Reaction Mechanism
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What is the characteristic of the SN2 nucleophilic substitution mechanism?

  • It involves a two-step mechanism with a slow first step.
  • It involves a collision-based mechanism with a single transition state. (correct)
  • It is a free radical substitution reaction.
  • It is a free radical reaction.

    • What type of alkyl halides works well with SN2 nucleophilic substitution?

  • Methyl or primary alkyl halides (correct)
  • Aromatic alkyl halides
  • Secondary alkyl halides
  • Tertiary alkyl halides

    • What is the characteristic of the energy diagram of SN2 nucleophilic substitution?

  • It has a slow first step and a faster second step.
  • It has two transition states and two activation energies.
  • It has a single transition state with two activation energies.
  • It has one transition state and one activation energy. (correct)

    • What is the characteristic of the SN1 nucleophilic substitution mechanism?

    <p>It involves a two-step mechanism with a slow first step and a faster second step.</p> Signup and view all the answers

    What type of alkyl halides works well with SN1 nucleophilic substitution?

    <p>Tertiary alkyl halides</p> Signup and view all the answers

    What is the consequence of steric hindrance in SN2 reactions involving secondary and tertiary alkyl halides?

    <p>The reaction rate decreases</p> Signup and view all the answers

    What is the geometry of the transition state in the SN2 reaction mechanism?

    <p>Trigonal bipyramidal</p> Signup and view all the answers

    What is the requirement for the nucleophile to attack the carbon center in an SN2 reaction?

    <p>There must be enough space for the attack to be effective</p> Signup and view all the answers

    What is the rate law for the SN2 reaction?

    <p>Rate = k[RX][Nu:-]</p> Signup and view all the answers

    What is the consequence of a negative ΔG in a reaction?

    <p>The reaction is spontaneous</p> Signup and view all the answers

    What is the characteristic of the transition state in the SN2 reaction mechanism?

    <p>Trigonal bipyramidal with partial chemical bonds</p> Signup and view all the answers

    Why do tertiary alkyl halides not undergo substitution by the SN2 mechanism?

    <p>Due to steric hindrance</p> Signup and view all the answers

    What is the rate law for the SN1 reaction mechanism?

    <p>Rate = k[RX]</p> Signup and view all the answers

    What is the role of a polar solvent in the SN1 reaction mechanism?

    <p>To solvate the Br- ion when it detaches</p> Signup and view all the answers

    Why do tertiary alkyl halides give faster reactions with the SN1 mechanism?

    <p>Due to the stability of the carbocation</p> Signup and view all the answers

    What is the preferred mechanism of reaction for primary or methyl alkyl halides?

    <p>SN2 mechanism</p> Signup and view all the answers

    What is the effect of methyl groups on the stability of a carbocation?

    <p>They decrease the positive charge</p> Signup and view all the answers

    Which of the following is a characteristic of the SN1 reaction?

    <p>It involves a slow first step and a faster second step</p> Signup and view all the answers

    What is the effect of increasing the concentration of RX on the rate of an SN1 reaction?

    <p>It increases the rate of the reaction</p> Signup and view all the answers

    What is the difference between SN1 and SN2 reactions?

    <p>SN1 involves a primary or methyl alkyl halide, while SN2 involves a tertiary alkyl halide</p> Signup and view all the answers

    What is the result of homolytic cleavage in bond breaking?

    <p>Formation of two free radicals</p> Signup and view all the answers

    Which type of bond formation is associated with polar reactions?

    <p>Heterolytic bond formation</p> Signup and view all the answers

    What is a characteristic of a free radical?

    <p>It is missing an octet and is very reactive</p> Signup and view all the answers

    In an SN2 reaction mechanism, what is the likely effect of steric hindrance on the rate of the reaction?

    <p>It decreases the rate of the reaction</p> Signup and view all the answers

    What is the result of a free radical seeking another electron in a free radical addition reaction?

    <p>The pi bond breaks homolytically</p> Signup and view all the answers

    What is the type of reaction that involves heterolytic bond breaking and heterogenic bond formation?

    <p>Polar reaction</p> Signup and view all the answers

    Which of the following alkyl halides is most likely to undergo an SN1 reaction mechanism?

    <p>(CH₃)₃CCl</p> Signup and view all the answers

    In an SN2 reaction mechanism, which bond is formed in the rate-determining step?

    <p>Carbon-nucleophile bond</p> Signup and view all the answers

    What is the order of bond formation and breaking in an SN2 reaction mechanism?

    <p>Simultaneous bond breaking and formation</p> Signup and view all the answers

    Which of the following factors does not facilitate an SN1 reaction mechanism?

    <p>High concentrations of nucleophiles</p> Signup and view all the answers

    What is the purpose of using UV light or heat in the initiation step of the free radical addition chain reaction?

    <p>To initiate the formation of free radicals</p> Signup and view all the answers

    What is the characteristic of the propagation steps in the free radical addition chain reaction?

