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Does Phenol Give Ceric Ammonium Nitrate Test?

In the field of organic chemistry, identifying and distinguishing different classes of organic compounds is crucial. One common analytical method used for identifying alcohols and phenols is the ceric ammonium nitrate test (CAN test). But does phenol give ceric ammonium nitrate test? In this article, we’ll explore the reaction mechanism of phenol with ceric ammonium nitrate and explain why this particular test works for certain compounds but not others.

What is the Ceric Ammonium Nitrate Test?

The ceric ammonium nitrate test is commonly used to detect the presence of alcohols in a compound. In this test, a yellow solution of ceric ammonium nitrate (Ce(NH₄)₂(NO₃)₆) reacts with alcohols to form a red or reddish-brown complex. This color change is a positive indication of the presence of alcohol groups. The test works well for primary and secondary alcohols but has limited applicability to other functional groups.

Does Phenol React with Ceric Ammonium Nitrate?

Does phenol give ceric ammonium nitrate test like other alcohols? The answer is no. Phenol, although structurally similar to alcohols (due to the hydroxyl group attached to an aromatic ring), does not give a positive result in the ceric ammonium nitrate test. The test is specifically sensitive to alcohols in which the hydroxyl group is attached to a saturated carbon atom, such as in primary or secondary alcohols.

The reason phenol does not react with ceric ammonium nitrate lies in the electronic nature of the phenol’s hydroxyl group. In phenol, the -OH group is attached directly to an aromatic ring, and this ring strongly influences the behavior of the hydroxyl group. The resonance in the aromatic ring makes the oxygen less nucleophilic and less likely to participate in the reaction that causes the color change seen with other alcohols.

The Mechanism Behind the Reaction

In alcohols, the hydroxyl (-OH) group can coordinate with the cerium ion (Ce⁴⁺), which is responsible for the color change. When alcohols react with ceric ammonium nitrate, the Ce⁴⁺ gets reduced to Ce³⁺, causing a distinct color change to red. However, phenol’s resonance structure and the delocalization of electrons in the aromatic ring reduce the nucleophilicity of the oxygen, preventing effective coordination with cerium ions. As a result, phenols do not give a color change in the CAN test.

Alternative Tests for Phenols

Since phenol does not give a ceric ammonium nitrate test, alternative methods must be used to identify phenolic compounds. One common test for phenols is the ferric chloride test. In this test, phenols form a colored complex (often violet, blue, or green) when reacted with ferric chloride (FeCl₃). This provides a quick and reliable way to detect phenols specifically, without confusion with alcohols.

Conclusion

To answer the question, does phenol give ceric ammonium nitrate test, the simple response is no. While alcohols typically produce a color change in the ceric ammonium nitrate test, phenols do not due to their unique electronic structure. For identifying phenols, other tests like the ferric chloride test are more suitable. Understanding the underlying chemistry of these tests is essential for properly identifying compounds in the laboratory.