Cannizzaro Reaction Mechanism - Overview, Steps, Scope, Uses & Applications, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:27 PM IST

The Cannizzaro reaction is a disproportionation process in which two molecules of an aldehyde combine with a hydroxide base to generate a primary alcohol and a carboxylic acid. This is exemplified in the example of benzaldehyde which creates benzyl alcohol to benzoic acid. And disproportion is a redox reaction in which a mid-oxidation chemical transforms into two distinct compounds, one high and the other low.

This Story also Contains

Cannizzaro reaction mechanism:
Step by step mechanism of Cannizzaro reaction
Crossed reaction of Cannizzaro
Scope of Cannizzaro reaction:
Cannizzaro reaction applications

Cannizzaro Reaction Mechanism - Overview, Steps, Scope, Uses & Applications, FAQs

Cannizzaro reaction examples include vanilline, benzaldehyde, syringaldehyde and formaldehyde, which are lacking active hydrogen. They are subjected to a strong base (NaOH) intramolecular and intermolecular oxidation process to create a carboxylic acid and alcohol molecule

Cannizzaro reaction mechanism:

Cannizzaro reaction mechanism describes in detail the way of obtaining one alcohol molecule and one carboxylic acid molecule from two aldehyde molecules. Scientist Stanislao Cannizzaro, benzyl alcohol and potassium benzoate were acquired from benzaldehyde in 1853. An aldehyde is replaced by nucleophile acyl in the leaving group where the other aldehyde is attacked. The consequence of a hydroxide attack on a carbonyl is a tetrahedral intermediate. This intermediate tetrahedral collapses and reforms the carbonyl and moves a hydride that assaults another colony.

Cannizzaro reaction

Now, an acid-and-alcoholic ion proton is swapped. The aldehyde generates an anion with a charge of 2 if a base with high concentration is supplied. A hydride ion, which is made of carboxylate and alcohol, is transmitted to a second molecule of the aldehyde. The alcohol ion additionally acquires a proton for the reaction from the solvent.

Step by step mechanism of Cannizzaro reaction

Step 1: A nucleophile, as hydroxide, is utilised to attack the group of carbonyl in the aldehyde in question, which causes a disproportionate reaction and leads to a two negative charges carrying anion.

Cannizzaro reaction step 1

Step 2: This intermediate product can now work as a reduction in hydride. The intermediate releases a hydride anion because of its unstable nature. This anion hydride attacks another molecule of aldehyde. Now, the doubly charged anion becomes an anion for carboxylate and the aldehyde becomes anion for alcohol.

Cannizzaro reaction step 2

Step 3: In this final stage, water provides the alcohol anion with a proton that creates the final alcohol product. The reaction might take place because the alcohol is basic rather than water. Now, when acid is utilised, the carboxylate ion creates the ultimate product of carboxylic acid (the acid workup is required since carboxylate is less basic than water and therefore cannot obtain a proton from water).

Cannizzaro reaction step 3

In general, the response follows kinetics in the third order. In aldehyde it is second and in basic it is first:

Temporary = k[RCHO]²[OH⁻]

A second way (k') is necessary for very high foundations, which is second order in base:

Temporary rate = k[RCHO]

2[RCHO] + k'[OH⁻]²

A reaction involving doubly charged anion (RCHO₂²⁻) and aldehyde is involved in the k' trajectory. Direct transmission of hydride ions is obvious from the finding that no deuterium is bound to the α-carbon in the recuperated alcohol when the reaction is carried out when D₂O occurs.

Related Topics

Crossed reaction of Cannizzaro

Crossed Cannizzaro reaction is not unexpected that only 50% of the alcohol and carboxylic acid necessary in the optimal conditions is produced by the reaction. Therefore, the crossover reaction of Cannizzaro is more widely utilised. Sacrificial aldehyde and a more valuable molecule are mixed, and sodium oxidation is reduced by formaldehyde. Reduction of other aldehyde chemicals obtains the necessary alcohol. The yield of the useful chemistry is boosted when two separate aldehydes can be fully transformed into the needed product. Finally, it can be utilised to disproportionate a non-enolizable aldehyde with the Cannizzaro reaction. The reaction from the cross cannizzaro reaction is used to boost the yield of the precious product.

Scope of Cannizzaro reaction:

Aldehydes with alpha hydrogen atom(s) have been decongested, causing enolates and potential aldol reactions, due to very alkaline reactions. The process only yields 50% alcohol and carboxylic acid under optimal conditions (it takes two aldehydes to produce one acid and one alcohol). In order to prevent low yields, the crossing Cannizzaro reaction, which combines sacrificial aldehyde with a more valuable molecule, can be conducted more frequently.

