A. L. Abdulkareem Hamad Ayfan Overview

 Name Reaction  Rules for writing reaction mechanism  Introduction of Stanislao Cannizzaro  What is Cannizzaro Reaction?  Mechanism of Cannizzaro Reaction  Limitation  The Biological Analogue of the Cannizzaro Reaction  Application  Microscale Techniques

Name Reaction  Visit Google and search under the specific Name Reaction.  http://www.organic-chemistry.org/namedreactions  http://www.monomerchem.com/display4.html  http://orgchem.chem.uconn.edu/namereact/named.html  http://www.ecompound.com/Reaction%20reference/reaction_index.html  http://www.liv.ac.uk/Chemistry/Links/reactions.html

Name Reactions: A Collection of Detailed Reaction Mechanisms by Jie Jack Li (Hardcover - August 29, 2006)

Rules for writing reaction mechanism

“ ” was used in Resonance Structure

*Resonance structures cannot be distinguished chemically “ ” was used in Resonance Structure  For example “ ” was used in Equilibrium

(a) Different sigma bonding pattern, (b) Geometrical change (e.g., isomerization) “ ” was used in Equilibrium  For example Questions: A: R1 R 1 B: (1) I I R2 R2 R3 R3

(2)

CHO

CH2OH H OH H O H H OH H (3) OH H OH OH H OH H OH H OH

CH2OH “ ” for two-electron movement

The arrowtail is drawn from (a) a lone pair of electrons

(b) from two electrons making up a bond “ ” for a single electron movement

The arrow tail is drawn from (a) a bond made up two electrons

(b) from a center having a single valence electron. Example of radical reaction Stanislao Cannizzaro  An Italian Chemist  July 13, 1826-May 10, 1910

Major Contribution  Cyanamide  Cannizzaro Reaction  The first to clarify the distinction between molecular and atomic weights

What is Cannizzaro Reaction?  Definition: containing NO α-hydrogen undergo a self-oxidation-reduction reaction when treated with concentrated aqueous , and The oxidation product is a and the reduction product is an alcohol.  involves the base-induced of an lacking a hydrogen atom in the alpha position

Example:

30% KOH 2 O2N CHO O2N CH2OH O2N COOH

Mechanism of Cannizzaro Reaction

Step 1. Nucleophilic addition

O O OH R H R H OH Mechanism of Cannizzaro Reaction

Step 2. Hydride (H-) transfer

O O O O

R H R H R R H OH OH H

Mechanism of Cannizzaro Reaction

Step 3. Rapid acid-base reaction

H O O O O R H R H

R O H H R O H Example of Cannizzaro Reaction

 For example: Application of Cannizzaro Reaction  Crossed Cannizzaro Reaction

 Intramolecular Cannizzaro Reaction α-Keto aldehydes give the product of an intramolecular disproportionation in excellent yields.

O O OH O (1) HO R OH (2) H+ R H H Application of Cannizzaro Reaction

Traditional Industrial Method:

Cl O OH O NaOH H OH H OH HCl H H glycolic acid

New Method: O O OH O (1) HO H OH (2) H+ H H H

Mechanism of Intramolecular Cannizzaro Reaction

O O O O Stept (1) OH R H

R H OH

O O O O

Step (2) R OH R OH

H H

O O OH O

Stept (3) R OH R O

H H Limitation  Cannizzaro reaction is limited to aldehydes such as and , which has no hydrogen on the carbon next to the –CHO group.

O O Strong Base 2 HO H O

*Only aldehydes that cannot form an enolate ion undergo the Cannizaro reaction.

Aldehyde and containing hydrogen attached to their α-Carbons undergoes an aldol (aldehyde + alcohol) condensation.

O O O

H2O H HO CH H H CH2 2

O

H O H O O O H O OH HO

H CH2 H C H H C H H2 H2 The Biological Analogue of the Cannizzaro Reaction  Enzymes catalyze the reduction of aldehydes and using NADH as the source of the equivalent of H-  The transfer resembles that in the Cannizzaro reaction but the carbonyl of the acceptor is polarized by an acid from the enzyme, lowering the barrier Microscale Techniques  materials in the 0.005-0.5 gram range  Use different glassware

Microscale Glassware Macroscale >> chemicals on the order of 2-100 g Macroscale >> glassware containing between 25 and 500 mL of liquids Microscale techniques

Pros and Cons  Decrease the economic and environmental costs less cost of chemicals, storage, and disposal.  Increase safety, minimize accident  More difficult to use, especially in distillation, extraction  Macroscale procedures are required in multiple steps of .

200mL x 8 20mL x 8 10% NaOH 10% NaOH

Carrying out reaction Distillation

Solvent heavier than water

Solvent lighter than water

Thank You!

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