Reactions of furan & Derivative of pyridine
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Questions and Answers

What is the primary mechanism involved in the nitration of furan?

  • Addition-elimination mechanism (correct)
  • Elimination-addition mechanism
  • Nucleophilic substitution mechanism
  • Electrophilic addition mechanism

What is the role of pyridine in the nitration reaction of furan?

  • It acts as a base to eliminate acetic acid (correct)
  • It acts as a catalyst
  • It acts as a solvent
  • It acts as an acid

Where does electrophilic substitution normally occur in 2,5-disubstituted heterocycles?

  • At the 5-position
  • At the 3-position (correct)
  • At the 4-position
  • At the 2-position

What is the result of sulfonating furan with the usual strong acid reagents?

<p>Decomposition of furan (D)</p> Signup and view all the answers

What is the complex used to sulfonate furan and its derivatives?

<p>Pyridine-sulfur-trioxide complex (C)</p> Signup and view all the answers

What is the condition required for the disubstitution of furan to occur?

<p>Room temperature (B)</p> Signup and view all the answers

What is the position of sulfonation in furan substituted with an electron-withdrawing substituent at the 2-position?

<p>5-position (B)</p> Signup and view all the answers

What is the reagent used to sulfonate furan substituted with an electron-withdrawing substituent at the 2-position?

<p>Oleum (D)</p> Signup and view all the answers

What is the reaction of furan with iodine at room temperature?

<p>It does not react at all (D)</p> Signup and view all the answers

What is the product of bromination of furan in dimethylformamide at room temperature?

<p>2-bromo-furan or 2,5-dibromo-furan (A)</p> Signup and view all the answers

What is the reagent used to produce 2-bromo-furan at -5°C?

<p>Dioxane-dibromide (D)</p> Signup and view all the answers

What is the major product of bromination of furan substituted with an electron-withdrawing substituent at the position-2?

<p>5-bromo-derivative (B)</p> Signup and view all the answers

What is the product of oxidation of pyridine by peracids?

<p>N-oxide pyridine (B)</p> Signup and view all the answers

What is the characteristic of N-oxide pyridine?

<p>It is more activated for electrophilic and nucleophilic attack (D)</p> Signup and view all the answers

What is the advantage of N-oxide pyridine?

<p>It is very important intermediates for preparing pyridine derivatives (C)</p> Signup and view all the answers

What is the primary position of nitration of pyridine?

<p>Position 3 (D)</p> Signup and view all the answers

What is the distribution of charges in N-oxide pyridine?

<p>Positive and negative charges at positions 2 and 4 (B)</p> Signup and view all the answers

Why is 3-aminopyridine most conveniently made via nicotinic acid?

<p>Because of the difficulty of nitrating pyridine (C)</p> Signup and view all the answers

What is the role of peroxy-benzoic acid in pyridine conversion?

<p>It converts pyridine into its N-oxide (B)</p> Signup and view all the answers

What is the primary position of nitration of pyridine N-oxide?

<p>Position 4 (B)</p> Signup and view all the answers

Why does 2-aminopyridine undergo nitration or sulfonation under milder conditions?

<p>Because of the electron donating nature of the amine group (D)</p> Signup and view all the answers

What is the relative basicity of amines (RCH2NH2) compared to imines (RCH=NH) and nitriles (RCN)?

<p>Amines are more basic than imines and nitriles (B)</p> Signup and view all the answers

Why does pyridine N-oxide undergo nitration more readily than pyridine itself?

<p>Because of the electron withdrawing nature of the oxygen atom (C)</p> Signup and view all the answers

What is the synthesis of 3-aminopyridine from beta-picoline?

<p>Through reduction of nicotinic acid followed by decarboxylation (A)</p> Signup and view all the answers

What is the major reason for the difficulty of nitration of pyridine?

<p>Pyridine has a low electron density at the 3-position (C)</p> Signup and view all the answers

Which of the following statements is true about the nitration of pyridine N-oxide?

<p>It occurs at the 4-position (A)</p> Signup and view all the answers

What is the primary reason for the difference in reactivity between pyridine and pyridine N-oxide towards nitration?

<p>Pyridine N-oxide has a higher electron density (D)</p> Signup and view all the answers

Why is 2-aminopyridine more susceptible to nitration and sulfonation than pyridine?

<p>It has a higher electron density at the 5-position (A)</p> Signup and view all the answers

What is the role of peroxy-benzoic acid in the conversion of pyridine?

<p>It is an oxidizing agent (B)</p> Signup and view all the answers

What is the primary reason for the low yield of nitration of pyridine?

<p>Pyridine has a low electron density at the 3-position (B)</p> Signup and view all the answers

What is the relative basicity of amines (RCH2NH2) compared to imines (RCH=NH) and nitriles (RCN)?

<p>Amine &gt; imine &gt; nitrile (D)</p> Signup and view all the answers

What is the primary advantage of using pyridine N-oxide in nitration reactions?

<p>It is more susceptible to nitration (B)</p> Signup and view all the answers

Why is the synthesis of 3-aminopyridine from beta-picoline a convenient route?

<p>It avoids the difficulties of nitrating pyridine (D)</p> Signup and view all the answers

What is the primary reason for the difference in reactivity between pyridine and its derivatives towards electrophiles?

<p>The derivatives have a higher electron density (A)</p> Signup and view all the answers

What is the primary reason for the difference in reactivity between pyridine and pyridine N-oxide towards nitration?

<p>The electron-withdrawing property of the oxide group (A)</p> Signup and view all the answers

Why is the synthesis of 3-aminopyridine from beta-picoline a convenient route?

<p>It avoids the difficult nitration of pyridine (C)</p> Signup and view all the answers

What is the primary reason for the substitution occurring chiefly at the 5-position in 2-aminopyridine?

<p>The presence of the amino group increases the electron density at the 5-position (D)</p> Signup and view all the answers

What is the role of the oxygen in pyridine N-oxide in the nitration reaction?

<p>It directs the nitration to the 4-position (B)</p> Signup and view all the answers

What is the advantage of using pyridine N-oxide in nitration reactions?

<p>It directs the nitration to a more favorable position (A)</p> Signup and view all the answers

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