Is chloroform, \(\mathrm{CHCl}_{3}\), a polar molecule? If it is, draw the dipole moment vector for the entire molecule and show where the \(\delta+\) and \(\delta-\) regions of the molecule are.

Chloroform has the molecular formula CHCl3. It consists of a central carbon atom bonded to one hydrogen atom and three chlorine atoms. The central carbon atom has four single bonds according to its tetravalent (valency 4) nature, yielding a total of eight valence electrons around it. This results in a tetrahedral molecular geometry, with bond angles approximately 109.5 degrees between the bonded pairs.

In order to determine if chloroform is polar, we need to check the polarities of its individual C-H and C-Cl bonds. Bond polarity depends on the difference in electronegativity between the two bonded atoms. In chloroform, the electronegativity difference between carbon and hydrogen is ΔEN = 2.5 - 2.2 = 0.3, which is quite small. Therefore, the C-H bond can be considered as nonpolar. However, the electronegativity difference between carbon and chlorine is ΔEN = 3.2 - 2.5 = 0.7, which is significant, making the C-Cl bonds polar.

Since the C-Cl bonds are polar, it means that there is an uneven distribution of electron density around the carbon atom, with the electron density being higher around the chlorine atoms. This results in the formation of δ- regions near chlorine atoms and a δ+ region near the central carbon atom. The tetrahedral geometry of chloroform causes the three C-Cl bonds to have their dipole moments pointing towards chlorine atoms, and since these dipole moments don't cancel out, there is a net dipole moment for the entire molecule. Therefore, chloroform (CHCl3) is a polar molecule.

The net dipole moment of chloroform can be represented by a vector, originating from the central carbon atom (δ+ region) and pointing towards the direction of electron density, i.e., towards the average position of the three chlorine atoms (the δ- region). Below is an illustration of the chloroform molecule, indicating the δ+ and δ- regions and the dipole moment vector: [img src=https://www.uwoprovidence.org/style/image/chloroform-polarity.png style="max-width:100%;" /] In summary, chloroform (CHCl3) is a polar molecule due to its tetrahedral geometry and the presence of polar C-Cl bonds. The dipole moment vector starts from the central carbon atom (δ+) and points towards the average position of the chlorine atoms (δ-).