Question

what is proportion of attractive force in dipole-dipole? ​

Answer 1

Answer:

Dipole-Dipole interactions occur between polar molecules.  In section 8.8 we learned that polar covalent bonds occur between atoms of different electronegativity (section 8.7), where the more electronegative atom attracts the electrons more than the electropositive atom, and base on the geometry, this may or may not result in a polar molecule.  If the center of positive charge (defined by the nuclei) does not coincide with the center of negative charge (defined by the electron orbitals), the molecule is polar, which is easiest to visualize for nonsymmetric orientations of bonds between atoms of different electronegativities.  That is, a polar molecule with a permanent dipole results if all the bond dipole vectors add to a net dipole.  In this case the molecule's center of positive charge (denoted by δ+) does not coincide with the center of negative charge (denoted by δ-) and the molecular dipole moment (μ

μ

) is this partial charge times the distance between them.  Please review sections 8.7 and 8.8  if needed, and remember that if bond dipoles are of symmetric orientation, like in the linear carbon dioxide, they cancel each other and the molecule is non-polar.  So polar bonds can result in non-polar molecules!  You should also note that the center of positive charge need not be where there is a nucleus.  For example, in water, the center of positive charge is half way between the two hydrogens.

clipboard_e1b55adb90bcd2389bdf57afa6e62c5be.png

Figure 11.3.1

11.3.

1

:  Water's dipole moment has a positive center between the two nuclei of the hydrogens.

Although molecules in a liquid are in constant motion, they tend to align in the lowest energy orientation, which would be to maximize attractions (parts a & b of fig. 11.3.1) and minimize repulsion (parts c & d of fig. 11.3.1). This follows the same logic we used for ion-dipole interactions, in that the attractive interactions cause dipoles of opposite charge to be closer, resulting in stronger interactions, while dipoles of like charge tend to be farther apart, resulting in reduced interactions.  Therefore, unlike ion-ion interactions, but like ion-dipole interactions, dipole-dipole are always attractive.

Explanation: