Textbook Question
Practice your electron-pushing skills by drawing a mechanism for the following E2 reactions.
(b)
749
views
8. Elimination Reactions
E2 Mechanism
6:23 minutesProblem 111e
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-
Verified step by step guidance1
Identify the substrate: The given compound is 3-chloro-3-ethyl-2,2-dimethylpentane. It is a tertiary alkyl halide, which is highly favorable for elimination reactions like E2 due to steric hindrance that disfavors substitution.
Determine the base: The base provided is ethoxide (CH3CH2O⁻), which is a strong base. Strong bases favor the E2 elimination mechanism, where the base abstracts a proton from a β-carbon, leading to the formation of a double bond.
Locate the β-hydrogens: In the structure of 3-chloro-3-ethyl-2,2-dimethylpentane, identify all β-carbons (carbons adjacent to the carbon bearing the leaving group, Cl). Check which β-carbons have hydrogens available for elimination.
Predict the major product: In an E2 reaction, the major product is determined by Zaitsev's rule, which states that the more substituted alkene is generally favored. Analyze the possible alkenes that can form and determine which is the most substituted (i.e., has the most alkyl groups attached to the double bond).
Consider stereoisomers: If the elimination can lead to stereoisomeric alkenes (E/Z isomers), determine the stereochemistry of the products. For E2 reactions, the β-hydrogen and the leaving group must be anti-periplanar (in opposite planes). Use this geometry to predict the stereoisomers formed and indicate whether the E (trans) or Z (cis) isomer is favored.
Verified video answer for a similar problem:This video solution was recommended by our tutors as helpful for the problem above
Video duration:
6mKey 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 involved in E2 reactions is crucial, as the orientation of the substituents can affect the stereoisomers produced.
Recommended video:
Guided course
09:36
Drawing the E2 Mechanism.
Stereoisomerism
Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity but differ in the spatial arrangement of atoms. In the context of elimination reactions, stereoisomers can arise from the different orientations of substituents around the double bond formed during the reaction. Identifying and drawing these stereoisomers is essential for accurately representing the products of E2 reactions.
Recommended video:
Guided course
01:58Determining when molecules are stereoisomers.
Regioselectivity
Regioselectivity in elimination reactions refers to the preference for the formation of one constitutional isomer over others when multiple products are possible. In E2 reactions, the stability of the resulting alkene can influence which product is favored. Understanding the factors that affect regioselectivity, such as sterics and electronic effects, is important for predicting the major elimination products.
Recommended video:
Guided course
05:09Heck Reaction
Related Videos
Related Practice