Question

Shown on the left is a cationic intermediate for the electrophilic addition of chlorine to the para position of phenol. Draw the resonance structure that is the major contributor. Include all nonbonding electrons.

Answer 1

Concepts and reason

Resonance structures are the Lewis structures which have the same placement of atoms but different in the arrangement of electrons. A hybrid of the contributing structures represents the real structure of the molecule and is known as resonance hybrid.

Resonance structures can be formed when the double bonds are in conjugation. It also occurs when the double bond is separated by a lone pair through a single bond. Only the electrons (pi electrons and lone pairs) will move, atoms never move. So, the number of electrons in the molecule does not change.

Fundamentals

A double headed arrow () is used to represent different resonating structures.

More stable resonating structures have negative charge on more electronegative atom.

The curved arrow shows the movement of the electron pair. Curved arrow is represented as:

The tail of the arrow begins at an electron pair and the head represents that moving of an electron pair.

More stable resonance structure is known as major contributor and the less stable resonance structures are known as minor contributors.

The resonance structures in which every atom has an octet will be more stable.

The resonance structures are as follows:

The resonance structure is as follows:

Ans:

Thus, the major resonance contributor is as follows: