How do you know if a molecular compound has a dipole-dipole attraction?

Answer 1

A dipole moment is defined as a measure of the molecular polarity of a compound; the magnitude of the partial charges on the ends of a molecule times the distance between them (in meters). In order for there to be a dipole moment the element must must have molecular polarity which results from molecules with a net imbalance of charge (often a result of differences in electronegativity). If the molecule has more than two atoms, both shape and bond polarity determines the molecular polarity. In general look for a difference in electronegativity of the elements of a molecule which results in polarity and thus a possible dipole moment. Note that molecular shape influence polarity so molecules with the same elements but a different shape (and vice versa) won't have the same dipole moment.

Answer 2

A molecular compound has dipole-dipole attractions if it contains polar covalent bonds (unequal sharing of electrons) and asymmetrical molecular geometry resulting in an unequal distribution of charge. An easy way to assess this is by looking at the electronegativity difference between the atoms in the molecule – if it is significant, the compound likely exhibits dipole-dipole attractions.