Passage: Consider the following reaction sequence in which J , K , L and M are the major products. The volume of 1 M aqueous H _2 SO _4 required to completely neutralize the ammonia evolved from 5.72 g of L in Kjeldahl's method of nitrogen estimation is ____ mL.
A. A
The reaction sequence proceeds as follows: 1. Friedel-Crafts Acylation: Reaction of m-xylene (1,3-dimethylbenzene) with chloroacetyl chloride ( ClCH _2 COCl ) in the presence of anhydrous AlCl _3 occurs at the less sterically hindered activated position (position 4) to give 1-(2,4-dimethylphenyl)-2-chloroethan-1-one. 2. Finkelstein Reaction: Heating with NaI replaces the chloride with iodide, yielding 1-(2,4-dimethylphenyl)-2-iodoethan-1-one. 3. Williamson Ether Synthesis: Reaction with sodium 3-nitrophenoxide gives compound J , which is 1-(2,4-dimethylphenyl)-2-(3-nitrophenoxy)ethan-1-one. 4. Reduction and Bromination: NaBH _4 reduces the ketone group in J to a secondary alcohol without affecting the nitro group. Subsequent reaction with PBr _3 converts the alcohol to a bromide, yielding compound K , 1-(1-bromo-2-(3-nitrophenoxy)ethyl)-2,4-dimethylbenzene. The molecular formula of K is C _ 16 H _ 16 BrNO _3. Molar mass of K = (16 12) + (16 1) + 80 + 14 + (3 16) = 192 + 16 + 80 + 14 + 48 = 350 g/mol , which matches the given data. 5. Amination: Reaction of K with excess NH _3 results in nucleophilic substitution of the bromide to form a primary amine, compound L , 1-(2,4-dimethylphenyl)-2-(3-nitrophenoxy)ethanamine. The molecular formula of L is C _ 16 H _ 18 N _2 O _3. Molar mass of L = (16 12) + (18 1) + (2 14) + (3 16) = 192 + 18 + 28 + 48 = 286 g/mol . Moles of L taken = 5.72 g 286 g/mol = 0.02 mol . In Kjeldahl's method, nitrogen present in nitro (- NO _2) groups is not converted to ammonium sulfate and thus is not estimated. Only the nitrogen from the primary amine (- NH _2) group will evolve as ammonia ( NH _3). Therefore, 1 mole of L yields 1 mole of NH _3. Moles of NH _3 evolved = 0.02 mol . The neutralization reaction with sulfuric acid is: 2 NH _3 + H _2 SO _4 ( NH _4)_2 SO _4 Moles of H _2 SO _4 required = 0.02 2 = 0.01 mol . Given the molarity of H _2 SO _4 is 1 M : Volume of H _2 SO _4 = Moles Molarity = 0.01 mol 1 mol/L = 0.01 L = 10 mL . Answer: 10
Related: Chemistry — Amines · All PYQ Banks