Phenolic group can be identified by a positive
- Lucas test
- Carbylamine test
- Phthalein test
- Tollen's test
The Correct Option is C
Approach Solution - 1
The question is about identifying the phenolic group using a specific chemical test. Here's a step-by-step explanation:
A phenolic group is characterized by a hydroxyl group (-OH) attached to an aromatic ring.
To test for the presence of phenolic groups, various chemical tests can be employed. The key here is choosing the correct test from the given options.
- Lucas Test: This test is used to distinguish between primary, secondary, and tertiary alcohols based on their reactivity with Lucas reagent. It is not suitable for identifying phenolic groups.
- Carbylamine Test: This test is specific for primary amines and involves the formation of isocyanides (carbylamines), which are detected by their foul odor. It is not applicable to phenolic groups.
- Phthalein Test: This test is specific for phenols. It involves the reaction of phenolic compounds with phthalic anhydride in the presence of a dehydrating agent to form a colored phthalein dye, such as phenolphthalein. This is the correct test for identifying phenolic groups.
- Tollen's Test: This test is used to detect aldehydes. When a compound containing an aldehyde group is reacted with Tollen's reagent, a silver mirror forms on the inner walls of the test tube. It is not used for phenolic groups.
Conclusion: The phthalein test is specifically used to identify the presence of phenolic groups. Therefore, the correct answer is Phthalein test.
Approach Solution -2
Phthalein dye test is a specific test for phenolic groups and involves the formation of colored compounds.
Carbylamine test is used for the identification of primary amines.
Lucas test differentiates between 1°, 2°, and 3° alcohols.
Tollen’s test is used for the identification of aldehydes.
Thus, the phenolic group can be identified by a positive Phthalein dye test.
The correct option is (C) :Phthalein test
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Concepts Used:
Phenols
Phenol is a different class of organic compounds that are usually found in wide usage in an extensive range of industries and also for domestic purposes. Phenol is formed when a hydrogen atom in a benzene molecule is replaced by the chemical -OH group.
Phenol is also called as Carbolic acid. It is an aromatic organic compound having the molecular formula C6H5OH. It is a volatile white crystalline solid. The molecule consists of a phenyl group (−C6H5) bonded to a hydroxy group (−OH). Phenol is mildly acidic, it requires careful handling because it can cause chemical burns.
Classification of Phenol
On the basis of the different number of hydroxyl groups attached, the phenols can be classified further into three types.
- Monohydric phenols: These contain one -OH group.
- Dihydric phenols: These contain two -OH groups. These may be ortho-, meta- or para- derivative.
- Trihydric phenols: These contain three -OH groups.
Properties of Phenol
- Phenol is an organic compound that is appreciably soluble in water, with about 84.2 g dissolving in 1000 mL (0.895 M).
- It is a weak acid.
- is highly reactive toward electrophilic aromatic substitution.