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Med Chem > Lecture 2 (Intro to MedChem) > Flashcards

Lecture 2 (Intro to MedChem) Flashcards

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1
Q

Free bases or acids are often ____

A

liquid (oils)

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2
Q

Are they better or worse than a salt?

A

WORSE

  • less water soluble than ionized form
  • difficult to measure (because they are hygroscopic)
  • difficult to make into a dosage form
  • less stable
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3
Q

Why do we want to make a salt out of the free acids/bases?

A

because they are easier/better to work with (see previous card) and are more stable

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4
Q

Drug absorption across biological membranes is better in the ______ state

A

unionized

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5
Q

T or F: good drugs have only either lipid or water solubility

A

FALSE

-most efficient drugs have some degree of water and lipid solubility

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6
Q

explain solubility

A

for a chemical to dissolve in a particular solvent the compound must be able to form attractive forces with the molecules of the solvent

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7
Q

it is possible to estimate the solubility properties of drug by examining its _____

A

structure

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8
Q

Can we alter the solubility of a drug?

explain the 3 ways

A

YES
-use acid or base to make the drug into a salt
OR
-add substituents that are very water soluble:
-adding groups that are H bond donors and acceptors
-adding groups that can ionize
OR
-changing dose form

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9
Q

Are dispersion forces strong or weak?

A

weak

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10
Q

Dispersion forces are called ??

A 
london forces
(wrongly called van der waals attraction)
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11
Q

Where do dispersion forces occur?

A

between induced and instantaneous formed dipoles

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12
Q

As molecule gets larger, dispersion forces get _____

A

larger

disperson forces increase as the total area for interaction between molecules increases

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13
Q

Why do larger molecules become liquids? (ex. butane, hexanes, and octane are liquids but methane, ethane, and propane are gases)

A

increasing size = increasing dispersion forces

also increasing weight is a factor

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14
Q

What is stronger: dispersion forces or dipole-dipole bonds?

A

dipole-dipole bonding

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15
Q

Where does a dipole-dipole bond occur?

A

happens between permanent dipoles

note** these are not formal charges (that would be an ionic rxn)

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16
Q

H-bonding is a special kind of ??

A

dipole-dipole bonding

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17
Q

H-bonding is _____ than ordinary dipole-dipole bonding

A

stronger

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18
Q

When does H-bonding happen?

A

-happens between atoms with highly electronegative atoms attached to H

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19
Q

H-bonding plays a big role in making things more ??

A

hydrophilic (water soluble)

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20
Q

Molecules with many H-bond donors and acceptors are more ____ soluble

A

water

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21
Q

What is the H-bond donor?

A

electronegative atom with an attached hydrogen

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22
Q

What is the H-bond acceptor?

A

electronegative atom with a FREE (not tied up in resonance) lone pair of electrons

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23
Q

Are S, Cl, and F, weak or strong H-bond acceptors?

A

weak

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24
Q

SH is NOT an H-bond ____

A

donator

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25
Q

Amide N is NOT an H-bond _____

A

acceptor (lone pair on amide N cannot accept H-bonding due to resonance)

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26
Q

Why are intermolecular H-bonds between drug molecules in solution very uncommon?

A

Because H2O molecules will out compete the other drug molecules

in order to form a H-bond between drug molecules, it would first have to break the H-bonds formed with water (and this would require energy)

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27
Q

Explain how intramolecular H-bonds form in water (Note** very different than intermolecular H-bonds which we just previously deduced were very uncommon in water)

A

Bc the H-bonding pair are always super close in proximity it is easier to form H-bonds

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28
Q

What is intramolecular H-bonds forming in water known as?

A

effect of local concentration

bc it is similar to having high concentrations of each other

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29
Q

How does having too many H-bonds affect absorption?

A

those H-bonds have to be broken in order to cross the lipid membrane

**this represents the idea of having a practical limit H-bonds

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30
Q

Breaking H-bonds with water (in order to cross membranes) is _____

A

unfavorable

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31
Q

You don’t want to have too many H-bond donors and acceptors or the drug will not _____

A

absorb

32
Q

What is an ionic bond?

A

electrostatic interaction between cations and anions

33
Q

Are ionic bonds strong?

A

yeah man

34
Q

What is an ion-dipole bond?

A

electrostatic interaction between a nation/anion and a dipole

35
Q

When are ion-dipole bonds important?

