UPSC Exam > UPSC Notes > Chemistry Optional Notes for UPSC > Benzoin Condensation and Stobbe Condensation
Benzoin Condensation and Stobbe Condensation | Chemistry Optional Notes for UPSC PDF Download
| Download, print and study this document offline |
Please wait while the PDF view is loading
Page 1
______________________________________________________________ ___
1. Learning Outcomes
After studying this module, you shall be able to:
? Know what are Benzoin condensation and Stobbe condensation reactions
? Learn mechanism of Benzoin and Stobbe condensation reactions
? Know about the role of CN
-
ion in Benzoin condensation
? Identify the products of reduction and oxidation of Benzoin condensation
? Understand the product formation in Benzoin and Stobbe condensation.
2. Introduction
A condensation reaction, also commonly referred to as dehydration synthesis, is a
chemical reaction in which two molecules or moieties (functional groups) combine to
form a larger molecule, together with the loss of a small molecule. Generally the small
molecules lost are water, hydrogen chloride, methanol, or acetic acid but most commonly
in a biological reaction it is water.
In organic synthesis, by far the most important activating groups are the carbonyl and
carboxylic ester groups. Removal of a proton from the a-carbon atom of a carbonyl
compound with base produces the corresponding a-carbanion, which are resonance
stabilized via enolate anion. These enolate ions are involved in base catalysed reactions
of carbonyl compounds.
Amongst these base catalysed reactions, the Stobbe reaction between dialkyl succinate
and aldehyde or a ketone is a good method for making carbon-carbon bonds.
Another important reaction for C-C bond formation is Benzoin condensation, in which
aromatic aldehydes (with no a- hydrogens) in the presence of CN
-
condensed to form
Page 2
______________________________________________________________ ___
1. Learning Outcomes
After studying this module, you shall be able to:
? Know what are Benzoin condensation and Stobbe condensation reactions
? Learn mechanism of Benzoin and Stobbe condensation reactions
? Know about the role of CN
-
ion in Benzoin condensation
? Identify the products of reduction and oxidation of Benzoin condensation
? Understand the product formation in Benzoin and Stobbe condensation.
2. Introduction
A condensation reaction, also commonly referred to as dehydration synthesis, is a
chemical reaction in which two molecules or moieties (functional groups) combine to
form a larger molecule, together with the loss of a small molecule. Generally the small
molecules lost are water, hydrogen chloride, methanol, or acetic acid but most commonly
in a biological reaction it is water.
In organic synthesis, by far the most important activating groups are the carbonyl and
carboxylic ester groups. Removal of a proton from the a-carbon atom of a carbonyl
compound with base produces the corresponding a-carbanion, which are resonance
stabilized via enolate anion. These enolate ions are involved in base catalysed reactions
of carbonyl compounds.
Amongst these base catalysed reactions, the Stobbe reaction between dialkyl succinate
and aldehyde or a ketone is a good method for making carbon-carbon bonds.
Another important reaction for C-C bond formation is Benzoin condensation, in which
aromatic aldehydes (with no a- hydrogens) in the presence of CN
-
condensed to form
_______________________________________________________________ ___
benzoin. In majority of simple cases, as a result of this
reaction, double the number of carbon atoms are present in the final product as compared
to the starting molecule.
3. Benzoin Condensation
The benzoin condensation is a reaction (often called a condensation reaction, for
historical reasons) between two aromatic aldehydes, particularly benzaldehyde. The
reaction is catalyzed by a nucleophile such as the cyanide anion or an N-heterocyclic
carbene. The reaction product is an aromatic acyloin with benzoin as the parent
compound.
An early version of the reaction was developed in 1832 by Justus von Liebig and
Friedrich Woehler during their research on bitter almond oil. The catalytic version of the
reaction was developed by Nikolay Zinin in the late 1830s, and the reaction mechanism
for this organic reaction was proposed in 1903 by A. J. Lapworth.