In this variant, formaldehyde is the reducer that is oxidised to formate sodium while alcohol is reduced to the other aldehyde molecule. In this case, one aldehyde can be converted to its matching product fully, instead of losing 50% of a single reactant for each of two products. Therefore, while the atomic economy is still low, the valuable chemical's output is high.

There has been a solvent-free process, including the grinding of fluid 2-chlorobenzaldehyde in a mortar and pestle by potassium hydroxide:

Cannizzaro reaction

Also read :

NCERT Exemplar Class 11th Chemistry Solutions	NCERT notes Class 12 Chemistry Chapter 12 Aldehydes, Ketones and Carboxylic Acids
NCERT Exemplar Class 12th Chemistry Solutions	NCERT solutions for Class 12 Chemistry Chapter 12 Aldehydes, Ketones and Carboxylic Acids
NCERT Exemplar Solutions for All Subjects	NCERT Exemplar Class 12 Chemistry solutions Chapter 12 Aldehydes, Ketones and Carboxylic Acids

NEET Highest Scoring Chapters & Topics

This ebook serves as a valuable study guide for NEET exams, specifically designed to assist students in light of recent changes and the removal of certain topics from the NEET exam.

Download EBook

Cannizzaro reaction applications

In the industry, polyols are made via the combination of crossed Cannizzaro reactions and aldol condensation. Polyols are very valuable and they have numerous industrial uses.

For the production of resins in the aeroplane or on board, varnish coatings, synthetic lubricants and plasticizers, Neopentyl glycol is employed in polyesters. The structure of neopentyl provides high light, heat and hydrolysis resistance.
As a raw ingredient, pentaerythritol is explosive in the varnish industry. Some esters of pentaerythritol are utilised as oil additives, plastifying agents and emulsifiers with higher fatty acids.
In a number of applications, Trimethylolpropane is employed for alkaline resin and polyester and polyurethane preparation as replacement glycerine.

Also read -

Frequently Asked Questions (FAQs)

1. What are the Cannizzaro reaction products?

Primary alcohols and carboxylic acids generated in a Cannizzaro reaction.

2. What are the benefits of the cross Cannizzaro reaction ?

The yield of the intended product is improved by this adjustment of the reaction. Both aldehydes are completely converted to products, avoiding the waste of valuable reactant chemicals. The process's atom economy is likewise low.

3. Why is acetaldehyde not involved in the Cannizzaro reaction?

The alkaline environment causes the alpha-hydrogen to deprotonate. Due to its three alpha hydrogen, acetaldehyde rapidly generates enolates ions when deprotonate and so cannot participate in the process.

4. When KOH or NaOH is used, what compounds are produced?

The potassium carboxylate salt or the sodium carboxylate salt of the corresponding carboxylic acid is formed when potassium hydroxide or sodium hydroxide is used in the base-induced disproportionation process.

5. What is the Cannizzaro reaction?

The Cannizzaro reaction is a disproportionation reaction of aldehydes that lack an α-hydrogen. In this reaction, one molecule of aldehyde is oxidized to a carboxylic acid while another is reduced to an alcohol. It typically occurs in the presence of a strong base.

6. What are the main products of the Cannizzaro reaction?

The main products of the Cannizzaro reaction are a primary alcohol and the salt of a carboxylic acid. Half of the aldehyde molecules are reduced to alcohols, while the other half are oxidized to carboxylic acids (which are then converted to their salt form in the basic conditions).

7. How does formaldehyde behave differently in the Cannizzaro reaction compared to other aldehydes?

Formaldehyde is unique in the Cannizzaro reaction because it lacks any carbon-hydrogen bonds except those in the aldehyde group. As a result, the reaction produces methanol and formic acid (or formate salt), whereas other aldehydes produce more complex alcohols and carboxylic acids.

8. How does the concentration of the base affect the Cannizzaro reaction?

The concentration of the base significantly affects the Cannizzaro reaction. Higher concentrations of base generally lead to faster reaction rates and higher yields. However, extremely high base concentrations can lead to side reactions or decomposition of products, so an optimal concentration is typically used.

9. Can the Cannizzaro reaction be reversed?

The Cannizzaro reaction is generally not reversible under normal conditions. The formation of a carboxylic acid salt and an alcohol is thermodynamically favorable, and the energy required to reverse the process is substantial. The products are typically stable under the reaction conditions.

