Question

Choose the incorrect IUPAC name. (A) 3,4 -dimethyl hexane (B) \(2,2,4\)-trimethyl pentane (C) 1-cyclobutyl-1-cyclopropyl pentane (D) 2-methyl-3-ethyl pentane

Short answer

The incorrect IUPAC name among the given options is (C) 1-cyclobutyl-1-cyclopropyl pentane, as it is not possible to have both a cyclobutyl group and a cyclopropyl group attached at position 1 in a pentane backbone.

Step-by-step solution

Review IUPAC nomenclature rules

To determine if the given IUPAC names are correct, we need to be familiar with the following nomenclature rules: 1. The longest continuous carbon chain in the molecule is named as the parent alkane. 2. Substituents are named as prefixes, according to their position on the carbon chain. 3. The carbon atoms are numbered, starting from the end nearest to the first substituent. 4. Substituents are listed in alphabetical order. 5. If there are multiple substituents of the same type, use the prefixes di-, tri-, tetra-, etc., to indicate how many there are.

Evaluate option (A)

We have '3,4-dimethyl hexane,' which implies that there is a hexane (6 carbon chain) backbone with 2 methyl groups at positions 3 and 4. This name follows the IUPAC nomenclature rules as described in Step 1. Thus, this option is correct.

Evaluate option (B)

We have '2,2,4-trimethyl pentane,' which implies that there is a pentane (5 carbon chain) backbone with 3 methyl groups at positions 2, 2, and 4. This name follows the IUPAC nomenclature rules as described in Step 1. Thus, this option is correct.

Evaluate option (C)

We have '1-cyclobutyl-1-cyclopropyl pentane,' which implies that there is a pentane (5 carbon chain) backbone with a cyclobutyl group and a cyclopropyl group, both attached at position 1. This is not possible, as there is only one hydrogen available for substitution at position 1. Thus, this option is incorrect. Since we found an incorrect option, we can stop here.

Evaluate option (D) (optional)

We have '2-methyl-3-ethyl pentane,' which implies that there is a pentane (5 carbon chain) backbone with a methyl group at position 2 and an ethyl group at position 3. This name follows the IUPAC nomenclature rules as described in Step 1. Thus, this option is correct. To summarize, the incorrect IUPAC name among the given options is (C) 1-cyclobutyl-1-cyclopropyl pentane.

Key concepts

Organic Chemistry

Organic chemistry is a subfield of chemistry that deals with the study of the structure, properties, composition, reactions, and preparation of carbon-containing compounds. These include not only hydrocarbons but also compounds with any number of other elements, including hydrogen, nitrogen, oxygen, halogens, phosphorus, silicon, and sulfur.

This branch of chemistry is vital for a myriad of industries, including pharmaceuticals, petrochemicals, food, explosives, and cosmetics. Organic molecules form the basis of all earthly life and thus have a direct bearing on biochemistry. The complexity of the organic compounds, ranging from simple molecules like methane to complex molecules like deoxyribonucleic acid (DNA) and proteins, forms the basis of innumerable physical material properties.

Understanding organic chemistry is fundamental for scientists and researchers, as it underpins the synthesis of new compounds for innovative treatments and products. For students, mastering the basics of organic chemistry is not only crucial for academic purposes but also for real-world applications that might one day contribute to significant scientific advancements.

Chemical Nomenclature

Chemical nomenclature in organic chemistry is a systematic method of naming organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC). It aims to provide a unique and standardized name for each chemical compound, which allows chemists to communicate efficiently and unambiguously about chemical substances.

The IUPAC rules for nomenclature are methodical and are based on the structure of a compound. The system incorporates features like the longest chain rule, substituent prefixes, numbering of carbon atoms, and alphabetical listing of substituents to ensure that each compound's name reflects its molecular structure. For example, a compound's name can reveal the length of the carbon chain, the types, and numbers of functional groups, and their positions on the carbon skeleton.

Applying these rules might seem daunting, but with practice, students gain familiarity and can tackle even the most challenging names. Mastery of IUPAC nomenclature is not only crucial for academic assessments but also essential for anyone planning a career in chemistry-related fields.

JEE Main and Advanced Preparation

The Joint Entrance Examination (JEE) Main and Advanced are crucial tests for students in India aiming to pursue undergraduate engineering and other technical degrees at premier institutions like IITs and NITs. The syllabus covers a breadth of knowledge across physics, chemistry, and mathematics.

In the pursuit of cracking these competitive exams, your grasp on organic chemistry and, more specifically, IUPAC nomenclature can play a pivotal role. The JEE tests not only test conceptual understanding but also problem-solving skills and the ability to apply concepts in novel situations.

To excel in these exams, students should adopt a disciplined study schedule, clarify their concepts, practice with a variety of problems, and take as many mock tests as possible to gain confidence and improve time management. Understanding the core concepts of organic chemistry and being proficient in chemical nomenclature is vital as it forms the basis for more complex topics and problem-solving in the exams.