Question

Draw a structural formula for each of the following aromatic or substituted aromatic compounds. a. naphthalene b. 2 -bromophenol c. 3 -methylstyrene d. 4 -nitrochlorobenzene e. 1,3 -dinitrobenzene

Short answer

The structural formulas for the given aromatic compounds are as follows: a. Naphthalene: Two benzene rings fused together with alternating double bonds. b. 2-Bromophenol: A benzene ring with a bromine atom at the second carbon atom and a hydroxyl group (-OH) at the first carbon atom. c. 3-Methylstyrene: A benzene ring with a vinyl group (CH=CH2) at the first carbon atom and a methyl group (CH3) at the third carbon atom. d. 4-Nitrochlorobenzene: A benzene ring with a nitro group (-NO2) at the first carbon atom and a chlorine atom (Cl) at the fourth carbon atom. e. 1,3-Dinitrobenzene: A benzene ring with two nitro groups (-NO2) at positions 1 and 3.

Step-by-step solution

a. Naphthalene

Naphthalene is a polycyclic aromatic hydrocarbon containing two benzene rings fused together. To draw its structural formula, follow the steps: 1. Draw two benzene rings in a hexagonal shape and connect them by sharing two adjacent carbon atoms. 2. Arrange double bonds in an alternating pattern in both rings. 3. Add hydrogen atoms to each carbon atom, ensuring each carbon has a total of four bonds. No need to draw hydrogen if it complicates the structure.

b. 2-Bromophenol

2-Bromophenol is an aromatic compound in which a bromine atom and a hydroxyl group (-OH) are attached to a benzene ring at positions 2 and 1, respectively. To draw its structural formula, follow the steps: 1. Draw a benzene ring in a hexagonal shape with alternating double bonds. 2. Attach a bromine atom (Br) to the second carbon atom in the ring. 3. Attach a hydroxyl group (-OH) to the first carbon atom in the ring.

c. 3-Methylstyrene

3-Methylstyrene is an aromatic compound containing a benzene ring, a vinyl group (CH=CH2) at position 1, and a methyl group (CH3) at position 3. To draw its structural formula, follow the steps: 1. Draw a benzene ring in a hexagonal shape with alternating double bonds. 2. Attach a vinyl group (CH=CH2) to the first carbon atom in the ring. 3. Attach a methyl group (CH3) to the third carbon atom in the ring.

d. 4-Nitrochlorobenzene

4-Nitrochlorobenzene is an aromatic compound containing a benzene ring, a nitro group (-NO2) at position 1, and a chlorine atom at position 4. To draw its structural formula, follow the steps: 1. Draw a benzene ring in a hexagonal shape with alternating double bonds. 2. Attach a nitro group (-NO2) to the first carbon atom in the ring. 3. Attach a chlorine atom (Cl) to the fourth carbon atom in the ring.

e. 1,3-Dinitrobenzene

1,3-Dinitrobenzene is an aromatic compound containing a benzene ring, with two nitro groups (-NO2) at positions 1 and 3. To draw its structural formula, follow the steps: 1. Draw a benzene ring in a hexagonal shape with alternating double bonds. 2. Attach a nitro group (-NO2) to the first carbon atom in the ring. 3. Attach another nitro group (-NO2) to the third carbon atom in the ring.

Key concepts

Polycyclic Aromatic Hydrocarbons

Polycyclic Aromatic Hydrocarbons, or PAHs, are fascinating organic compounds that consist of multiple aromatic rings fused together. These compounds are a group of chemicals that occur naturally in coal, crude oil, and gasoline. One of the simplest examples is naphthalene, which features two benzene rings sharing two adjacent carbon atoms. This structure is fundamental to understanding how PAHs form complex and stable compounds. These compounds are highly stable due to the resonance within the fused benzene rings, meaning the electrons are delocalized across the rings.
PAHs are often found in the environment because they can be produced during the combustion of fossil fuels, wood, or tobacco. They have significant industrial and environmental implications. For students in organic chemistry, learning to draw the structural formulas of PAHs is essential, as they form the basis for understanding larger, more complex molecules.

Substituted Aromatic Compounds

Substituted aromatic compounds feature a central benzene ring to which various atoms or functional groups are attached in place of hydrogen atoms. These attachments significantly alter the properties and reactivity of the benzene ring, opening up a vast field of study in organic chemistry. Examples from your exercise include compounds like 2-bromophenol, where a bromine atom substitutes one hydrogen, and a hydroxyl group (-OH) substitutes another. The placement of these substituents can dramatically change the physical and chemical properties of the compound.
The positions where these groups attach to the benzene ring are denoted using numbers, like the 2-position in 2-bromophenol or the 4-position in 4-nitrochlorobenzene, indicating their relative placement on the carbon atoms of the benzene. Understanding the nomenclature and the effect of different substitutions is vital for organic chemistry students as it lays the groundwork for predicting reactivity and properties of complex compounds.

Structural Formula Drawing

Structural formula drawing is a technique used in chemistry to represent the possible structure of a chemical compound in a visual way. It's like a blueprint of the molecule, showing each atom's position and how they are connected. Learning to draw structural formulas helps in understanding the molecular geometry and potential functional groups of a compound.
In organic chemistry, this can mean sketching intricate hexagonal shapes for benzene rings or indicating the positioning of double bonds, as seen in many aromatic compounds. It also involves marking functional groups like hydroxyl (-OH) or nitro (-NO2) attached to a benzene ring. This exercise is crucial as it allows students to visualize complex molecules and anticipate how different structures might behave or react.

Organic Chemistry

Organic chemistry is the branch of chemistry dedicated to the study of carbon-based compounds. This field covers a vast array of substances, including the development and behavior of aromatic and substituted aromatic compounds. Organic chemistry is known for combining elements of mathematics and physical science to explain how molecules form, interact, and transform.
The study of aromatic compounds such as benzene and its derivatives is a key part of understanding organic chemistry because these compounds serve as the building blocks for many complex materials. Gaining proficiency in topics such as drawing structural formulas, exploring polycyclic aromatic compounds, and investigating the effects of substituents on a benzine ring, equips students to delve into fields like pharmaceuticals, petrochemical industries, and environmental science.