Question

Draw and name all derivatives of benzene having the formula (a) \(\mathrm{C}_{8} \mathrm{H}_{10} ;\) (b) \(\mathrm{C}_{9} \mathrm{H}_{12}\).

Short answer

The derivatives of benzene for the formula \(\mathrm{C}_8\mathrm{H}_{10}\) could include toluene, o-xylene, m-xylene, and p-xylene. The derivatives for the formula \(\mathrm{C}_9\mathrm{H}_{12}\) could include ethyltoluene, o-isopropyltoluene, m-isopropyltoluene, and p-isopropyltoluene.

Step-by-step solution

Drawing for \(\mathrm{C}_8\mathrm{H}_{10}\)

Firstly, draw a benzene ring which is a hexagon with a circle inside, representing \(\mathrm{C}_6\mathrm{H}_6\). Then, add two more carbons as a side chain or substituent. Add hydrogens to the carbons so that each carbon shares four bonds (each line represents a bond). The attached hydrogen atoms are normally omitted in these kinds of diagrams, but they are present as needed to make four bonds per carbon. For this molecular formula, the possible structures could be a toluene (one benzene ring with a methyl group and an ethyl group as substituents), or o-xylene, m-xylene, and p-xylene (a benzene ring with two methyl substitute at different positions).

Drawing for \(\mathrm{C}_9\mathrm{H}_{12}\)

Again, draw a benzene ring for \(\mathrm{C}_6\mathrm{H}_6\). Then, add three more carbons as a side chain or substituent. Attach hydrogens to the carbons so that each carbon forms four bonds. For this molecular formula, some of the possible structures could be ethyltoluene (one benzene ring with an ethyl group and a methyl group as substituents), or o-, m-, p-isopropyltoluene (a benzene ring with an isopropyl group and a methyl group at different positions).

Key concepts

Organic Chemistry

Organic chemistry is the branch of chemistry focusing on the study of carbon-containing compounds. It's an incredibly diverse field, encompassing everything from the simplest molecules, like methane, to complex structures such as proteins and DNA. One of the core concepts in organic chemistry is the organization of organic molecules into functional groups which dictate the chemical behavior of the molecule.
Benzene is one of the most foundational molecules studied in organic chemistry. Its stability and ability to form derivatives make it a crucial starting point for understanding many organic compounds. The benzene ring, composed of six carbon atoms bonded in a resonant ring structure, allows for the substitution of hydrogen atoms with other atoms or groups, leading to a wide variety of derivatives.

Molecular Structures

Molecular structures describe how atoms are arranged in a molecule, influencing its properties and reactions. When dealing with benzene derivatives, understanding molecular structures helps us predict the behavior of molecules when new groups are added.
In the problem, the benzene ring is the base structure. Then, you add substituents like methyl ( -CH₃ ) or ethyl ( -CH₂CH₃ groups to create new compounds. The position of these groups on the benzene ring significantly affects the molecule's properties. For example, in xylene, methyl groups are positioned as ortho (adjacent), meta (separated by one carbon), or para (opposite) to each other. These small changes in structure significantly influence the physical and chemical behavior, like boiling points and reactivity.

Hydrocarbon Substituents

Hydrocarbon substituents are groups derived from hydrocarbons that are attached to a molecule, changing its structure and reactivity. When discussing benzene derivatives, hydrocarbon substituents like methyl and ethyl groups are central.
These substituents are single chains of carbon and hydrogen atoms that can attach to the benzene ring in various positions. The varied positions, such as ortho, meta, or para, allow for multiple isomers. Isomers are compounds that have the same chemical formula but different arrangements of atoms, leading to different properties.
With the formula C₈H₁₀, examples include toluene with one methyl group, or xylene, with two. Altering these positions gives rise to a set of compounds with distinct characteristics, expanding the possible applications and interactions in organic chemistry.