An alkyl bromide produces a single alkene when it reacts...

Name: Problem 59, Chapter 4: The Pearson Guide to Organic Chemistry for the JEE Advanced
Uploaded: 2021-07-15T14:29:08-08:00
Duration: 2 min 47 s
Channel: Alkendra Singh
Description: An alkyl bromide produces a single alkene when it reacts with sodium ethoxide and ethanol. This alkene undergoes hydrogenation and produces 2- methylbutane. What is the identify of the alkyl bromide? (a) 1-bromobutane (b) 1-bromo- 2-methylbutane (c) 2 -bromo-2-methylbutane (d) 1-bromo-2, 2-dimethylpropane

An alkyl bromide produces a single alkene when it reacts with sodium ethoxide and ethanol. This alkene undergoes hydrogenation and produces 2- methylbutane. What is the identify of the alkyl bromide? (a) 1-bromobutane (b) 1-bromo- 2-methylbutane (c) 2 -bromo-2-methylbutane (d) 1-bromo-2, 2-dimethylpropane

An alkyl bromide produces a single alkene when it reacts with sodium ethoxide and ethanol. This alkene undergoes hydrogenation and produces 2- methylbutane. What is the identify of the alkyl bromide?
(a) 1-bromobutane
(b) 1-bromo- 2-methylbutane
(c) 2 -bromo-2-methylbutane
(d) 1-bromo-2, 2-dimethylpropane

Key Concepts

Alkene Hydrogenation

Hydrogenation is a catalytic addition reaction in which hydrogen (H2) is added across the double bond of an alkene, converting it into an alkane. This reaction is typically catalyzed by metals such as palladium, platinum, or nickel and is used to confirm the structure of the alkene by reducing it to a known alkane.

Structure-Dependent Reaction Outcome

The nature and position of substituents in an alkyl halide greatly influence which elimination products can be formed. When the structure restricts the availability of beta hydrogens to only one possibility, the elimination reaction yields a single alkene. This concept is crucial to understanding how molecular architecture directs the course and selectivity of elimination reactions.

E2 Elimination Reaction

This is a bimolecular elimination process in which a base removes a beta hydrogen while the leaving group departs simultaneously. The reaction occurs in a single concerted step and requires that the hydrogen and leaving group be arranged anti?periplanar to one another. It is a key method for converting alkyl halides into alkenes and is influenced by the substrate’s structure and the strength of the base.

Regioselectivity and Zaitsev’s Rule

In elimination reactions, regioselectivity determines which alkene is preferentially formed. Zaitsev’s rule predicts that the more substituted (and generally more stable) alkene will be the major product when multiple elimination pathways are possible. The structure of the alkyl halide and the distribution of available beta hydrogens largely control this selectivity, sometimes limiting the reaction to only one eliminable pathway.

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