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Markovnikov Rule - Meaning, Definition, Applications, FAQs

Markovnikov Rule - Meaning, Definition, Applications, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:36 PM IST

In 1869, Vladimir Vasilyevich Markovnikov generalized a rule which describes the mechanism of addition reactions of protic acid to an asymmetrically substituted alkene and this rule is termed as Markovnikov rule or Markownikoff rule.

Markovnikov Rule Definition

It states that when a protic acid (specifically hydrogen halides) is added to an unsymmetrical alkene, then the hydrogen atom of the protic acid will form a bond with the doubly bonded carbon atom bearing the greater number of hydrogen atoms while the anionic part of the acid will form a bond with carbon atom which is more substituted (contain lesser number of hydrogen atoms).

This Story also Contains
  1. Markovnikov Rule Definition
  2. Mechanism of Markovnikov Rule
  3. Practical applications of Markovnikov rule
  4. What is the Anti-Markovnikov rule?

In other words, this rule can be simplified as “rich get richer” i.e., if a reaction involves the addition of atoms where the hydrogen atom and other group are added, then the doubly bonded carbon consisting of the greatest number of hydrogen atoms initially, will receive the hydrogen atoms and will get richer in H atoms. An example of Markovnikov rule is as follows:

Background wave


Markovnikov Rule Definition

It is clearly observed from the reaction that two products are obtained from addition reaction of unsymmetrical alkene i.e., a major product which is formed according to Markovnikov rule and a minor product which is formed according to Anti-Markovnikov rule (we might discuss this rule later in this article). Thus, these reactions are regioselective because there is a preference for forming one regioisomer over the other during the reaction.

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Mechanism of Markovnikov Rule

For better understanding of the mechanism, let us consider the example which we illustrated earlier i.e., addition reaction of hydrogen chloride (hydrochloric acid) with propene. The mechanism of Markovnikov rule involves several steps which are as follows:

Step-1: Dissociation of hydrogen chloride (HCl) into its respective ions:

1637218731138

Step-2: Protonation of alkene takes place and most stable carbocation is formed as an intermediate after the reaction as follows:

Mechanism of Markovnikov Rule

Thus, the intermediate involved during the addition of HCl to propene is carbocation and as the 2" carbocation is relatively more stable than 1º carbocation because of the greater inductive effect, so its formation is preferred over the formation of primary carbocation.

Step-3: The chloride ion acts as a nucleophile and attacks the carbocation due to which deprotonation of carbon atom takes place as per following reaction:

Mechanism of Markovnikov Rule

Since secondary carbocation is preferred over primary carbocation, so the reaction will yield 2-chloropropane as the major product.

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Practical applications of Markovnikov rule

1. Formation of halohydrin (in alcohol and water)-

This reaction involves breaking off the pi bond of alkene and forming a halohydrin (halo means halogen and hydrin means hydroxyl group) in its place. This reaction takes place in water and yields a product which follows the Markovnikov rule. An example for this reaction is as follows:

1. Formation of halohydrin (in alcohol and water)-

2. Oxymercuration Demercuration-

It is a reaction which results in the Markovnikov additions of hydrogen and a hydroxyl group on the alkene and forming an alcohol. The intermediate involved in the reaction is mercurinium ion instead of carbocation and proceeds in the presence of Hg(OAc)2, H2O (for oxidation) and NaBH4 for reduction. An example for this reaction is as follows:

Oxymercuration Demercuration-

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3. Acid catalysed hydration reactions-

This reaction results in the Markovnikov addition of a hydrogen and a hydroxyl group across an alkene forming an alcohol. Intermediate in this reaction is carbocation and no stereospecificity is associated with this reaction. An example of this reaction is hydration of propene in the presence of dilute sulphuric acid and the reaction is represented as follows:

Acid catalysed hydration reactions-

These reactions are involved in the industrial usages of Markovnikov’s rule and are widely used in a variety of chemical processes.

What is the Anti-Markovnikov rule?

