Question

Which of the following is/are incorrect IUPAC name? (A) 3 -Ethyl butane (B) 1 -Methyl heptane (c) 2,5 -Diethyl hexane (D) \(2,2,2\)-Trimethyl pentane

Short answer

(A) 3-Ethyl butane is the incorrect IUPAC name; the correct name should be Ethyl butane.

Step-by-step solution

Brief recap of IUPAC rules

Before we start, let's quickly recap the main IUPAC rules for naming alkanes: 1. Identify the longest continuous chain of carbon atoms, which is called the parent chain. 2. Number the carbon atoms in the parent chain, starting from the end nearest to a side chain (substituent). 3. Name each side chain by changing the suffix of the parent alkane from -ane to -yl. 4. List the substituents in alphabetical order and give them a number to indicate their position on the parent chain. 5. Use commas to separate numbers and hyphens to separate words. Now, let's evaluate the given IUPAC names one by one.

Evaluate the IUPAC name (A)

(A) 3 -Ethyl butane Using the IUPAC rules, we can determine that the parent chain contains 4 carbon atoms (butane). The side chain contains 2 carbon atoms (ethyl), and its position is denoted by the number 3. However, since there is only one side chain, it's not necessary to indicate the position numerically, the substituent should be assumed to be at the first position. Therefore, the correct IUPAC name should be: Ethyl butane.

Evaluate the IUPAC name (B)

(B) 1 -Methyl heptane In this case, the parent chain contains 7 carbon atoms (heptane). The side chain contains 1 carbon atom (methyl), and its position is denoted by the number 1. Since the substituent is already at the first position, no change is required in the name, and hence the given IUPAC name is correct.

Evaluate the IUPAC name (C)

(C) 2,5 -Diethyl hexane The parent chain contains 6 carbon atoms (hexane). There are two side chains containing 2 carbon atoms each (ethyl), and their positions are denoted by the numbers 2 and 5. Since there are multiple substituents of the same type, the prefix 'di' is used correctly. Therefore, the given IUPAC name is correct.

Evaluate the IUPAC name (D)

(D) \(2,2,2\)-Trimethyl pentane In this case, the parent chain contains 5 carbon atoms (pentane). There are three side chains, each containing 1 carbon atom (methyl), all at position 2. The prefix 'tri' is used correctly since there are three substituents of the same type, and their positions are correctly indicated in the name. Therefore, the given IUPAC name is correct. Summary: After analyzing each given IUPAC name based on the rules, we conclude that the incorrect IUPAC name is: (A) 3 -Ethyl butane, which should be Ethyl butane.

Key concepts

Organic Chemistry

Organic chemistry is a fascinating and robust field of science that plays a critical role in various industries, from pharmaceuticals to materials science. At its core, organic chemistry is the study of carbon-containing compounds and their reactions. Carbon is a uniquely versatile element that can form strong covalent bonds with other carbon atoms and a wide array of other elements, creating an incredible diversity of organic molecules. The complexity of these organic structures is such that a systematic method of naming them is required, which is where the International Union of Pure and Applied Chemistry (IUPAC) naming rules come into play. Understanding how to decipher and apply the IUPAC naming conventions is essential for students and professionals alike to communicate efficiently about molecular structures and reactions in organic chemistry.

Alkane Nomenclature

Alkane nomenclature is an integral aspect of organic chemistry that involves the systematic naming of alkanes according to IUPAC rules. Alkanes are the simplest form of hydrocarbons, characterized by having only single bonds and the general formula C_nH_2n+2. Consistent naming is crucial for clear communication and involves several steps, as seen in the exercise, where incorrectly named alkanes can cause confusion. Key rules include identifying the longest carbon chain to determine the parent alkane's name and numbering the chain to assign the lowest possible numbers to substituents or branches, known as alkyl groups. The names of these groups are derived by replacing the 'ane' suffix of the corresponding alkane with 'yl'. The correct placement of numbers, hyphens, and commas in the name is just as vital as the words themselves, as it ensures accuracy and clarity. In summary, the nomenclature of alkanes requires careful analysis, and a standardized approach is necessary for coherence and understanding in the scientific community.

Chemical Structure Analysis

Chemical structure analysis is the examination of the arrangement of atoms within a molecule and provides insights into the molecule's properties and behavior. In the context of IUPAC nomenclature, analyzing a chemical structure enables us to assign a systematic name to an organic compound. As exemplified in the exercise, students must pay close attention to the details of molecular structure, such as the number of carbon atoms in the longest chain (parent chain) and the nature and position of any substituents (side chains). Incorrectly analyzing the structure could lead to mistakes in naming, as evidenced by the incorrect label '3-Ethyl butane' in the given choices. It's important to note that sometimes structural analysis goes beyond what is visible at first glance. For instance, the presence of isomers—compounds with the same molecular formula but different arrangements—may affect naming. Techniques for analyzing structures include not only visual inspection of structural formulas but also the use of instrumental methods such as spectroscopy and crystallography for more complex molecules. A solid grasp on structural analysis underpins the correct application of IUPAC rules and ensures precise communication in organic chemistry.