Alkyl Halides
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Questions and Answers

What is the result of reacting tertiary alcohols with HX?

  • Slow reaction
  • Rearrangement
  • No reaction
  • Fast and effective reaction (correct)

    • Why are alternative methods used for primary and secondary alcohols?

  • They are not used in organic chemistry
  • They react very slowly and often rearrange (correct)
  • They react too quickly
  • They are not reactive

    • What is used to prepare alkyl halides from primary and secondary alcohols?

  • HX gas
  • NaOH
  • H2O
  • SOCl2 or PBr3 (correct)

    • What type of reaction do alkyl halides undergo with nucleophiles?

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

    What type of reaction do alkyl halides undergo with Brønsted-Lowry bases?

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

    How many components are necessary in any substitution reaction?

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

    What is the purpose of adding HCl or HBr gas into an ether solution of tertiary alcohol?

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

    What is formed when a tertiary alcohol reacts with HX?

    <p>Alkyl halide</p> Signup and view all the answers

    Why are phosphorous halides used in the preparation of alkyl halides?

    <p>They are useful for primary and secondary alcohols</p> Signup and view all the answers

    What is the general term for the reaction of an alkyl halide with a nucleophile or a base?

    <p>Substitution or elimination</p> Signup and view all the answers

    What is the kinetic order of an SN2 reaction?

    <p>Second order</p> Signup and view all the answers

    What is the effect of bulky R groups on the SN2 reaction rate?

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

    Why do 3° alkyl halides not undergo SN2 reactions?

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

    What is the key feature of the SN1 mechanism?

    <p>Two-step mechanism</p> Signup and view all the answers

    What is the role of the nucleophile in the SN1 reaction rate?

    <p>Has no effect on the reaction rate</p> Signup and view all the answers

    What is the type of reaction mechanism exemplified by reaction 1?

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

    What is the effect of the number of R groups on the carbon with the leaving group on the SN2 reaction rate?

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

    What is the reactivity of methyl and 1° alkyl halides in SN2 reactions?

    <p>They react with ease</p> Signup and view all the answers

    What is the kinetic order of an SN1 reaction?

    <p>First order</p> Signup and view all the answers

    What is the characteristic of the reaction site in an SN2 reaction?

    <p>Attack from the back</p> Signup and view all the answers

    What is the most common type of base used in elimination reactions?

    <p>Negatively charged oxygen compounds</p> Signup and view all the answers

    How do you identify the α carbon in an elimination reaction?

    <p>By finding the carbon with the leaving group</p> Signup and view all the answers

    What is the result of removing the elements of H and X from the α and β carbons in an elimination reaction?

    <p>Formation of a π bond</p> Signup and view all the answers

    How many mechanisms of elimination are there?

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

    What is the name of the bimolecular elimination mechanism?

    <p>E2</p> Signup and view all the answers

    What is the name of the unimolecular elimination mechanism?

    <p>E1</p> Signup and view all the answers

    What is the relationship between the E2 and SN2 mechanisms?

    <p>They have some features in common</p> Signup and view all the answers

    What is the relationship between the E1 and SN1 mechanisms?

    <p>They have some features in common</p> Signup and view all the answers

    What is the first step in drawing the product of dehydrohalogenation?

    <p>Identify the α carbon</p> Signup and view all the answers

    What is the purpose of identifying the β carbon in an elimination reaction?

    <p>To identify the site of H atom removal</p> Signup and view all the answers

    I¯ is a good nucleophile and a strong base.

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

    DBU is a bulky nucleophilic base that favors substitution.

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

    CH3COO¯ is a strong base that favors elimination.

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

    KOC(CH3)3 is a good nucleophile that favors substitution.

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

    Tertiary alcohols react with HX to form alkyl halides.

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

    Bulky R groups increase the SN2 reaction rate.

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

    E2 reactions involve the formation of a carbocation intermediate.

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

    HS¯ is a weak base that favors substitution.

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

    DBN is a good nucleophile that favors substitution.

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

    Br¯ is a strong base that favors elimination.

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

    Study Notes

    Alkyl Halides

    • Alkyl halides are organic molecules containing a halogen atom bonded to an sp3 hybridized carbon atom.
    • The halogen atom is often denoted by the symbol X.
    • Alkyl halides are classified as primary (1°), secondary (2°), or tertiary (3°), depending on the number of carbons bonded to the carbon with the halogen atom.

