Amines · Question 39

Consider the following sequence of reactions: [figure] 11.25 mg of chlorobenzene will produce 10-1 mg of product B. (Consider the reactions result in complete conversion.) [Given molar mass of C, H, O, N and Cl as 12, 1, 16, 14 and 35.5 g mol-1 respectively]

Answer

93

Solution

C6H5Cl Mg, dry ether C6H5MgCl [H3O+]CO2 C6H5COOH NH3, C6H5CONH2 (A, benzamide)

C6H5CONH2 Br2, NaOH C6H5NH2 (B, aniline) — Hoffmann bromamide degradation

Every step is 1 : 1, so moles of B = moles of chlorobenzene.

Molar mass of C6H5Cl = 72 + 5 + 35.5 = 112.5 g mol-1

Moles = 11.25 mg112.5 g mol-1 = 0.1 mmol

Molar mass of C6H5NH2 = 72 + 7 + 14 = 93 g mol-1

Mass of B = 0.1 93 = 9.3 mg = 93 10-1 mg

Answer: 93