration aggregates to form micelles in the bulk phase and in this manner the free
energy of the system is reduced.
It affects some physical properties of the system. Some properties show increasing trend while some
other shows decreasing trend.
E.g. the surface tension decreases up to the CMC and above the CMC, the surface tension remains
constant, this shows that the interface is saturated and micelle formation has taken place in the bulk phase.

Question 59

factors affecting CMC and micelle size

Answer 59

-nature of hydrophobic group
-nature of hydrophilic group
-effct of ion concentration
-effect of hydrophobic group
-addition of electrolytes
-effect of temperature

Question 60

nature of the hydrophobic group

Answer 60

 Hydrophobic group plays important role in determining type of association of group. Micellar
amphiphiles have hydrocarbon groups’ constracted from hydrocarbon chains. Increase in length of this
chain will decrease CMC and increase aggregation number.
 Many drugs are surface active agents and form micelles. For example, diphenyl methane drugs.
(diphenhydramine, orpheradrine, chlorphennoxamine etc.)
 Hydrophilicity/ Hydrophobicity and substitute on such drugs play very important role in the
determination of CMC and Aggregation number
 Some representative examples: Antiparkinoism Drugs are used to reduce muscular rigidity
neurological disorder marked by hypokinesia (abnormally diminished motor activity tremor and
muscular rigidity).
 Other Examples:
o PHENOTHIAZINE TRANQULIZER
 Priomazine
 Chlorpromazine
 Promethazine
o ANTIDEPRESSANTS
 Imipramine
 Amitriptyline
 Nor-triptyline
They have tricyclic hydrophilic moieties.

 Many aromatic and hetero aromatic ring structure (dyes, purines, pyrimidine) associate in nonmicellar
process.

Question 61

nature of hydrophillic group

Answer 61

 Ionic hydrophilic groups of amphiphiles show different properties then Non- ionic hydrophilic groups
may be due to difference in charge.
 In general, non-ionic surfactants have “low CMC” and high aggregation numbers although they have
same length of hydrocarbon chain. This is because in non-ionic surfactant no electrical work during
the process of micellization.

Question 62

effect of counter-ion

Answer 62

 In case of cationic surfactant as the counter ion is charged in series, Cl-
, Br-
, I-
, micelle size is an

increase in order for Cl- < Br- < I-
.

 In case of anionic surfactant as the counter ion is charged in series, Na+
, K+
, Cs+
, micelle size is an

increase in order for Na+ < K+ < Cs+
.

 More weakly hydrated a counter ion larger the micelle formed.

Question 63

effect of hydrophoic griup

Answer 63

 If hydrophobic group is aromatic, micelle does not form.
 Length of hydrocarbon chain is directly proportional to micelle size & inversely proportional to CMC.
We express this in mathematical term,

Log [CMC] = A – Bm

Where,
 A & B are homologous series constant.
 m is the no. of carbon atom in chain.

Question 64

addition of electrolytes

Answer 64

Electrolytes reduce the charges (force) on ionic surfactants so there is reduction in the magnitude of
the force of repulsion between the charges had groups on the micelles. Hence, there is reduction in CMC and
increase in aggregation number.

Question 65

effect of temperature

Answer 65

 This effect in particularly seen in non-ionic surfactants.
 Solution of non-ionic surfactants when heated they turn turbid at a characteristic temperature known
as “cloud temperature”.
 Turbidity at “cloud point” is due to separation of the solution into “two” phases. i.e. dispersed phase
of dispersion medium.
 At temperature up to cloud point there is increase in Aggregation No. and decrease in CMC.
Temperature has no profound effect on CMC and aggregation No. of Ionic Surfactant.

Question 66

application

Answer 66

 Micelle increases bioavailability of poorly soluble drugs.
 Polymeric micelle is used to target the tumor site by passive as well as active mechanism.
 Micelle is used in ophthalmic drug delivery system that effectively delivers the drug to posterior tissue
of eyeball.
 Micelle is used to encapsulate the antibiotic & anticancer drugs.