Question

Draw the structure for each compound. \begin{equation}\begin{array}{l}{\text { a. isopropylbenzene }} \\ {\text { b. } \text {meta-dibromobenzene}} \\ {\text { c. } 1 \text { -chloro- }-4 \text { -methylbenzene }}\end{array}\end{equation}

Short answer

Isopropylbenzene has an isopropyl group attached to the benzene ring. Meta-dibromobenzene has bromine atoms on the 1 and 3 positions of the ring. 1-chloro-4-methylbenzene has a chlorine atom on carbon 1 and a methyl group on carbon 4 of the benzene ring.

Step-by-step solution

Draw the Benzene Ring

For each compound, start by drawing a hexagon to represent the benzene ring. Inside the hexagon, draw a circle to represent the delocalized electrons.

Add the Isopropyl Group for Isopropylbenzene

To draw isopropylbenzene, add an isopropyl group (i.e., (CH3)2CH-) attached to the benzene ring at any position as all positions are equivalent in this unsubstituted benzene ring.

Add the Bromine Atoms for meta-Dibromobenzene

For meta-dibromobenzene, attach a bromine atom to the benzene ring such that they occupy the meta positions (1,3-positions). This means that the bromine atoms are separated by one carbon atom.

Add the Chloro and Methyl Groups for 1-Chloro-4-methylbenzene

To draw 1-chloro-4-methylbenzene, attach a chlorine (Cl) atom at carbon 1 and a methyl (CH3) group at carbon 4 of the benzene ring, counting the carbon atoms in a clock or counter-clockwise direction from the chlorine atom.

Key concepts

Benzene Ring Structure

Understanding the structure of benzene is fundamental in organic chemistry. Benzene is depicted as a hexagon with alternating double bonds and a circle in the middle, symbolizing delocalized electrons. These electrons are shared equally by all six carbon atoms, giving stability to the molecule.

This resonance, or electron delocalization, is crucial because it reduces the ring's reactivity, differentiating benzene from other less stable polyenes. In benzene, all carbon-carbon bonds are of equal length, positioned between a single and double bond, often referred to as a one-and-a-half bond.

Isopropylbenzene

Isopropylbenzene, also known as cumene, is an organic compound that combines a benzene ring with an isopropyl group. To draw it, you first sketch the benzene ring. Then, add the isopropyl group \text{\((CH}_3\text{)}_2\text{CH-}\) at any carbon atom on the ring, since the ring is symmetrical.

It's this simple connection of the isopropyl group to the benzene that showcases the diversity of organic compounds. Isopropylbenzene is a precursor to more complex chemicals and plays a pivotal role in the production of phenol and acetone.

Meta-Dibromobenzene

Meta-dibromobenzene features two bromine atoms attached to a benzene ring. The term 'meta' refers to the positioning of the substituents: when two groups are separated by one carbon atom, they are said to be in the meta position. To draw this compound accurately, two bromine atoms are placed on the 1st and 3rd carbon atoms of the ring.

The placement significantly affects the molecule's chemistry, as the bromine atoms influence each other’s reactivity, often seen in the reactivity patterns during further chemical reactions.

1-Chloro-4-methylbenzene

This molecule has a chloro group and a methyl group attached to the benzene ring. The numbering indicates the positions of the substituents. In 1-chloro-4-methylbenzene, the chlorine atom is bound to the first carbon atom and the methyl group to the fourth.

When drawing, one starts at the chlorine and counts either clockwise or counter-clockwise to place the methyl group correctly. This precise placement matters because it affects the compound's physical properties and the outcomes of chemical reactions it may undergo.

Organic Chemistry Notation

Organic chemistry notation is a standardized way of representing molecules and their structure. Common elements include the use of lines to represent chemical bonds, letters for elements, and numbers for position or quantity. Double lines indicate double bonds, while wedges and dashed lines show three-dimensional configuration.

Learning to read and write this notation is akin to learning a language—it's a gateway to understanding organic chemistry's deeper concepts. Symbols and structural representations streamline communication among chemists and are essential tools for thinking about and predicting chemical behavior.