Question

Following is a retrosynthetic analysis for the acaracide (killing mites and ticks) and fungicide dinocap. (a) Given this analysis, propose a synthesis for dinocap from phenol and 1 -octene. (b) Is dinocap chiral? If so, which of the possible stereoisomers are formed in this synthesis?

Short answer

Question: Describe a possible synthesis of dinocap from phenol and 1-octene, and determine whether dinocap is chiral and which stereoisomers are formed. Answer: A possible synthesis of dinocap from phenol and 1-octene involves nitration of phenol to form 2,4-dinitrophenol, octylation of 2,4-dinitrophenol to form 2,4-dinitro-6-octylphenol, formation of crotonic acid from crotonyl chloride, and Fischer esterification between 2,4-dinitro-6-octylphenol and crotonic acid. Dinocap is not chiral but can form stereoisomers due to the alkene moiety (C=C), resulting in both E and Z stereoisomers being formed in this synthesis.

Step-by-step solution

Understand the synthesis of dinocap

To design a synthesis for dinocap from phenol and 1-octene, it is essential to know the structure of dinocap. Dinocap is 2,4-dinitro-6-octylphenyl crotonate. The retrosynthetic analysis will give a general strategy for synthesizing dinocap from the starting materials.

Retrosynthetic analysis of dinocap

The retrosynthetic analysis can be divided into two steps: 1. Disconnection of the ester bond (O-C bond) between the phenyl ring and the crotonyl group, which can be re-formed by a Fischer esterification reaction. 2. Disconnection of the two nitro groups and the octyl group from the phenyl ring, which can be re-introduced via aromatic electrophilic substitution reactions.

Synthesis of dinocap from phenol and 1-octene

The synthesis can be carried out in the following steps: 1. Nitration of phenol: Treat phenol with a mixture of nitric acid (HNO3) and sulfuric acid (H2SO4) to introduce the two nitro groups forming 2,4-dinitrophenol. 2. Octylation of 2,4-dinitrophenol: Treat 2,4-dinitrophenol with 1-octene and a Lewis acid catalyst (e.g., AlCl3) to form 2,4-dinitro-6-octylphenol. 3. Formation of crotonic acid: Treat crotonyl chloride with water to form crotonic acid. 4. Fischer esterification: Combine 2,4-dinitro-6-octylphenol and crotonic acid in the presence of an acid catalyst such as concentrated sulfuric acid (H2SO4) to form the desired product, dinocap.

Check for chirality and possible stereoisomers

Dinocap contains an alkene moiety (C=C), which gives rise to E/Z-isomers. In this synthesis, since there is no stereoselectivity in the steps involved, both E and Z stereoisomers of dinocap could be formed. In conclusion, the synthesis of dinocap can be achieved from phenol and 1-octene in multiple steps with retrosynthetic analysis guiding the process. Dinocap can indeed form stereoisomers, and in this synthesis, both E and Z stereoisomers can be formed.