This rule describes the regiochemistry where the electronegative part of the reagent is bonded to a less substituted carbon atom rather than the more substituted carbon atom. This rule is followed only when hydrogen bromide HBr reacts with unsymmetrical alkenes in the presence of hydrogen peroxide and free radical is the intermediate involved in this process. An example for this reaction is given as follows:

Anti-Markovnikov rule

Practical applications of Anti-Markovnikov rule:

Hydroboration-oxidation-

It is a type of anti-Markovnikov reaction in which a hydroxyl group form a bond with the less substituted carbon atom and it is a two-step reaction which includes a hydroboration step in which alkene is treated with BH3 in the presence of non-polar solvent like THF(tetrahydrofuran) and an oxidation step in which hyperoxide ion reacts to form respective alcohol. An example for the reaction is given as follows:

Hydroboration-oxidation-

Thus, we can conclude that Markovnikov addition basically involves protonation of a double bond to give a cation on a more substituted carbon atom, which traps a nucleophile to form final saturated products. The attack of nucleophile control over two important aspects in the formation of a product i.e., regioselectivity and stereoselectivity.

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NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. 1. State Markovnikov rule.

Markovnikov rule states that the electronegative part of the adding molecule will form a bond to that doubly bonded carbon atom which is highly substituted.

2. 2. The Markovnikov rule mechanism involves which reaction intermediate?

The reaction intermediate involved in the Markovnikov addition reaction is carbocation.

3. 3. Compare and contrast one point between the Markovnikov rule and Anti-Markovnikov rule.

Markovnikov rule explains that in addition reaction of alkenes, the proton is added to the carbon atom which consist of greatest number of hydrogen atoms while Anti-Markovnikov rule (peroxide effect) explains that in addition reaction of alkenes, the proton is added to the carbon atom which has the least number of hydrogen atom associated to it.

4. 4. What is the only condition in which the anti-Markovnikov addition can be observed and why?

In the presence of hydrogen bromide HBr and peroxide like H2O2 only, the product will be formed according to anti-Markovnikov rule because halogens other than bromine does not undergo free radical addition to alkenes as the abstraction of proton is an endothermic reaction and the new bond formed after addition cannot compensate the amount of energy provided. In case of bromine, the abstraction of proton and bromine radical is exothermic and thus, reaction is feasible.

5. 5. Which of the given concepts explains Markovnikov's rule as applied to addition of HBr to propene?

A. the Aufbau principle

B. the nucleophilicity of bromide anion

C. the acidity of HBr

D. the relative strength of carbocations

Ans. Option (D) is correct.

