Tutorial 1: States Of Matter

Question 0

What properties to liquid crystals have?

Answer 0

Flow properties similar to liquid

Optical properties similar to solid

Question 1

What are liquid crystals?

Answer 1

An intermediate state of matter with an ordered arrangement of atoms or molecules

Question 2

How are liquid crystals described?

Answer 2

With having birefringence

Question 3

What is birefrengence?

Answer 3

The ability to split light into 2 rays travelling at different speeds, directions and refractive indexes

Question 4

What are three different structures and arrangements of crystals?

Answer 4

Lyotropic LC: long ranged orientational order achieved by the additions of a solvent
Thermotropic LC: occur within a certain temperature range
Metallotropic LC: contains metals

Question 5

What is polarised light?

Answer 5

Light that travels in one single direction

Question 6

What are the two filtering units of the polarised light microscope?

Answer 6

Polariser which is added to the optical pathway beneath the specimen. This filters the light

Analyser which is placed over the front of the lens objective in the body of the microscope

Question 7

What happens to the polarised light if the sample displays biefrengence?

Answer 7

Some of the light will go through the molecule, one of the rays will be blocked by the analyser

Question 8

What substance are isotropic?

Answer 8

Substances which do not display birefrengence e.g. Water, amorphous solid

Question 9

What substances are anisotropic?

Answer 9

Substances which do display birefrengence e.g. Liquid crystals, crystalline solid

Question 10

What is seen in an isotropic sample under a polarised microscope?

Answer 10

Light goes through sample without a change in direction will be blocked by the analyser, so you see a black background

Question 11

What is seen in an anisotropic sample under a polarised microscope?

Answer 11

You see shininess with a dark background.
Dark background is due to the light being blocked by the analyser
The shininess is due to some light being able to pass through due to the sample displaying birefrengence

Question 12

Why would some systems retain their optical properties when mixed with other components while other systems dont?

Answer 12

If the system is dissolved in the other component the optical properties will be lost as the system will no longer be liquid crystalline, however if a system is not dissolved and is suspended in the other component, its optical properties will be retained as it has not lost its crystalline structure

Question 13

What are the benefits and disadvantages of choosing a crystalline solid as a dosage form for a drug?

Answer 13

+ drug is very stable
+ there is a sharp melting point

• harder to dissolve
• so harder to absorb
• cknsequently, lower bioavailability

Question 14

What are the advantages and disadvantages of using an amorphous solid as a drug formulation?

Answer 14

+ easier to dissolve
+ easily absorbed
+ higher bioavailability
- less stable, has a variable melting point

Question 15

What are the four different types of solid forms?

Answer 15

Polymorphs, amorphous, solvate, salt

Question 16

What are the different kinds of particles that can constitute the different solid forms?

Answer 16

Active molecule
Solvent molecule
Acid
Deprotonated molecule
Protonated active molecule

Question 17

What is crystalline arrangement?

Answer 17

Ordered arrangement of atoms or molecules
Often organised in Long range order and symmetrical
The compounds can have more than one crystalline arrangement, such compounds are called polymorphs

Question 18

What is amorphous structure?

Answer 18

Structure of solids which have a random arrangement of atoms or molecules

This lacks long range order characteristic of crystals

Question 19

What is the difference between liquids and liquid crystals?

Answer 19

Liquids have a random arrangement of atoms or molecules
Liquid crystals are an intermediate state of matter and have an ordered arrangement of atoms or molecules

They display flow properties similar to liquids

Question 20

What is anisotropic property?

Answer 20

Where a substance displays differences in the optical properties of a material when measured along different axes

The substance has optical properties that vary with the orientation of incident light

They affect light differently in different directions

Question 21

What are isotropic properties?

Answer 21

Where molecules of a substance are in random motion and orientation

The optical properties of the material is identical in all directions so no birefrengence is observed

Question 22

What are some examples of anisotropic materials?

Answer 22

Cetrinide antiseptic

Cetostearyl alcohol

Question 23

What are examples of isotropic substances?

Answer 23

Liquid paraffin in oil ohase
Water in aqueous phase,
Cod liver oil in oil phase

Question 24

What must be considered when developing a formulation?

Answer 24

When drug substance is first produced it has to be certain that the desired solid form is obtained in a consistent, pure and reproducible manner

During formulation, must ensure that no undesireable transformation takes place

Solvents that generate solvates should be avoided

(If solvate is generated and then desolvated during the final formulation step then the final polymorph could differ from the original one)

The solid form should not be transformed during storage

Changes in the solubility after taking the drug may make the drug ineffective or toxic

Question 25

In the choice of a crystalline or amorphous formulation for a drug which one is better?

Answer 25

Crystalline because it is the most thermodynamically stable polymorph.
Although it has low solubility and bioavailablility, this is a small price to pay for the large advantage of chemical stability

Solubility can be improved using techniques like cosolvent addition, complexation, salt forms, etc.

Question 26

What are some examples of polymorphic drugs?

Answer 26

Ranitidine HCl
aspirin
Paracetemol
Carbamazepine

Question 27

What are the differences between different forms of ranitidine-HCl?

Answer 27

The drug is an H2 receptor atagonist
FormI MP: 134-140°C
FormII MP: 140-144°C

In environments of high humidity there is a preferential lose of form II so form I more stable in high humdity

Question 28

What are the differences between polymorphs of aspirin?

Answer 28

Form II reverts back to form I at ambient temperatures

This indicates that I is more stable than II

Question 29

What are the differences in polymorphs of paracetemol?

Answer 29

Form I has a MP of 169°C
Form II has a MP of 157°C
Form III is highly unstable
It also has poor compression properties

Question 30

What are the differences between the polymorphs of carbamazepine?

Answer 30

Beta polymorph was developed from solvent of high dielectric constant (i.e. High polarity)

Alpha polymorph was developed from a solvent of low dielectric constant

Question 31

In the gibbs triangle, where do we find 100% of a substance?

Answer 31

At the tip/edge

Question 32

What are the ideal properties of a cosolvent?

Answer 32

It increases the solubility of the solute in the solvent
It increases the miscibility of the other two components
It must be miscible in both components

Question 33

What happens when the cosolvent is soluble in both liquids?

Answer 33

The mutual solubility of the liquid pair is increased