    Types of Alkyl Halides

    • Vinyl halides have a halogen atom bonded to a C-C double bond.
    • Aryl halides have a halogen atom bonded to a benzene ring.
    • Allylic halides have X bonded to the carbon atom adjacent to a C-C double bond.
    • Benzylic halides have X bonded to the carbon atom adjacent to a benzene ring.

    Nomenclature of Alkyl Halides

    • Common names are often used for simple alkyl halides.
    • To assign a common name:
    • Name all the carbon atoms of the molecule as a single alkyl group.
    • Name the halogen bonded to the alkyl group.
    • Combine the names of the alkyl group and halide, separating the words with a space.

    Polarity of Alkyl Halides

    • Alkyl halides are weakly polar molecules.
    • They exhibit dipole-dipole interactions due to their polar C-X bond.
    • They are incapable of intermolecular hydrogen bonding.

    Simple Alkyl Halide of Medical Importance

    • Halothane (CF3CHCLBr) is a safe general anesthetic that has replaced other organic anesthetics.

    The Polar Carbon-Halogen Bond

    • The electronegative halogen atom in alkyl halides creates a polar C-X bond, making the carbon atom electron deficient.
    • Electrostatic potential maps illustrate this point.

    Preparing Alkyl Halides

    • From alkanes: Radical halogenation replaces C-H with C-X, but gives mixtures.
    • From alkenes: Addition of HX to alkenes gives Markovnikov product.
    • From alcohols: Reaction of tertiary C-OH with HX is fast and effective.

    Reaction Types for Alkyl Halides

    • Alkyl halides undergo substitution reactions with nucleophiles.
    • Alkyl halides undergo elimination reactions with Brønsted-Lowry bases.

    Substitution Reactions

    • Three components are necessary: sp3 hybridized carbon with the leaving group, nucleophile, and leaving group.
    • To draw any nucleophilic substitution product: find the sp3 hybridized carbon with the leaving group, identify the nucleophile, and substitute the nucleophile for the leaving group.

    Nucleophiles

    • Nucleophiles are Lewis bases that can be negatively charged or neutral.
    • Examples: HO-, HS-, and CH3COO-.
    • Nucleophiles differ from bases in what they attack.

    Leaving Groups

    • The weaker the base, the better the leaving group.
    • Good leaving groups: H2O, Cl-, Br-, I-, and ROSO3-.
    • Poor leaving groups: HO-, RO-, and H-.

    SN2 Mechanism

    • Concerted mechanism with a one-step process.
    • Rate depends on the concentration of both reactants.
    • Rate equation is second order.

    SN1 Mechanism

    • Two-step mechanism with a carbocation intermediate.
    • Rate depends on the concentration of RX only.
    • Rate equation is first order.

    Kinetics and Mechanisms

    • Consider reaction kinetics to determine the mechanism.
    • SN2 reactions exhibit second-order kinetics, while SN1 reactions exhibit first-order kinetics.

    Steric Effects on Nucleophile Strength

    • Steric hindrance decreases nucleophilicity but not basicity.
    • Sterically hindered bases that are poor nucleophiles are called nonnucleophilic bases.

    Bond Breaking and Making in Nucleophilic Substitution Mechanisms

    • There are three possibilities: bond making and breaking occur at the same time, bond breaking occurs first, or bond making occurs first.

    Predicting the Mechanism of Nucleophilic Substitutions

    • Four factors are relevant in predicting the mechanism: the alkyl halide, the nucleophile, the leaving group, and the solvent.

    SN1 and E1 Reactions

    • Both have the same first step: formation of a carbocation.
    • They differ in what happens to the carbocation.

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    Related Documents

    Alkyl Halides Part 1 PDF
    Alkyl Halides Part 2 PDF
    Alkyl Halides Part 3 PDF
    Alkyl Halides Part 4 PDF

    Description

    Learn about alkyl halides, their classification, and types. Understand the structure and properties of primary, secondary, and tertiary alkyl halides, and vinyl halides. This quiz covers the basics of alkyl halides in organic chemistry.

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