Physicochemical properties

Question 1

Solution

Answer 1

Mixture of 2 or more components that form a homogenous molecular dispersion

Question 2

Single phase system

Answer 2

Not another phase dispersed in another

Question 3

Solvent

Answer 3

Component present in greater amounts

Question 4

Solute

Answer 4

Component present in smaller amounts

Question 5

Saturated solution

Answer 5

Where the solute is at the limit of its solubility at a given temp. + pressure

Question 6

Solution = _______ phase

Answer 6

Single

solid solute dissolved into solvent to make it a single phase

Question 7

Suspension/emulsion = _________ phase

Answer 7

Two

Question 8

2 types of solution

Answer 8

liquid in liquid

solid in liquid

Question 9

2 categories in liquid in liquid

Answer 9

Partially miscible

Completely miscible

Question 10

Example of completely miscible

Answer 10

Ethanol + water

Question 11

Example of partially miscible

Answer 11

Ether + water

Question 12

What affects partially miscible

Answer 12

Temperature

Question 13

2 solutions in solid in liquid

Answer 13

Solution of non-electrolytes (non-ionic)

Solution of electrolytes (form ions in solution)

Question 14

Examples of solution of non-electrolytes

Answer 14

Organic molecules (sucrose, phenol)

Question 15

Example of solution of electrolytes

Answer 15

strong electrolytes = NaCl

weak electrolytes = depends on ph

Question 16

When is the structure of water disrupted

Answer 16

Ions in solution (when solid dissolves)

Question 17

Partitioning

Answer 17

Distribution of a substance between two immiscible phases

Question 18

Partition coefficient

Answer 18

Co / Cw
Co = conc. in organic phase
Cw = conc. in aqueous phase
Measure of relative affinity of the solute for an aqueous + lipid phase @ equilibrium

Question 19

What does partition coefficient apply to

Answer 19

Dilute solutions e.g. ideal solutions

Question 20

2 commonly used liquids to calculate P

Answer 20

Octanol + water

Question 21

Why is octanol used?

Answer 21

Produces p values which correlate better with in vivo biological data

Question 22

How is P calculated

Answer 22

Drug is added to separating funnel which contains the 2 immiscible liquids
Flask is shaken for up to 1 hour then left for phases to separate out
Concentration of aqueous phase is determined by either spectroscopy or titration
Concentration of organic phase is determined by subtraction
P can then be calculated

Question 23

A suspension can become a…

Answer 23

Solution (+vice versa)

Question 24

What can affect solubility

Answer 24

Solute substituents

Question 25

How does solubility changes happen

Answer 25

Solute - solute

Question 26

Highest relative permittivity of solvent

Answer 26

Water

Question 27

What influences solubility of weak acid + weak base

Answer 27

pH

Question 28

Calculate activity coefficient (y)

Answer 28

activity / concentration

Question 29

when y (activity coefficient) = 1....

Answer 29

activity = concentration

Question 30

When should activity be used

Answer 30

when dealing with strong electrolytes / weak electrolytes in solution with other salts

Question 31

When can non-electrolytes + weak electrolytes have their activity = concentration

Answer 31

When present as the only species

Question 32

Activity

Answer 32

reduction in the effective concentration

Question 33

Real solution

Answer 33

Interactions between dissolved solutes which reduce the effective concentration

Question 34

What solutions have their activity = concentration?

Answer 34

Ideal + dilute real solutions

Question 35

Example of polar solvents

Answer 35

Water, methanol, acetic acid

Question 36

What is the relative permittivity of polar solvents

Answer 36

High relative permittivity

Question 37

What do polar solvents dissolve + how

Answer 37

Ionic solutes by reducing force of attraction between oppositely charged ions in crystalline solids

Question 38

What bonds can polar solvents break

Answer 38

Covalent bonds

Question 39

What solvent can solvate molecules + ions + how?