6. What is the Markovnikov Rule?
The Markovnikov Rule is a principle in organic chemistry that predicts the outcome of addition reactions between unsymmetrical alkenes and hydrogen halides. It states that the hydrogen atom from the hydrogen halide will add to the carbon of the double bond that has more hydrogen atoms attached to it, while the halide ion will add to the carbon with fewer hydrogen atoms.
7. Who discovered the Markovnikov Rule?
The Markovnikov Rule was discovered by Russian chemist Vladimir Markovnikov in 1870. He observed the pattern of addition reactions while studying the hydration of alkenes.
8. How does the Markovnikov Rule apply to cyclic alkenes?
For cyclic alkenes, the Markovnikov Rule applies in the same way as for linear alkenes. The hydrogen from HX will add to the carbon of the double bond with more hydrogen atoms, while the halide will add to the carbon with fewer hydrogen atoms, considering the ring structure and any substituents.
9. What is the importance of understanding the Markovnikov Rule in organic synthesis?
Understanding the Markovnikov Rule is crucial in organic synthesis because it allows chemists to predict and control the outcome of addition reactions. This knowledge is essential for designing synthetic routes, optimizing reaction conditions, and understanding reaction mechanisms in complex organic transformations.
10. What is the relationship between the Markovnikov Rule and Kharasch addition?
Kharasch addition, also known as atom transfer radical addition, is a type of anti-Markovnikov addition. While the Markovnikov Rule predicts addition based on carbocation stability, Kharasch addition proceeds through a radical mechanism, often resulting in the opposite regioselectivity.
11. How does the Markovnikov Rule relate to carbocation stability?
The Markovnikov Rule is based on the stability of carbocations formed during the reaction mechanism. The more substituted carbocation (with more alkyl groups) is more stable, leading to the preferred product. This stability determines the orientation of the addition reaction.
12. What is the role of carbocation intermediates in Markovnikov addition?
Carbocation intermediates play a crucial role in Markovnikov addition. The reaction proceeds through the formation of a carbocation, and the more stable carbocation (usually the more substituted one) leads to the major product. This stability determines the regioselectivity of the reaction.
13. What is the relationship between the Markovnikov Rule and Hammond's postulate?
Hammond's postulate states that the structure of a transition state resembles the structure of the nearest stable species. In Markovnikov additions, this means the transition state resembles the more stable carbocation intermediate, which leads to the observed regioselectivity.
14. Can you explain the concept of regioselectivity in relation to the Markovnikov Rule?
Regioselectivity refers to the preferential formation of one constitutional isomer over another in a chemical reaction. The Markovnikov Rule predicts the regioselectivity of addition reactions by determining which carbon of the double bond will receive the electrophile (H+) and which will receive the nucleophile (X-).
15. How does electronegativity affect the Markovnikov Rule?
Electronegativity plays a role in the Markovnikov Rule by influencing the stability of the carbocation intermediate. More electronegative groups can stabilize adjacent carbocations through inductive effects, potentially affecting the regioselectivity of the addition reaction.
16. Why is the Markovnikov Rule important in organic chemistry?
The Markovnikov Rule is important because it helps predict the major product of addition reactions involving unsymmetrical alkenes and hydrogen halides. This prediction is crucial for understanding reaction mechanisms and synthesizing specific organic compounds.
17. Can the Markovnikov Rule be applied to alkynes?
Yes, the Markovnikov Rule can be applied to alkynes, particularly in the first addition step. For terminal alkynes, the hydrogen from HX will add to the carbon with the hydrogen, while the halide will add to the other carbon. For internal alkynes, the addition follows the same principle as with alkenes.
18. What types of reactions does the Markovnikov Rule apply to?
The Markovnikov Rule primarily applies to electrophilic addition reactions, particularly those involving unsymmetrical alkenes and hydrogen halides (HX, where X is a halogen). It can also be extended to other addition reactions, such as hydration of alkenes.
19. How does solvent polarity affect Markovnikov addition reactions?
Solvent polarity can affect the rate and sometimes the regioselectivity of Markovnikov addition reactions. Polar solvents can stabilize charged intermediates (like carbocations) and transition states, potentially influencing the reaction outcome and rate.
20. Can you explain the concept of "Markovnikov-like" additions?
"Markovnikov-like" additions refer to reactions that follow the same regioselectivity as predicted by the Markovnikov Rule but proceed through different mechanisms. These may include certain pericyclic reactions or additions that don't involve carbocation intermediates but still result in the same product orientation.
21. What is an anti-Markovnikov addition?
An anti-Markovnikov addition is a reaction that results in the opposite product predicted by the Markovnikov Rule. In these reactions, the hydrogen adds to the less substituted carbon of the double bond, while the halide (or other group) adds to the more substituted carbon.
22. How can you achieve anti-Markovnikov addition?
Anti-Markovnikov addition can be achieved through radical addition reactions, such as the addition of HBr in the presence of peroxides (known as the peroxide effect). Other methods include hydroboration-oxidation reactions and certain transition metal-catalyzed reactions.