10. How does the mechanism of the Cannizzaro reaction explain the observed products?

The mechanism of the Cannizzaro reaction explains the observed products through several key steps: 1) Base attack on the carbonyl group, 2) Hydride transfer from one aldehyde molecule to another, 3) Formation of a tetrahedral intermediate, and 4) Breakdown of this intermediate to form the alcohol and carboxylate products. This mechanism accounts for the simultaneous reduction and oxidation of aldehyde molecules.

11. How does the Cannizzaro reaction contribute to our understanding of carbonyl chemistry?

The Cannizzaro reaction provides important insights into carbonyl chemistry, demonstrating the dual nature of the carbonyl group as both an electrophile and a potential reducing agent. It illustrates concepts like hydride transfer, the effect of α-hydrogens on reactivity, and the influence of substituents on carbonyl reactions, contributing to our broader understanding of organic reaction mechanisms.

12. How does the Cannizzaro reaction demonstrate the amphoteric nature of aldehydes?

The Cannizzaro reaction clearly demonstrates the amphoteric nature of aldehydes by showing that they can act as both reducing agents and oxidizing agents in the same reaction. One aldehyde molecule is reduced (acting as an oxidizing agent), while another is oxidized (acting as a reducing agent), highlighting the dual reactive nature of the carbonyl group.

13. What is the stereochemistry of the alcohol product in the Cannizzaro reaction?

The alcohol product formed in the Cannizzaro reaction is achiral (not optically active) if the starting aldehyde is symmetrical. If the starting aldehyde is chiral, the alcohol product will be racemic (an equal mixture of both enantiomers) due to the non-stereospecific nature of the hydride transfer.

14. What is the significance of the Cannizzaro reaction in the history of organic chemistry?

The Cannizzaro reaction, discovered by Stanislao Cannizzaro in 1853, played a significant role in the development of organic chemistry. It provided early insights into the reactivity of carbonyl compounds, helped establish the concept of oxidation states in organic molecules, and contributed to the understanding of reaction mechanisms. It remains an important named reaction in organic chemistry curricula.

15. What is the cross-Cannizzaro reaction?

The cross-Cannizzaro reaction is a variation of the standard Cannizzaro reaction where two different aldehydes are used as reactants. One aldehyde (usually formaldehyde) acts as the reducing agent and is oxidized to a carboxylic acid, while the other aldehyde is reduced to an alcohol.

16. How does the Cannizzaro reaction differ from the Tishchenko reaction?

While both reactions involve aldehydes, the Cannizzaro reaction results in the formation of an alcohol and a carboxylic acid salt, whereas the Tishchenko reaction produces an ester. The Tishchenko reaction typically uses aluminum alkoxides as catalysts instead of strong bases and doesn't involve a redox process.

17. Can the Cannizzaro reaction occur intramolecularly?

Yes, the Cannizzaro reaction can occur intramolecularly in certain molecules that contain two aldehyde groups. This intramolecular version is called the Cannizzaro-Tishchenko reaction, where one aldehyde group is reduced to an alcohol while the other is oxidized to a carboxylic acid, forming a cyclic ester (lactone).

18. How does the Cannizzaro reaction compare to other methods of reducing aldehydes?

The Cannizzaro reaction is unique among aldehyde reduction methods as it simultaneously produces both reduced (alcohol) and oxidized (carboxylic acid) products. Other reduction methods, like using NaBH4 or LiAlH4, only produce alcohols. The Cannizzaro reaction is also specific to aldehydes without α-hydrogens, unlike many other reduction methods.

19. Can the Cannizzaro reaction be used with aromatic aldehydes?

Yes, the Cannizzaro reaction works well with aromatic aldehydes, especially those without α-hydrogens. Benzaldehyde is a classic example, reacting to form benzyl alcohol and sodium benzoate. The reaction is often faster with aromatic aldehydes due to the stabilizing effect of the aromatic ring on the intermediate.

20. Why can't ketones undergo the Cannizzaro reaction?

Ketones cannot undergo the Cannizzaro reaction because they lack a hydrogen atom directly attached to the carbonyl carbon. This hydrogen is essential for the reaction mechanism, as it is removed in the oxidation step to form the carboxylic acid.

21. How does the absence of an α-hydrogen affect the Cannizzaro reaction?

The absence of an α-hydrogen is crucial for the Cannizzaro reaction to occur. Aldehydes without α-hydrogens cannot undergo alternative reactions like aldol condensation, making the Cannizzaro reaction the primary pathway. This absence allows for the disproportionation to proceed without competition from other reactions.