3.1 Mechanism of Benzoin Condensation
In the first step, the cyanide anion (as sodium cyanide) attacks the carbonyl carbon of the
aldehyde in a nucleophilic addition. Rearrangement of the intermediate results in polarity
reversal of the carbonyl group, which then adds to the carbonyl group of the other
aromatic aldehyde (instead of H
+
transfer as that of Cannizzaro reaction). Proton transfer
and elimination of the cyanide ion results in benzoin as the product.
Mechanism involved:
Page 3
______________________________________________________________ ___
1. Learning Outcomes
After studying this module, you shall be able to:
? Know what are Benzoin condensation and Stobbe condensation reactions
? Learn mechanism of Benzoin and Stobbe condensation reactions
? Know about the role of CN
-
ion in Benzoin condensation
? Identify the products of reduction and oxidation of Benzoin condensation
? Understand the product formation in Benzoin and Stobbe condensation.
2. Introduction
A condensation reaction, also commonly referred to as dehydration synthesis, is a
chemical reaction in which two molecules or moieties (functional groups) combine to
form a larger molecule, together with the loss of a small molecule. Generally the small
molecules lost are water, hydrogen chloride, methanol, or acetic acid but most commonly
in a biological reaction it is water.
In organic synthesis, by far the most important activating groups are the carbonyl and
carboxylic ester groups. Removal of a proton from the a-carbon atom of a carbonyl
compound with base produces the corresponding a-carbanion, which are resonance
stabilized via enolate anion. These enolate ions are involved in base catalysed reactions
of carbonyl compounds.
Amongst these base catalysed reactions, the Stobbe reaction between dialkyl succinate
and aldehyde or a ketone is a good method for making carbon-carbon bonds.
Another important reaction for C-C bond formation is Benzoin condensation, in which
aromatic aldehydes (with no a- hydrogens) in the presence of CN
-
condensed to form
_______________________________________________________________ ___
benzoin. In majority of simple cases, as a result of this
reaction, double the number of carbon atoms are present in the final product as compared
to the starting molecule.
3. Benzoin Condensation
The benzoin condensation is a reaction (often called a condensation reaction, for
historical reasons) between two aromatic aldehydes, particularly benzaldehyde. The
reaction is catalyzed by a nucleophile such as the cyanide anion or an N-heterocyclic
carbene. The reaction product is an aromatic acyloin with benzoin as the parent
compound.
An early version of the reaction was developed in 1832 by Justus von Liebig and
Friedrich Woehler during their research on bitter almond oil. The catalytic version of the
reaction was developed by Nikolay Zinin in the late 1830s, and the reaction mechanism
for this organic reaction was proposed in 1903 by A. J. Lapworth.
3.1 Mechanism of Benzoin Condensation
In the first step, the cyanide anion (as sodium cyanide) attacks the carbonyl carbon of the
aldehyde in a nucleophilic addition. Rearrangement of the intermediate results in polarity
reversal of the carbonyl group, which then adds to the carbonyl group of the other
aromatic aldehyde (instead of H
+
transfer as that of Cannizzaro reaction). Proton transfer
and elimination of the cyanide ion results in benzoin as the product.
Mechanism involved:
____________________________________________________________________________________________________
3.2 Characteristics of Benzoin Condensation
? This reaction is completely reversible, the reversibility is indicated by the fact that
benzoin is heated with another aromatic aldehyde mixed products are obtained.
? Cyanide ion catalyzes the reaction because:
(i) It is good nucleophile
(ii) It is good leaving group
(iii) It increases the acidity of the C-H bond and stabilizes the carbanion that
results from the loss of proton from C.
Page 4
______________________________________________________________ ___
1. Learning Outcomes
After studying this module, you shall be able to:
? Know what are Benzoin condensation and Stobbe condensation reactions
? Learn mechanism of Benzoin and Stobbe condensation reactions
? Know about the role of CN
-
ion in Benzoin condensation
? Identify the products of reduction and oxidation of Benzoin condensation
? Understand the product formation in Benzoin and Stobbe condensation.
