posted by Anonymous .
Regarding "hydrogen" bonding
How come the compounds CH2O and CH3OCH3 do not exhibit hydrogen bonding, as opposed to compounds like CH3CH2OH and CH3NH2?
It's indicated in my solutions manual that the two compounds that don't exhibit hydrogen bonding can be H-bond acceptors, not donors. I'm not quite sure what this means...
Frankly I don't know what it means either, especially since HCOOH (is that what you meant by CH2O?) does have hydrogen bonding. Compounds like CH3CH2OH and CH3NH2 have highly electronegative O or N attached to H atoms which makes the N or O slightly - and H slightly + and that's how they H bond. It works the same way with HCOOH. With ethers, however, such as CH3OCH3, the O atom is there but there is no slightly + H atom anywhere to be found. CH3OCH3 isn't highly polar as are the amine, alcohol, and acid.
in order for the hydrogen bond to form in a molecule, the molecule must have an hydrogen atom attached to either oxygen, nitrogen or fluorine. so, the oxygen in C=O bond is not attached to hydrogen and so can't form hydrogen bond.