Question

In benzyne, the triple bond consists of
A. One sp-sp sigma bond and two p-p pi bond
B. two sp-sp sigma bond and one p-p pi bond
C. One $s{{p}^{2}}-s{{p}^{2}}$ sigma bond and two p-p pi bond
D. One $s{{p}^{2}}-s{{p}^{2}}$ sigma bond, one $s{{p}^{2}}-s{{p}^{2}}$ pi bond and one p-p pi bond

Answer 1

Benzyne is a reaction intermediate. Benzyne is also known as 1,2-dehydrobenzeile of an aryne. It is a neutral and highly reactive reaction intermediate.

Complete step by step solution:
Benzyne is a neutral intermediate in which the aromatic character is not markedly distributed as it is distributed in benzene. It is formed as an intermediate during the reaction of nucleophilic substitution of the aromatic compounds. Benzyne contains a carbon - carbon triple bond in the benzene ring and involves the formation of new weaker carbon - carbon bond by the sideways overlapping of the $s{{p}^{2}}$ hybridized orbitals of the two adjacent carbon atoms. Hence in benzyne there are one $s{{p}^{2}}-s{{p}^{2}}$ sigma bond, one $s{{p}^{2}}-s{{p}^{2}}$ pi bond and one p-p pi bond

Hence the correct answer is option (D) i.e. in benzyne, the triple bond consists of one $s{{p}^{2}}-s{{p}^{2}}$ sigma bond, one $s{{p}^{2}}-s{{p}^{2}}$ pi bond and one p-p pi bond.

Additional information:
Benzyne is produced by the reaction of de halogenation of 2-bromofluorobenzene in the presence of magnesium. The anthranilic acid can be converted into the 2-diaminobenzene-1-carboxylate by the reaction of diazotization and neutralization. Zwitter ionic which is an explosive is a convenient and inexpensive precursor to benzyne.

Note: Benzynes are highly reactive species due to the presence of the triple bond. Triple bond in alkynes usually is the reason behind the linear geometry to facilitate the orbital overlap. However in benzyne the p orbitals present will be distorted to accommodate the triple bond within the ring system which reduces their effective overlapping.