2. Introduction
A condensation reaction, also commonly referred to as dehydration synthesis, is a
chemical reaction in which two molecules or moieties (functional groups) combine to
form a larger molecule, together with the loss of a small molecule. Generally the small
molecules lost are water, hydrogen chloride, methanol, or acetic acid but most commonly
in a biological reaction it is water.
In organic synthesis, by far the most important activating groups are the carbonyl and
carboxylic ester groups. Removal of a proton from the a-carbon atom of a carbonyl
compound with base produces the corresponding a-carbanion, which are resonance
stabilized via enolate anion. These enolate ions are involved in base catalysed reactions
of carbonyl compounds.
Amongst these base catalysed reactions, the Stobbe reaction between dialkyl succinate
and aldehyde or a ketone is a good method for making carbon-carbon bonds.
Another important reaction for C-C bond formation is Benzoin condensation, in which
aromatic aldehydes (with no a- hydrogens) in the presence of CN
-
condensed to form
_______________________________________________________________ ___
benzoin. In majority of simple cases, as a result of this
reaction, double the number of carbon atoms are present in the final product as compared
to the starting molecule.
3. Benzoin Condensation
The benzoin condensation is a reaction (often called a condensation reaction, for
historical reasons) between two aromatic aldehydes, particularly benzaldehyde. The
reaction is catalyzed by a nucleophile such as the cyanide anion or an N-heterocyclic
carbene. The reaction product is an aromatic acyloin with benzoin as the parent
compound.
An early version of the reaction was developed in 1832 by Justus von Liebig and
Friedrich Woehler during their research on bitter almond oil. The catalytic version of the
reaction was developed by Nikolay Zinin in the late 1830s, and the reaction mechanism
for this organic reaction was proposed in 1903 by A. J. Lapworth.
3.1 Mechanism of Benzoin Condensation
In the first step, the cyanide anion (as sodium cyanide) attacks the carbonyl carbon of the
aldehyde in a nucleophilic addition. Rearrangement of the intermediate results in polarity
reversal of the carbonyl group, which then adds to the carbonyl group of the other
aromatic aldehyde (instead of H
+
transfer as that of Cannizzaro reaction). Proton transfer
and elimination of the cyanide ion results in benzoin as the product.
Mechanism involved:
____________________________________________________________________________________________________
3.2 Characteristics of Benzoin Condensation
? This reaction is completely reversible, the reversibility is indicated by the fact that
benzoin is heated with another aromatic aldehyde mixed products are obtained.
? Cyanide ion catalyzes the reaction because:
(i) It is good nucleophile
(ii) It is good leaving group
(iii) It increases the acidity of the C-H bond and stabilizes the carbanion that
results from the loss of proton from C.
____________________________________________________________________________________________________
? The benzoin condensation is in effect a
dimerization and not a condensation because a small molecule like water is not
released in this reaction. For this reason the reaction is also called a benzoin
addition.
? In this reaction, the two aldehydes serve different purposes; one aldehyde donates
a proton and one aldehyde accepts a proton. In this way it is possible to synthesize
mixed benzoins, i.e. products with different groups on each half of the product.
? Rate law of Benzoin condensation, r = [ ArCHO]
2
[CN
-
]
? Benzoin is colorless solid (M.P. 157 C) which assumed to tautomerise to ene diol.
3.3 Reactions of Benzoin
3.3.1. Reduction of Benzoin:
Benzoin is sensitive to reduction and can be reduced to different products using
different reaction conditions and catalysts.
(i) Reduction with Na/ EtOH gives hydrobenzoin.
(ii) Reduction with Sn/HCl results in the formation of Deoxybenzoin.
(iii) Clemmensen reduction results in stilbene.
(iv) Complete reduction product dibenzyl is obtained on reducing in the presence of
Ni catalyst.
Page 5
______________________________________________________________ ___
1. Learning Outcomes
After studying this module, you shall be able to:
? Know what are Benzoin condensation and Stobbe condensation reactions
? Learn mechanism of Benzoin and Stobbe condensation reactions
? Know about the role of CN
-
ion in Benzoin condensation
? Identify the products of reduction and oxidation of Benzoin condensation
? Understand the product formation in Benzoin and Stobbe condensation.
