Question

Identify the class of compound for each of the following hydrocarbon derivatives: (a) \(\mathrm{R}-\mathrm{O}-\mathrm{R}^{\prime}\) (b) \(\mathrm{R}-\mathrm{X}\) (c) \(\mathrm{Ar}-\mathrm{OH}\) (d) \(\mathrm{R}-\mathrm{NH}_{2}\)

Short answer

(a) Ether, (b) Alkyl halide, (c) Phenol, (d) Amine

Step-by-step solution

Analyze the Structure (a)

The structure (a) is represented by \(\mathrm{R}-\mathrm{O}-\mathrm{R}^{\prime}\). Here, \(\mathrm{R}\) and \(\mathrm{R}^{\prime}\) represent hydrocarbon groups. The oxygen atom is bonded to two hydrocarbon groups. This structure is characteristic of an ether, where an oxygen atom connects two alkyl or aryl groups.

Examine the Structure (b)

The structure (b) is represented by \(\mathrm{R}-\mathrm{X}\), where \(\mathrm{R}\) is a hydrocarbon group and \(\mathrm{X}\) is a halogen atom. This is the typical structure for an alkyl halide (or haloalkane), where a halogen replaces a hydrogen atom in an alkane.

Review the Structure (c)

The structure (c) is \(\mathrm{Ar}-\mathrm{OH}\). In this structure, \(\mathrm{Ar}\) represents an aromatic group bonded to an \(\mathrm{OH}\) (hydroxyl) group. This is the defining structure of a phenol, where a hydroxyl group is directly bonded to an aromatic ring.

Identify the Structure (d)

The structure (d) is \(\mathrm{R}-\mathrm{NH}_{2}\), in which \(\mathrm{R}\) represents a hydrocarbon group. The \(\mathrm{NH}_{2}\) group is an amino group attached to the hydrocarbon. This structure is characteristic of an amine, specifically a primary amine, where an amino group is attached to an alkyl chain or aryl group.

Key concepts

Hydrocarbon Derivatives

In organic chemistry, hydrocarbon derivatives are compounds formed by replacing one or more hydrogen atoms in hydrocarbons with functional groups. These functional groups determine the properties and reactivity of the resulting compound. The major types of hydrocarbon derivatives include alcohols, ethers, alkyl halides, phenols, and amines. Understanding these derivatives is essential for recognizing the vast diversity of organic compounds and predicting their behavior in chemical reactions.

In this context:

• Alcohols have an \(-\mathrm{OH}\) group bonded to a carbon atom.
• Ethers contain an \(-\mathrm{O}-\) linkage between two carbon atoms.
• Alkyl halides have a halogen atom \(\mathrm{X}\) attached to an alkyl group's carbon.
• Phenols consist of an \(-\mathrm{OH}\) group directly attached to an aromatic ring.
• Amines feature an amino group \(\mathrm{-NH}_{2}\) attached to carbon chains or rings.

Ether

Ethers are a class of organic compounds characterized by an oxygen atom connected to two alkyl or aryl groups, represented generally as \(\mathrm{R}-\mathrm{O}-\mathrm{R}^{\prime}\). This structural feature gives ethers distinct physical and chemical properties.

Some key points about ethers include:

• Ethers are generally less reactive compared to alcohols due to the absence of hydrogen bonding between molecules.
• They have lower boiling points than alcohols of similar molecular weight.
• Ethers are excellent solvents in organic reactions because they are relatively inert.
• Common examples include diethyl ether and tetrahydrofuran (THF).

Alkyl Halide

Alkyl halides, also known as haloalkanes, are a group of compounds where one or more hydrogen atoms in an alkane are replaced by halogen atoms (\(\mathrm{F, Cl, Br, or I}\)). Represented as \(\mathrm{R}-\mathrm{X}\), alkyl halides are crucial in organic synthesis and industrial applications.

Key characteristics of alkyl halides include:

• They serve as intermediates in the preparation of more complex molecules.
• The presence of the halogen atom affects the molecule's reactivity, making them effective in substitution and elimination reactions.
• Alkyl halides can be categorized based on the carbon type bonded to the halogen, such as primary, secondary, or tertiary.
• Industrial uses include solvents, refrigerants, and as starting materials for polymers.

Phenol

Phenols are compounds where a hydroxyl group \(\mathrm{-OH}\) is bonded directly to an aromatic ring, distinguishing them from alcohols. This unique structure, shown as \(\mathrm{Ar}-\mathrm{OH}\), imparts specific properties not seen in aliphatic alcohols.

Important aspects of phenols include:

• They are more acidic than regular alcohols due to resonance stabilization of the phenoxide ion, which forms upon deprotonation.
• Phenols can undergo electrophilic aromatic substitution reactions more easily due to the \(\mathrm{-OH}\) group activating the ring.
• They are commonly found in natural products and serve as key intermediates in the synthesis of dyes, plastics, and pharmaceuticals.
• Common examples include phenol itself and catechol.

Amine

Amines are organic compounds and functional groups that contain a nitrogen atom bonded to one or more alkyl or aryl groups, represented as \(\mathrm{R}-\mathrm{NH}_{2}\) for primary amines. They are structurally related to ammonia and play a vital role in the chemistry of life.

Key features of amines include:

• Amines can be classified as primary, secondary, or tertiary, based on the number of carbon-containing groups attached to the nitrogen.
• They exhibit basicity, which means they can accept a proton due to the lone pair of electrons on the nitrogen atom.
• In organic synthesis, amines are often involved in the formation of amides and imines.
• Some amines, like aniline, are used in the production of dyes and pharmaceuticals.