Consider the following reactions sequence When the product (P) is subjected to Carius analysis using AgNO_3, 1.0 g of the product (P) will produce _______ g of the precipitate of AgBr. (Nearest Integer) (Given: molar mass in g mol^ -1 C : 12, H : 1, O : 16, N : 14, Br : 80, Ag : 108)
A. A
The given reactant is p-nitrotoluene. Step (i): Reduction with Sn/HCl followed by OH^- converts the -NO_2 group to an -NH_2 group, yielding p-toluidine. Step (ii): Reaction with acetic anhydride, (CH_3CO)_2O, protects the amino group by forming N-(4-methylphenyl)acetamide. Step (iii): Bromination with Br_2/AlBr_3 directs the incoming bromine to the ortho position relative to the strongly activating -NHCOCH_3 group (the para position is blocked by the methyl group). This yields 2-bromo-4-methylacetanilide. Step (iv): Acid hydrolysis with H_3O^+ removes the acetyl group, yielding 2-bromo-4-methylaniline as the major product (P). The molecular formula of product P (2-bromo-4-methylaniline) is C_7H_8NBr. Molar mass of P = (7 12) + (8 1) + 14 + 80 = 186 g mol ^ -1 . In Carius analysis, the bromine in the organic compound is quantitatively converted to silver bromide (AgBr). Molar mass of AgBr = 108 + 80 = 188 g mol ^ -1 . Since one molecule of P contains one bromine atom, 1 mole of P produces 1 mole of AgBr. Moles of P in 1.0 g = 1.0 186 mol . Moles of AgBr produced = 1.0 186 mol . Mass of AgBr produced = 1.0 186 188 g 1.01 g . Rounding to the nearest integer, the mass of the AgBr precipitate is 1 g. Answer: 1
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