Question

What is the feature found in all ortho-para directing groups?
A. An oxygen is directly attached to the aromatic ring
B. The atom attached to the aromatic ring possess un unshared pair of electrons
C. The group has the ability to delocalize the positive charge of the arenium ions
D. The atom directly attached to the aromatic ring is more electromagnetic than carbon

Answer 1

Hint: We need to first understand what ortho-para directing groups are and find the common feature found in all such groups. When handled with an electrophile, a monosubstituted benzene can undergo three electrophilic aromatic substitution processes. The organic result of each reaction is a disubstituted benzene, which may be recognised using the descriptors ortho, meta, and para.

Complete answer:
If the ortho and para products have greater relative yields than the meta product, the substituent on the benzene ring in the monosubstituted benzene is referred to as an ortho, para directing group. If the inverse is seen, the substituent is referred to as a meta directing group. Electron-donating groups are ortho and para directing groups, whereas electron-drawing groups are meta directing groups. The exception is halide ions, which are electron-withdrawing but ortho, para directing. Some of the common ortho-para directing groups are: -OR (where R=H, alkyl, aryl or acyl), -NR2 (where R=H, alkyl, aryl or acyl or any combination thereof), -R (R=alkyl, aryl), etc.
The ortho-para directing group enhances electron density within the ring, therefore stabilising the arenium ion by positive charge delocalization.

So, the correct answer is “Option C”.

Note:
Note that substituents that produce the above outcome are referred to as "ortho-, para-directors." Hydroxyl groups, ethers, amines, alkyl groups, thiols, and halogens are examples of ortho- and para- directors. If you go over the list of ortho- and para-directors, you'll see that many of them also lead activating groups. In comparison to hydrogen, activating groups accelerate the rate of electrophilic aromatic substitution.