Question

Draw structural formulas for the following compounds: (a) 1,3 -dichlorobenzene (alternatively called \(m\) dichlorobenzene) (b) 1 -bromo-4-methylbenzene (alternatively called p-bromotoluene)

Short answer

1,3-dichlorobenzene has Cl on positions 1 and 3; 1-bromo-4-methylbenzene has Br on position 1 and CH₃ on position 4.

Step-by-step solution

Understanding Benzene Compounds

Benzene is a ring structure consisting of six carbon atoms with alternating double and single bonds. Each carbon in benzene is also bonded to a hydrogen atom, unless substituted by another group.

Drawing the Benzene Ring

Start by drawing a hexagonal ring to represent benzene. Add alternating double bonds to illustrate the delocalized electrons in the benzene ring.

Substituting for 1,3-dichlorobenzene

Locate the 1 and 3 positions on the benzene ring. Number one of the carbons in the benzene ring as position 1. Move two positions (counting the current as 1) clockwise or counterclockwise to find position 3. Substitute the hydrogen atoms at these positions with chlorine (Cl) atoms.

Substituting for 1-bromo-4-methylbenzene

Locate the 1 and 4 positions on the benzene ring. Number one carbon as position 1. Move three positions (counting the current as 1) to arrive at position 4. Substitute the hydrogen atom at position 1 with a bromo (Br) group and the one at position 4 with a methyl (CH₃) group.

Finalizing the Structural Formulas

Redraw both benzene rings with their respective substitutions. For 1,3-dichlorobenzene, make sure each chlorine is attached to the correct carbon. For 1-bromo-4-methylbenzene, ensure the bromine and methyl groups are correctly placed.

Key concepts

Benzene Compounds

Benzene compounds are a fascinating class of organic molecules with a unique ring-like structure. These compounds all share the characteristic benzene core, which is made up of six carbon atoms. In this hexagonal ring, every carbon atom is bonded to a hydrogen atom. The distinctive feature of benzene is its alternating double and single bonds, which arise due to the delocalization of electrons. This gives benzene a stable structure and makes it a cornerstone of organic chemistry.

Benzene itself is a building block for many derivatives we encounter in chemistry, especially in aromatic compounds. Some common benzene derivatives include toluene, phenol, and xylene, each with their own unique properties derived from the benzene core. Understanding these compounds is crucial for studying organic reactions and synthesis.

Chemical Structure Drawing

Drawing chemical structures, like those of benzene derivatives, is an essential skill in chemistry. It involves representing the molecular composition and connectivity of atoms in a clear and accurate way. For benzene compounds, this starts with drawing a hexagonal ring. This hexagon symbolizes the six carbon atoms, each with alternating double and single bonds, indicating the delocalization of electrons.

In chemical drawings, special attention must be paid to accurately representing substitutions on the benzene ring. Sometimes numbers or letters are used to indicate the position of these substitutions. This form of illustration not only helps in visualizing the compound but also in understanding its potential reactivity and interaction in the chemical universe.

• Begin with the hexagon shape for benzene.
• Add alternating double bonds.
• Include any substituents at the correct positions as indicated by the compound's name.

Accurate chemical drawing is an invaluable tool for chemists, students, and scientists alike in communicating intricate molecular information.

Substitution on Benzene Ring

Substitution on a benzene ring is a common phenomenon where hydrogen atoms attached to the benzene ring are replaced with other atoms or groups. This process gives rise to a vast array of benzene derivatives, each possessing unique chemical and physical properties. The naming of these substitutions often involves numbering the carbons to specify the positions of the substituents, creating a clear method to depict the structure.

For example, in 1,3-dichlorobenzene, the chlorine atoms substitute for the hydrogen atoms at the 1 and 3 positions on the benzene ring. To locate these positions, you start numbering from any carbon atom as position 1, then count clockwise or counterclockwise to determine subsequent positions. Similarly, in the compound 1-bromo-4-methylbenzene, the bromine and methyl groups replace hydrogens at 1 and 4 positions, respectively.

• Identify a starting position on the benzene ring as position 1.
• Count to the designated position for each substituent.
• Replace the hydrogen at these positions with the respective substituting group.

This substitution method enriches the versatility and complexity of benzene compounds in chemical reactions.