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


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.


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

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