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Wittig reactions with alpha-chloroethers can be used for the synthesis of aldehydes and ketones....

Question:

Wittig reactions with α-chloroethers can be used for the synthesis of aldehydes and ketones.

Draw the structure of the product formed by treating the Wittig reagent derived from this chloroether with cyclohexanone.

CICH₂OCH₂C₆H₅

i. Ignore alkene stereochemistry.

ii. When drawing products of the wittin reaction, draw only the alkene formed, do not include triphenylphosphine oxide.

iii. Draw witting reagents in a yield form.

iv. Draw one structure per sketcher. Add additional sketchers using the dropdown menu in the bottom right comer.

v. Separate structures with +signs from the dropdown menu.

Wittig Reaction

The Wittig reaction involves the conversion of a carbonyl group into an alkene. The phosphorous ylide which acts as the reagent in this reaction in generated by the treatment of an alkyl halide with triphenylphosphine followed by a strong base like n-BuLi. The reaction between the carbonyl compound and the ylide proceeds via 4-membered oxaphosphetane ring intermediate. This intermediate breaks down to give the alkene and triphenylphosphine oxide is eliminated as a side product.

An interesting point about the Wittig reaction is that it can be modified to generate aldehydes and ketones. Let us see how this works.

Answer and Explanation:

If the phosphorous ylide is generated from an {eq}\alpha {/eq}-Halo ether then the final Wittig product will be an enol ether. The ether can be cleaved to generate a ketone or aldehyde via tautomerization. This is illustrated below:-


Learn more about this topic:

The Wittig Reaction & Alkene Synthesis: Definition & Examples
The Wittig Reaction & Alkene Synthesis: Definition & Examples

from Chemistry 304: Organic Chemistry II

Chapter 2 / Lesson 14
548

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