Question

Write structures for each of the following names: (a) m-cresol (b) 3 -hydroxybenzenesulfonamide (c) 3 -chloro-1, 2 -benzoquinone (d) o-methoxyphenol (e) \(\mathrm{p}(\mathrm{t}-\) tolyl \()\) azophenol (f) benzyl pheny 1 ether (g) \(3-\) (o-hydroxy phenyl pentanoic acid) (h) 2 -methoxy-1, 4 -naphthoquinone

Short answer

The structures for the given compound names are: (a) m-cresol: \( HO-C_{6}H_{4}-CH_{3} \) (b) 3-hydroxybenzenesulfonamide: \( NH_{2}-SO_{2}-C_{6}H_{4}-OH \) (c) 3-chloro-1,2-benzoquinone: \( O=C-C_{6}H_{3}-C(=O)-Cl \) (d) o-methoxyphenol: \( HOC_{6}H_{4}-OCH_{3} \) (e) p(t-tolyl)azophenol: \(C_{7}H_{7}-N=N-C_{6}H_{4}-OH \) (f) benzyl phenyl ether: \( C_{6}H_{5}-O-CH_{2}-C_{6}H_{5} \) (g) 3-(o-hydroxy phenyl pentanoic acid): \( HO-C_{6}H_{4}-CH_{2}-CH_{2}-CH_{2}-CH_{2}-COOH \) (h) 2-methoxy-1,4-naphthoquinone: \( O=C-C_{10}H_{5}-C(=O)-OCH_{3} \)

Step-by-step solution

(a) m-cresol

To draw the structure for m-cresol, we need to know that cresol is a methylated phenol, and the "m" indicates a substitution on the meta position. This gives us a phenol with a methyl group on the meta position, which is in position 3. The structure for m-cresol is: \[ HO-C_{6}H_{4}-CH_{3} \]

(b) 3-hydroxybenzenesulfonamide

To draw the 3-hydroxybenzenesulfonamide structure, we need to start with the benzenesulfonamide. A sulfonamide group is attached to benzene. The hydroxybenzene part indicates a hydroxyl group on the benzene ring, and with the number 3, the hydroxyl group is in position 3. The structure for 3-hydroxybenzenesulfonamide is: \[ NH_{2}-SO_{2}-C_{6}H_{4}-OH \]

(c) 3-chloro-1,2-benzoquinone

To draw the 3-chloro-1,2-benzoquinone structure, we need to know that benzoquinone is a benzene ring with two carbonyl groups on position 1 and 2. The 3-chloro adds a chlorine atom to position 3. The structure for 3-chloro-1,2-benzoquinone is: \[ O=C-C_{6}H_{3}-C(=O)-Cl \]

(d) o-methoxyphenol

To draw the structure for o-methoxyphenol, we need to know that the "o" stands for ortho, which is the 1-2 position. This means that the methoxy (OCH3) group is attached to the position next to the hydroxyl group in a phenol molecule. The structure for o-methoxyphenol is: \[ HOC_{6}H_{4}-OCH_{3} \]

(e) p(t-tolyl)azophenol

To draw the structure of p(t-tolyl)azophenol, we need to know that "p" stands for the para position, which is the 1-4 position. Tolyl is a benzene ring with a methyl group attached. The azophenol part indicates a phenol ring with a nitrogen double bond (azo) linking to the t-tolyl group. The structure is: \[N=N-C_{6}H_{4}-OH \] ⟹ \[C_{7}H_{7}-N=N-C_{6}H_{4}-OH \]

(f) benzyl phenyl ether

The benzyl phenyl ether structure consists of two benzene rings. One has a phenyl ether substituent (O) and the other has a benzyl group (CH2) attached. The structure for benzyl phenyl ether is: \[ C_{6}H_{5}-O-CH_{2}-C_{6}H_{5} \]

(g) 3-(o-hydroxy phenyl pentanoic acid)

We need to draw a structure of an o-hydroxy phenyl group attached to a pentanoic acid (5 carbon chain) with a carboxyl group at one end. The structure is: \[ HO-C_{6}H_{4}-CH_{2}-CH_{2}-CH_{2}-CH_{2}-COOH \]

(h) 2-methoxy-1,4-naphthoquinone

To draw the structure for 2-methoxy-1,4-naphthoquinone, we need to know that naphthoquinone is a naphthalene ring with carbonyl groups at the 1 and 4 positions. The 2-methoxy part means that the methoxy group is attached to position 2. The structure for 2-methoxy-1,4-naphthoquinone is: \[ O=C-C_{10}H_{5}-C(=O)-OCH_{3} \]

Key concepts

Molecular Structure Representation

In organic chemistry, molecular structure representation is essential for understanding complex molecules. These structures can be represented in several ways, including structural formulas, which display the arrangement of atoms in a molecule. A structural formula provides detailed positions of atoms and bonds in a compound.

For instance, when discussing structural formulas, chemists frequently use condensed structural formulas to give a quick overview of a molecule's framework with reduced detail, though still depicting the essential structure. For example, a molecule represented as \(CH_3CH_2OH\) is showing ethanol in a concise manner, with each group indicating a part of the molecular structure.

Understanding such representations can aid in visualizing how molecules interact and react in the real world. This is particularly useful for larger compounds with multiple functional groups, each of which contributes unique chemical properties.

Functional Groups in Organic Chemistry

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. Each functional group exhibits relatively consistent behavior across different substances.

Examples of common functional groups include:

• Hydroxyl group (\(-OH\)): found in alcohols and phenols and is responsible for their solubility in water and reactivity.
• Carbonyl group (C=O): found in ketones and aldehydes, where the group determines reactivity, affecting things like boiling points and formation of addition products.
• Carboxyl group (\(-COOH\)): characteristic of carboxylic acids, affecting acidity and reactivity with bases to form salt and water.
• Amino group (\(-NH_2\)): found in amines and amino acids, which influences basicity and the formation of amide bonds in proteins.

In organic chemistry, understanding functional groups is crucial as they determine the types of chemical reactions the molecule can undergo. They also help in classifying compounds based on their chemical behaviors.

Aromatic Compounds

Aromatic compounds are a unique class of organic molecules characterized by their ring-like structure with delocalized π-electrons. Benzene is the most common example, featuring a six-carbon ring with alternating double bonds, known as an aromatic ring.

These compounds are identified by:

• Cyclic structure: Must be a stable ring.
• Planar: All atoms in the ring lie in the same plane.
• Conjugated system: Have p-orbitals that overlap, allowing the delocalization of π-electrons across the ring.
• Adherence to Huckel's Rule: For aromatic stability, a compound must have \(4n+2\) π-electrons (where \(n\) is a non-negative integer).

Aromaticity imparts several key properties such as enhanced stability compared to similar non-aromatic rings, which is why benzene rings make a frequent appearance in various chemical compounds.

In practice, aromatic compounds (also referred to as arenes) can participate in substitutions such as electrophilic aromatic substitution reactions, where conjugation within the ring plays a pivotal role in determining reaction routes and rates. Understanding their structure and properties is vital for applications ranging from medicine to materials science.