Question

Analyze the polarity of each bond in the following organic compound. Which bond, other than the C-C bond, is the least polar in the molecule? C=O C-Cl C-H Which carbon atom has the most partial positive character? the left C the right C no difference

Answer 1

Concepts and reason

If the electronegativity of the two bonded atoms are different then the bond is polar. As the difference in electronegativity of the two bonded atoms increases, the polarity of the bond increases.

Fundamentals

If one atom is highly electronegative than the other atom in the bond, then the highly electronegative atom attracts the bonded pair of electrons more than its share. Hence, partial negative charge is developed on the highly electronegative atom and partial positive charge is developed on the less electronegative atom.

Part a

The structure of the compound is as follows:

Calculate the electronegativity difference as follows:

$\begin{array}{l}\\{\rm{The}}\,\,{\rm{electronegativity}}\,\,{\rm{difference}}\,\,{\rm{between}}\,\,{\rm{C}}\,\,{\rm{and}}\,\,{\rm{O}}\,\,{\rm{in}}\,\,{\rm{C}}\,{\rm{ = }}\,{\rm{O}}\,\,{\rm{bond}}\,\,{\rm{:}}\,\,\,{\rm{3}}{\rm{.5}} - 2.5\,\, = \,\,1.0\\\\{\rm{The}}\,\,{\rm{electronegativity}}\,\,{\rm{difference}}\,\,{\rm{between}}\,\,{\rm{C}}\,\,{\rm{and}}\,\,{\rm{Cl}}\,\,{\rm{in}}\,\,{\rm{C}}\, - \,{\rm{Cl}}\,\,{\rm{bond}}\,\,{\rm{:}}\,\,\,{\rm{3}}{\rm{.0}} - 2.5\,\, = \,\,0.5\\\\{\rm{The}}\,\,{\rm{electronegativity}}\,\,{\rm{difference}}\,\,{\rm{between}}\,\,{\rm{C}}\,\,{\rm{and}}\,\,{\rm{H}}\,\,{\rm{in}}\,\,{\rm{C}}\, - \,{\rm{H}}\,\,{\rm{bond}}\,\,{\rm{:}}\,\,\,2.5 - 2.1\,\, = \,\,0.4\\\end{array}$

The electronegativity difference is low for ${\rm{C}}\, - \,{\rm{H}}\,\,{\rm{bond}}$ . Hence, the least polar bond is ${\rm{C}}\, - \,{\rm{H}}\,\,{\rm{bond}}$ .

Part b

The carbon atom which has the most positive character is as follows:

As the right carbon is attached to two highly electronegative atoms, the right C has the most partial positive character.

Ans: Part a

The least polar bond is ${\rm{C}}\, - \,{\rm{H}}\,\,{\rm{bond}}$ .

Part b

The right C has the most partial positive character.