Answer to Question #61904 in General Chemistry for Iris

Question

How come that the oxygen on a ketone group can have two hydrogen bonds while an ester group with two oxygen will also have two hydrogen bonds? Wouldnt it be four hydrogen bonds since there are two oxygen atoms?

Answer 1

Contrary to ketone, ester group has only one similar oxygen containing group C=O and the other is -O-R which is actually blocked with some radical -R. Thus, it is sterically impossible to bond both of them and only C=O is suitable for hydrogen bonding.