Functional groups with basic behaviour

Question 1

What are the properties of basic functional groups (3)

Answer 1

1. Groups that can accept protons
2. Strong bases shift equilibrium to the right - large Kb small pKb
3. Weak bases (don’t have much of a tendency to form bonds with protons) shift the equilibrium to the left - small Kb large pKb

Question 2

What are the properties of amines (4)

Answer 2

1. N acts as an H bond acceptor and if R = H, then it acts as an H bond donor
2. high density of electrons on the nitrogen producing a polarity in the bond
3. No R is ammonia; one R is a primary amine followed by secondary, tertiary and quaternary ammonium salt.
4. Nitrogen is a bond acceptor which can react with water, producing an OH by-product.

Question 3

What are the properties of aromatic amines (3)

Answer 3

1. The aromatic ring is an electron-withdrawing group
2. Aromatic amines have a pKa of 4.6, aromatic amines without the double bonds have a pKa of 10.6
3. The lone pair is delocalised on the aromatic ring giving rise to resonance.

Question 4

What are other basic functions (8)

Answer 4

Question 5

What is the significance of acids/bases in drugs (3)

Answer 5

1. When an acidic or a basic structure is present on a drug, only the non-ionised form crosses membranes
2. Ka = [A-][H+]/[HA]
3. pKa = log [HA]/[A-] + pH

Question 6

What is water solubiity pivitol for (4)

Answer 6

1. the efficacy of a drug cruicially depends on its water solubility:

Water solubility is pivitol for:

1. drug formulation (e.g. preparing drug solutions)
2. distrubution (e.g. the drug is transported by the blood)
3. the formation of ammonium salts is advantageous too