A

between drugs and water

36
Q

Can covalent bonds happen between drugs and solvent?

A

NO WAY JOSE

37
Q

Where can covalent bonds be present?

A

can be part of drug receptor interactions (but this is rare)

38
Q

Why is a covalent interaction between a drug and receptor BAD?

A
  • because if the receptor is covalently attached to the drug - the receptor is not the receptor anymore
  • it is now a foreign protein that the body attacks
39
Q

What is the solubility o fa drug a function of?

A

It is a function of the lipophilic and hydrophilic groups within its STRUCTURE

40
Q

How can we determine the relative solubility of a drug?

A

-can be determined with the PARTITION COEFFICIENT

41
Q

What is the partition coefficient?

A

P = [drug in hydrophobic/lipophilic solvent (ex. octanol)]/ [drug in hydrophilic solvent (water)]

42
Q

logP = ?

A

pi (not actual pi) - different kind of pi

43
Q

What are the 2 very common functional groups that often increase water solubility?
Explain yourself

A

N and O

-they polarize the molecule and act as H-bond acceptors and donors (with an attached hydrogen)

44
Q

Ionizable groups increase ____ solubility

A

water

45
Q

Give 3 examples of groups that increase lipid solubility

A

alkyl chains
alkyl rings
aromatic groups

46
Q

Hydrophilic groups have a _____ pi value

A

negative

47
Q

Lipophilic groups have a _____ pi value

A

positive

48
Q

LogPcalc value greater than +0.5 = ?

A

lipophilic

49
Q

LogPcalc values less than +0.5 = ?

A

hydrophilic

50
Q

understand slide 21

A

ok man

51
Q

one of the most important factors effecting the ____ of drugs is the LogP

A

potency

52
Q

Explain the 3 types of ways to cross biological membranes

A
  • passive diffusion through aqueous channels
  • passive diffusion through lipid (most important mechanism of absorption across membranes)
  • facilitated transport (energy required)
53
Q

What is 1 other important thing to consider when thinking about the ways that molecules can move through biological membranes?

A

blood flow

**once a drug crosses the membrane and if the blood takes it away then it will make an equilibrium so as to drag more drug across the membrane

54
Q

Why do drugs need to be hydrophilic?

A

Dissolution:
-needs to have sufficient solubility so they dissolve out of solid dosage forms

Distribution:
-needs to have some solubility in biological fluids to transport to site of action

55
Q

Why won’t drugs that are too hydrophilic be absorbed across biological membranes?

A

-because they form too many H-bonds that need to be broken (which causes energy) in order for absorption to occur

56
Q

When _____ there is sufficient lipophilicity to cross membranes

A

unionized

57
Q

When ____ there is sufficient water solubility for dissolution and distribution

A

ionized

58
Q

About 85 % of drugs have functional groups that are ___ to some extent

A

ionized

59
Q

What is ionization controlled by?

A

pKa and external pH

60
Q

pH of blood

A

7.4

61
Q

pH of sweat/saliva

A

6

62
Q

pH of fasting stomach

A

1

63
Q

pH of fed stomach

A

3-7

64
Q

pH of fasting duodenum

A

5

65
Q

pH of fed duodenum

A

6

66
Q

pH of colon

A

7-8

67
Q

Why don’t we absorb too many drugs in the stomach?

A

due to mucous layer

68
Q

Where does a lot of absorption occur?

A

small intestine (specifically duodenum)

69
Q

When you put an acidic drug into a decreasing pH (acidic environment) it will increase the ____ form

A

unionized

70
Q

The unionized form of the drug is better at ???

A

crossing biological membranes

*remember the unionized form is more lipophilic (i.e. can cross those lipid membranes better than the ionized form which is more water soluble)

71
Q

When you put a basic drug into an increasing pH (basic environment) it will increase the ____ form

A

unionized

72
Q

addition of base or hydroxide ion will ___ pH

A

increase

73
Q

addition of acid or hydrogen ion will ___ pH

A

decrease

74
Q

unionized form of the drug ____ better

A

absorbs

75
Q

Describe interfacial tension

A

-when you put a lipophilic compound into water - you get few but stronger water-water H bonds at the non-polar/water interface

76
Q

Water molecules at the interface are more orientation ally restricted which results in a ____ of entropy (change in S)

A

decrease

Med Chem (11 decks)

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