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Substitution vs elimination competition

36 questions on Substitution vs elimination competition from the Organic Reaction Mechanisms IV: Elimination chapter: 6 NEET level, 13 JEE Main, 17 JEE Advanced. Each one opens with its answer and solution.

Practice this topic All Organic Reaction Mechanisms IV: Elimination topics

2-Bromo-2-methylpropane is heated with NaOEt in ethanol. The principal product is NEET level
Bromoethane is treated separately with aqueous KOH and with alcoholic KOH. The main products are, respectively, NEET level
In which of the following is the substitution product expected to be the major product? NEET level
1-Bromobutane gives mainly butyl ethyl ether with NaOEt/ethanol but mainly but-1-ene with (CH3)3COK/(CH3)3COH. The best explanation is that JEE Main level
In ethanol with no added base, 2-bromo-2-methylpropane gives an ether (SN1) and an alkene (E1) through the same carbocation. On raising the temperature the frac... JEE Main level
2-Bromopropane is treated with NaI in acetone. The major product is JEE Main level
Which of the following bromides has no beta-hydrogen and therefore cannot undergo a direct one-step E2 dehydrohalogenation (without rearrangement)? JEE Main level
For 2-bromobutane, the reagent that gives mainly the substitution product is JEE Main level
With NaOEt in ethanol, the order of increasing proportion of elimination (alkene) for CH3CH2Br, (CH3)2CHBr and (CH3)3CBr is JEE Main level
Which of the following changes favour E2 elimination over SN2 for a secondary alkyl halide? (select all that apply) JEE Main level
2-Bromo-3,3-dimethylbutane is (i) treated with NaOEt/ethanol (E2 conditions), and (ii) warmed in aqueous ethanol without base (E1/SN1 conditions). The principal... JEE Advanced level
2-Bromo-2-methylbutane is subjected to three conditions. Select all correct statements. JEE Advanced level
For the solvolysis of a tertiary alkyl halide in ethanol, the ratio of rate constants for elimination and substitution, k_E/k_S, is 0.25 at 300 K and 0.40 at 33... JEE Advanced level
Which of the following reactions proceed through a carbanion intermediate formed by deprotonation (E1cB mechanism)? JEE Advanced level
The second-order rate constant for alkene formation from (CH3)2CHBr with NaOEt in ethanol at 25 degC is 4.02x10^-4 L mol^-1 s^-1. For (CD3)2CHBr under the same ... JEE Advanced level
When 2-bromobutane reacts with KOH in dry ethanol, the major product is but-2-ene. If the ethanol is progressively replaced by water, the proportion of butan-2-... JEE Advanced level
An optically active alkyl bromide C5H11Br is heated with alcoholic KOH (E2, no rearrangement) and gives exactly three alkenes, when E and Z isomers are counted ... JEE Advanced level
Assertion (A): Sodium ethoxide converts 2-bromo-2-methylpropane mainly into 2-methylpropene, while 1-bromopropane gives mainly propyl ethyl ether. Reason (R): a... JEE Advanced level
Potassium tert-butoxide, (CH3)3COK, favours elimination over substitution with alkyl halides mainly because it is NEET level
1-Bromopropane is treated with NaI in acetone. The major product is NEET level
To convert bromoethane mainly into ethene, the best conditions are NEET level
2-Bromo-2-methylpropane is heated with NaOEt in ethanol. The major product is JEE Main level
2-Bromo-2-methylbutane is heated with (CH3)3COK in (CH3)3COH. The major alkene is JEE Main level
1-Bromopropane is treated with NaCN in DMSO at room temperature. The major product is JEE Main level
Raising the temperature of a reaction of a secondary alkyl halide with a base increases the proportion of elimination relative to substitution mainly because JEE Main level
2-Bromo-2-methylpropane is dissolved in 80% aqueous ethanol at 25 degC with no added base. The main products are JEE Main level
Neopentyl bromide, (CH3)3C-CH2Br, is treated with NaOEt in ethanol. Which statement is correct? JEE Main level
Which reactions give mainly an elimination product (alkene)? JEE Advanced level
1.510 g of 2-bromo-2-methylbutane (M = 151 g mol^-1) was heated in ethanol. Isolation gave 0.140 g of alkenes (C5H10, M = 70) and 0.812 g of 2-ethoxy-2-methylbu... JEE Advanced level
2-Bromo-2-methylpropane is heated with NaOEt in ethanol to give a gas X. X is then treated with HBr in the presence of an organic peroxide. The final product is JEE Advanced level
Which statements about substitution versus elimination are correct? JEE Advanced level
1-Bromopropane is heated with alcoholic KOH to give Y. Y is treated with HBr (no peroxide) to give Z, and Z is then treated with NaN3 in DMF. The final product ... JEE Advanced level
2-Methylbutan-2-ol is treated separately with (i) conc. HBr at room temperature and (ii) conc. H2SO4 at 440 K. The main products are, respectively, JEE Advanced level
Ethanol (4.6 g, M = 46) is converted completely (a) into diethyl ether (M = 74) by conc. H2SO4 at 413 K with excess alcohol (an SN2 path), and (b) into ethene (... JEE Advanced level
Which pairs of reagents are suitable for preparing the ether in good yield by the Williamson method (SN2 on the alkyl halide)? JEE Advanced level
(R)-2-Bromobutane reacts with NaN3 in DMF by a single SN2 step. The major product and its configuration are JEE Advanced level