Question

Draw the structure for each compound. a. ethylbenzene b. 1 -iodo-2-methylbenzene c. para-diethylbenzene

Short answer

Ethylbenzene has a benzene ring with one ethyl group attached. 1-Iodo-2-Methylbenzene has a benzene ring with an iodine atom attached to the first carbon and a methyl group on the second carbon. Para-Diethylbenzene has a benzene ring with ethyl groups attached to carbon 1 and 4 (opposite each other).

Step-by-step solution

Drawing Ethylbenzene

First, draw the benzene ring, which is a hexagon with alternating double bonds. Next, add a two-carbon ethyl group (–CH2–CH3) attached to any carbon on the benzene ring. Since the benzene ring is symmetrical, it does not matter which carbon the ethyl group is attached to.

Drawing 1-Iodo-2-Methylbenzene

Start by drawing the benzene ring. Then, at the carbon atom number 1 (starting from any arbitrary point, as it will define the numbering), attach an iodine atom (I). At the carbon atom number 2 (the next carbon in the ring), attach a methyl group (–CH3). Ensure the numbering is consistent with the placement of the iodine and methyl groups to indicate their positions.

Drawing para-Diethylbenzene

Draw the benzene ring again. The term 'para' refers to the positions across from each other on the benzene ring. Place one ethyl group (–CH2–CH3) on one carbon atom, and place another ethyl group directly across from the first, on the opposite carbon atom of the benzene ring. The two ethyl groups should be on carbons 1 and 4 if you number the ring.

Key concepts

Benzene Ring Structure

Understanding the structure of a benzene ring is foundational in organic chemistry. A benzene ring consists of six carbon atoms arranged in a hexagonal shape, with alternating single and double bonds between the carbons. This unique configuration creates a stable and symmetrical structure, often represented by a circle inside a hexagon to signify the delocalized electrons. The delocalization contributes to the ring's chemical stability and is a key aspect of its reactivity.

Moreover, each carbon atom in the ring has one hydrogen atom attached. Because of the ring's symmetry, adding substituents to the benzene ring will result in different compounds. However, due to this symmetry, the position of a single substituent does not change the compound's identity, which is why in the drawing steps for compounds like ethylbenzene, the specific carbon to which the ethyl group is attached can be any of the six carbons.

Ethylbenzene

Ethylbenzene is a straightforward derivative of benzene, where an ethyl group (–CH2CH3) is attached to the ring. When drawing ethylbenzene, start with the benzene ring and then add the ethyl group to any carbon, since the ring is symmetrical.

This compound is significant in industry and is used predominantly as a precursor to styrene, which is further polymerized to polystyrene, a widely used plastic material. Its relatively simple structure also makes it an excellent starting point for learning about substituents on the benzene ring in organic chemistry.

1-Iodo-2-Methylbenzene

Drawing 1-iodo-2-methylbenzene requires an understanding of organic chemistry nomenclature and attachment of substituents at specific positions on the benzene ring. The numeral '1' indicates the position of the first substituent—iodine (I), and '2' the position of the second—methyl group (–CH3).

The numbering of carbon atoms in the benzene ring is crucial: carbon atoms are numbered starting from where the first substituent is attached and then in a direction that gives the lowest possible numbers to the other substituents. This compound showcases the importance of position in determining the unique identity of benzene derivatives.

Para-Diethylbenzene

Para-diethylbenzene involves adding two ethyl groups to opposite sides of the benzene ring. In chemistry, 'para' describes two substituents that are across from each other on the ring structure, which corresponds to the 1 and 4 positions.

When drawing para-diethylbenzene, you begin with the benzene ring, then place one ethyl group (–CH2CH3) at carbon 1 and another at carbon 4. This specific configuration is essential for the compound's properties and can be compared to 'ortho' (adjacent positions) and 'meta' (with one carbon in between) placements.

Organic Chemistry Nomenclature

The nomenclature in organic chemistry is the system used to name compounds according to their structure. It relies on a set of rules and conventions established by the International Union of Pure and Applied Chemistry (IUPAC). This system ensures that each compound's name conveys structural information, allowing chemists to draw its structure from the name alone.

Key principles include identifying the main carbon chain, numbering carbons to give substituents the lowest numbers, and using prefixes and suffixes to indicate the types and positions of substituents. For instance, in '1-iodo-2-methylbenzene', '1-iodo-' tells us that an iodine is attached at the first carbon, and '2-methyl' tells us that a methyl group is attached at the second carbon, ensuring clear communication within the scientific community.