E2 Mechanism Practice Problems
Why is the E2 elimination for the cis form of the compound below faster than its trans form?
Explain the reason why stronger bases such as sodium hydride (NaH) lead to a faster E2 elimination compared to sodium methoxide (CH3ONa) by using the reaction's coordinate diagram.
Using electron-pushing arrows, propose the mechanism for the E2 reaction shown below.
What is/are the main product(s) of the elimination reaction? (Note: Consider stereochemistry.)
Determine the major product of the E2 reaction between the alkyl halide given below and the hydroxide ion.
Identify the major product of the E2 reaction between the alkyl halide provided below and the hydroxide ion.
Identify the major product of the E2 reaction between sodium hydroxide and the alkyl halide given below.
Identify the more reactive alkyl halide among each pair in an E2 reaction with hydroxide ion.
Which of the following isomers undergoes an E2 reaction more rapidly? Provide a short explanation of your answer.
- trans-1-(tert-butyl)-4-chlorocyclohexane or cis-1-(tert-butyl)-4-chlorocyclohexane
Which alkyl halide from each of the given pairs reacts more rapidly in an elimination reaction? Provide a short explanation of your answer.
Determine the product that would be obtained in greatest yield in an E2 reaction of the alkyl halide 1-bromo-2-ethyl-1,2-dimethylcyclohexane and sodium ethoxide.
Identify the stereoisomer that would be obtained in the highest yield in an E2 reaction of the alkyl halide 3-bromo-2,2,5,5-tetramethylheptane.
I) Draw the major stereoisomer formed in the E2 reaction of the following alkyl halide with the methoxide ion.
II) Would the product differ depending on whether the reactant was an (R) or (S) enantiomer?
Explain why the following reaction produces only a substitution product and no elimination product.
a. Explain why both SN2 and SN1 reactions are not feasible for 1-(chloromethyl)-1-methylcyclohexane.
b. Are E2 and E1 reactions feasible for it?
Explain why an alkyne is formed rather than a cumulated diene in the reaction shown below.
Draw the major elimination product of the E2 reaction between (3 R, 4R)-3-chloro-4-methylhexane and sodium methoxide. If any stereoisomers are possible, specify which stereoisomers are produced.
Show the major elimination product of the E2 reaction between (3R,4S)-3-chloro-4-methylhexane and sodium methoxide. Label the product as E/Z if possible.
Two alkenes (1,3-dimethyl-2-methylenecyclopentane and 1,2,3-trimethylcyclopent-1-ene) are formed by the elimination reaction of 1-bromo-1,2,5-trimethylcyclopentane with a strong base. Which of the following base would yield:
a. The highest percentage of 1,3-dimethyl-2-methylenecyclopentane?
b. The highest percentage of 1,2,3-trimethylcyclopent-1-ene?
When cis-4-iodocyclohexanethiol and trans-4-iodocyclohexanethiol react with HO−, they produce the same elimination product. Draw the mechanisms that explain the formation of the elimination product.
The reactions given below were conducted under the same conditions. The second reaction was found to be much slower than the first reaction. What can we conclude about the mechanism of the reaction? (Note that a carbon-deuterium bond is stronger than a carbon-hydrogen bond.)
Determine the elimination product(s) of the E2 reaction between (1R,2S)-1-chloro-1,2-diphenylbutane and sodium ethoxide. Assign an appropriate configuration to the product(s) formed.
When cis-1-chloro-2-methylcyclohexane and trans-1-chloro-2-methylcyclohexane undergo an E2 elimination, why do they produce different major products?
A) For cis-1-chloro-2-methylcyclohexane, the methyl group occupies the equatorial position, while trans-1-chloro-2-methylcyclohexane contains the methyl group at the axial position.
B) cis-1-chloro-2-methylcyclohexane corresponds to fewer diaxial interactions than trans-1-chloro-2-methylcyclohexane.
C) In the reaction of cis-1-chloro-2-methylcyclohexane, the axial hydrogen at the β-carbon bonded to the methyl group reacts, whereas in the reaction of trans-1-chloro-2-methylcyclohexane, it is the axial hydrogen at the β-carbon that is not bonded to the methyl substituent.
D) In the reaction of cis-1-chloro-2-methylcyclohexane, the β-hydrogen bonded to the methyl group is axial, while it is equatorial in trans-1-chloro-2-methylcyclohexane.
Determine the major product of the elimination reaction of the alkyl halide given below and the hydroxide ion.
Which of the two parts of the acid-catalyzed hydrolysis mechanism of an ester and an amide are similar?
Draw the two elimination products formed in the following reaction. Indicate the major and minor products. (Hint: A C—D bond is stronger than a C—H bond.)
Draw the product(s) expected to form in the E2 reaction of the alkyl halide shown below.
Predict the major product expected to form in the E2 reaction of the alkyl halide given below.
Two different alkenes are obtained in the E2 elimination reaction between 2-chloro-3-phenylbutane and sodium methoxide. The major product is the Zaitsev product.
(i) When one pure stereoisomer of 2-chloro-3-phenylbutane reacts, only one pure stereoisomer of the major product is obtained. For example, the product obtained when (2R,3R)-2-chloro-3-phenylbutane reacts is the stereoisomer with the methyl groups cis. Explain the reason behind this stereospecificity using a Newman projection of the transition state.
(ii) Predict the major product of elimination of (2S,3R)-2-chloro-3-phenylbutane using a Newman projection of the transition state.
(iii) By taking into account the results in part (i), predict the major product from elimination of (2S,3S)-2-chloro-3-phenylbutane.