23. How does the structure of the alkene affect the application of the Markovnikov Rule?
The structure of the alkene, particularly its symmetry and substitution pattern, affects how the Markovnikov Rule is applied. For symmetrical alkenes, there is no Markovnikov vs. anti-Markovnikov distinction. For unsymmetrical alkenes, the rule helps predict which carbon will receive the electrophile based on the number of hydrogen atoms attached to each carbon of the double bond.
24. What are some common exceptions to the Markovnikov Rule?
Common exceptions to the Markovnikov Rule include:
25. What is the difference between Markovnikov and Zaitsev's rule?
While both rules deal with regioselectivity in organic reactions, they apply to different types of reactions. The Markovnikov Rule predicts the product of addition reactions to alkenes, while Zaitsev's Rule predicts the major product in elimination reactions, favoring the formation of the more substituted alkene.
26. How does resonance affect the application of the Markovnikov Rule?
Resonance can affect the stability of carbocation intermediates, potentially influencing the regioselectivity predicted by the Markovnikov Rule. When resonance structures can delocalize the positive charge of a carbocation, it may lead to unexpected product distributions.
27. How does the presence of electron-withdrawing groups affect Markovnikov addition?
Electron-withdrawing groups can affect Markovnikov addition by influencing the stability of carbocation intermediates. These groups can destabilize adjacent carbocations, potentially altering the regioselectivity of the addition reaction or favoring alternative reaction pathways.
28. Can you explain the concept of "partial Markovnikov" character?
"Partial Markovnikov" character refers to reactions where the product distribution doesn't fully align with the Markovnikov Rule prediction. This can occur when competing factors influence the reaction outcome, resulting in a mixture of Markovnikov and anti-Markovnikov products.
29. How does temperature affect Markovnikov addition reactions?
Temperature can affect Markovnikov addition reactions by influencing reaction rates and potentially the product distribution. Higher temperatures may lead to a greater proportion of the thermodynamic product, which often aligns with the Markovnikov prediction, but can also promote side reactions or alternative pathways.
30. What role does stereochemistry play in Markovnikov addition reactions?
Stereochemistry is important in Markovnikov addition reactions, particularly for cyclic systems or when considering the three-dimensional structure of the product. The addition typically occurs in an anti fashion, with the hydrogen and halide adding from opposite sides of the alkene plane.
31. How can you use spectroscopic techniques to confirm Markovnikov addition products?
Spectroscopic techniques such as NMR, IR, and mass spectrometry can be used to confirm Markovnikov addition products. NMR can show the position of the newly added groups, IR can indicate the presence of specific bonds, and mass spectrometry can confirm the molecular mass and fragmentation pattern of the product.
32. How does the Markovnikov Rule apply to addition reactions of unsymmetrical dienes?
For unsymmetrical dienes, the Markovnikov Rule applies to each double bond individually. The more substituted double bond typically reacts first, and the addition follows the Markovnikov orientation for that specific double bond.
33. Can you explain the concept of "Markovnikov control" in synthesis?
"Markovnikov control" in synthesis refers to designing reactions or choosing conditions that favor the Markovnikov product. This involves promoting carbocation formation and stability, using appropriate solvents, and avoiding conditions that might lead to radical or alternative reaction pathways.
34. How does the strength of the acid (HX) affect Markovnikov addition?
The strength of the acid (HX) can affect the rate and sometimes the regioselectivity of Markovnikov addition. Stronger acids generally lead to faster reactions and may promote side reactions or rearrangements. Weaker acids might allow for more selective additions or enable competing reaction pathways.
35. What is the significance of the Markovnikov Rule in understanding reaction mechanisms?
The Markovnikov Rule is significant in understanding reaction mechanisms because it provides insight into the formation and stability of reaction intermediates, particularly carbocations. This understanding helps chemists predict reaction outcomes, design new reactions, and explain observed product distributions.
36. How does the Markovnikov Rule apply to intramolecular addition reactions?
In intramolecular addition reactions, the Markovnikov Rule still applies, but the outcome may be influenced by ring size and strain considerations. The regioselectivity follows the same principles, with the electrophile adding to the more substituted carbon of the alkene, but molecular geometry can play a crucial role.
37. Can you explain the concept of "anti-Markovnikov control" in synthesis?
"Anti-Markovnikov control" in synthesis involves designing reactions or choosing conditions that favor the anti-Markovnikov product. This often involves using radical mechanisms (e.g., peroxide-initiated reactions), hydroboration-oxidation sequences, or specific catalysts that alter the reaction pathway to avoid carbocation intermediates.
38. How does the presence of neighboring group participation affect Markovnikov addition?
Neighboring group participation can affect Markovnikov addition by stabilizing reaction intermediates or providing alternative reaction pathways. This can lead to unexpected products or stereochemistry, potentially overriding the usual Markovnikov regioselectivity.
39. What is the relationship between the Markovnikov Rule and the concept of kinetic vs. thermodynamic control?
