C6H5NH2 and C6H5CH2NH2 can be distinguished by 1 (a) Fehling’s test (b) Isocyanide test (c) Adding NaNO2 + HCl (d) Iodoform test

To differentiate between C6H5NH2 (aniline) and C6H5CH2NH2 (benzylamine), we can utilize specific chemical tests that exploit their distinct functional groups. Among the options provided, the most effective method is (c) Adding NaNO2 + HCl. Let’s delve into why this is the case and briefly touch on the other tests for clarity.

Understanding the Compounds

First, let's clarify what these compounds are. Aniline (C6H5NH2) is an aromatic amine, while benzylamine (C6H5CH2NH2) is an aliphatic amine attached to a benzyl group. The key difference lies in the structure: aniline has the amino group directly attached to the benzene ring, whereas benzylamine has a -CH2- group connecting the amino group to the benzene ring.

Why NaNO2 + HCl Works

When you add sodium nitrite (NaNO2) to hydrochloric acid (HCl), it generates nitrous acid (HNO2). This reaction is particularly significant for aniline. Aniline reacts with nitrous acid to form a diazonium salt, which is a stable compound under cold conditions. In contrast, benzylamine does not form a stable diazonium salt under these conditions and instead leads to the formation of a different product that can be further analyzed.

Other Tests Explained

• Fehling’s Test: This test is primarily used to detect reducing sugars and aldehydes, not amines. Therefore, it is not suitable for distinguishing between aniline and benzylamine.
• Isocyanide Test: This test is used to identify primary amines by forming isocyanides. Both aniline and benzylamine can give a positive result, making this test ineffective for differentiation.
• Iodoform Test: This test is used to identify methyl ketones and some alcohols. Neither aniline nor benzylamine will give a positive result, so it is not applicable here.

Conclusion on Distinguishing Tests

In summary, the most reliable method to distinguish between aniline and benzylamine is by using sodium nitrite and hydrochloric acid, which will yield different outcomes for each compound. Aniline will form a diazonium salt, while benzylamine will not, allowing for clear differentiation. Understanding these reactions not only helps in identifying these compounds but also illustrates the fascinating chemistry of amines and their reactivity.