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Chapter 22: Problem 574

A colorless basic liquid \(\mathrm{C}_{7} \mathrm{H}_{9} \mathrm{~N}(\mathrm{~A})\) reacts immediately with sodium nitrite in cold dilute sulfuric acid to give a neutral yellow oil (B) . Reaction of A with acetic anhydride in pyridine solution gives a neutral white solid (C), the nmr spectrum of which shows a singlet at \(\delta 1.9\), a singlet at \(\delta 3.5\), and a multiplet at \(\delta 7.3\) with intensities of \(1: 1: 1.67\), respectively. Assign structures to \(\mathrm{A}, \mathrm{B}\), and \(\mathrm{C}\).

Short Answer

Expert verified
The structures of compounds A, B, and C are as follows: A: Aniline (\(C_6H_5NH_2\)) B: Phenol (\(C_6H_5OH\)) C: N-Acetylaniline (\(C_6H_5NHCOCH_3\))

Step by step solution

01

Identify the functional group present in A based on its basic nature

A basic liquid suggests the presence of a basic nitrogen atom in the compound A. This nitrogen atom could be part of an amine group, which is basic due to the lone pair of electrons on the nitrogen atom.
02

Analyze the reaction of A with sodium nitrite and sulfuric acid to form B

The reaction of amines with sodium nitrite and sulfuric acid usually results in the formation of diazonium salts, which can further react with different nucleophiles. Since we are dealing with a neutral yellow oil (B), the diazonium salt might have undergone a Sandmeyer (or similar) reaction.
03

Analyze the reaction of A with acetic anhydride in pyridine to form solid C

In this reaction, the amine group in A reacts with the acetic anhydride to form an amide. This reaction gives us solid C, for which we have the NMR data.
04

Interpret the NMR spectrum of C

The NMR spectrum of C shows a singlet at δ 1.9, a singlet at δ 3.5, and a multiplet at δ 7.3 with intensities of 1:1:1.67, respectively. These peaks could be assigned to the protons of the different fragments of the molecule: the methyl group from the added acetyl, the methylene group attached to the nitrogen atom, and the aromatic protons, respectively. Based on these assignments and the reaction mechanism, the compound A should be 1º aromatic amine.
05

Determine the structure of A

Since the molecular formula of A is \(C_7H_9N\), and we have confirmed that it is a primary aromatic amine, the structure of A can be determined as aniline (\(C_6H_5NH_2\)).
06

Determine the structure of B

Based on the reaction of aniline with sodium nitrite and sulfuric acid, we can predict that compound B is the product of a Sandmeyer reaction (or similar), with the diazonium group being replaced by a single halogen atom. The most likely candidate for a yellow oil is phenol, which has the formula \(C_6H_5OH\).
07

Determine the structure of C

Since compound A (aniline) reacts with acetic anhydride to form amide, the structure of compound C can be established as \(N\)-acetylaniline, which has the formula \(C_6H_5NHCOCH_3\). In summary, the structures of compounds A, B, and C are as follows: A: Aniline (\(C_6H_5NH_2\)) B: Phenol (\(C_6H_5OH\)) C: N-Acetylaniline (\(C_6H_5NHCOCH_3\))

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Most popular questions from this chapter

The \(\mathrm{pK}_{\mathrm{a}}\) of \(\mathrm{NH}_{4}^{+}\) is \(9.24\), that of \(\mathrm{CH}_{3} \mathrm{NH}_{3}^{+}\) is \(10.64\). Is methylamine a stronger or a weaker base than ammonia? How many times stronger or weaker? What do you think this difference is due to?

Show how one could synthesize-and resolve methylethylallylamine oxide from allylamine, with the knowledge that amine oxides are somewhat basic substances having \(\mathrm{K}_{\mathrm{B}}\) values at about \(10^{-11}\).

At room temperature, the nmr spectrum of 1 -ethylaziridine + CYCLOA shows the triplet-quartet of an ethyl group, and two other signals of equal peak area. When the temperature is raised to \(120^{\circ}\), the latter two signals merge into a single signal. How do you interpret these observations?

An azo compound is cleaved at the azo linkage by stannous chloride, \(\mathrm{Sn} \mathrm{Cl}_{2}\), to form two amines, (a) What is the structure of the azo compound that is cleaved to 3-bromo-4-aminotoluene and 2-methy1-4-aminophenol? (b) Outline a synthesis of this azo compound, starting with toluene.

Predict the products expected in the reactions of the following amines with nitrous acid (prepared from \(\mathrm{NaNO}_{2}+\mathrm{HCl}\) in aqueous solution):
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