SOLID STATELEC 1

By Dr Manal AL Soub

STATES OF MATTER SOLIDS

•Particles of solids are tightly packed, vibrating about a fixed position.

•Solids have a definite shape and a definite volume.

STATES OF MATTERLIQUID

Particles of liquids are tightly packed, but are far enough apart to slide over one another.

Liquids have an indefinite shape and a definite volume.

STATES OF MATTERGAS

Particles of gases are very far apart and move freely.

Gases have an indefinite shape and an indefinite volume.

Solidrefers to the state of matter in which the particles are

locked into place without much freedom of movement. They can be locked into crystal lattices or just kind of stuck together with intermolecular forces so tightly that they can’t really move around.

Solids differ from liquids in that the particles in liquids, while still stuck together, do have some freedom of motion.

Solids differ from gases in that gas molecules really don’t interact with each other much, flying all over the place

PHASE CHANGESDescription of Phase Change

Term for Phase Change

Heat Movement DuringPhase Change

Solid to liquid

MeltingHeat goes into the solid as it melts.

Liquid to solid Freezing

Heat leaves the liquid as it freezes.

PHASE CHANGESDescription

of Phase Change

Term for Phase Change

Heat Movement During

Phase Change

Liquid to gas

Vaporization, which includes boiling and evaporation

Heat goes into the liquid as it vaporizes.

Gas to liquid Condensation Heat leaves the gas as it condenses.

Solid to gas Sublimation Heat goes into the solid as it sublimates.

STATES OF MATTER

SOLID LIQUID GAS

Tightly packed, in a regular pattern

Vibrate, but do not move from place to

place

Close together with no regular

arrangement.Vibrate, move

about, and slide past each other

Well separated with no regular

arrangement.Vibrate and move

freely at high speeds

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What is solid…..to pharmacy?

Majority of drugs and excipients exist as solidsVarious dosage forms are prepared

e.g. tablets, emulsions

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Classification of Solids• Amorphous

• Crystalline

– Polymorphism

– Solvate and hydrates

–Co-crystal

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Crystalline Solids• E.g. diamond, graphite

• Regular shape i.e. fixed geometric patterns

• Incompressible

• Definite /specific boiling points

• Diffract X-rays

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Crystal Structure

• Crystals contain highly ordered molecules or atoms held together by non-covalent interactions

• E.g. NaCl has the cubic structure

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Can be defined on the basis of variations on the themes of 7 systems

Types of Crystal Structure

1. Cubic- sodium chloride

2. Tetragonal- urea

3. Hexagonal - iodoform

4. Rhombic- iodine

5. Monoclinic- sucrose

6. Triclinic- boric acid

7. Trigonal

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Angles & lengths that describe crystal habit α = between length & breadthβ = between breadth & heightγ = between length & height

Crystal Angle of axes Length of axes Examples

Cubic (regular) α = β = γ = 90º x =y =z NaCl

Tetragonal α = β = γ = 90º x =y ≠z NiSO4

Orthorhombic α = β = γ = 90º x ≠y ≠z K2MNO4

Monoclinic α = β = γ ≠ 90º x ≠y ≠z Sucrose

Triclinic (asymmetric) α ≠β ≠ γ ≠ 90º x ≠y ≠z CuSO4

Trigonal (rhombohedral) α = β = γ ≠90º x =y =z NaNO3

Hexagonal Z at 90º to base - AgNO3

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Triclinic

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Monoclinic

simple monoclinic

centered monoclinic

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Tetragonal

simple tetragonal body-centeredtetragonal

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Orthorhombic xtals

simple orthorhombic

base-centeredorthorhombic

body-centeredorthorhombic

face-centeredorthorhombic

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Bravais Lattices1. End-centred

i. Monoclinic

ii. orthorombic

2. Face-centredi. Cubic (NaCl)

ii. Orthorombic

3. Body-centredi. Cubic tetragonal

ii. Orthorombic

Total of 14 possible types of unit cells

For drugs, only 3 types:

1. Triclinic

2. Monoclinic

3. Orthorombic

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FCC Structure of NaCl• Small spheres

represent Na+ ions, large spheres represent Cl- ions.• Each sodium ion is

octahedrally surrounded by six chloride ions and vice versa.

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CrystallisationCrystallisation steps from solution:-

1. Supersaturation of the solutione.g. cooling, evaporation, addition of precipitant or chemical reaction

2. Formation of crystal nucleie.g. collision of molecules, deliberate seeding

3. Crystal growth around the nuclei

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Crystal GrowthSteps involved:1. Transport of molecules to the surface2. Arrangement in the lattice

Degree of agitation in the system affects the diffusion coefficient, thus affects crystal growth.

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Precipitation

1. Induced by altering pH of solution to reach saturation solubility.

2. By chemical reaction to produce precipitate from a homogeneous solution.

The rate of reaction is important in determining habit.

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Crystallization from Supersaturated Solutions of Sodium Acetate

• Description: A supersaturated solution of sodium acetate is crystallized by pouring it onto a seed crystal, forming a stalagmite-like solid. Heat is radiated from the solid.

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Polymorphisms

• When compounds crystallise as different polymorphs, properties change.

• Molecules arrange in two or more ways in the crystal: packed differently in crystal lattice, different orientation, different in conformation of molecules at lattice site.

• X-ray diffraction patterns change.

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Polymorphism of Spironolactone• A diuretic (no potassium loss)• 2 polymorphic forms and 4 solvated crystalline• Form 1: spironolactone powder is dissolved in

acetone at a temperature near boiling point and cooled to 0 deg. C within a few hours – needle-like

• Form 2: powder dissolved in acetone or dioxane or chloroform and acetone allowed to evaporate for several weeks – prism

28 PHM1213 Physical Pharmacy 1 2008/9

Polymorphs of spironolactone

1

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Amorphous Solids• E.g. silica gel, synthetic plastics/polymers• Irregular shape

- molecules are arranged in a random manner• No definite melting point

- no crystal lattice to break• Exhibit characteristic glass transition temperature, Tg• Flow when subject to pressure over time• Isotropic i.e. same properties in all direction• Affect therapeutic activity e.g. amorphous antibiotic

novobiocin is readily absorbed and therapeutically active compared to the crystalline form