2
$\begingroup$

I have a reaction to which I must find the majority organic product.

The reaction in question

I think I found the correct product but the fact that the reaction takes two moles of propylmagnesiumbromide confuses me a bit. I added an image of the product I think would be the result.

The product I think it should make

I would like to know if I found the right product, and if the two moles of propylmagnesiumbromide means that there is a second part to this reaction.

$\endgroup$
4
  • 1
    $\begingroup$ chemistrysteps.com/… This will help you. You can Google 'acyl chloride grignard' for more explanations. $\endgroup$
    – orthocresol
    May 23 at 21:12
  • $\begingroup$ Your product would exist in the reaction medium as the MgBr alkoxide; it is unstable. You have a second equivalent of Grignard remaining. $\endgroup$
    – user55119
    May 23 at 22:44
  • $\begingroup$ Correct me if I'm wrong but shouldn't the grignard reagent here attack the carbonyl twice and give 4-cyclopropylHeptan-4-ol? $\endgroup$ May 24 at 2:22
  • 1
    $\begingroup$ Cl will leave after the first grignard attack and you get a ketone again. the next eqv. reacts to give a 3 degree alcohol. $\endgroup$ May 24 at 2:56
2
$\begingroup$

The following paragraph from Acid Halide Chemistry[1] sums up the answer to your question:

Acid chlorides react with Grignard reagents to produce tertiary alcohols. Two equivalents of the Grignard reagent are needed because the first equivalent reacts to form a ketone which then reacts with the second equivalent. Because of the high reactivity of the Grigard reagent, the reaction can NOT be stopped at the ketone. Acyl chloride reaction with Grignard reagent

Coming to your specific case the reaction would proceed with the following mechanism:

Acyl halide + Grignard reagent


Reference:

(1) Acid Halide Chemistry https://chem.libretexts.org/@go/page/183124 (accessed May 24, 2021).

$\endgroup$
3
  • 1
    $\begingroup$ To prevent dehydration of this product (because it is a tertiary alcohol) keep in mind that a neutralization (during workup) with an aqueous solution of $\ce{NH4Cl}$ may be safer than the addition of $\ce{HCl}$. $\endgroup$
    – Buttonwood
    May 24 at 10:25
  • $\begingroup$ @Buttonwood I absolutely agree with you on that. $\endgroup$ May 24 at 11:06
  • 1
    $\begingroup$ Grignard reagents aren't ionic salts, they don't have a negative charge, so technically the arrow should be drawn from the C–Mg bond. $\endgroup$
    – orthocresol
    May 24 at 11:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.