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Drug Design > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

bond angles vary with?

A

size of substituent

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2
Q

what does a higher electronegativity on the oxygen atom mean?

A

the lone pair of electrons on the oxygen atom is less likely to be protonated than those on the nitrogen atom.

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3
Q

bonding molecular orbitals and antibonding molecular orbitals.

A
  • bonding molecular orbitals = less energy than parent molecular orbitals
  • antibonding molecular orbitals = more energy than parent molecular orbitals.
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4
Q

atomic orbitals combine most effectively to molecular orbitals if…

A

they have similar shape and energy

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5
Q

bond order equation

A

bond order = (electrons in bonding MO - electrons in antibonding MO)/2

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6
Q

molecular oxygen in increasing energy

A

ground state triplet, ground state singlet, excited state singlet

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7
Q

multiplicity of energy levels equation

A

M = 2S + 1

S = sum of spin values in highest occupied molecular orbital (HOMO)

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8
Q

what does the molecular orbital theory predict about oxygen?

A

molecular oxygen is a diradical

  • a molecular species with 2 electrons occupying 2 degenerate molecular orbitals.
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9
Q

what does the loss of an alcohol function mean?

A

it does not negate biological activity

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10
Q

what does the loss of an amino group mean?

A

results in loss of biological activity

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11
Q

what are alcohols with 2 or 3 hydroxyl groups known as ?

A

diols (glycols) or triols

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12
Q

what are hydrocarbons with more than 3 hydroxyl groups knows as?

A

polyols (e.g carbohydrates)

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13
Q

why are phenols much stronger acids than alcohols?

A

due to delocalisation of the negative charge on the conjugate base (phenoxide ion)

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14
Q

what properties does a more acidic phenol have?

A

good antibacterial properties

(e.g. triclosan, which is added to toothpaste and household detergents due to its antibacterial action.)

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15
Q

phenols are…

A

special alcohols and antioxidants

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16
Q

homolytic and heterolytic

A
  • homolytic = oxidation
  • heterolytic = ionisation
17
Q

what happens when the phenoxy radical preferentially tends to dimerse?

A

it terminates the radical chain reaction

18
Q

ethers properties

A
  • much less polar than parent alcohols
  • formerly used in anaesthesia (diethyl ether) before non-flammable homologues were discovered to have similar biological activity (haloethane) by reacting with nerve cell membranes.
  • ethers are liable to have potentially explosive epoxides in presence of molecular oxygen and UV light.
19
Q

cyclic ethers are known as…

A

epoxides

20
Q

why are 3 membered ring epoxides highly reactive?

A

because of torsional strain.

21
Q

what are commonly found in the structure of drug molecules?

A

ketones

22
Q

why are aldehydes less commonly found in the structure of drug molecules?

A

because of their higher reactivity towards nucleophiles

23
Q

how are aldehydes found?

A

in the open chain form of reducing sugars

24
Q

what does the high reactivity of aldehydes result in?

A

general cytotoxicity

25
Q

what is the acidity of carboxylic acids due to?

A

the efficient resonance delocalisation - of the negative charge - of the carboxylate ions.

26
Q

what affects the acidity of carboxylic acids?

A

electronic effects (inductive and resonance)

27
Q

EWG AND EDG on acidity

A
  • EWG increase acidity by charge delocalisation
  • EDG decrease acidity by charge localisation
28
Q

how does h-bonding affect acidity in salicylic acid?

A

intramolecular h-bonding contributes to the charge delocalisation of the conjugate base.

intramolecular h-bonding is not possible in aspirin

29
Q

what increases the aqueous solubility of drugs with carboxylic funtions?

A

formation of salts with alkali

30
Q

what is the aqueous solubility of drugs limited by?

A

size and lipophilicity of carboxylate ion.

31
Q

sulfur compared to oxygen

A
  • sulfur belongs to oxygen periodic group
  • shares some properties of oxygen
  • larger atomic radius
  • lower electronegativity
  • empty 3d orbitals avaliable for bonding.
32
Q

a larger sulfur atom is what?

A

better at delocalising charge than oxygen.

hence thiols (S-H) are more acidic than alcohols

33
Q

thiols on heavy metals

A
  • large binding affinity for heavy metals
  • therefore used to treat heavy metal poisoning by forming water soluble complexes which can be excreted
34
Q

what are thiols responsible for

A
  • forming -S-S - bridges by crystalline residues
  • detoxifying properties of glutathione (GSH)

Drug Design (9 decks)

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