2. Introduction
A condensation reaction, also commonly referred to as dehydration synthesis, is a
chemical reaction in which two molecules or moieties (functional groups) combine to
form a larger molecule, together with the loss of a small molecule. Generally the small
molecules lost are water, hydrogen chloride, methanol, or acetic acid but most commonly
in a biological reaction it is water.
In organic synthesis, by far the most important activating groups are the carbonyl and
carboxylic ester groups. Removal of a proton from the a-carbon atom of a carbonyl
compound with base produces the corresponding a-carbanion, which are resonance
stabilized via enolate anion. These enolate ions are involved in base catalysed reactions
of carbonyl compounds.
Amongst these base catalysed reactions, the Stobbe reaction between dialkyl succinate
and aldehyde or a ketone is a good method for making carbon-carbon bonds.
Another important reaction for C-C bond formation is Benzoin condensation, in which
aromatic aldehydes (with no a- hydrogens) in the presence of CN
-
condensed to form
_______________________________________________________________ ___
benzoin. In majority of simple cases, as a result of this
reaction, double the number of carbon atoms are present in the final product as compared
to the starting molecule.
3. Benzoin Condensation
The benzoin condensation is a reaction (often called a condensation reaction, for
historical reasons) between two aromatic aldehydes, particularly benzaldehyde. The
reaction is catalyzed by a nucleophile such as the cyanide anion or an N-heterocyclic
carbene. The reaction product is an aromatic acyloin with benzoin as the parent
compound.
An early version of the reaction was developed in 1832 by Justus von Liebig and
Friedrich Woehler during their research on bitter almond oil. The catalytic version of the
reaction was developed by Nikolay Zinin in the late 1830s, and the reaction mechanism
for this organic reaction was proposed in 1903 by A. J. Lapworth.
3.1 Mechanism of Benzoin Condensation
In the first step, the cyanide anion (as sodium cyanide) attacks the carbonyl carbon of the
aldehyde in a nucleophilic addition. Rearrangement of the intermediate results in polarity
reversal of the carbonyl group, which then adds to the carbonyl group of the other
aromatic aldehyde (instead of H
+
transfer as that of Cannizzaro reaction). Proton transfer
and elimination of the cyanide ion results in benzoin as the product.
Mechanism involved:
____________________________________________________________________________________________________
3.2 Characteristics of Benzoin Condensation
? This reaction is completely reversible, the reversibility is indicated by the fact that
benzoin is heated with another aromatic aldehyde mixed products are obtained.
? Cyanide ion catalyzes the reaction because:
(i) It is good nucleophile
(ii) It is good leaving group
(iii) It increases the acidity of the C-H bond and stabilizes the carbanion that
results from the loss of proton from C.
____________________________________________________________________________________________________
? The benzoin condensation is in effect a
dimerization and not a condensation because a small molecule like water is not
released in this reaction. For this reason the reaction is also called a benzoin
addition.
? In this reaction, the two aldehydes serve different purposes; one aldehyde donates
a proton and one aldehyde accepts a proton. In this way it is possible to synthesize
mixed benzoins, i.e. products with different groups on each half of the product.
? Rate law of Benzoin condensation, r = [ ArCHO]
2
[CN
-
]
? Benzoin is colorless solid (M.P. 157 C) which assumed to tautomerise to ene diol.
3.3 Reactions of Benzoin
3.3.1. Reduction of Benzoin:
Benzoin is sensitive to reduction and can be reduced to different products using
different reaction conditions and catalysts.
(i) Reduction with Na/ EtOH gives hydrobenzoin.
(ii) Reduction with Sn/HCl results in the formation of Deoxybenzoin.
(iii) Clemmensen reduction results in stilbene.
(iv) Complete reduction product dibenzyl is obtained on reducing in the presence of
Ni catalyst.