    <p>It produces most of the product formed</p> Signup and view all the answers

    What is the reason for the first step being slow in the free radical addition chain reaction?

    <p>It involves the breaking of a pi bond</p> Signup and view all the answers

    What is the geometry of the carbocation intermediate in the electrophilic addition of HX?

    <p>Trigonal planar</p> Signup and view all the answers

    What is the characteristic of the termination steps in the free radical addition chain reaction?

    <p>They are rare steps in the reaction</p> Signup and view all the answers

    What is the purpose of the energy diagram in the free radical addition chain reaction?

    <p>To explain why the first step is slow and the second step is fast</p> Signup and view all the answers

    What is the role of UV light in the initiation step of the free radical addition chain reaction?

    <p>To break down a stable molecule into two free radicals</p> Signup and view all the answers

    What is the characteristic of the free radicals in the propagation steps of the free radical addition chain reaction?

    <p>They are highly reactive molecules</p> Signup and view all the answers

    What is the reason for the second step being fast in the free radical addition chain reaction?

    <p>It involves the attack of a fully negative particle on the fully positive carbocation</p> Signup and view all the answers

    What is the purpose of the propagation steps in the free radical addition chain reaction?

    <p>To produce most of the product formed</p> Signup and view all the answers

    What is the primary difference between the SN2 and SN1 reaction mechanisms?

    <p>The number of steps involved in the mechanism</p> Signup and view all the answers

    Which of the following alkyl halides would be most likely to exhibit steric hindrance in an SN2 reaction?

    <p>Tertiary alkyl halide</p> Signup and view all the answers

    What is the effect of steric hindrance on the rate of an SN2 reaction?

    <p>It decreases the rate of the reaction</p> Signup and view all the answers

    Which of the following best describes the mechanism of an SN2 reaction?

    <p>A one-step mechanism involving a collision-based reaction</p> Signup and view all the answers

    What is the primary reason why tertiary alkyl halides undergo SN1 reactions more easily than SN2 reactions?

    <p>They have a more stable carbocation intermediate</p> Signup and view all the answers

    What is the reason why tertiary alkyl halides cannot undergo substitution by the SN2 mechanism?

    <p>Steric hindrance prevents the nucleophile from attacking the alkyl halide</p> Signup and view all the answers

    What is the characteristic of the transition state in the SN2 reaction mechanism?

    <p>It has a trigonal bipyramidal geometry with partial chemical bonds</p> Signup and view all the answers

    What is the role of the polar solvent in the SN1 reaction mechanism?

    <p>It solvates the leaving group, making it more stable</p> Signup and view all the answers

    What is the difference between the SN1 and SN2 reaction mechanisms?

    <p>The SN1 reaction involves a carbocation intermediate, while the SN2 reaction does not</p> Signup and view all the answers

    What is the rate law for the SN1 reaction mechanism?

    <p>Rate = k[RX]</p> Signup and view all the answers

    What is the significance of the Markovnikov's Rule in electrophilic addition reactions of HX to an alkene?

    <p>It dictates the regiospecificity of the reaction</p> Signup and view all the answers

    What is the effect of steric hindrance on the SN2 reaction mechanism?

    <p>It slows down the reaction</p> Signup and view all the answers

    What is the outcome of homolytic cleavage in bond breaking?

    <p>Formation of two free radicals</p> Signup and view all the answers

    Which type of reaction is characterized by heterolytic bond breaking and heterogenic bond formation?

    <p>Polar reaction</p> Signup and view all the answers

    What is the characteristic of the transition state in the SN2 reaction mechanism?

    <p>Trigonal bipyramidal geometry</p> Signup and view all the answers

    What is the effect of steric hindrance on the rate of SN2 reactions?

    <p>It decreases the rate of the reaction</p> Signup and view all the answers

    Which type of alkyl halides is more likely to undergo an SN2 reaction mechanism?

    <p>Primary and methyl alkyl halides</p> Signup and view all the answers

    What is the role of the leaving group in the SN2 reaction mechanism?

    <p>It is connected to the carbon that is attacked by the nucleophile</p> Signup and view all the answers

    Which type of alkyl halides is more likely to undergo an SN2 reaction mechanism?

    <p>Primary alkyl halides</p> Signup and view all the answers

    What is the role of the nucleophile in an SN2 reaction mechanism?

    <p>To form a bond with the carbon center</p> Signup and view all the answers

    Which type of alkyl halides reacts through an SN2 mechanism?

    <p>Primary or methyl alkyl halides</p> Signup and view all the answers

    What is the effect of increasing the concentration of RX on the rate of an SN2 reaction?

    <p>It increases the rate</p> Signup and view all the answers

    Why do methyl groups donate electron density to the positive C atom in a carbocation?

    <p>To reduce the total positive charge</p> Signup and view all the answers

    What is the characteristic of the transition state in an SN1 reaction?

