Question

Phenol is the starting material for the synthesis of \(2,3,4,5,6\)-pentachlorophenol, known alternatively as pentachlorophenol, or more simply as penta. At one time, penta was widely used as a wood preservative for decks, siding, and outdoor wood furniture. Draw the structural formula for pentachlorophenol and describe its synthesis from phenol.

Short answer

Answer: The structural formula for pentachlorophenol is a benzene ring with a hydroxyl group (-OH) and five chlorine atoms (Cl) at positions 2, 3, 4, 5, and 6. It can be synthesized from phenol through a reaction with chlorine gas in the presence of a catalyst, such as aluminum chloride or ferric chloride, which leads to the substitution of five hydrogen atoms on the benzene ring with five chlorine atoms. The reaction is as follows: C6H5OH + 5 Cl2 -> C6HCl5OH + 5 HCl.

Step-by-step solution

Understand the structure of phenol

Phenol is an aromatic compound with the chemical formula C6H5OH. The molecule consists of a benzene ring with a hydroxyl group (-OH) attached to one of the carbon atoms. It is important to understand its structure in order to describe the synthesis of pentachlorophenol.

Identify the chlorinating agents

To synthesize pentachlorophenol from phenol, we need to add chlorine atoms to the phenol molecule. Chlorine reacts with phenol to form chlorophenols in the presence of a catalyst, such as aluminum chloride or ferric chloride. Therefore, we will use a chlorinating agent, such as chlorine gas (Cl2) or a compound containing chlorine atoms, to synthesize pentachlorophenol.

Synthesize pentachlorophenol

Phenol reacts with chlorine gas to form a series of products with different numbers of chlorine atoms attached to the benzene ring. To synthesize pentachlorophenol specifically, we need to control the reaction conditions to obtain a product with five chlorine atoms. The reaction is as follows: C6H5OH + 5 Cl2 -> C6HCl5OH + 5 HCl Phenol reacts with chlorine gas in the presence of a catalyst (such as aluminum chloride or ferric chloride), resulting in the substitution of five hydrogen atoms on the benzene ring with five chlorine atoms. The five chlorine atoms are added to the 2, 3, 4, 5, and 6 positions on the phenol molecule.

Draw the structural formula for pentachlorophenol

Having synthesized pentachlorophenol from phenol, we can now draw its structural formula. The molecule consists of a benzene ring with a hydroxyl group (-OH) and five chlorine atoms (Cl) at positions 2, 3, 4, 5, and 6. The structural formula for pentachlorophenol is as follows: Cl | Cl — C — C — Cl | | _ | Cl Remember that the double bonds in the benzene ring alternate in resonance structures, so the above drawing is just one way to represent pentachlorophenol.