L4 - The role of oxygen and sulphur in drug molecules

what happens to the lone pair of electrons on oxygen atoms due to the higher electronegativity

its less likely to be protonated that those on a nitrogen atom

oxygen an its orbital hybrids

how can biological activity be lost

with the loss of an amino group

does a loss of alcohol function negate biological activity

no

why does a loss of alcohol function not negate biological activity whereas the loss of an amino group does result in loss of biological activity

a loss of alchol means that the molecule might still be active even thoguh it is weaker, yet a loss of amino group abolishes biological activity beccause it destroys key binding interactions

oh groups are polar and can form hydrogen bonds and bond to water and protiens, but its not essensial for binding to a receptor or enzyme. even if lost, it could still fit in using van der waals or hydrophobic forces, while amino groups are ONLY required for biological activity as they are key essensial pharmacophores.

why are ethers less polar than alcohols

no hydrogen bond doner

what are cyclic ethers known as 

epoxides

why are 3 memebered ring epoxides highly reactive

due to torsional strain

why are aldehydes less commonlyly found in drug molecules

due to their higher reactivity towards nucleophiles

why are carboxylic acids so acidic

due to the effecient resonance of the negative charge of the carboxylate anions

how can electronic effects affect the acidity of carboxylic acids

electron withdrawing groups increase acidity by charge delocalisation

electron donating groups decrease acidicity by charge localisation

how can hydrogen bonding affect acidicity

hydrogen bonding contributes to the charge delocalisation of the conjugate base of salicliyic acid.

what can increase the aqeous solubility of drugs with carboxylic functions

formation of salts with alkali, its limited by the size and lipophilicity of thte carboxylate anion

why are thiols more acidic than alcohols

the larger sulphur atom is better at delocalising charge than oxygen

how do thiols form -s-s- bridges

by cysteine residues