Chemistry

Difference Between Markovnikov Rule and Anti Markovnikov Rule

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Main Difference

The main difference between Markovnikov Rule and Anti Markovnikov Rule is that Markovnikov Rule specifies that hydrogen atoms present in an addition reaction involved by having many hydrogen substituents with a carbon atom, whereas Anti Markovnikov Rule specifies that hydrogen atoms present in an addition reaction are involved by having minimum hydrogen substituents with a carbon atom.

Markovnikov Rule vs. Anti Markovnikov Rule

Markovnikov rule usually explains that when the addition of protic acid of an alkene, the H attaches to double bonds with a more significant number of substituted hydrogen atoms attached to the carbon atom. In contrast, anti markovnikov rule explains when HBr added to alkene in the occurrence of catalyst peroxide, the H atom bonded to C that contains less substituted H whereas Br bonded to C having more H. The hydrogen atom will always get attached to that carbon atom that has maximum number of hydrogen substituents attached to carbon atom by according to markovnikov rule; on the contrary, the hydrogen atom will always attach to that carbon atom having least number of hydrogen substituents by according to anti markovnikov rule.

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The part of addendum that is negative (such as X or Cl/Br) usually goes to the carbon which consists of least number of hydrogen atoms attached to carbon atom in markovnikov rule; on the contrary, the part of addendum that is negative attaches to the carbon atom that consists of highest number of hydrogen atoms attached to the carbon atom in anti markovnikov rule. The mechanism of markovnikov rule is an ionic mechanism in chemistry; on the flip side, the mechanism of anti markovnikov rule is a free radical mechanism. The reactants which are used in markovnikov rule are HBr, HI, HCL, and H2O; on the other hand, the free reactant, which is used in anti markovnikov rule, is only HBr and not HCl, or HI underwent in this type of addition reaction.

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No medium or catalyst is generally required in markovnikov rule; on the flip side, the medium/ catalyst is required that is peroxide or ultraviolet, which must be present to carry out the anti-markovnikov rule. The markovnikov accumulation of hydrogen halide to olefin results in the production of carbocation as the reaction intermediary; on the other hand, the creation of carbon-free radical as the reaction intermediary in anti markovnikov rule. The attack on the carbon-carbon double bond is started by hydrogen ion from reactant HX in markovnikov rule; on the contrary, the attack on carbon-carbon double bond is usually started by halogen-free radicals X which is produced by the communication in between HX and the radical peroxide in anti markovnikov rule.

The major product is given by HBr from (CH3) 2C = CHCH3 will produce (CH3) 2CBrCH2CH3 in markovnikov rule; on the contrary, in the presence of peroxide, the main product will be given as (CH3) 2CHCH(Br)CH3 in an anti markovnikov addition reaction. In markovnikov addition reaction, the intermediary which is formed is carbocation, then undergoes a rearrangement, and the stability of carbocation becomes increases. In contrast, in anti markovnikov rule, the produced intermediary does not undergo rearrangement of products.

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Comparison Chart

Markovnikov RuleAnti Markovnikov Rule
Markovnikov rule defines the result of some additional reactions besides simple reactions.Anti Markovnikov rule defines the halogen atoms that have less substituted hydrogen atoms attached to the carbon atom.
Explains
Explains when the addition of protic acid of an alkene, the H attaches to double bonds with a greater number of Substituted hydrogen atoms attached to the carbon atomExplains HBr is added to an alkene in the occurrence of catalyst peroxide, the H atom bonded to C that contains less substituted H whereas Br bonded to C having more H
Electronegativity
Goes to the carbon which consists of least number of hydrogen atoms attached to carbonGoes to the carbon which consists of the maximum number of hydrogen atoms attached to carbon
Mechanism
Ionic mechanismFree radical mechanism
Reactants
HBr, HI, HCL, and H2OHBr
Medium/Catalyst
No medium is obligatoryUltraviolet or peroxide is obligatory
Intermediate Formation
The production of carbocation as the reaction intermediaryThe creation of carbon-free radical as the reaction intermediary
Arrangement of Products
Undergo rearrangementDoes not undergo rearrangements

What is the Markovnikov Rule?

The rule of markovnikov explains that some addition reactions of alkenes or alkynes, the proton gets attached to that carbon atom that has a maximum number of hydrogen substituents attached to a carbon atom — the markovnikov rule assists in calculating the end products of certain chemical reactions.

