8: Nucleophilic Substitution Reactions
- Page ID
- 391344
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 8.1: Alkyl Halides - Structure and Physical Properties
- Alkyl halides are classified based upon the structure of the carbon atom bonded to the halogen. Common names and physical properties are discussed.
- 8.2: Reactions of Alkyl Halides- Substitution and Elimination
- The two major reaction pathways for alkyl halides (substitution and elimination) are introduced.
- 8.3: The Sₙ2 Reaction
- The SN2 mechanism is described mechanistically and kinetically as a one-step (concerted) reaction between two reactants (bimolecular) that inverts the configuration of the carbon at the reactive site. The terms nucleophile, electrophile, and leaving group are explained by application to SN2 reactions.
- 8.4: Characteristics of the Sₙ2 Reaction
- In order of decreasing importance, the factors impacting SN2 reaction pathways are the structure of the alkyl halide, the strength of the nucleophile, the stability of the leaving group, and the type of solvent.
- 8.5: Stereochemistry of the SN2 Reaction
- The SN2 reaction is stereospecific. A stereospecific reaction is one in which different stereoisomers react to give different stereoisomers of the product.
- 8.6: The Sₙ1 Reaction
- In the SN1 reaction, the solvent helps pull apart the halogen and carbon to form a halide and carbocation. A nucleophile can now form a bond with the carbocation to create a new product. The mechanism is explained with stereochemistry and reaction kinetics.
- 8.7: Characteristics of the Sₙ1 Reaction
- The formation and stability of the carbocation intermediate strongly influence the SN1 mechanism. The structure of the alkyl halide, the stability of the leaving group, and the type of solvent influence the reaction pathway. Since the nucleophile is not involved in the rate determining step, the strength of the nucleophile has low importance.
- 8.8: Rearrangements of the Carbocation and Sₙ1 Reactions
- Carbocation rearrangements are structural reorganizational shifts within an ion to a more stable state (lower energy).
- 8.9: The Hammond Postulate and Transition States
- The Hammond postulate states that a transition state resembles the structure of the nearest stable species and helps explain the product distribution differences observed between exergonic and endergonic reactions.
- 8.10: Comparison of SN1 and SN2 Reactions
- In comparing the SN1 and SN2 mechanisms, the structure of the alkyl halide (electrophile), the strength of the nucleophile, and the reaction solvent are the primary considerations. The leaving group will have a similar effect for both reactions, so it is not of interest when comparing the mechanistic pathways.
- 8.11: Biological Substitution Reactions
- A few examples of biochemical SN1 and SN2 mechanisms are introduced with an emphasis on the effects of the leaving group.