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Pharmaceutics > Solubility Phenomena > Flashcards

Solubility Phenomena Flashcards

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
Q

Polar Solvents Outline

A

Consists of strong dipolar molecules. Has H bonding. Eg water

26
Q

Semipolar Solvents Outline

A

Strong dipolar molecules. Dipole bonds (no H bonds) eg acetone

27
Q

Non-polar solvents

A

Small/ no dipole character eg benzene

28
Q

Amphoteric Def.

A

Substances that can be positively and negatively charged

29
Q

Anionic Substances

A

Weak and strong acids

30
Q

Cationic Substances

A

Weak and strong bases

31
Q

Zwitterion Def.

A

Molecule that can hold both positive and negative charge at the same time Eg amino (positive) acids (negative)

32
Q

Relationship between pH, counter ions and ionisation

A

Ionisation of weak electrolytes (eg weak acid/base) is controlled by pH and counter ions. Ionisation is reversible

33
Q

Dissociate Def.

A

To break apart

34
Q

Electrolyte Def.

A

Substances that dissociate into constitutive ions when dissolved in suitable solvent. Dissociation results in ionisation leaving electrolytes conductive of electricity

35
Q

Strong Electrolytes Def.

A

Substances undergoing complete dissociation

36
Q

Weak Electrolytes Def.

A

Substance undergoing partial dissociation

37
Q

Non-electrolytes def.

A

Non-ionic substance that don’t dissociate

38
Q

How to increase dissociation

A

Add salt to compound

39
Q

adding electrolytes to electrolyes in solution

A

increases di-electric constant = increase solubility

40
Q

Adding a very soluble electrolyte to a non-electrolyte (or visa-versa)

A

Di-electric constant decreases. Solubility of substance in original solution decreases

41
Q

How electrolyres effect the solubility of non

A

Salting out (organic substances precipitate) or Salting In (organic substances more soluble (less frequent)

42
Q

Miscible Def

A

2 substances form homogenous molecular sol. when mixed in any proportion. Works in all states but is mainly liquids

43
Q

Partial Miscible Def.

A

2 substance form homogenous molecular sol when mixed in specific proportions at specific temp and pressure

44
Q

Immiscibility

A

A negligible amount of 2 substances mix to form solution. Results in emulsions

45
Q

What substances chemical composition make them more hydrophillic

A

OH, conjugate acid and conjugate base

46
Q

What substances are the lipophilic

A

organic compounds (carbon chains)

47
Q

Log S Outline

A

Intrinsic Solubility

48
Q

Tm Outline

A

Melting point. Increased Tm = decreased log S

49
Q

Log P Outline

A

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
Q

What does Log P = x or Log P = -x mean

A

Substance is 10^x times more likely to dissolve in octanol/water

51
Q

Brick Dust Def.

A

Stable crystalline materials with strong intermolecular bonds. Low aqueous solubility

52
Q

Grease Balls Def.

A

Highly lipophilic drugs unable to form bonds with water

53
Q

Log P Drug development

A

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
Q

Why do differnt cells have different optimal Log P

A

Their barriers require different powers of permeation eg skin 1-4, ophtalmic (cornea) 1-2 and small intestine 1-5

55
Q

POlarity Test of solvent

A

High Performance Chromotography

56
Q

What can help reduces the reuired log P of drug

A

If cell contains complementary transporters and concentration gradients

57
Q

Solvent Def.

A

Liquid in which solute dissolves to form solution

58
Q

Polarity def.

A

Measure of electric distribution within molecule. Measured by dipole moment (distance opposite charges are seperated)

59
Q

Dielectric Constant Def.

A

Measure of ease vehicle/medium seperates opposite charges. Ratio of material capacitance to reference. Polar = high, non-polar = low

60
Q

Polar Solvation Mechanisms

A

Dipole moments, dielectric constant and H bonding potential

61
Q

Non-polar Solvation Mechanisms

A

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 (14 decks)

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