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The following of markovnikov rule is because of the most stable product, i.e., carbocation, which is the intermediary product of markovnikov rule. The stability of carbocation become increases when it undergoes rearrangements in the chemical reactions. The involvement of hydrogen atom to the carbon atom forms the double bond in carbon, which provides other vinyl carbon atom a positive charge. For producing the stable end product, the carbocation must be a stable intermediary carbocation product. After the production of the precise carbocation, the Cl then attaches to the positively charged carbon atom.

Though, after the completion of the reaction, a mixture of products is produced, which is formed of products given by stable carbocation or unstable carbocation.

What is Anti Markovnikov Rule?

The rule of anti markovnikov explains that in various addition reactions of alkenes and alkynes, the proton gets attached to that carbon atom that has a minimum number of hydrogen atoms. The end product obtained from this rule is known as an anti markovnikov product. The carbocation is not formed in anti markovnikov rule as an intermediary product. The chemical reaction of anti markovnikov could be obtained into reactions that produce anti markovnikov product is by adding the catalyst peroxide like HOOH in the reaction mixture, which will then give carbon free radicals as products of anti markovnikov rule.

A peroxide could alter the regioselectivity (the production of bonds at a specific atom above all other possible atoms) of an anti markovnikov’s addition reaction. The effect of peroxide takes a long time. That’s why the peroxide acts as a catalyst/ medium in anti markovnikov rule reactions.

Key Differences

  1. Markovnikov rule usually describes that proton is convoluted to that carbon atom that has the greatest number of hydrogen atoms attached to it. On the other hand, anti markovnikov rule gives details that proton is involved in that carbon atom that has a minimum number of hydrogen atoms attached to it.
  2. According to markovnikov rule, the hydrogen atom will always get attached to that carbon atom that has a maximum number of hydrogen substituents attached to it; on the contrary, according to anti markovnikov rule, the hydrogen atom will always attach to that carbon atom having least number of hydrogen substituents.
  3. The electronegative part of alkyl halide usually goes to the carbon, which consists of the least number of hydrogen atoms attached to a carbon atom in markovnikov rule. On the contrary, the electronegative part of alkyl halide attaches to the carbon atom that consists of the highest number of hydrogen atoms attached to the carbon atom in anti markovnikov rule.
  4. The mechanism of markovnikov rule in chemistry is an ionic mechanism; on the flip side, the mechanism of anti markovnikov rule is a free radical mechanism.
  5. HBr, HI, HCL, and H2O are the reactants that are used in markovnikov rule; on the other hand, HBr is the only free reactant that is used in anti markovnikov rule, and HCl, or HI do not undergo in this kind of addition reaction.
  6. No medium is generally required in markovnikov rule; on the flip side, to carry out the anti-markovnikov rule, the medium is must require which is peroxide or ultraviolet.
  7. The markovnikov addition of hydrogen halide to olefin usually results in the production of carbocation as the reaction intermediary; on the other hand, the creation of carbon-free radical is generally known as the reaction intermediary in anti markovnikov rule.
  8. In markovnikov addition reaction, the carbocation, which is the intermediary in this reaction, then undergoes a rearrangement, which increases the stability of carbocation. In contrast, in anti markovnikov rule, the produced intermediary does not undergo in the rearrangement of products.
  9. The hydrogen ion from reactant HX in markovnikov rule starts the attack on the carbon-carbon double bond. On the contrary, halogen-free radical X, which is formed by the communication between HX and the radical peroxide, usually starts the attack on carbon-carbon double bond in anti markovnikov rule.
  10. The major product is given by HBr from (CH3) 2C = CHCH3 will produce (CH3) 2CBrCH2CH3 in markovnikov rule; on the contrary, in the presence of peroxide, in anti markovnikov addition reaction, the main product will be given as (CH3) 2CHCH(Br)CH3.

Conclusion

Above discussion concludes that the both markovnikov and anti markovnikov rules are important in predicting the products of chemical reactions in which markovnikov rule describes that proton is convoluted to that carbon atom that has the maximum number of hydrogen atoms attached to it; on the other hand, anti markovnikov rule give details that proton is involved to that carbon atom that has minimum number of hydrogen atoms attached to it.

Harlon Moss

Harlon currently works as a quality moderator and content writer for Difference Wiki. He graduated from the University of California in 2010 with a degree in Computer Science. Follow him on Twitter @HarlonMoss

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