Question

Draw the structure for each of the following phenols: (a) ortho-chlorophenol (b) meta-ethylphenol

Short answer

ortho-Chlorophenol: -OH at C1, Cl at C2; meta-Ethylphenol: -OH at C1, C2H5 at C3.

Step-by-step solution

Understanding Phenol Structure

Phenol is a benzene ring (a six-carbon ring with alternating double bonds) with a hydroxyl group (-OH) attached to one of the carbon atoms.

Identify Ortho, Meta, and Para Positions

In a benzene ring, the position relative to a substituent, such as the hydroxyl group, can be classified as ortho, meta, or para. For phenols: - Ortho refers to the adjacent position (carbon 2 or 6). - Meta refers to the position separated by one ring member (carbon 3 or 5). - Para refers to the position opposite on the ring (carbon 4).

Draw ortho-Chlorophenol

First, draw the phenol (benzene ring with the hydroxyl group, -OH, at carbon 1). Next, add the chlorine atom (Cl) to the ortho position, which is carbon 2. The structure shows Cl at C2 and -OH at C1.

Draw meta-Ethylphenol

Begin with phenol, where the hydroxyl group (-OH) is at carbon 1. Then, add an ethyl group (C2H5) to the meta position, which is carbon 3. This completes the structure with C2H5 at C3 and -OH at C1.

Key concepts

Benzene Ring

The benzene ring is at the heart of many organic compounds, including phenols. It consists of six carbon atoms arranged in a hexagonal shape, forming what is known as a cyclic structure. Importantly, benzene is known for its alternating double bonds, which can be represented by a circle within the hexagon to denote delocalized electrons. This gives benzene its unique stability and chemical properties.

In organic chemistry, the benzene ring is often depicted as a simple hexagon with a circle inside or with alternating double and single bonds. This representation highlights its resonance stability. The uniformity and symmetry of the benzene ring make it a vital framework upon which many compounds, like phenols, are built. Understanding its structure is crucial for recognizing how additional groups or substituents, such as the hydroxyl group, interact with the ring.

Hydroxyl Group

The hydroxyl group is a fundamental part of phenols. It is composed of one oxygen and one hydrogen atom, symbolized as -OH. In the context of phenols, the hydroxyl group is directly bonded to the benzene ring. This bonding imparts unique properties to phenols, differentiating them from other simple aromatic hydrocarbons.

When the hydroxyl group is attached to the benzene ring, it engages in interactions that significantly influence the chemical behavior of the compound. This linkage endows phenols with distinct acidity, due to the ability of the hydroxyl group to donate a hydrogen ion. The presence of this group can also enable hydrogen bonding, affecting the solubility and boiling points of the compound.

The positioning of the hydroxyl group is essential, as it serves as a reference point for any other substituents on the benzene ring, thereby defining the ortho, meta, and para designations used to describe their locations.

Ortho, Meta, Para Positions

The terms ortho, meta, and para are used to describe the relative positions of substituents on the benzene ring. These positions are crucial for understanding the structure of various derivatives, such as phenols.

• **Ortho Position**: Located adjacent to the reference group (such as the hydroxyl group), these are the 2 and 6 positions on the benzene ring.
• **Meta Position**: These are one carbon away from the reference point, located at the 3 and 5 positions. This set lies between—or skips over—one carbon.
• **Para Position**: Directly opposite to the reference group, the para position is at the 4th carbon.

These locators are essential for properly drawing and naming phenol derivatives. For example, in ortho-chlorophenol, the chlorine atom is placed in an adjacent ortho position, specifically at position 2, next to the hydroxyl group at position 1. Conversely, in meta-ethylphenol, the ethyl group resides in a meta position, one carbon away, at position 3. Understanding these positions allows chemists to predict the physical and chemical properties of the compounds accurately.