Question

Draw a structural formula for each compound. (a) 1-Bromo-2-chloro-4-ethylbenzene (b) \(m\)-Nitrocumene (c) 4-Chloro- 1,2 -dimethylbenzene (d) 3,5 -Dinitrotoluene (e) \(2,4,6\)-Trinitrotoluene (f) \((2 S, 4 R)\)-4-Phenyl-2-pentanol (g) \(p\)-Cresol (h) Pentachlorophenol (i) 1-Phenylcyclopropanol (j) Triphenylmethane (k) Phenylethylene (styrene) (I) Benzyl bromide (m) 1-Phenyl-1-butyne (n) \((E)\)-3-Phenyl-2-propen-1-ol

Short answer

Now it's your turn! Based on the provided step-by-step solutions, try to draw the structural formulas for the following compounds: (a) 3-Chloro-2-methylbenzoic acid (b) (S)-2-Chloropropanoic acid (c) m-Nitroaniline Upon completion, compare your drawn structures with the structural formulas given in your textbook or online resources to check for accuracy.

Step-by-step solution

(a) 1-Bromo-2-chloro-4-ethylbenzene

Identify substituents and their positions on a benzene ring: one bromo group in position 1, one chloro group in position 2, and one ethyl group in position 4. Draw the benzene ring and add the substituents according to their positions in the name. Here is the structural formula for 1-Bromo-2-chloro-4-ethylbenzene: ``` Br Cl \ / |\ | -C- / C ```

(c) 4-Chloro- 1,2 -dimethylbenzene

Identify substituents and their positions on a benzene ring: one chloro group in position 4, one methyl group in position 1, and another methyl group in position 2. Draw the benzene ring and add the substituents according to their positions in the name. Here is the structural formula for 4-Chloro- 1,2 -dimethylbenzene: ``` Cl | C /|\/ C-C \/| C ```

(f) (2S, 4R)-4-Phenyl-2-pentanol

Understand the name: (2S, 4R) are the stereochemical configurations at positions 2 and 4 of a pentane chain. Position 2 carries a hydroxyl group (OH), and position 4 carries a phenyl group (C6H5). Pentane has five carbons in a chain. Draw the pentane chain, add the substituents OH and phenyl group at positions 2 and 4, respectively, and mark the chiral centers with stereochemical configurations (S) and (R). Here is the structural formula for (2S, 4R)-4-Phenyl-2-pentanol: ``` C-Phenyl (at position 4, with R configuration) H | | C-H C-OH (at position 2, with S configuration) | | C-H | C-H | H ```

(h) Pentachlorophenol

Understand the name: penta meaning five chloro groups attached to a phenol group, which is a benzene ring with a hydroxyl group (OH). Draw the benzene ring, add the hydroxyl group, and then add five chloro groups at the remaining carbon positions. Here is the structural formula for Pentachlorophenol: ``` Cl Cl \|/ --C--O-H / \ Cl Cl \/ C | Cl ```

(k) Phenylethylene (styrene)

Understand the name: phenylethylene or styrene is composed of a phenyl (C6H5) group attached to an ethylene (C=C) double bond. Draw the ethylene double bond and attach the phenyl group to one of the carbons in the ethylene. Here is the structural formula for Phenylethylene (styrene): ``` C/=C | C /|\ C--C |_| \| ```

Key concepts

Benzene Substituents

Benzene is a key component in organic chemistry and serves as the backbone for many aromatic compounds. Substituents can attach to the benzene ring, altering its chemical properties and reactivity. Common substituents include groups like -Br (bromo), -Cl (chloro), -NO₂ (nitro), and alkyl groups (like ethyl or methyl). When a substituent is added to benzene, it is important to specify its position.
The positions on the benzene ring are numbered, starting from one substituent and moving clockwise or counterclockwise. Familiar terms used in naming include ortho (1,2-), meta (1,3-), and para (1,4-) for adjacent, separated by one carbon, and opposite positions, respectively. These positions help define the structural framework.
Identifying these substituents and their positions is crucial when drawing structural formulas, as evidenced by the exercise with compounds like 1-bromo-2-chloro-4-ethylbenzene. Here, we recognize the arrangement and sequence of groups added to benzene, emphasizing the importance of precise positions for understanding and sketching complex organic molecules.

Stereochemistry

Stereochemistry examines how molecules are arranged in three-dimensional space. It is essential in organic chemistry as it influences the function and reaction pathways of the molecules. Two key elements of stereochemistry are *chiral centers* and stereoisomers, such as (R) and (S) configurations.
A chiral center typically involves a carbon atom bonded to four different substituents. These substituents can rearrange spatially in unique configurations, denominated as either (R) for right or (S) for left. This notation is based on the Cahn-Ingold-Prelog priority rules. Consider `(2S, 4R)-4-Phenyl-2-pentanol`, which has chiral centers at carbon 2 and 4.
Producing accurate structural formulas for these compounds requires acknowledging both spatial configurations. These arrangements are not only significant for nomenclature but also crucial for distinguishing between molecules that may share the same formula but possess differing 3D structures, affecting properties like optical activity and biological interaction.

Functional Groups

Functional groups are specific atoms or clusters of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. Important functional groups in organic chemistry include hydroxyl groups (-OH), phenyl groups (C₆H₅), and others like amino or carbonyl groups.
Each functional group confers unique properties to the compound. For example, in compounds like phenylethylene (styrene), the phenyl (C₆H₅) group contributes to aromatic characteristics while the vinyl (-CH=CH₂) group offers reactivity typical of alkenes.
Understanding functional groups aids in predicting the behavior and transformation of molecules during chemical reactions. For instance, pentachlorophenol contains a phenol group which is modified with chloro groups, impacting its reactivity and use. Clearly identifying these groups allows chemists to both predict reactions and guide the synthesis of complex organic compounds, ensuring they understand how various functional groups interact and transform.