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crystalline vs armorphous Flashcards

1
Q

why do we not just take the drug why do we need to put it in another form

A

poor physical and chemical properties, need to control dosage for patient requirements

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2
Q

what is a crystal

A

regular, geometric, ordered

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3
Q

what is a amorphous

A

non-crystalline, un-orgnaised, not ordered, glass

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4
Q

what is it called when a crystal goes from solid to liquid

A

melting point (Tm), has lattice energy

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5
Q

what is it called when an amorphous goes from solid to liquid

A

glass transition (Tg) , has no lattice energy

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6
Q

what does it mean to be stable

A

lowest free energy state, cant spontaneously change

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7
Q

what does meta-stable mean

A

not lowest free energy state, can potentially spontaneously change, all amorphous material are meta-stable

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8
Q

why are crystals preferred in formulation

A

amorphous material has higher solubility and dissolution rate, more unstable and more likely to recrystallise, changes in medicine is bad

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9
Q

which type of material is preferred in formulations

A

crystals

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10
Q

what does lattice mean

A

array of points, identical surroundings

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11
Q

what does motif mean

A

atoms associated with lattice point

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12
Q

what is lattice energy

A

large energy input required to change state from solid to liquid (melting enthalpy)

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13
Q

what is translational symmetry

A

repeating patterns of the crystal structure

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14
Q

how does lattice energy form

A

lattice interactions over long distances

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15
Q

what is a polymorph

A

different forms of the same compound
-same composition, can have different chemical properties

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16
Q

give some examples of multicomponent solids

A

co-crytals, salts, hydrates, salts

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17
Q

difference between cocrystals and salt

A

salt- proton transfer, 2 separate ions hold lattice together, can be crystalline, amorphous, polymorphs

cocrystals- hydrogen bonding, charge separation, unionised, crystalline, polymorphs

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18
Q

what are the purposes of using multicomponent solids

A

modify drugs

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19
Q

why use salts

A

improves properties
eg. improves solubility, powder flow, chemical/physical stability

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20
Q

how to make a salt of an API/drug

A

use the counterion

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21
Q

what do acidic drugs form and what counterions can be used to make salts of it

A

-forms anions
-aluminium, calcium, diethanolamine

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22
Q

what do basic drugs form and what counterions can be used to make salts of it

A

-cations
-acetate, benzoate, chloride

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23
Q

why cant all APIs form salt from the drug

A

some dont have ionisable groups, can make cocrystals instead

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24
Q

how to distinguish between polymorphs

A

melting point

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25
what are hydrates
crystals that contain a water molecule in the lattice
26
what are solvates
crystals that contain a solvent
27
are hydrates and solvates stable and why
they are unstable due to solvent loss, if solvent is lost into the drug molecule then the physical properties of the solid form will change
28
example of a hydrate
ampicillin trihydrate (antibiotic)
29
example of a solvate
darunavir ethanolate (AIDS treatment)
30
what does colligative mean
physical changes that result from adding a solute to solvent, only dependent on the concentration of solute, detects concentration of impurity
31
how to see presence of impurities in a substance
measure the melting point of a pure substance and the sample to compare, presence of impurities will lower the melting point
32
how will the presence of impurities affect melting point of a substance
impurites will decrease the melting point
33
describe the presence of impurities in solid crystals
crystals are closely packed, cant fit impurities, can only have impurities in sample but not inside the crystal, insoluble impurities
34
describe the presence of impurities in liquid crystals
molecules not closely packed, impurities soluble in liquid state, mixed together
35
what are the effects of impurities in melted crystals (liquid)
impurities are soluble, entropy of mixing, free energy is lowered, liquid stabilised, melting point lowered
36
what happens as you add impurities
greater stabilisation, greater entropy of mixing in liquid state, greater depression of melting point, entropy of solid to liquid increases, melting point decreases
37
melting point equation at equilibrium
Tm =∆H (solid−liquid)/ ∆S (solid−liquid)
38
free energy equation at equilibrium
∆G = ∆H (solid−liquid) −Tm ∆S (solid−liquid) = 0
39
what happens to ∆H and ∆S when impurities are added
∆H- unaffected ∆S- increases, melting point decreases
40
schroder-van laar equation
1/ = 1/ - Rlnx/ Tm T0 ∆H Tm=melting point of mixture T0=melting point of pure substance R=ideal gas constant x=mole fraction of solute ∆H=enthalpy of melting of the solute
41
summary of melting point
impurities can enter liquids but not solids due to close packing, impurities increase entropy of liquids but not solids, free energy also lowered, liquid stabilised so mp decreases
42
what properties can you test to determine whether a material is crystalline or amorphous
lattice energy- yes=crystal translational symmetry- yes=crystal optical order/disorder ability to exclude/include other molecules- crystals exclude impurities
43
what techniques can be used to analyse solids
x ray powder diffraction (XRPD), calorimetry, optical microscopy
44
how does XRPD work
works due to the interferences between waves coming into a sample
45
how to read a XRPD graph to determine if a material is crystalline or amorphous
peaks= crystalline broad halo= amorphous -whole pattern is important -measures spacing between atoms (x axis) and location of atoms (y axis)
46
what is constructive interference
when two waves are in the same direction and same phase, their amplitude gets added together and a resultant wave is obtained -resultant wave will be higher than the original
47
what does in phase mean
peaks line up
48
what is destructive interference
waves cancel each other out, sum of waves is zero
49
how does a wave change phase
changes the path length
50
what happens when the wavelength of light is bigger than the object
no interaction
51
what happens when the wavelength of light is smaller than the object
shadow forms
52
what happens when the wavelength of light is the same as the object
diffraction
53
how to describe a XRPD graph for polymorphs
-graph will have more than one line -crystalline/amorphous and state if it is the same structure or not
54
what does DSC stand for
differential scanning calorimetry
55
what does calorimetry measure
changes in heat input/output when heating a material, exo/endothermic stuff
56
how does DSC work
-sample pan and reference pan -measure the heat required to heat the pans up and any changes in heat input is related to the sample
57
why is doing DSC with a reference pan good
allows us to exclude changes caused by fluctuations in room temperature
58
describe the 2 methods to do DSC
1. same energy input, measure temperature difference 2. maintain same heating rate for both and measure energy required
59
describe the DSC graph (exothermic up) for amorphous and crystals
amorphous- decreases crystal- dips down, decreases then increases
60
describe a more complex DSC graph (exothermic down) for a crystal
big peak=melt small dip=crystallisation melt peak points up so it is endothermic
61
how to distinguish between crystal and amorphous using optical microsopy
crystals- birefringence if not cubic (most pharma crystals arent cubic), light shows through crossed polars amorphous- no birefringence
62
what does optical microscopy use to distinguish crystals and amorphous materials
polarised light

Science of medicine (7 decks)

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