Q.65. Question: Hydrocarbons like benz... [FREE SOLUTION]

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Chapter 4: Q.65. (page 128)

Question: Hydrocarbons like benzene are metabolized in the body to arene oxides, which rearrange to form phenols. This is an example of a general process in the body, in which an unwanted compound (benzene) is converted to a more water-soluble derivative called a metabolite, so that it can be excreted more readily from the body.
a. Classify each of these reactions as oxidation, reduction, or neither.
b. Explain why phenol is more water soluble than benzene. This means that phenol dissolves in urine, which is largely water, to a greater extent than benzene.

Short Answer

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Answer

The conversion of benzene to arene oxide is an oxidation reaction. The conversion of arene oxide to phenol is neither a reduction reaction nor an oxidation reaction.
Phenol is more soluble in water because it is a polar compound with an O-H bond that binds with the molecules of water.

Step by step solution

Oxidation reactions

Oxidation reactions are characterized either by the gain of an electronegative element or the loss of an electropositive element.

Reduction reactions

Reduction reactions are characterized either by the gain of an electropositive element or the loss of an electronegative element.

Solubility

Like dissolves like;polar solvents dissolve only polar compounds into them. In contrast, non-polar solvents dissolve only non-polar compounds.

For example, water (polar solvent) dissolves ethanol, salts, some bases, and acids. On the contrary, benzene (non-polar solvent) can dissolve only non-polar substances such as some ketones, ethers, and substituted benzene compounds.

Types of reaction in the given compounds

a. In the reaction of benzene to form arene oxide in step [1], two C-O bonds are added to the benzene ring. Hence, benzene is said to be oxidized.

In the reaction of arene oxide to form phenol in step [2], a C-O bond and a C-H bond are broken. Hence, this reaction is neither reduction nor oxidation.

Types of Reactions

b. Phenol is a polar compound with an O-H bond. These O-H groups bind with the water molecules. Hence, phenol is more soluble in water, a polar solvent, than in benzene, which is a non-polar solvent.