Problem 187 - A Complete Resource Book in Chemistry for JEE Main

Question

The correct decreasing order of priority for the functional groups of organic compounds in the IUPAC sys- 19 tem of nomenclature is (a) \(-\mathrm{COOH},-\mathrm{SO}_{3} \mathrm{H},-\mathrm{CONH}_{2},-\mathrm{CHO}\) (b) \(-\mathrm{SO}_{3} \mathrm{H},-\mathrm{COOH},-\mathrm{CONH}_{2},-\mathrm{CHO}\) (c) \(-\mathrm{CHO},-\mathrm{COOH},-\mathrm{SO}_{3} \mathrm{H},-\mathrm{CONH}_{2}\) (d) \(-\mathrm{CONH}_{2},-\mathrm{CHO},-\mathrm{SO}_{3} \mathrm{H},-\mathrm{COOH}\)

Step-by-Step Solution

Answer

The correct answer is (a) \\(-\mathrm{COOH}, -\mathrm{SO}_{3}\mathrm{H}, -\mathrm{CONH}_{2}, -\mathrm{CHO}\\).

Step 1: Identify Key Functional Groups

To answer the question, first we need to identify the functional groups mentioned in the options. These include carboxylic acid \(-\mathrm{COOH}\), sulfonic acid \(-\mathrm{SO}_{3}\mathrm{H}\), amide \(-\mathrm{CONH}_{2}\), and aldehyde \(-\mathrm{CHO}\).

Step 2: Understand IUPAC Priority Order

The IUPAC system has a specific priority order for naming functional groups. Generally, carboxylic acids (\(-\mathrm{COOH}\)) have the highest priority, followed by sulfonic acids (\(-\mathrm{SO}_{3}\mathrm{H}\)), then amides (\(-\mathrm{CONH}_{2}\)), and finally aldehydes (\(-\mathrm{CHO}\)).

Step 3: Analyze Option (a)

Option (a) lists the groups in the order: \(-\mathrm{COOH}, -\mathrm{SO}_{3}\mathrm{H}, -\mathrm{CONH}_{2}, -\mathrm{CHO}\). This matches the IUPAC priority order as identified in Step 2.

Step 4: Evaluate Other Options

Check the other options for correct order: - Option (b): \(-\mathrm{SO}_{3}\mathrm{H}, -\mathrm{COOH}, -\mathrm{CONH}_{2}, -\mathrm{CHO}\) - incorrect order.- Option (c): \(-\mathrm{CHO}, -\mathrm{COOH}, -\mathrm{SO}_{3}\mathrm{H}, -\mathrm{CONH}_{2}\) - incorrect order.- Option (d): \(-\mathrm{CONH}_{2}, -\mathrm{CHO}, -\mathrm{SO}_{3}\mathrm{H}, -\mathrm{COOH}\) - incorrect order.

Step 5: Confirm the Correct Answer

Based on the above analysis, Option (a) correctly follows the IUPAC priority order of functional groups, making it the right choice.

Key Concepts

Functional Group Priority

Understanding the priority of functional groups is crucial when learning about IUPAC nomenclature. Functional groups are specific groups of atoms within molecules that determine the characteristic reactions of those molecules. In the IUPAC system, each functional group is assigned a priority based on its chemical properties and reactivity. This priority affects the order in which the groups are named in a compound.
- **Highest Priority:** Carboxylic acids (\(-\text{COOH}\)) are given the highest priority in the IUPAC naming system. They are usually placed at the end of the compound's name.- **Next Priority:** Sulfonic acids (\(-\text{SO}_{3}\text{H}\)) come after carboxylic acids.- **Mid-priority:** Amides (\(-\text{CONH}_{2}\)) follow in the order of importance.- **Lowest Priority among these:** Aldehydes (\(-\text{CHO}\)) have the lowest priority among the groups listed here.
By understanding this order, students can correctly apply IUPAC naming conventions to accurately describe chemical compounds.

Organic Chemistry

In the realm of organic chemistry, recognizing different functional groups is essential. Organic molecules are primarily composed of carbon and hydrogen but can have a variety of other elements, such as oxygen, nitrogen, or sulfur, which often appear as part of a functional group. Each functional group imparts a distinct set of properties and reactivities to the molecule, making chemistry an intricate puzzle to solve.
Organic chemistry also focuses on the study of carbon-containing compounds and their transformations. Because carbon can form stable bonds with many elements, it leads to a wide array of molecular diversity. This diversity is managed systematically by using specific rules and guidelines for each molecule's structure and functional groups, all to navigate through the millions of possible organic compounds.
As students delve deeper into organic chemistry, they encounter a vast network of reactions and compounds, each explained by understanding functional groups and their interactions.

Naming Conventions

The IUPAC naming system, developed by the International Union of Pure and Applied Chemistry, is the standard method for naming chemical compounds. It ensures a consistent approach across various molecules, making it easier for chemists around the world to communicate. Naming conventions are based on the structure of the molecule, including the longest carbon chain, functional group priorities, and substituent naming.
When naming a molecule, **the following steps** are generally observed:

• Identify the longest carbon chain that contains the principal functional group, which dictates the suffix in the name.
• Assign priorities to the functional groups, ensuring the highest priority group gets the lowest number when naming the position on the chain.
• Identify and name substituents, which are other groups attached to the main carbon chain, and place them at the beginning of the molecule's name.
• Combine these elements into a systematic name, ensuring clarity and consistency with IUPAC standards.

By following these conventions, students can correctly name even complex organic compounds, which aids in effectively communicating chemical information.