Question

How many of the following compounds has Double bond equivalent \(=4 ?\) (i) Carbolic acid (ii) Benzene (iii) Benzoic acid (iv) \(\mathrm{Ph}-\mathrm{Ph}\) (v) C=CC(C)CC(=O)O (vi) (vii) (viii) O=CC1C=CC(C(=O)O)CC1

Short answer

There are 3 compounds with Double bond equivalent = 4: (i) Carbolic acid (Phenol), (ii) Benzene, and (viii) O=CC1C=CC(C(=O)O)CC1.

Step-by-step solution

Identify the compounds and their molecular formulas

(i) Carbolic acid (Phenol): C6H6O (ii) Benzene: C6H6 (iii) Benzoic acid: C7H6O2 (iv) Ph-Ph (Biphenyl): C12H10 (v) C=CC(C)CC(=O)O: C6H10O2 (vi) [smiles]: Not given (vii) [smiles]: Not given (viii) O=CC1C=CC(C(=O)O)CC1: C7H8O3

Calculate the DBE for each compound

(i) Carbolic acid (Phenol): DBE = (6 - 6/2 +1) = 4 (ii) Benzene: DBE = (6 - 6/2 +1) = 4 (iii) Benzoic acid: DBE = (7 - 6/2 + 1) = 5 (iv) Ph-Ph (Biphenyl): DBE = (12 - 10/2 + 1) = 8 (v) C=CC(C)CC(=O)O: DBE = (6 - 10/2 + 1) = 2 (viii) O=CC1C=CC(C(=O)O)CC1: DBE = (7 - 8/2 + 1) = 4

Identify compounds with DBE = 4

Based on the calculated DBE values, the compounds with DBE = 4 are: (i) Carbolic acid (Phenol) (ii) Benzene (viii) O=CC1C=CC(C(=O)O)CC1 Therefore, there are 3 compounds with Double bond equivalent = 4.

Key concepts

Understanding Double Bond Equivalent

The concept of Double Bond Equivalent (DBE), also known as the degree of unsaturation, is a crucial aspect of organic chemistry that provides insight into the saturation level of a compound. DBE helps determine the number of rings and multiple bonds present in a molecule without having the molecular structure. The formula used to calculate DBE is:
\[ DBE = C + 1 + \frac{N}{2} - \frac{H}{2} - \frac{X}{2} + \frac{H_{al}}{2} \]
where C is the number of carbon atoms, N is the number of nitrogen atoms, H is the number of hydrogen atoms, X is the number of halogen atoms, and H_al is the number of alkali metals such as sodium or potassium. The DBE value reflects how many \'units of unsaturation\' a compound has, where each unit can be a double bond or a ring. Understanding DBE is essential not only in analyzing and designing organic compounds but also when tackling problems in higher-level exams like JEE Main and Advanced.

Organic Chemistry in JEE Main and Advanced

When preparing for competitive exams such as JEE Main and Advanced, proficiency in organic chemistry is vital. It's a significant portion of the chemistry syllabus offering a mix of conceptual understanding and practical problem-solving skills. The key to success in these exams is a deep understanding of fundamental concepts such as DBE, IUPAC naming, reaction mechanisms, and stereochemistry. Students are expected to efficiently solve problems often by applying multiple concepts
For mastering organic chemistry in JEE, specific strategies can be employed. Practice is paramount; tackling a variety of problems, understanding the 'why' behind each reaction, and utilizing mnemonic devices for complex nomenclature can be immensely helpful. Additionally, forming a study group and discussing various approaches to the same problem can lead to a deeper understanding and better retention of concepts.

Solving Problems in Organic Chemistry

Problems in organic chemistry can often seem overwhelming due to the intricacies of chemical reactions and the vast number of compounds to be familiar with. A systematic approach is paramount to solving these problems, especially for exams such as JEE.
Here's a simplified approach to tackling organic chemistry problems:

• Begin with identifying the functional groups and the general framework of the compound.
• Apply basic principles such as DBE to understand the underlying structure and reactivity.
• Consider the stereochemistry for reactions and product prediction.
• Create reaction mechanisms and pathways for complex transformations.
• Finally, practice retrosynthetic analysis for multi-step syntheses.

In the context of a problem involving DBE calculation, after finding the DBE, additional steps may involve deducing possible structures, which can then lead to further analysis regarding reactivity and properties. Regular practice with a focus on foundational concepts will ensure a robust understanding of organic chemistry problems, paving the way for success in competitive exams and beyond.