Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

DYS Pharmaceutics > Physiochemical properties 1 > Flashcards

Physiochemical properties 1 Flashcards

1
Q

What is a SOLUTION?

A

A mixture of 2 or more components that form a homogeneous molecular dispersion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a SINGLE PHASE SYSTEM?

A

Not another phase dispersed in another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a SOLVENT?

A

The component present in greater amount (usually liquid)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a SOLUTE?

A

The component present in smaller amount (usually solid or liquid)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is SATURATED SOLUTION?

A

Where the solute is at the limit of its solubility at a given temperature and pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the 2 types of solution?

A
  1. Liquid in Liquid

2. Solid in Liquid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe liquid in liquid

A
  • solutions of this type can be divided into 2 categories:
  • Completely miscible, e.g. ethanol + water- one phase
  • Partially miscible, e.g. water + ether- two phases
  • Miscibility: Mutual solubility of components in liquid in liquid system
  • Partial miscibility is affected by temperature
  • Partially miscible binary liquid mixtures are used with a separating funnel to determine partition coefficients.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe solid in liquid

A
  • solutions of non-electrolytes (non ionic) e.g. organic molecules phenol, sucrose
  • solutions of electrolytes (forms ions in solution)
  • strong electrolytes (fully ionised over a wide ph range_
  • weak electrolytes (ionisation dependent on ph)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do drugs enter solution?

A

Dissolution of a solid solute

  1. solute molecule leaves particle
  2. creation of a cavity in the solvent
  3. solute molecule enters the cavity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is solvation and hydration?

A

Solvation: process of binding of solvent to solute molecules.
Hydration: solvation when the solvent is water.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the structure of water?

A
  • tetrahedral structure, angle 104.5

- Flickering cluster model: involves clusters of H-bonded ‘ice like’ water within pools of unbound water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is an IDEAL SOLUTION?

A

There are no interactions between dissolved solutes and obey Raoult’s law

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a REAL SOLUTION?

A

Interaction occur between dissolved solutes which reduce the effective concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Activity coefficient

A

= activity/concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe polar solvents

A
  • water, methanol, acetic acid have a high relative permittivity (dielectric constant)
  • Dissolve ionic solutes by reducing the force of attraction between oppositely charged ions in crystalline solids
  • They can break covalent bonds
  • They can solvate molecules and ions through dipole-dipole forces.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe Semi-polar solvents

A
  • Acetone, methanol, ethanol
  • Can dissolve polar and non-polar substances
  • Solvent molecules dipole movement or H-bonding groups enable POLAR solutes to be dissolved
  • SEMI-POLAR solvents can induce a degree of polarity in NON-POLAR solvent molecules.
17
Q

Describe Non-polar solvents

A
  • Hexane, pentane, oils&fats
  • Low dielectric constant, lack H-bonding groups prevent these solvents from dissolving ionic or polar solutes
  • Unable to break covalent bonds
  • Dissolve NON-POLAR compounds only
  • Non-polar solutes are held in solution through Van Der Waals interactions with the solvent.
18
Q

Solubility of weak electrolytes

A

ph and ionisation:

  • The solubility of weak acids and bases is influenced by ph
  • By modifying the ph we can alter the solubility of a drug
  • ionised species is more soluble than the unionised species
19
Q

Weakly Acidic Drugs

  • name examples
  • solubility Equation
  • ph at which drug will start to precipitate
A
  • Warfarin , NSAIDs
  • ionised species of these will be hydrated and more soluble
  • The solubility can be determined by Henderson-Hasselbatch equation:
    Pka= ph + log [HA]/[A-]
  • ph= pka + log s-so/so
  • s= saturation solubility at a given ph
  • so= solubility of undissociated drug (FREE BASE)
20
Q

Weakly Basic Drugs

  • name examples
  • solubility equation
  • ph at which drug will start to precipitate
A
  • Ranitidine, Cimetidine
  • pka= ph + log [BH+]/[B]
  • ph= pka + log so/s-so
21
Q

What is an Amphoteric drug?

- isoelectric point

A
  • Oxytetracycline, nitrazapam
  • Contain both ACIDIC and BASIC groups so will have 2 or more pka values
  • ISOELECTRIC POINT- is the ph at which the drug carries no net electric charge
    ph = (pka1 + pka2)/2
22
Q

Define partitioning

- Partition coefficient equation

A

The distribution of a substance between 2 immiscible phases

- p= Co/Cw

23
Q

How is partition coefficient calculated?

A
  • Drug added to a separating funnel containing 2 immisicible liquids
  • The flask is shaken for up to 1 hr and then left so that the 2 phases separate out
  • Conc in the aqueous phase is determined by spectroscopy or
  • Conc in the organic phase would be determined by subtraction
24
Q

Apparent partition coefficient

- for weak acids and bases

A

WEAK ACID:
Log [p/papp - 1] = ph - pka

WEAK BASE:
Log [p/papp - 1] = pka - ph

25
Q

What are the limitations of the ph- partition theory?

A
  • The small intestine are designed for absorption
  • Surface area of up to 200m2 as a result of microvilli
  • long residence time and excellent blood flow
26
Q

Active transport

A
  • Molecules may be particularly vital to the body that active transport mechanisms exist
  • mechanisms exist for substances such as: Ions, glucose, vitamins, amino acids
  • Active transport means that molecules may be absorbed even if they are ionised or highly hydrophillic

DYS Pharmaceutics (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions