Question

Supply a name or structural formula for each of the following. (a) \(p\) -phenylphenol (b) 3 -hydroxy- 4 -isopropyltoluene (thymol- -flavor constituent of the herb thyme)

Short answer

The structural formula for \(p\)-phenylphenol is a benzene ring with a \(OH\) group attached and another benzene ring attached across from it. The structural formula for 3 -hydroxy- 4 -isopropyltoluene is a benzene ring with a methyl group, hydroxyl group and an isopropyl group attached at 1st, 3rd and 4th carbon atoms respectively of the benzene ring

Step-by-step solution

Analyzing \(p\)-phenylphenol

The \(p\) in \(p\)-phenylphenol refers to para position. So it indicates the position of the phenyl substituent group. A phenol is a compound with a hydroxyl \(OH\) group attached to a benzene ring. A \(p\)-phenylphenol therefore, is a phenol with another phenyl (benzene ring) group attached to it in the para position.

Drawing the structure for \(p\)-phenylphenol

Start with a standard phenol, which is a benzene ring with a single \(OH\) group attached. Then add an additional benzene ring (the phenyl group here) directly across from the \(OH\) group. This is the structure of \(p\)-phenylphenol.

Analyzing 3 -hydroxy- 4 -isopropyltoluene

Toluene is a benzene ring with a single methyl \(CH_3\) group attached to it. This compound is a derivative of toluene where: '-hydroxy-' signifies a \(OH\) group and '-isopropyl-' signifies a \(CH(CH_3)_2\) group.

Drawing 3 -hydroxy- 4 -isopropyltoluene

Draw a benzene ring with a methyl group attached, this forms the basic toluene structure. Substitutive numbering begins from here as position 1. Add a hydroxyl group to the third carbon atom and an isopropyl group to the fourth carbon atom on the benzene ring. Thus, we have the structure of 3-hydroxy-4-isopropyltoluene.

Key concepts

Phenyl Group

Understanding organic chemistry involves getting to know various functional groups and structural features that are part of larger molecules. One such important feature is the phenyl group. A phenyl group consists of a benzene ring that is missing a hydrogen atom, which allows it to attach to another atom or molecule.

Think of the phenyl group as a hexagonal ring, symbolizing a benzene molecule with alternating double and single bonds, from which one hydrogen has been removed. This gives the phenyl group the formula C₆H₅. It is a common substituent in organic chemistry and can impact the chemical behavior of the molecule it’s a part of. For example, in the exercise given, a molecule of phenol becomes p-phenylphenol when a phenyl group is attached to the para position, that is, directly across from the existing hydroxyl group on the phenol's benzene ring.

Substitutive Nomenclature

When it comes to naming organic compounds, substitutive nomenclature is a set of rules set out by IUPAC (International Union of Pure and Applied Chemistry) that we apply systematically. This method is based on identifying the longest continuous carbon chain as the parent structure and naming the various substituents as prefixes to this.

The location of the substituents is indicated by numbers, with the chain numbered in such a way to give the substituents the lowest possible numbers. For instance, when referring to 3-hydroxy-4-isopropyltoluene, 'toluene' sets the base structure, while '3-hydroxy' and '4-isopropyl' describe the hydroxyl and isopropyl groups at the third and fourth positions, respectively. It's important to use these numbers to avoid ambiguity and ensure that anyone reading the compound name can draw its exact structure.

Benzene Ring Derivatives

The benzene ring is not just a fundamental structure in organic chemistry; it's also the parent compound for an immense variety of derivatives, known as benzene ring derivatives. These derivatives are formed by replacing one or more hydrogen atoms on the benzene ring with different atoms or groups of atoms, known as substituents.

Substituents can vary widely, from simple ones like a hydroxyl group (-OH) or a methyl group (-CH₃), to more complex ones like isopropyl (-CH(CH₃)₂). The way these substituents are attached to the benzene ring defines the derivative's physical and chemical properties. For example, thymol, mentioned in the exercise, is a benzene ring derivative where the methyl group of toluene is further substituted with hydroxyl and isopropyl groups at specific positions, contributing to its unique flavor and smell characteristics used in the herb thyme.