Give plausible explanation for each of t | Class 12 Chemistry Chapter Aldehydes Ketones and Carboxylic Acids, Aldehydes Ketones and Carboxylic Acids NCERT Solutions

Welcome to the NCERT Solutions for Class 12 Chemistry - Chapter Aldehydes Ketones and Carboxylic Acids. This page offers a step-by-step solution to the specific question from Exercise 2, Question 18: . With detailed answers and explanations for each chapter, students can strengthen their understanding and prepare confidently for exams. Ideal for CBSE and other board students, this resource will simplify your study experience.

Question 18:

Give plausible explanation for each of the following:

(i) Cyclohexanone forms cyanohydrin in good yield but 2, 2, 6 trimethylcyclohexanone does not.

(ii) There are two -NH2 groups in semicarbazide. However, only one is involved in the formation of semicarbazones.

(iii) During the preparation of esters from a carboxylic acid and an alcohol in the presence of an acid catalyst, the water or the ester should be removed as soon as it is formed.

Answer:

(i) Cyclohexanones form cyanohydrins according to the following equation.

In this case, the nucleophile CN - can easily attack without any steric hindrance. However, in the case of 2, 2, 6 trimethylcydohexanone, methyl groups at α-positions offer steric hindrances and as a result, CN - cannot attack effectively.

For this reason, it does not form a cyanohydrin.

 

(ii) Semicarbazide undergoes resonance involving only one of the two - NH2 groups, which is attached directly to the carbonyl-carbon atom.

Therefore, the electron density on - NH2 group involved in the resonance also decreases. As a result, it cannot act as a nucleophile. Since the other - NH2 group is not involved in resonance; it can act as a nucleophile and can attack carbonyl-carbon atoms of aldehydes and ketones to produce semicarbazones.

 

(iii) Ester along with water is formed reversibly from a carboxylic acid and an alcohol in presence of an acid.

If either water or ester is not removed as soon as it is formed, then it reacts to give back the reactants as the reaction is reversible. Therefore, to shift the equilibrium in the forward direction i.e., to produce more ester, either of the two should be removed.


Study Tips for Answering NCERT Questions:

NCERT questions are designed to test your understanding of the concepts and theories discussed in the chapter. Here are some tips to help you answer NCERT questions effectively:

  • Read the question carefully and focus on the core concept being asked.
  • Reference examples and data from the chapter when answering questions about Aldehydes Ketones and Carboxylic Acids.
  • Review previous year question papers to get an idea of how such questions may be framed in exams.
  • Practice answering questions within the time limit to improve your speed and accuracy.
  • Discuss your answers with your teachers or peers to get feedback and improve your understanding.

Latest Blog Posts

Stay updated with our latest educational content and study tips

How to Recognize and Prevent Online Scams Targeting Kids

The internet is full of entertaining apps, games and movies for kids of all ages. However not everything online is safe. Hidden among these entertaining platforms are internet frauds that target children with phony gifts, free game currencies or friendly looking people. As a parent, you may believe that scammers only target adults; yet children […]

Read More

How to Talk to Kids About Screen Time rules Without Conflict

Did you know? The average teenager spends 7 – 8 hours daily on screens . That’s almost like working a full – time job in front of a screen – except kids aren’t earning a paycheck; instead they’re often trading sleep, focus and health for digital time. In today’s world, screens are everywhere – TV, […]

Read More

10 Online Safety Rules Every Parent Should Teach Their Kids

Children are spending more time online than ever before in today’s digital world.  The internet provides enjoyment and knowledge through social media and online education, but it also has unspoken risks. Parents frequently worry about harmful information, internet predators and cyberbullying. The good news is that most problems can be avoided by teaching children basic […]

Read More

Top 8 internet Safety terms Parents Must Know to Keep Children Safe

The internet has become an inseparable part of our daily lives . From online learning to social media most systems we use today are fully digitized and processed by computers. While this digital shift has created immense opportunities it has also opened new challenges – especially for children and teenagers. Social media, gaming platforms and […]

Read More

Comments

  • Subhangini
  • Jul 27, 2019

Thank u so much for providing the answers


  • Ak
  • Mar 11, 2019

Thanks


  • None
  • Mar 10, 2019

Many conversions are wrong


Add Comment

Welcome to the NCERT Solutions for Class 12 Chemistry - Chapter . This page offers a step-by-step solution to the specific question from Excercise 2 , Question 18: Give plausible explanation for each of the following: (i) Cyclohexanone forms cyanohydrin in good....