Question

Supply a name or structural formula for each of the following. (a) phenylacetylene (b) $m$ -dichlorobenzene

Short answer

The chemical structure of Phenylacetylene is represented as $C_6{H}_5-C\equiv CH$. The 'm' in m-Dichlorobenzene stands for meta, meaning the two chlorine atoms are adjacent to each other on the benzene ring, hence it's represented as $C_6{H}_{4}C{l}_2$ with the two chlorines at the 1 and 3 positions.

Step-by-step solution

Naming Phenylacetylene

Phenylacetylene is an organic compound that consists of a phenyl group ($C_6{H}_5$), attached to an acetylene ($C_{2}H$) group. The phenyl group is a six-membered aromatic ring, while the acetylene unit consists of a carbon-carbon triple bond. This bond occurs between the phenyl group and one of the carbon atoms of the acetylene.

Structural Formula for Phenylacetylene

Start by drawing a six-membered ring for the phenyl group and represent each carbon atom in the ring. Then, draw a carbon-carbon triple bond attached to the ring, representing the acetylene group. The structure should look like this: $$C_6{H}_5-C\equiv CH$$. The line connecting the ring and the acetylene group indicates a bond.

Naming m-Dichlorobenzene

m-Dichlorobenzene denotes a type of dichlorobenzene where the two chlorine atoms are adjacent to each other on the benzene ring. 'm' stands for meta, which in the context of organic chemistry, signifies that the two chlorines are placed at the 1 and 3 positions on the phenyl group.

Structural Formula for m-Dichlorobenzene

To draw the structure, start with a six-membered phenyl ring. Afterward, the two chlorine atoms should be placed in the 1 and 3 positions on the ring, because 'm' stands for 'meta', suggesting they are adjacent. The structure should look like this: $$C_6{H}_{4}C{l}_2$$, with the two chlorines at the 1 and 3 positions.

Key concepts

Organic Compounds

Organic compounds are fundamental to life and make up the bulk of the molecules in our bodies and the environment. They are primarily composed of carbon atoms, often linked in chains or rings, and are commonly bonded with hydrogen, oxygen, nitrogen, and other elements. A key feature of organic compounds is the variety in their structures, which leads to a vast diversity of properties and functions.

In our context, phenylacetylene is a prime example of an organic compound. It includes a phenyl group, which is an aromatic ring, bonded to an acetylene unit characterized by a carbon-carbon triple bond. These varied structural components give organic compounds their unique characteristics and behaviors, making the study of organic chemistry crucial for fields like medicine, biology, and materials science.

To better understand organic compounds, it's essential to familiarize oneself with the types of bonds and groups they consist of, such as:

• Aromatic rings like the phenyl group ($C_6{H}_5$).
• Triple bonds as seen in acetylene ($C\equiv C$).
• Functional groups that change the compound's properties depending on how they are arranged.

Structural Formulas

The structural formula of a compound provides detailed insight into its molecular structure, showing how atoms are arranged and connected. This is crucial for understanding the chemical properties and reactions that the compound can undergo.

For instance, in the case of phenylacetylene, the structural formula is drawn with a six-membered aromatic ring for the phenyl group, with a carbon-carbon triple bond extending outwards, representing the acetylene group. This can be visually represented as $$C_6{H}_5-C\equiv CH$$. Understanding these formulas helps in predicting the behavior of the molecule under different conditions.

Additionally, m-dichlorobenzene's structural formula is illustrated by placing two chlorine atoms on the 1 and 3 positions of a benzene ring, signifying a 'meta' positioning, resulting in the formula $$C_6{H}_{4}C{l}_2$$. Structural formulas are valuable as they allow chemists to easily envision:

• The spatial arrangement of atoms.
• The connectivity among different atoms and functional groups.
• Potential sites for chemical reactions or interactions.

Aromatic Compounds

Aromatic compounds are a special class of organic compounds known for their stability and distinct ring structures. They typically consist of one or more conjugated rings that maintain delocalized electrons, a concept most easily visualized in the benzene ring, which is emblematic of aromatic compounds.

Benzene, a simple aromatic compound, serves as the building block for complex structures like phenylacetylene and m-dichlorobenzene. In these compounds, the aromatic ring contributes to the molecule's overall stability and unique chemical properties.

The features that typically define aromatic compounds include:

• Stable ring structures often depicted as alternating single and double bonds, although the electrons are actually delocalized over the ring.
• High resonance energy due to this electron delocalization, rendering them less reactive than typical alkenes.
• A tendency to undergo substitution reactions rather than addition reactions, preserving the aromatic ring.

By learning about aromatic compounds, students can gain insights into the complex interactions and transformations that can occur within these stable structures.