22. Can the Cannizzaro reaction occur in acidic conditions?

No, the Cannizzaro reaction requires strongly basic conditions. It does not occur in acidic environments because the mechanism relies on the base to initiate the reaction and facilitate the hydride transfer.

23. How does the structure of the aldehyde affect the rate of the Cannizzaro reaction?

The structure of the aldehyde can significantly affect the rate of the Cannizzaro reaction. Generally, aldehydes with electron-withdrawing groups react faster because they make the carbonyl carbon more electrophilic, facilitating the initial attack by the base. Steric hindrance around the carbonyl group can slow down the reaction.

24. What is the importance of the Cannizzaro reaction in organic synthesis?

The Cannizzaro reaction is important in organic synthesis as it provides a method to convert aldehydes into useful products like alcohols and carboxylic acids. It's particularly valuable for aldehydes that can't undergo aldol condensation, offering a way to functionalize these molecules.

25. What is the role of the strong base in the Cannizzaro reaction?

The strong base serves multiple purposes in the Cannizzaro reaction: it initiates the reaction by attacking the carbonyl group, it facilitates the transfer of a hydride ion between aldehyde molecules, and it neutralizes the carboxylic acid product formed during the reaction.

26. What is the significance of the hydride transfer in the Cannizzaro reaction mechanism?

The hydride transfer is a crucial step in the Cannizzaro reaction mechanism. It involves the movement of a hydride ion (H-) from one aldehyde molecule to another, facilitating the simultaneous reduction of one molecule to an alcohol and the oxidation of another to a carboxylic acid.

27. What is meant by "disproportionation" in the context of the Cannizzaro reaction?

Disproportionation in the Cannizzaro reaction refers to the simultaneous oxidation and reduction of the same compound (the aldehyde). One molecule of aldehyde is oxidized (loses electrons) to form a carboxylic acid, while another is reduced (gains electrons) to form an alcohol.

28. Why is the Cannizzaro reaction considered a redox reaction?

The Cannizzaro reaction is considered a redox (reduction-oxidation) reaction because it involves the simultaneous reduction of one aldehyde molecule to an alcohol (gaining electrons) and the oxidation of another aldehyde molecule to a carboxylic acid (losing electrons).

29. What is the role of the solvent in the Cannizzaro reaction?

The solvent in the Cannizzaro reaction plays several important roles. It helps dissolve the reactants and base, facilitates the transfer of heat, and can affect the reaction rate and yield. Protic solvents like water or alcohols are often used, as they can stabilize the ionic intermediates formed during the reaction.

30. What are some alternatives to the Cannizzaro reaction for synthesizing primary alcohols from aldehydes?

Alternatives to the Cannizzaro reaction for synthesizing primary alcohols from aldehydes include: 1) Reduction with sodium borohydride (NaBH4) or lithium aluminum hydride (LiAlH4), 2) Catalytic hydrogenation using H2 gas and a metal catalyst, 3) Transfer hydrogenation methods like the Meerwein-Ponndorf-Verley reduction, and 4) Electrochemical reduction. These methods often offer better selectivity and yield of the alcohol product.

31. How does temperature affect the Cannizzaro reaction?

Temperature generally affects the rate of the Cannizzaro reaction. Higher temperatures typically increase the reaction rate by providing more energy for molecular collisions. However, very high temperatures can lead to side reactions or decomposition of reactants or products, so optimal temperature control is important.

32. What are some industrial applications of the Cannizzaro reaction?

The Cannizzaro reaction has several industrial applications, including the production of benzyl alcohol and sodium benzoate from benzaldehyde, the synthesis of trimethylolpropane from formaldehyde and propanal, and the production of certain fragrances and pharmaceutical intermediates.

33. How does the presence of an α-hydrogen in an aldehyde affect its ability to undergo the Cannizzaro reaction?

The presence of an α-hydrogen in an aldehyde typically prevents it from undergoing the Cannizzaro reaction under normal conditions. Aldehydes with α-hydrogens preferentially undergo aldol condensation reactions in basic conditions, as the α-hydrogen can be easily removed to form an enolate intermediate.

34. What is the effect of substituents on the aromatic ring in the Cannizzaro reaction of aromatic aldehydes?

Substituents on the aromatic ring can significantly affect the rate and yield of the Cannizzaro reaction. Electron-withdrawing groups (like -NO2 or -Cl) increase the electrophilicity of the carbonyl carbon, making it more reactive towards the base and speeding up the reaction. Electron-donating groups (like -OCH3 or -NH2) have the opposite effect.

