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Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides
Bruice - Organic Chemistry 8th Edition
Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook
All textbooksBruice 8th EditionCh. 9 - Substitution and Elimination Reactions of Alkyl HalidesProblem 111c
Chapter 10, Problem 111c

Draw the elimination products for each of the following E2 reactions; if the products can exist as stereoisomers, indicate which stereoisomers are obtained.
c. (2R,3S)-2-chloro-3-methylpentane + high concentration of CH3O-

Verified step by step guidance
1
Identify the type of reaction: This is an E2 elimination reaction, which is a one-step concerted mechanism where a base abstracts a proton (β-hydrogen) from a β-carbon, and a leaving group (Cl⁻ in this case) departs simultaneously, forming a double bond.
Analyze the structure of the substrate: The given compound is (2R,3S)-2-chloro-3-methylpentane. The chlorine atom is attached to the second carbon, and the methyl group is attached to the third carbon. The stereochemistry is specified as (2R,3S).
Determine the β-hydrogens: For an E2 reaction, β-hydrogens are hydrogens attached to carbons adjacent to the carbon bearing the leaving group (C2 in this case). The β-carbons are C1 and C3. Check the stereochemistry to identify the anti-periplanar β-hydrogens (hydrogens that are opposite to the leaving group in the same plane).
Predict the elimination products: The base (CH₃O⁻) will abstract an anti-periplanar β-hydrogen, leading to the formation of a double bond between C2 and the β-carbon (either C1 or C3). This can result in two possible alkenes: one with a double bond between C1 and C2, and another with a double bond between C2 and C3. Consider Zaitsev's rule, which states that the more substituted alkene is generally the major product.
Determine stereoisomers: If the double bond formed can have cis/trans (E/Z) stereoisomers, analyze the substituents on the double-bonded carbons to determine the possible stereoisomers. For example, if the double bond is between C2 and C3, the substituents on these carbons will dictate whether the product is E (trans) or Z (cis).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

E2 Mechanism

The E2 mechanism is a type of elimination reaction where a base removes a proton from a β-carbon, leading to the simultaneous departure of a leaving group from the α-carbon. This concerted process results in the formation of a double bond. Understanding the stereochemistry and the orientation of the substituents is crucial, as it influences the formation of stereoisomers.
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Stereochemistry

Stereochemistry refers to the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In E2 reactions, the stereochemistry of the starting material can lead to different stereoisomers in the products. The configuration of the reactants, such as (2R,3S)-2-chloro-3-methylpentane, plays a significant role in determining the stereochemical outcome of the elimination products.
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Stereoisomers

Stereoisomers are compounds that have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of their atoms. In the context of E2 reactions, the formation of stereoisomers can occur due to the different orientations of the substituents around the double bond formed during the elimination process. Identifying and drawing these stereoisomers is essential for a complete understanding of the reaction products.
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Related Practice
Textbook Question

Draw the elimination products for each of the following E2 reactions; if the products can exist as stereoisomers, indicate which stereoisomers are obtained.

d. (2R,3R)-2-chloro-3-methylpentane + high concentration of CH3O-

1473
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Textbook Question

Draw the major elimination product that would be obtained from each of the following reactants with a strong base and with a weak base:

a.

1671
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Textbook Question

Draw the substitution products for each of the following SN2 reactions. If the ­products can exist as stereoisomers, show which stereoisomers are formed:

a. (3S,4S)-3-bromo-4-methylhexane + CH3O-

b. (3S,4R)-3-bromo-4-methylhexane + CH3O-

958
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Textbook Question

Draw the elimination products for each of the following E2 reactions; if the products can exist as stereoisomers, indicate which stereoisomers are obtained.

a. (2S,3S)-2-chloro-3-methylpentane + high concentration of CH3O−

b. (2S,3R)-2-chloro-3-methylpentane + high concentration of CH3O−

726
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Textbook Question

Draw the elimination products for each of the following E2 reactions; if the products can exist as stereoisomers, indicate which stereoisomers are obtained.

e. 3-chloro-3-ethyl-2,2-dimethylpentane + high concentration of CH3CH2O-

872
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Textbook Question

Draw the substitution products for each of the following SN2 reactions. If the ­products can exist as stereoisomers, show which stereoisomers are formed:

c. (3R,4R)-3-bromo-4-methylhexane + CH3O-

d. (3R,4S)-3-bromo-4-methylhexane + CH3O-

863
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