____________________________________________________________________________________________________
3.3.2. Oxidation of Benzoin:
Benzoin can be easily oxidised using various oxidising agents. One of the most important
product of benzoin oxidation is benzil.
(i) Oxidation with CrO3 results in the formation of an aromatic aldehyde and one
benzoin acid derivative.
(ii) Oxidation of benzoin with nitric acid gives benzil.
(iii) And benzoin oxidation
Read More
FAQs on Benzoin Condensation and Stobbe Condensation - Chemistry Optional Notes for UPSC
| 1. What is the Benzoin Condensation? |  |
Ans. Benzoin condensation is a chemical reaction in which two molecules of benzaldehyde react with a catalytic amount of a base to form a benzoin compound. This reaction is a type of nucleophilic addition reaction and is commonly used in organic synthesis.
| 2. How does the Benzoin Condensation reaction occur? | |
Ans. The Benzoin Condensation reaction occurs when benzaldehyde molecules are treated with a base, such as sodium hydroxide, in the presence of a catalytic amount of thiamine hydrochloride. The base deprotonates one of the benzaldehyde molecules, creating a nucleophile that attacks the carbonyl carbon of another benzaldehyde molecule. This leads to the formation of an intermediate called a benzoin, which undergoes further reaction to form the final benzoin product.
| 3. What are the applications of Benzoin Condensation? | |
Ans. Benzoin condensation has several applications in organic synthesis. It is commonly used to synthesize benzoin derivatives, which can be further transformed into various compounds with pharmaceutical and biological activities. Benzoin condensation is also used in the synthesis of chalcones, which are important intermediates in the production of flavonoids.
| 4. What is Stobbe Condensation? | |
Ans. Stobbe condensation is a type of condensation reaction in organic chemistry. It involves the reaction of an ester with an α,β-unsaturated ketone or aldehyde in the presence of a base to form a β-keto ester. This reaction is named after the German chemist Hermann Stobbe, who first reported it in 1901.
| 5. How does the Stobbe Condensation reaction occur? | |
Ans. The Stobbe Condensation reaction occurs when an ester is treated with an α,β-unsaturated ketone or aldehyde in the presence of a base, such as sodium ethoxide. The base deprotonates the α-carbon of the α,β-unsaturated ketone or aldehyde, creating a nucleophile that attacks the carbonyl carbon of the ester. This leads to the formation of an intermediate, which undergoes further reaction to form the final β-keto ester product.
Related Exams
About this Document
|
Nov 21, 2024 Last updated |
Document Description: Benzoin Condensation and Stobbe Condensation for UPSC 2024 is part of Chemistry Optional Notes for UPSC preparation.
The notes and questions for Benzoin Condensation and Stobbe Condensation have been prepared according to the UPSC exam syllabus. Information about Benzoin Condensation and Stobbe Condensation covers topics
like and Benzoin Condensation and Stobbe Condensation Example, for UPSC 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises and tests below for Benzoin Condensation and Stobbe Condensation.
Introduction of Benzoin Condensation and Stobbe Condensation in English is available as part of our Chemistry Optional Notes for UPSC
for UPSC & Benzoin Condensation and Stobbe Condensation in Hindi for Chemistry Optional Notes for UPSC course.
