A hydrogen bond occurs in a molecule when hydrogen is covalently bonded to a highly electronegative atom.
That means that if we are looking for a compound in which there is no hydrogen bonding, we are actually looking for the compound in which hydrogen is not directly linked to an electronegative atom.
If we look at the options carefully, the compound that has such characteristic is only (CH3)2N(CH2) which is a tertiary amine. The nitrogen is directly linked to three alkyl groups and no hydrogen atom hence the molecule does not exhibit hydrogen bonding.
because B is wrong as it doesn't have the same mass number. C is wrong as it has different number of neutrons. D is wrong as it has more neutrons than protons.
