Which of the following molecules would you expect to have a molecular dipole moment? A. CH3OH B. CCl4. Explain.
A. A the simplest alcohol, known as methanol, and is of high industrial and everyday life use. We start by drawing the Lewis structure for this organic compound (not sure how to draw here, so I will skip this for now). By drawing the Lewis structure and by checking the electronegativity difference of the covalent bonds found in methanol we see that all C-H will experience very low dipole moments, two of which will even cancel out, but the C-O-H bond will experience stronger dipole moments as both C-O and O-H high high enough electronegativity difference. O is more electronegative than either C or H and so there will be two dipole moments both pointing towards oxygen. However, because the electronegativity difference between O-H is higher than that of C-O the molecular dipole moment will be pointing towards C-O (with a diagram this will be clearer). Overall this molecule will experience a molecular dipole moment. B. Using the sample principle, we will notice here that even though the electronegativity difference between C and Cl here is high enough, there is perfect symmetry in the molecule and given its geometry the dipole moment vector will cancel out and the dipole moments will cancel out overall. Therefore this molecule will not experience a molecular dipole moment.