W202122

Question 1

Unit cell definition

Answer 1

defined 3D shape that contains the smallest repeating pattern of molecule
- this repeats in 3D to build up to create crystalline structure

Question 2

7 basic unit cell geometries - first three

Answer 2

1. Triclinic
2. monoclinic
3. ortho/rhom/bic

Question 3

Crystal habit definition and its 6 different habits

Answer 3

macroscopic shape of a crystal viewed under a microscope = made of repeated unit cells
- tabular
- columnar
- equant (cube)
- plate
- blade
- acicular

AB(P)CTE

Question 4

relationship between unit cell and crystal habit

Answer 4

Crystal habit = made of repeated unit cells

• but unit cell shape ≠ crystal habit shape (not always)
• you can’t know anything about unit cell in a crystal habit since they are too small

Question 5

importance of crystal habit

Answer 5

affects the processability of the drug

Question 6

How to control crystal habit

Answer 6

1. solvent selection
   - can affect properties/state of FG
   - make that face more preferential for crystal growth to make a specific habit
2. addition of habit modifiers
   - polymer bind to specific faces on crystals to block/prevent crystal growth on that face

Question 7

Crystal formation process

Answer 7

1. supersaturated solution of dissolved molecules
   - molecules separated via two methods
   1) vaporise so that molecules are free floating in air
   2) dissolve in solvent
2. formation of crystal nuclei
3. crystal growth on nuclei

Question 8

Polymorphism definition

Answer 8

ability of a solid material to exist in more than one crystal structure

Question 9

importance of polymorphisms

Answer 9

different unit cells –> different packing –> different macroscopic crystal behaviour –> different physical/chemical properties –> different therapeutic effect

Question 10

in thermodynamics point of view, ___ with____ ___ is most stable
- importance of thermodynamics of polymorphs

Answer 10

polymorphs with lowest energy is most stable
- metastable polymorph: requires less energy to break apart THUS dissolves and absorbs into bloodstream faster = higher bioavailability

• most stable polymorphs = requires more energy THUS dissolves and absorbs into bloodstream worst = lower bioavailability

Question 11

who has lower solubility - hydrates vs anhydrates

Answer 11

hydrates = due to strong HB ald

Question 12

amorphous material definition and example

Answer 12

structure of a liquid but viscosity of a solid
- lack regular repeating pattern
- random arrangment of particles
- bonded together by almost nothing
- but still remain in a solid state

1. glass/lens
2. jelly
3. chocolate

Question 13

phase diagram of glassy state

Answer 13

case 1: temp reduced slowly
- KE dec- crystalise (not metastable form) - when it forms crystals it have lowest volume so will have biggest drop in volume
- as temp dec further, volume further decreases

case 2: temp reduced rapidly
- no enough time to align crystal form
- remains as liquid below its MP = supercooled liquid
- further cooling of liquid causes it to become glass at Tg (glass transition temp

Case 3: theoretical
- material continues to cool
- volume reduces until vollume of liquid like structure becomes less than volume of crystaline structure
- this can’t happen

Question 14

Liquid - ( ) - glass

Answer 14

supercooled liquid

Question 15

below / above Tg = glass transition temp
whats Tm

Answer 15

below Tg = brittle, can’t flow
above Tg -= rubbery, can flow

Tm: MP . condensing point

Question 16

methods of making amorphous material more stable

Answer 16

• freeze drying
• adding polymers to prevent mc from moving around

Question 17

explain the second step of crystallisation process

Answer 17

2. formation of crystal nuclei = very slow process

a. crystal nuclei = small cluster of mc joined together

b. primary nucleation = 2 randomly moving mc align to form interactions AND THEN more molecules join to form nucleus

c. secondary nucleation = scratching glass w/glass rod
–> speeds up crystal nuclei formation
–> by creating sharp scratches/imperfections on glass surface
–> which act as nucleation points where molecules can condense on to

1) forming the nucleus in the first place is slow
- You have to get exactly the right molecules coming tgt in exactly the right orientation to form a nucleus

2) crystal growth is almost instant
- mc want to crystallise but don’t know in what pattern
- so as soon as you give them a pattern, it instantilly will crystallise