Skip to main content
Ch. 19 - Amines
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Wade 9th EditionCh. 19 - Amines문제 12
19장, 문제 12

Propose a mechanism for the sulfonation of pyridine, and point out why sulfonation occurs at the 3-position.

검증된 단계별 안내
1
Step 1: Recognize that sulfonation of pyridine involves electrophilic aromatic substitution. The electrophile in this reaction is the sulfur trioxide (SO₃) molecule, which is generated from fuming sulfuric acid (H₂SO₄). The reaction occurs under high temperature (230 °C) to overcome pyridine's reduced reactivity due to the electron-withdrawing nitrogen atom.
Step 2: Analyze the electronic structure of pyridine. The nitrogen atom in pyridine is electronegative and withdraws electron density from the ring, making the ring less reactive toward electrophiles. Additionally, the nitrogen's lone pair is not delocalized into the aromatic system, further reducing the ring's electron density.
Step 3: Consider the regioselectivity of the sulfonation. Electrophilic substitution on pyridine typically occurs at the 3-position because the 2- and 4-positions are destabilized by the positive charge that would result on the nitrogen atom in the intermediate resonance structures. Substitution at the 3-position avoids this destabilization.
Step 4: Propose the mechanism. First, the sulfur trioxide (SO₃) electrophile attacks the 3-position of pyridine, forming a sigma complex (arenium ion). This intermediate is stabilized by resonance, avoiding structures that place a positive charge on the nitrogen atom.
Step 5: Complete the reaction. The sigma complex undergoes deprotonation to restore aromaticity, resulting in the formation of 3-sulfonated pyridine. The sulfonic acid group (-SO₃H) is attached at the 3-position, as shown in the product structure.

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.
영상 길이:
7m

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Electrophilic Aromatic Substitution (EAS)

Electrophilic Aromatic Substitution is a fundamental reaction mechanism in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. In the case of pyridine, the nitrogen atom's lone pair can influence the reactivity and orientation of the substitution, making it crucial to understand how electrophiles interact with the aromatic system.
추천 영상:
03:07
EAS Review

Pyridine Structure and Reactivity

Pyridine is a six-membered aromatic ring containing a nitrogen atom, which affects its electronic properties. The nitrogen atom is electron-withdrawing, which alters the electron density on the ring and influences the position where electrophilic substitution occurs. Understanding the electronic effects of the nitrogen is essential for predicting the site of sulfonation.
추천 영상:
가이드 코스
1:33
EAS Reactions of Pyridine Concept 1

Regioselectivity in Sulfonation

Regioselectivity refers to the preference of a chemical reaction to occur at one site over another in a molecule. In the sulfonation of pyridine, the 3-position is favored due to the resonance stabilization of the intermediate cation formed during the reaction. This concept is vital for explaining why sulfonation predominantly occurs at this position rather than others.
추천 영상:
04:33
Forcing Ortho substitution
관련 실천
교과서 질문

(a) Propose a mechanism for the reaction of 2-bromopyridine with sodium amide to give 2-aminopyridine.

956
views
교과서 질문

The proton and 13C NMR spectra of a compound of formula C4H11N are shown here. Determine the structure of this amine, and give peak assignments for all of the protons in the structure.

<IMAGE>

2656
views
1
rank
교과서 질문

We have considered nucleophilic aromatic substitution of pyridine at the 2-position and 3-position but not at the 4-position. Complete the three possible cases by showing the mechanism for the reaction of methoxide ion with 4-chloropyridine. Show how the intermediate is stabilized by delocalization of the charge onto the nitrogen atom.

1209
views
교과서 질문

(b) When 3-bromopyridine is used in this reaction, stronger reaction conditions are required and a mixture of 3-aminopyridine and 4-aminopyridine results. Propose a mechanism to explain this curious result.

688
views
교과서 질문

Propose a mechanism for nitration of pyridine at the 4-position, and show why this orientation is not observed.

1151
views
교과서 질문

Rank each set of compounds in order of increasing basicity.

(d) pyrrole, imidazole, 3-nitropyrrole

1338
views