Physical properties and analytical chemistry

Question 1

Physical properties

Answer 1

Characteristics of matter that can be measure or observed without a change in chemical composition

Question 2

Intensive property

Answer 2

• Not dependant on the amount of substance e.g. temperature

Question 3

Extensive properties

Answer 3

Dependant on the amount of substance e.g. mass/volume

Question 4

Dipole-dipole interaction

Answer 4

• Interactions between the postive end of one dipole and the negative end of another dipole

Question 5

Vander waals forces

Answer 5

• Weak forces of attraction that exists between non polar molecules
• Distance dependant interaction which are induced dipole-dipole

Question 6

Hydrogen bonding

Answer 6

• Attractive forces between H attached to an electronegative atom

Question 7

Melting point

Answer 7

• Used to characterise organic compounds and confirm purity and melting point of pure compounds are greater than impure

Question 8

Impure compound

Answer 8

• Increases the molecular weight but not regularity

Question 9

Boiling point

Answer 9

Temperature when the vapour pressure of the liquid is equal to the atmospheric pressure state changes from liquid to gas

Question 10

Wander waals forces

Answer 10

• Dependant on the area of contact between forces
• Increase as molecular size increases
• Greater amount of energy required to overcome the forces
• Branched alkanes are more compact so there is less surface area for force interactions

Question 11

Boiling point and hydrogen bonding

Answer 11

• The -OH is strongly polarised with the pair of electrons in the O so having more oxygen groups increases the boiling point

Question 12

Dipole-dipole atteraction and boiling point

Answer 12

• ## Polarised CO bond and non bonding electrons form a dipole moment

Question 13

Carboxylic acid and boiling point

Answer 13

• Forms a stable hydrogen bonding dimer very high boiling point

Question 14

Properties of H2O

Answer 14

• High polar solvent
• Excellent solvent for polor and ionic
• Poor solvent for non polar molecules

Question 15

Hydrophilicity and lipophobicity

Answer 15

• Ability for chemical compound or drug to go into solution in H2O
• Polar and ionic and form hydrogen bonds and dipole-dipole with solvent and the fat is insoluable so it cannot cross the cell membrane

Question 16

Hydrophobic and lipophilic

Answer 16

• Ability to chemical compound or drug to go into solution in lipids and non polar
• Are non-polar molecules, H2O insoluble, easily cross cell membrane, can enter target cells
• Biological membranes

Question 17

Bond polarity and bond dipole moments

Answer 17

• Amount of charge x distance between charges

Question 18

Polarity of a molecule

Answer 18

indicated by the molecular dipole moment of the entire molecule

Question 19

Molecular dipole moment

Answer 19

Equal to the vector sum (sign is important) of the all individual bond dipole moments

Question 20

Solubility

Answer 20

• Amount of a solute that can be dissolved in a specific solvent under given conditions. Measure of how much of the solute can be dissolved into the solvent at a specific temperature

Question 21

Solvation or hydration

Answer 21

Dissolving solute in solvent

Question 22

Polar Solute in a Nonpolar Solvent

Doesn’t dissolve

Answer 22

• Nonpolar molecules do not solvate ions very strongly
• Attractions of the ions in the solid for each other are much greater than their attractions for the solvent

Question 23

Nonpolar Solute in a Nonpolar Solvent

Dissolves

Answer 23

• Molecules of a nonpolar substance weakly attracted to each other, and these van der Waals attractions are easily overcome by van der Waals attractions with the solvent

Question 24

Nonpolar Solute in a Polar Solvent

Doesn’t disolve

Answer 24

• Nonpolar molecules are weakly attracted to each other little energy is required to break
• H2O molecules are strongly attracted to eachother due to hydrogen bonding

Question 25

Substance added to pair of immicible solvents

Answer 25

- Distributes itself between the two solvents according to its affinity for each phase - Polar compounds have greater affinity aqueous or polar phase - Non-polar has a higher affinity to the non aqueous or organic phase

Question 26

Partition law

Answer 26

- A given substance, at a given temperature, will partition itself between two immiscible solvents in a constant ratio of concentrations - P = organic/aqueous

Question 27

Partition coefficient

Answer 27

- Predict ADE of drugs within the body. - Predict the onset of action of drugs or the duration of action of drugs, - Calculate physical and chemical characteristics

Question 28

How to calculate partition

Answer 28

- Unionised/organic = Organic - Unionised/water = Aqueous - Organic/aqueous = Partition coefficient - % of drug = organic phase divided by total of drug

Question 29

Weak acid or weak base

Answer 29

ionisation to form an anion or a cation alters the solubility profile of the drug

Question 30

# Experimantal partition coefficient pH effect on partition coefficient

Answer 30

- Measure P of the unionised molecule - P value for acids: measured at low pH when the acid is unionised - P value for bases: measured at high pH to prevent ionisation

Question 31

Apparent partion coefficent

Answer 31

fraction of unionised x true partion coefficient

Question 32

Partition coeffient compartments

Answer 32

- Use 1-octanol collerates with in-vivo 8 carbon hydrophobic and OH is hydrophilic - Aqueous buffer represents blood plasma in the body

Question 33

# Shake flask method Obtaining organic solvent

Answer 33

- 2 phases are mixed together - 2 phases seperate and the drug is added the flask is then shaken - 2 phases are then allowed to seperate and the concentration of the drug the aqueous phase can be determied by spectroscopy or titration - Concentration of Octanol phase found by subtrating value of P calculated