Addition Reactions and Markovnikov's Rule
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Questions and Answers

According to Markovnikov's Rule, when adding HX to an asymmetric alkene, which product is favored?

  • Two equal products with symmetrical carbons
  • The product with the most substituted carbon (correct)
  • No specific product is favored
  • The product with the least substituted carbon

The addition reactions of alkenes are usually endothermic.

False (B)

What type of carbocation is formed when 1-bromopropane is produced from propene and HX?

secondary carbocation

In the reaction of CH₃CH₂CH=CH₂ with HX, the product CH₃CH₂CH-CH₃ demonstrates the concept of __________.

<p>stereocenter</p> Signup and view all the answers

Match the following alkene reactions with their respective descriptions:

<p>Addition of HX to alkenes = Forms a carbocation Markovnikov's Rule = Predicts the major product in asymmetric alkene additions Stereochemistry in alkene reactions = Involves the formation of chiral centers Radical addition mechanisms = Involves electrons added to unsaturated bonds</p> Signup and view all the answers

Which of the following describes the condition under which Anti-Markovnikov's addition occurs?

<p>Using peroxide and free radicals (C)</p> Signup and view all the answers

Markovnikov's Rule states that during the addition of HX to an alkene, the hydrogen atom bonds to the carbon atom with the most hydrogen substitutes.

<p>True (A)</p> Signup and view all the answers

What is produced when CH3-CH=CH2 reacts with HBr in the presence of peroxides?

<p>(CH3)2CHCHBr</p> Signup and view all the answers

The stable free radical formed during the anti-Markovnikov addition is indirectly attributed to __________.

<p>peroxides</p> Signup and view all the answers

Match the following reactions with their outcomes:

<p>CH3-CH=CH2 + HBr = CH3-CH2-CH2Br (CH3)2C=CH2 + HBr = (CH3)2CHCHBr CH3-CH=CH2 + H2SO4 = Propan-2-ol CH3-CH-CH2 + HBr = Isopropyl alcohol</p> Signup and view all the answers

Which of the following statements accurately describes Markovnikov's Rule in the context of electrophilic addition reactions?

<p>The more substituted carbon atom will typically receive the hydrogen atom. (D)</p> Signup and view all the answers

In hydroboration, the addition is considered anti-Markovnikov.

<p>True (A)</p> Signup and view all the answers

What reagent is used for the anti-Markovnikov addition of hydroxyl groups to alkenes?

<p>BH3 in THF</p> Signup and view all the answers

The process of adding bromine or chlorine to alkenes typically results in the formation of ________ dihalides.

<p>vicinal</p> Signup and view all the answers

Match the following reaction mechanisms to their characteristics:

<p>Oxymercuration = Adds OH to more substituted carbon Hydroboration = Adds OH to less substituted carbon Free Radical Addition = Involves free radical intermediates Electrophilic Addition = Forms vicinal dihalides</p> Signup and view all the answers

Flashcards

Markovnikov's Rule

When a hydrogen halide adds to an alkene, the hydrogen atom adds to the carbon with more hydrogens already attached.

Addition Reaction (Alkenes)

A reaction where a molecule adds across a double bond in an alkene.

Carbocation Intermediate

A positively charged carbon atom intermediate formed in the reaction of an alkene with an electrophile.

Symmetric alkene reaction

When the reactants have an equal number of carbons attached to the double bonds, it results in the same product, regardless of where the atoms attach.

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Asymmetric alkene reaction

Alkenes with varying numbers of substituents on the double bond result in products following Markovnikov's rule.

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Anti-Markovnikov Addition

An addition reaction where the hydrogen atom adds to the less substituted carbon of an alkene in the presence of a peroxide.

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Free Radical Chain Mechanism (with peroxides)

Hydrogen addition to an alkene, driven by a chain reaction initiated by peroxide. The mechanism involves initiation, propagation, and termination steps.

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Chain Initiation (peroxide)

The first step in a free radical chain reaction, involving the homolytic cleavage of the peroxide to create two radicals.

