Which of the following compounds experience the strongest dipole-dipole attractions?
a) CF4
b) CCl4
c) CF2Cl2
Neither CCl4 nor CF4 are dipoles.
To determine which of the compounds experience the strongest dipole-dipole attractions, we need to consider the polarity of each compound.
Dipole-dipole attractions occur between molecules that have polar bonds. A polar bond forms when there is an unequal sharing of electrons between atoms, resulting in a partial positive charge on one end of the bond and a partial negative charge on the other end. This creates regions of positive and negative charge within a molecule, known as dipoles.
For a molecule to have a dipole-dipole attraction, it must have a net molecular dipole. In other words, the overall molecule must have an asymmetrical distribution of its partial positive and negative charges.
Now let's analyze each compound:
a) CF4: Carbon tetrafluoride (CF4) has a symmetrical tetrahedral molecular geometry, with a central carbon atom bonded to four fluorine atoms. Since the fluorine atoms are all the same and have similar electronegativities, the polarities of the bonds cancel each other out, resulting in a molecule with no net dipole. Therefore, CF4 does not experience dipole-dipole attractions.
b) CCl4: Carbon tetrachloride (CCl4) also has a symmetrical tetrahedral molecular geometry, with a central carbon atom bonded to four chlorine atoms. Similar to CF4, the polarities of the bonds cancel each other out, resulting in a nonpolar molecule. Therefore, CCl4 does not experience dipole-dipole attractions.
c) CF2Cl2: Dichlorodifluoromethane (CF2Cl2) has a tetrahedral molecular geometry, with a central carbon atom bonded to two chlorine atoms and two fluorine atoms. The polarities of the bonds do not cancel each other out, resulting in a molecule with a net dipole. The chlorines are more electronegative than the fluorines, so the molecule has a partial negative charge near the chlorines and a partial positive charge near the fluorines. Therefore, CF2Cl2 experiences dipole-dipole attractions.
In summary, out of the given compounds, CF2Cl2 (option c) experiences the strongest dipole-dipole attractions, while CF4 (option a) and CCl4 (option b) do not have dipole-dipole attractions.