Download more important topics related with notes, lectures and mock test series for UPSC
Exam by signing up for free. UPSC: Benzoin Condensation and Stobbe Condensation | Chemistry Optional Notes for UPSC
Description
Full syllabus notes, lecture & questions for Benzoin Condensation and Stobbe Condensation | Chemistry Optional Notes for UPSC - UPSC | Plus excerises question with solution to help you revise complete syllabus for Chemistry Optional Notes for UPSC | Best notes, free PDF download
Information about Benzoin Condensation and Stobbe Condensation
In this doc you can find the meaning of Benzoin Condensation and Stobbe Condensation defined & explained in the simplest way possible. Besides explaining types of
Benzoin Condensation and Stobbe Condensation theory, EduRev gives you an ample number of questions to practice Benzoin Condensation and Stobbe Condensation tests, examples and also practice UPSC
tests
|
Explore Courses for UPSC exam
|
|
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
Related Searches
Free
,Important questions
,Benzoin Condensation and Stobbe Condensation | Chemistry Optional Notes for UPSC
,Viva Questions
,Semester Notes
,Sample Paper
,practice quizzes
,video lectures
,Extra Questions
,Summary
,MCQs
,Benzoin Condensation and Stobbe Condensation | Chemistry Optional Notes for UPSC
,ppt
,mock tests for examination
,Exam
,past year papers
,Objective type Questions
,Benzoin Condensation and Stobbe Condensation | Chemistry Optional Notes for UPSC
,shortcuts and tricks
,study material
,Previous Year Questions with Solutions
;
Additional Information about Benzoin Condensation and Stobbe Condensation for UPSC Preparation
Benzoin Condensation and Stobbe Condensation Free PDF Download
The Benzoin Condensation and Stobbe Condensation is an invaluable resource that delves deep into the core of the UPSC exam.
These study notes are curated by experts and cover all the essential topics and concepts, making your preparation more efficient and effective.
With the help of these notes, you can grasp complex subjects quickly, revise important points easily,
and reinforce your understanding of key concepts. The study notes are presented in a concise and easy-to-understand manner,
allowing you to optimize your learning process. Whether you're looking for best-recommended books, sample papers, study material,
or toppers' notes, this PDF has got you covered. Download the Benzoin Condensation and Stobbe Condensation now and kickstart your journey towards success in the UPSC exam.
Importance of Benzoin Condensation and Stobbe Condensation
The importance of Benzoin Condensation and Stobbe Condensation cannot be overstated, especially for UPSC aspirants.
This document holds the key to success in the UPSC exam.
It offers a detailed understanding of the concept, providing invaluable insights into the topic.
By knowing the concepts well in advance, students can plan their preparation effectively.
Utilize this indispensable guide for a well-rounded preparation and achieve your desired results.
Benzoin Condensation and Stobbe Condensation Notes
Benzoin Condensation and Stobbe Condensation Notes offer in-depth insights into the specific topic to help you master it with ease.
This comprehensive document covers all aspects related to Benzoin Condensation and Stobbe Condensation.
It includes detailed information about the exam syllabus, recommended books, and study materials for a well-rounded preparation.
Practice papers and question papers enable you to assess your progress effectively.
Additionally, the paper analysis provides valuable tips for tackling the exam strategically.
Access to Toppers' notes gives you an edge in understanding complex concepts.
Whether you're a beginner or aiming for advanced proficiency, Benzoin Condensation and Stobbe Condensation Notes on EduRev are your ultimate resource for success.
Benzoin Condensation and Stobbe Condensation UPSC Questions
The "Benzoin Condensation and Stobbe Condensation UPSC Questions" guide is a valuable resource for all aspiring students preparing for the
UPSC exam. It focuses on providing a wide range of practice questions to help students gauge
their understanding of the exam topics. These questions cover the entire syllabus, ensuring comprehensive preparation.
The guide includes previous years' question papers for students to familiarize themselves with the exam's format and difficulty level.
Additionally, it offers subject-specific question banks, allowing students to focus on weak areas and improve their performance.
Study Benzoin Condensation and Stobbe Condensation on the App
Students of UPSC can study Benzoin Condensation and Stobbe Condensation alongwith tests & analysis from the EduRev app,
which will help them while preparing for their exam. Apart from the Benzoin Condensation and Stobbe Condensation,
students can also utilize the EduRev App for other study materials such as previous year question papers, syllabus, important questions, etc.
The EduRev App will make your learning easier as you can access it from anywhere you want.
The content of Benzoin Condensation and Stobbe Condensation is prepared as per the latest UPSC syllabus.
|
© EduRev
|
Education Revolution
|
Follow Us
|
Signup on EduRev and stay on top of your study goals
10M+ students crushing their study goals daily