    <p>It is at a higher energy</p> Signup and view all the answers

    What is the effect of steric hindrance on the rate of an SN2 reaction?

    <p>It decreases the rate</p> Signup and view all the answers

    Which of the following is a characteristic of the transition state in the SN1 reaction mechanism?

    <p>A trigonal planar geometry with an empty 2p atomic orbital</p> Signup and view all the answers

    What is the effect of steric hindrance on the rate of an SN2 reaction?

    <p>It decreases the rate of the reaction</p> Signup and view all the answers

    Which of the following alkyl halides is most likely to undergo an SN1 reaction mechanism?

    <p>Tertiary alkyl halide</p> Signup and view all the answers

    What is the role of the nucleophile in an SN2 reaction mechanism?

    <p>It forms a bond with the carbon center before the leaving group leaves</p> Signup and view all the answers

    Which of the following is a characteristic of SN2 nucleophilic substitution reactions?

    <p>The rate of the reaction is dependent on the concentration of the nucleophile</p> Signup and view all the answers

    What is the primary difference between the SN1 and SN2 reaction mechanisms?

    <p>The rate-determining step</p> Signup and view all the answers

    Which type of alkyl halide is more likely to undergo an SN1 reaction mechanism?

    <p>Tertiary alkyl halides</p> Signup and view all the answers

    What is the effect of steric hindrance on the rate of an SN2 reaction?

    <p>It decreases the rate of the reaction</p> Signup and view all the answers

    In an SN2 reaction, what is the order of bond formation and breaking?

    <p>Simultaneous bond formation and breaking</p> Signup and view all the answers

    What is the role of a polar solvent in an SN1 reaction mechanism?

    <p>It stabilizes the carbocation intermediate</p> Signup and view all the answers

    Which factor does not facilitate an SN1 reaction mechanism?

    <p>Steric hindrance</p> Signup and view all the answers

    What is the characteristic of the energy diagram for an SN2 reaction?

    <p>It has a single transition state</p> Signup and view all the answers

    What is the purpose of using UV light in the initiation step of a free radical addition chain reaction?

    <p>To initiate the formation of free radicals</p> Signup and view all the answers

    Which of the following alkyl halides is most likely to undergo an SN2 reaction mechanism?

    <p>Primary alkyl halides</p> Signup and view all the answers

    What is the result of steric hindrance in SN2 reactions involving secondary and tertiary alkyl halides?

    <p>It decreases the rate of the reaction</p> Signup and view all the answers

    Study Notes

    Types of Organic Reactions

    • Free radical reactions: involve the formation of free radicals (species with an odd number of electrons)
    • Polar reactions: involve the formation of ions

    Free Radical Reactions

    • Two types:
      • Free radical substitution
      • Free radical addition
    • Free radical addition: a free radical seeking another electron to achieve stability causes the pi bond to break homolytically
    • Free radical substitution: involves three distinct steps - initiation, propagation, and termination
    • Initiation step: a stable molecule is broken down to two free radicals (slowest step)
    • Propagation steps: a free radical attacks a stable molecule and produces another free radical and another stable molecule (faster, most of the product is formed)
    • Termination steps: two free radicals react together (rare, very little product is formed)

    SN1 Reaction

    • Substitution, Nucleophilic, Unimolecular
    • Rate Law: Rate = k[RX] (does not depend on the nucleophile concentration)
    • First-order reaction
    • Mechanism: two-step process
      • Step 1: Bond breaks by itself (slow)
      • Step 2: Nucleophile attacks carbocation (fast)
    • Energy diagram: similar to electrophilic addition of HX to an alkene
    • Works best with tertiary alkyl halides
    • Factors that facilitate SN1 reaction:
      • Increasing [RX]
      • Using a polar solvent
      • Large X group

    SN2 Reaction

    • Substitution, Nucleophilic, Bimolecular
    • Rate Law: Rate = k[RX][Nu:-] (second-order reaction)
    • Mechanism: one-step process
      • Nucleophile attacks the carbon that is connected to the leaving group (collision-based reaction)
      • Transition state: trigonal bipyramidal geometry
    • Works well with methyl or primary alkyl halides
    • Factors that facilitate SN2 reaction:
      • Increasing [RX] and [Nu]
      • Increasing temperature (kinetic energy of collisions)

    Carbocation Stability

    • A more stable carbocation means a faster Step 1 in SN1 reaction
    • Methyl groups donate electron density to the positive C atom, reducing the total positive charge and making the carbocation more stable
    • Tertiary carbocation is the most stable, resulting in a faster reaction

    Electrophilic Addition of HX to an Alkene

    • Reaction intermediate: carbocation (sp2 hybridized, trigonal planar geometry, empty 2p atomic orbital)
    • Energy diagram: first step involves the breaking of a pi bond, and this requires energy; second step involves the attack of a fully negative particle (Br-) on the fully positive carbocation
    • Markovnikov's Rule: regiospecific reaction, atoms go in specific positions

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