If present in a molecule, which atom is least likely to participate in hydrogen bonds with water?

Hydrogen bonding occurs when the hydrogen atom in a molecule is bonded to an electronegative atom. The electronegativity of the atom attracts the electrons present in the bond to move toward it, creating a partial negative charge. Consequently, the hydrogen atom is left with a partial positive charge. These charges cause the molecules to be attracted to one another.

An example of a molecule where hydrogen bonding will not occur will be one where the hydrogen is not bonded to an electronegative atom, such as CH₃Cl (hydrogen bonded to carbon which is not electronegative)