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Pharmaceutics > Solubility Phenomena > Flashcards

Solubility Phenomena Flashcards

(61 cards)

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1
Q

Solution Def.

A

Mix of 2+ components forming homogenous phase down to molecular levels (pariticles<1nm)

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2
Q

Solubility Def.

A

Max conc of substance that will dissolve in give solution (usually water) volume at given temp

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3
Q

Are suspensions considered to have solubility

A

No. Substance must dissolve (have interactions at molecular level)

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4
Q

Dissolution Def.

A

Rate at which substance goes from solid state to solution in given solvent

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5
Q

Types of Solutions

A

Liquid-liquid (eg elixirs), solid-liquid, solid-solid (melting and resolidifying, gas-gas (anaesthetics, require high pressure), gas-liquid (HCl)

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6
Q

Solvent Def.

A

Component solute dissolves in, determines phase. Different polarities between solvents (eg water and ethanol). Considereed an excipient in dosage form

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7
Q

Solute

A

Dissolving Agent. Can be drug or excipient

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8
Q

Saturated Solution

A

Max dissolved solute has been reached. Equilibrium is reached between solute dissolved and being returned to solid state.

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9
Q

Measuring Solubility

A

No instruments. Measurably adding excess solute to solution of known volume at a fixed temperature

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10
Q

Concentration vs Solubility Expression

A

Concentration is solute in solution. Solubility is solute in solvent

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11
Q

Milliequivalents per Litre

A

mg equivilant weights of solute per litre of solution

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12
Q

Osmole Def.

A

1 mole of osmatic substance

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13
Q

Formation of Solution Outline

A

Increase in entropy (disorder) and increase in attractive forces

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14
Q

Free Energy Outline (delta G)

A

When free energy is negative there is chance a reaction will spontaneously happen. Factors are Heat Change, Change in Temperature abd change in entropy

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15
Q

Relationship between heat change(enthalpy) and free energy

A

The bigger the heat change the more positive the free energy (low chance of rection occuring)

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16
Q

Relationship Temp and Free energy

A

The bigger the temp = the more negative free energy

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17
Q

Relationship Change in entropy (disorder) and free energy

A

The higher the entropy = the more negative the free energy

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18
Q

Endothermic Dissolution Outline

A

Heat absorbed during dissolution(solution cools). Increase temp = increase solubility. More energy used when bonds are broken then formed. Drug doesn’t have enough heat

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19
Q

Exothermic Dissolution Outline

A

Releases heat during dissolution (solution warms). Increased temp = decreased solubility. More energy used when bonds are formed not broken

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20
Q

Can substances change dissolution type

A

Yes. Sodium sulfate decahydrate begins endothermic nut converts to exothermic as it loses water

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21
Q

Unsaturated solution Def.

A

Conc of dissolved solute is less then required for saturation at given temp. Made more in practice to account for evapouration

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22
Q

Supersaturated Solution Def.

A

Contains more dissolved solute then could normally contain at given temp. Not thermodynamically stable (precipitates to saturated)

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23
Q

Hydrophilic (lipophobic) Solutes

A

Polar substance soluble in water and other polar substances. Bonds with water to form aqueous solution

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24
Q

Hydrophobic (lipophilic) Solutes

A

Non-polar substance soluble in non-polar solvents. have low aqueos solubility

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25
Polar Solvents Outline
Consists of strong dipolar molecules. Has H bonding. Eg water
26
Semipolar Solvents Outline
Strong dipolar molecules. Dipole bonds (no H bonds) eg acetone
27
Non-polar solvents
Small/ no dipole character eg benzene
28
Amphoteric Def.
Substances that can be positively and negatively charged
29
Anionic Substances
Weak and strong acids
30
Cationic Substances
Weak and strong bases
31
Zwitterion Def.
Molecule that can hold both positive and negative charge at the same time Eg amino (positive) acids (negative)
32
Relationship between pH, counter ions and ionisation
Ionisation of weak electrolytes (eg weak acid/base) is controlled by pH and counter ions. Ionisation is reversible
33
Dissociate Def.
To break apart
34
Electrolyte Def.
Substances that dissociate into constitutive ions when dissolved in suitable solvent. Dissociation results in ionisation leaving electrolytes conductive of electricity
35
Strong Electrolytes Def.
Substances undergoing complete dissociation
36
Weak Electrolytes Def.
Substance undergoing partial dissociation
37
Non-electrolytes def.
Non-ionic substance that don't dissociate
38
How to increase dissociation
Add salt to compound
39
adding electrolytes to electrolyes in solution
increases di-electric constant = increase solubility
40
Adding a very soluble electrolyte to a non-electrolyte (or visa-versa)
Di-electric constant decreases. Solubility of substance in original solution decreases
41
How electrolyres effect the solubility of non
Salting out (organic substances precipitate) or Salting In (organic substances more soluble (less frequent)
42
Miscible Def
2 substances form homogenous molecular sol. when mixed in any proportion. Works in all states but is mainly liquids
43
Partial Miscible Def.
2 substance form homogenous molecular sol when mixed in specific proportions at specific temp and pressure
44
Immiscibility
A negligible amount of 2 substances mix to form solution. Results in emulsions
45
What substances chemical composition make them more hydrophillic
OH, conjugate acid and conjugate base
46
What substances are the lipophilic
organic compounds (carbon chains)
47
Log S Outline
Intrinsic Solubility
48
Tm Outline
Melting point. Increased Tm = decreased log S
49
Log P Outline
Partition coefficent (drug conc in non-polar solvent divided by conc in polar (in same container)). Measures whether substance would dissolve in polar (eg water) or non-polar (eg octanol) concentration. As log P increases, log S decreases. If log P is positive it's lipophilic if logP is negative it's hydrophilic
50
What does Log P = x or Log P = -x mean
Substance is 10^x times more likely to dissolve in octanol/water
51
Brick Dust Def.
Stable crystalline materials with strong intermolecular bonds. Low aqueous solubility
52
Grease Balls Def.
Highly lipophilic drugs unable to form bonds with water
53
Log P Drug development
Drugs Log P <0.5 are water soluble. Predicts ability to permeate membranes, correlation for drugs ability to bind to proteins (lipophilic bind), activity of preservatives and drug adsorption behaviour
54
Why do differnt cells have different optimal Log P
Their barriers require different powers of permeation eg skin 1-4, ophtalmic (cornea) 1-2 and small intestine 1-5
55
POlarity Test of solvent
High Performance Chromotography
56
What can help reduces the reuired log P of drug
If cell contains complementary transporters and concentration gradients
57
Solvent Def.
Liquid in which solute dissolves to form solution
58
Polarity def.
Measure of electric distribution within molecule. Measured by dipole moment (distance opposite charges are seperated)
59
Dielectric Constant Def.
Measure of ease vehicle/medium seperates opposite charges. Ratio of material capacitance to reference. Polar = high, non-polar = low
60
Polar Solvation Mechanisms
Dipole moments, dielectric constant and H bonding potential
61
Non-polar Solvation Mechanisms
Unabke to seperate ions of strong and weak electrolytes. Dissolves non-polar substance by induced dipoles and solute kept disperesed in solution via Van der Waals

Pharmaceutics (33 decks)

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