Physicochemical Properties 2 Flashcards
what happens to the pKa of acetic acids when you replace the H with F?
the pa reduces hence molecule becomes more acidic.
what is the difference b/w LogP and LogD?
LogP is the partition coefficient of non-ionised drugs.
LogD is the partition coefficient for ionised drugs at a specific pH.
A higher value = a higher lipophilicity
what are the various ways to investigate molecular size?
- electron density
- molecular weight
- polar surface area
- van der waals surface
- molar reactivity
what is the hammett substituent constant?
a measure of the electron withdrawing/donating influence of substituents
how do you workout the hammet substituent constant?
log (dissociation constant of substituent divided by dissociation constant of hydrogen)
with an electron withdrawing group, which has the higher dissociation constant, H or the substituent?
the substituent
with an electron donating group, which has the higher dissociation constant, H or the substituent?
H
what type of substitution takes place from electron-withdrawing due to an inductive effect only?
meta-substitution
what type of substitution takes place from electron-withdrawing due to an inductive and resonance effects?
para-substitution
what type of substitution takes place from electron-donating due to resonance and inductive effect?
para-substitution
need to check this!!!
how do you measure the aliphatic electronic effect?
by measuring the rates of hydrolysis of aliphatic esters
What effect do electron donating substituents have on the rate of hydrolysis of aliphatic esters?
reduces the hydrolysis rate
What effect do electron withdrawing substituents have on the rate of hydrolysis of aliphatic esters?
increase the rate of hydrolysis
what is molecular polar surface area?
the surface sum of all polar atoms present in the molecule.
What effect do rotatable bonds have on oral bioavailability of a drug?
rotatable bonds reduce oral bioavailability as they increase flexibility of the drug.