The Markovnikov Rule often aligns with thermodynamic control, as it predicts the formation of the more stable product. However, under certain conditions (e.g., low temperatures or with specific catalysts), kinetic control may lead to anti-Markovnikov products. Understanding this relationship is crucial for controlling reaction outcomes.
40. How does the Markovnikov Rule apply to addition reactions involving water (hydration of alkenes)?
The Markovnikov Rule applies to the hydration of alkenes in the same way as it does to hydrogen halide additions. The hydrogen from water adds to the carbon with more hydrogen atoms, while the hydroxyl group adds to the more substituted carbon, forming the more substituted alcohol as the major product.
41. Can you explain how the Markovnikov Rule relates to the concept of hyperconjugation?
Hyperconjugation is a stabilizing effect that influences carbocation stability, which is central to the Markovnikov Rule. More substituted carbocations are stabilized by hyperconjugation from adjacent C-H or C-C bonds, leading to the observed regioselectivity in Markovnikov additions.
42. How does the presence of aromatic rings affect Markovnikov addition to nearby alkenes?
Aromatic rings can influence Markovnikov addition to nearby alkenes through electronic effects. The aromatic system can stabilize certain carbocation intermediates through resonance, potentially affecting the regioselectivity of the addition or promoting rearrangements.
43. What is the significance of the Markovnikov Rule in understanding industrial processes?
The Markovnikov Rule is significant in industrial processes as it helps predict and control the outcome of large-scale addition reactions. This understanding is crucial for optimizing yields, designing efficient synthetic routes, and developing new processes for the production of important chemicals and materials.
44. How does the concept of microscopic reversibility relate to the Markovnikov Rule?
Microscopic reversibility states that the mechanism of a reverse reaction is exactly the reverse of the forward reaction. In the context of the Markovnikov Rule, this principle helps explain why the more stable carbocation intermediate leads to the major product, as the reverse reaction would preferentially form this more stable intermediate.
45. Can you explain how the Markovnikov Rule applies to addition reactions of alkenes with boron hydrides?
The addition of boron hydrides to alkenes (hydroboration) actually follows an anti-Markovnikov orientation. This is because the mechanism doesn't involve a carbocation intermediate but rather proceeds through a concerted process. The boron adds to the less substituted carbon, opposite to what the Markovnikov Rule would predict.
46. How does the Markovnikov Rule apply to addition reactions involving deuterated reagents (e.g., DBr instead of HBr)?
The Markovnikov Rule applies in the same way to deuterated reagents as it does to their non-deuterated counterparts. The deuterium (D) will add to the carbon of the double bond with more hydrogen atoms, while the halide will add to the carbon with fewer hydrogen atoms. This can be useful for mechanistic studies and isotope labeling experiments.
47. What is the relationship between the Markovnikov Rule and the Hammond-Leffler postulate?
The Hammond-Leffler postulate, which is an extension of Hammond's postulate, states that the transition state of a reaction step resembles the species (reactant or product) closest to it in energy. In Markovnikov additions, this helps explain why the more stable carbocation intermediate leads to the major product, as the transition state resembles this more stable species.
48. How does the presence of silicon in organosilicon compounds affect the application of the Markovnikov Rule?
Silicon can influence the application of the Markovnikov Rule in organosilicon compounds due to its ability to stabilize β-carbocations through hyperconjugation (known as the β-silicon effect). This can lead to unexpected regioselectivity in certain addition reactions involving silicon-containing alkenes.
49. Can you explain how the Markovnikov Rule relates to the concept of carbocation rearrangements?
Carbocation rearrangements can complicate the application of the Markovnikov Rule. While the initial carbocation formation may follow Markovnikov orientation, subsequent rearrangements (e.g., hydride or alkyl shifts) can lead to unexpected products. Understanding these rearrangements is crucial for accurately predicting reaction outcomes.
50. How does the Markovnikov Rule apply to addition reactions involving carbenes?
The Markovnikov Rule doesn't directly apply to carbene additions because these reactions don't proceed through carbocation intermediates. Carbene additions to alkenes typically result in cyclopropane formation, with the regioselectivity determined by steric and electronic factors specific to carbene chemistry.
51. What is the significance of the Markovnikov Rule in understanding solvolysis reactions?
While the Markovnikov Rule primarily deals with addition reactions, its underlying principles of carbocation stability are crucial in understanding solvolysis reactions. In solvolysis, the leaving group ability and carbocation stability determine the reaction rate and product distribution, often following similar trends to those seen in Markovnikov additions.
52. How does the presence of halogen substituents on the alkene affect Markovnikov addition?
Halogen substituents on the alkene can affect Markovnikov addition through both electronic and steric effects. Electronegative halogens can destabilize adjacent carbocations, potentially altering the regioselectivity. Additionally, the size of the halogen can influence the approach of the incoming electrophile, affecting the reaction outcome

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