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Chain Propagation (peroxide)

The repeating steps in a free radical chain reaction, where one radical reacts to produce another radical and a product. These steps regenerate the reactive radical.

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Oxymercuration Hydration

A two-step reaction that adds water to an alkene, forming an alcohol. The reaction proceeds via a mercurinium ion intermediate and results in Markovnikov addition of water.

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Harkonikov Addition

A type of addition reaction where the electrophile (in this case, the hydrogen atom) attaches to the carbon atom with the most hydrogen atoms already present. This means the OH group goes on the more substituted carbon atom.

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Hydroboration Hydration

A two-step reaction that adds water to an alkene, forming an alcohol. This reaction utilizes borane (BH3) and then hydrogen peroxide (H2O2) and sodium hydroxide (NaOH) to yield an anti-Markovnikov product.

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Electrophilic Addition of Br2/Cl2 to Alkenes

A reaction where bromine or chlorine molecules add to an alkene in a non-polar solvent, resulting in the formation of a vicinal dihalide (halogens on adjacent carbons).

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Identify the Major Product

Predict the main product of a reaction based on the reactivity and regiochemistry of the reactants. For example, in alkene reactions, consider Markovnikov's rule or anti-Markovnikov addition.

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Study Notes

Addition Reactions

  • Addition reactions involve the addition of atoms or groups to a molecule, typically across a double or triple bond.
  • Attacking the pi bond on an electrophile often forms a carbocation
  • Rich electron density is present on the C=C pi bond.
  • Addition of hydrogen halides to alkenes results in carbocations
  • Carbocation geometry is planar.
  • Symmetrical alkenes give equal numbers of carbons around the double bond.
  • Addition reactions proceed through secondary carbocations.
  • Hyperconjugation and inductive effect influence carbocation stability.
  • Reactions tend to be exothermic.

Markovnikov's Rule

  • In electrophilic addition reactions on alkenes, the electrophile (e.g., H+) generally attaches to the carbon of the double bond that already has more hydrogen atoms.
  • The product with the more highly substituted carbocation intermediate is favored.
  • Reaction often proceeds slower in the less substituted intermediate.
  • Constitutional isomers are formed, but one is predominantly formed (regioselectivity).

Exceptions to Markovnikov's Rule

  • Peroxide effect: Peroxides favor the "anti-Markovnikov" addition of hydrogen halides.
  • Free radical mechanisms bypass intermediate carbocations, leading to unexpected regiochemistry.

Acid-Catalyzed Hydration

  • Addition of water to an alkene in the presence of an acid catalyst (e.g., sulfuric acid) results in the formation of an alcohol.
  • A carbocation intermediate is formed.
  • The reaction proceeds via a protonation step, carbocation formation, and finally nucleophilic attack by water.
  • Tertiary carbocations are favored.

Mechanism of Addition Reactions (Examples)

  • Various mechanisms for addition exist (e.g., ionic, free radical, anti-Markovnikov).
  • Examples include addition of hydrogen halides, water, or halogens.
  • Key steps involve bond breaking, formation of carbocation(s), and nucleophilic attacks.
  • Acid-catalyzed hydration often leads to alcohol formation.
  • Understanding the stability of carbocation intermediates is crucial for predicting the major products.

Thermodynamics of Addition/Elimination Reactions

  • Thermodynamic factors affect the equilibrium of addition and elimination reactions
  • Equilibrium position depends on temperature and product stability .
  • Le Chatelier's principle can be used to predict how equilibrium will shift based on changing factors such as temperature.
  • Consider entropy effect on reaction equilibrium.

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Related Documents

Addition Reactions Notes PDF

Description

Explore the concepts of addition reactions in organic chemistry, focusing on the formation of carbocations and the influence of Markovnikov's Rule. Understand how electrophiles interact with alkenes and the importance of carbocation stability in these reactions. Test your knowledge on these fundamental principles of organic reactions.

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