Elimination question on alkyl halide

In summary, the elimination question on alkyl halides typically focuses on the mechanisms by which alkyl halides can undergo elimination reactions to form alkenes. This involves the removal of a halogen and a hydrogen atom, often facilitated by strong bases. The two primary mechanisms are E2, which occurs in a single concerted step, and E1, which involves a two-step process where the halide is first eliminated to form a carbocation. Factors influencing the choice of mechanism include the structure of the alkyl halide, the strength of the base, and reaction conditions. Understanding these concepts is crucial for predicting the products of elimination reactions.
  • #1
Zayan
24
3
Homework Statement
Find the major product
Relevant Equations
E1/E2/Sn1/Sn2
I firstly made the newman projection, aci/base on OH resulting in OH2+. Then NGP by neighbouring bromine and then the other bromine back attack. Then I simply did Finkelstein reaction and hence anti eliminating erythro iodine from vicinal positions making Trans 2 butene. The solution manual however has done something different. Normal external SN2 followed by Iodine removal(see the image). But the have done the anti elimination on threo iodine. It should give cis alkene, but they have given answer as trans alkene. So either I am somehow wrong, or the solution manual has done wrong mechanism. Please help.
Screenshot_2024-09-30-14-31-44-14_f9ee0578fe1cc94de7482bd41accb329.jpg
The above is the question.
Screenshot_2024-09-30-14-46-12-11_92460851df6f172a4592fca41cc2d2e6.jpg

This is the solution provided.
 

FAQ: Elimination question on alkyl halide

What is an elimination reaction involving alkyl halides?

An elimination reaction involving alkyl halides is a chemical process where a halogen atom and a hydrogen atom are removed from adjacent carbon atoms in a molecule, resulting in the formation of a double bond. This type of reaction typically leads to the formation of alkenes and can occur through either an E1 or E2 mechanism.

What factors influence the mechanism of elimination reactions in alkyl halides?

The mechanism of elimination reactions in alkyl halides is influenced by several factors, including the structure of the alkyl halide (primary, secondary, or tertiary), the strength and concentration of the base used, the solvent (polar protic or polar aprotic), and the temperature. Tertiary alkyl halides tend to favor E2 mechanisms, while secondary and primary halides may undergo E1 or E2 depending on the conditions.

What are the differences between E1 and E2 elimination mechanisms?

The E1 mechanism is a two-step process that involves the formation of a carbocation intermediate after the leaving group departs, followed by deprotonation to form the alkene. In contrast, the E2 mechanism is a one-step process where the base abstracts a proton while the leaving group departs simultaneously, leading to the formation of the alkene. E1 reactions are typically favored by weak bases and polar protic solvents, while E2 reactions require strong bases and can occur in a variety of solvents.

How do stereochemistry and regioselectivity play a role in elimination reactions?

Stereochemistry is important in elimination reactions because the formation of alkenes can result in different stereoisomers. For E2 reactions, the anti-periplanar arrangement of the leaving group and the hydrogen being removed is often required for optimal overlap of orbitals, leading to the formation of the more stable trans alkene. Regioselectivity refers to the preference for the formation of one alkene over another, which can be influenced by factors such as the stability of the resulting alkene (Zaitsev's rule) and steric hindrance.

What are some common applications of elimination reactions involving alkyl halides?

Elimination reactions involving alkyl halides are widely used in organic synthesis to produce alkenes, which are important intermediates in the synthesis of various compounds, including pharmaceuticals, agrochemicals, and polymers. They also play a crucial role in the preparation of more complex molecules through subsequent reactions such as hydrogenation, hydroboration, or polymerization.

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