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PHA111 > Polymorphic Forms > Flashcards

Polymorphic Forms Flashcards

1
Q

List a key property of polymorphic forms

A
  • atoms are packed in a high degree order

-

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2
Q

List a key property of amorphous forms

A
  • atoms are arranged in a random order
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3
Q

Give an example of a polymorph

A

sodium chloride

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4
Q

Give an example of an amorphous material

A

glass

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5
Q

What can the crystallographic structure be described as?

A

3D lattice, in which the unit cell is the repeating unit

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6
Q

What is the unit cell?

A

The building block of the crystal described by 3 dimensions

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7
Q

What are the dimensions and angles describing a unit cell?

lengths of axes and angles

A

lengths - a, b, c

angles - α, β, γ

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8
Q

How many basic crystal systems are there?

A

7 unit cells

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9
Q

How many advanced crystallographic systems are there?

A

14 unit cells

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10
Q

What do Bravais lattices consider the possibility of ?

A

The presence of centre atoms inside the cell or at edges of faces

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11
Q

What are the 7 basic crystal lattice systems?

A
  • cubic
  • tetragonal
  • orthorhombic
  • monoclinic
  • triclinic
  • trigonal
  • hexagonal
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12
Q

What does crystal habit describe?

A

The overall shape of the crystal

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13
Q

What is crystal habit a result of?

A

Different growth rates in each dimension

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14
Q

Two crystals with same habit may have different combinations of faces/angles

A

faces

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15
Q

How can crystal habit be modified?

A

Adding impurities

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16
Q

What is produced as a result of crystal habit modification using an anionic surfactant on adipic acid?

A

Thin long needle

17
Q

What is produced as a result of crystal habit modification using an cationic surfactant on adipic acid?

A

thin flaky plates

18
Q

Presence of surfactants in crystallisation solution can change crystal habit by absorbing/adsorbing onto crystal faces during crystal growth

A

adsorbing

19
Q

Polymorphic forms can have the same type of crystal ____ but different proportions of axes and angles

A

lattice

20
Q

Give 3 ways in which polymorphs differ

A
  • thermodynamic stability
  • free energies
  • physical properties e.g. m.p.
21
Q

How do polymorphs have an effect in pharmaceutics?

A
  • manufacture of dosage form
  • pharmacological activity
  • bioavailability
22
Q

What is fuels the transition between polymorphic forms?

A

heat or pressure

23
Q

Describe enantropic transition

A

between all forms

24
Q

Describe monotropic transition

A

metastable form into stable form

25
Q

Metastable forms are higher/lower energy polymorphs

A

higher

26
Q

Give 3 characteristics of stable polymorphs in comparison to higher energy polymorphs

A
  • lowest free energy
  • higher m.p.
  • lowest solubility
27
Q

Polymorphic form nomenclature use roman numerals in order of the highest _______ point

A

melting

28
Q

In drug delivery why is it better to have metastable forms?

A
  • better solubility, dissolution, and bioavailability
29
Q

Describe crystal solvates

A

crystals contain solvent of crystallisation

30
Q

Describe crystal hydrates

A

Water is the solvent of crystallisation

31
Q

Describe crystal anhydrates

A

crystals with no water of crystallisation

32
Q

What is a polymorphic solvate?

A

solvent interacts with crystal, and when crystals lose the solvent a new crystal form will be produced

33
Q

What is a pseudopolymorphic solvate?

A

No interaction between solvent and crystal bonding, when crystal solvates lose the solvent the lattice is not destroyed

34
Q

Hydrates are more/less soluble than anhydrates and more/less thermodynamically stable

A

less

more

35
Q

Give a possible crystal defect

A
  • missing atom

- impurity replacing the original atom

36
Q

How can defects influence crystals?

A

alter their physical properties

PHA111 (23 decks)

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