35. How does the Cannizzaro reaction compare to the Meerwein-Ponndorf-Verley reduction?

While both reactions can reduce aldehydes to alcohols, they differ significantly. The Cannizzaro reaction is a base-catalyzed disproportionation that works only for aldehydes without α-hydrogens, producing both alcohols and carboxylic acids. The Meerwein-Ponndorf-Verley reduction is a metal-catalyzed transfer hydrogenation that can reduce both aldehydes and ketones to alcohols without oxidizing any of the starting material.

36. What is the importance of the Cannizzaro reaction in the synthesis of polymers?

The Cannizzaro reaction is valuable in polymer synthesis, particularly in the production of certain polyesters and polyurethanes. For example, it's used in the synthesis of trimethylolpropane, a key component in many polyurethane formulations. The reaction allows for the creation of multifunctional monomers from simpler aldehyde precursors.

37. Can the Cannizzaro reaction be used as a test for aldehydes?

While the Cannizzaro reaction can occur with certain aldehydes, it's not typically used as a diagnostic test due to its specificity for aldehydes without α-hydrogens. More general tests like Tollens' reagent or Fehling's solution are preferred for detecting aldehydes, as they react with a broader range of aldehyde compounds.

38. What are some limitations of the Cannizzaro reaction?

The main limitations of the Cannizzaro reaction include: 1) It only works with aldehydes lacking α-hydrogens, 2) It requires strongly basic conditions which can be incompatible with sensitive functional groups, 3) It produces a mixture of products, which can be inefficient if only one product is desired, and 4) The reaction is not stereospecific, producing racemic mixtures for chiral aldehydes.

39. What is the role of water in the workup of a Cannizzaro reaction?

Water plays a crucial role in the workup of a Cannizzaro reaction. It helps to quench the reaction by neutralizing excess base, dissolves the carboxylate salt product, and facilitates the separation of the organic alcohol product from the aqueous carboxylate solution. The addition of acid during workup converts the carboxylate salt to the free carboxylic acid.

40. Can the Cannizzaro reaction be used to synthesize deuterated alcohols?

Yes, the Cannizzaro reaction can be used to synthesize deuterated alcohols if deuterated water (D2O) is used as the solvent or added during the workup. The hydride ion transferred during the reaction can exchange with deuterium from the solvent, resulting in the incorporation of deuterium into the alcohol product.

41. How does the Cannizzaro reaction compare to the Oppenauer oxidation?

While both reactions involve the transfer of hydrogen between molecules, they differ significantly. The Cannizzaro reaction is a base-catalyzed disproportionation of aldehydes, producing alcohols and carboxylic acids. The Oppenauer oxidation, conversely, is a metal-catalyzed reaction that oxidizes alcohols to aldehydes or ketones using a sacrificial ketone as the oxidant.

42. How does the electronic structure of the aldehyde influence its reactivity in the Cannizzaro reaction?

The electronic structure of the aldehyde significantly influences its reactivity in the Cannizzaro reaction. The electrophilicity of the carbonyl carbon is key - more electrophilic carbonyls react faster. Electron-withdrawing groups increase electrophilicity and reactivity, while electron-donating groups decrease it. The ability of the aldehyde to stabilize the hydride ion during transfer also affects reactivity.

43. Can the Cannizzaro reaction be performed under phase-transfer catalysis conditions?

Yes, the Cannizzaro reaction can be performed under phase-transfer catalysis conditions. This approach can be useful when dealing with water-insoluble aldehydes. The phase-transfer catalyst, typically a quaternary ammonium salt, facilitates the transfer of the hydroxide ion from the aqueous phase to the organic phase, allowing the reaction to proceed more efficiently.

44. How does the Cannizzaro reaction relate to the concept of oxidation numbers in organic chemistry?

The Cannizzaro reaction provides a clear illustration of changing oxidation numbers in organic reactions. The aldehyde carbon starts with an oxidation number of +1. In the product alcohol, this number decreases to -1 (reduction), while in the carboxylic acid product, it increases to +3 (oxidation). This demonstrates how oxidation numbers can be used to track electron transfers in organic reactions.

45. How does the Cannizzaro reaction demonstrate the principle of microscopic reversibility?

The Cannizzaro reaction demonstrates the principle of microscopic reversibility in its mechanism. The hydride transfer step, which is key to the reaction, is theoretically reversible at a microscopic level. The forward and reverse processes follow the same pathway, just in opposite directions. However, the overall reaction is not practically reversible due to thermodynamic factors.

46. Can the Cannizzaro reaction be used in the synthesis of natural products?

Yes, the Cannizzaro reaction has applications in natural product