Answer 39

Polar solvents through dipole-dipole forces

Question 40

What is wrong with ranitidine free base

Answer 40

Low aqueous solubility Unstable to light Sulfurous odour

Question 41

How can we make ranitidine free base be absorbed

Answer 41

Reacting with HCl = Ranitidine HCl (salt) | Becomes odourless, stable + greater solubility

Question 42

Examples of semi-polar solvents

Answer 42

Acetone, methanol, ethanol + other alcohols?

Question 43

What can semi-polar solvents dissolve

Answer 43

Polar + non-polar substances

Question 44

How do polar solutes dissolve

Answer 44

Dipole moment or H-bonding groups

Question 45

How can semi-polar solvents be soluble in non-polar solvents

Answer 45

Inducing a degree of polarity

Question 46

Examples of non-polar solvents

Answer 46

Hexane, Pentane, oils + fats, benzene

Question 47

What is the relative permittivity of non-polar solvents

Answer 47

Low

Question 48

What prevents non-polar solvents dissolving ionic/polar solutes

Answer 48

Lack of H-bonding

Question 49

Non-polar solvents are unable to...

Answer 49

break covalent bonds

Question 50

What can non-polar solutes dissolve

Answer 50

Non-polar compounds only

Question 51

How are non-polar solutes held in non-polar solvents

Answer 51

Through van der waals interactions

Question 52

Solubility equation of weakly acidic drugs

Answer 52

``` pKa = pH + log HA / A- pH = pKa + log S - So / So ```

Question 53

Solubility equation of weakly basic drugs

Answer 53

pH = pKa + log So / S - So

Question 54

S in solubility equation

Answer 54

Solubility of weakly acidic/basic drug at given pH

Question 55

So in solubility equation

Answer 55

Solubility of undissociated drug

Question 56

Example of amphoteric drugs

Answer 56

Oxytetracycline | Nitrazepam

Question 57

Amphoteric drugs

Answer 57

Both acidic + basic groups so will have 2+ pKa values

Question 58

What pH values can amphoteric drugs be ionised

Answer 58

All pH values

Question 59

Isoelectric point

Answer 59

pH at which drug carries no net electric charge (equal dissociation of acidic / basic drug group

Question 60

Calculate isoelectric point

Answer 60

(pKa1 + pKa2) / 2

Question 61

When are amphoteric drugs are at its least solubility

Answer 61

At the isoelectric point (no net charge)

Question 62

When do you use the basic drugs equation with amphoteric drugs

Answer 62

pH is below isoelectric point

Question 63

When do you use the acidic drugs equation with amphoteric drugs

Answer 63

pH is above isoelectric point

Question 64

Drugs with high log P can...

Answer 64

partition into rubber / plastic containers | - affecting many formulations

Question 65

Which drugs are affected with high log P partitioning

Answer 65

Storage of lipophilic drugs

Question 66

Ion-pairing

Answer 66

Ionised drugs combining with an oppositely charged ion | Ion pair behave as a neutral species and permeate through gastric mucosa

Question 67

Substances that use active transport

Answer 67

Ions Glucose Vitamins Amino acids

Question 68

Melphalan

Answer 68

Similar to phenylalanine | Absorbed in GI tract

Question 69

__________ drugs can also be absorbed in small intestines

Answer 69

Ionised

Question 70

Structure of Water

Answer 70

104.5 degree bond angle Tetrahedral Form H-bonds

Question 71

Flickering cluster model of water

Answer 71

Clusters of H-bonded ice-like water within pools of unbound (no hydrogen bonding) water - clusters surrounded by fluid non-hydrogen bonded water - ice-like clusters of H-bonded water

Question 72

hydration

Answer 72

Ions have a layer of tightly bound water | Most small monoatomic ions have 4 water molecules bound in first shell, therefore hydration number is 4

Question 73

What is Magnesium carbonate hydration number

Answer 73

5

Question 74

Weak bases are likely to be ionised in the stomach so...

Answer 74

Cannot pass lipophilic gastric mucosa

Question 75

How come ionised drugs can be absorbed in the small intestines

Answer 75

Large surface area Good blood flow Long residence time