July 21, 2019, 02:52:09 AM
Forum Rules: Read This Before Posting


Topic: synthesis of a phenyl cyclopentyl ketone  (Read 4328 times)

0 Members and 1 Guest are viewing this topic.

Offline portugal

  • Regular Member
  • ***
  • Posts: 68
  • Mole Snacks: +2/-5
synthesis of a phenyl cyclopentyl ketone
« on: March 11, 2008, 01:50:53 AM »
Who agrees that the starting products for these would be a 1 molar equivalent of cyclopentylmagnesium bromide and 1 molar equivalent methyl benzoate (in tetrahydrofuran) with an aqueous HCl workup

Offline Rico

  • Regular Member
  • ***
  • Posts: 73
  • Mole Snacks: +30/-0
Re: synthesis of a phenyl cyclopentyl ketone
« Reply #1 on: March 11, 2008, 03:56:01 AM »
hey portugal

I must say that I do not agree and the problem is that you choose to use an ester as starting material. The ketone-product, that is formed from addition of the grignard-reagent, is much more reactive (since it is more electrophilic) than the ester and once it is formed it will preferentiably react with the grignard. This will give a tertiary alcohol as product instead of the ketone (you will get a mixture of ketone and alcohol if you use 1 molar equivalent of grignard).
The solution to the problem is to use something which is more reactive than the ester, e.g. an acid chloride or to use an aldehyde and then afterwards oxidize the formed alcohol to the ketone.

Rico

Offline macman104

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1645
  • Mole Snacks: +168/-26
  • Gender: Male
Re: synthesis of a phenyl cyclopentyl ketone
« Reply #2 on: March 11, 2008, 05:35:35 AM »
Rico, true.  However, I get the feeling this is early organic course where such things may not be taken into consideration.  Furthermore, this is probably a book question and I'm pretty certain that with the specification of 1 molar equivalent the answer they are trying to drive at is the ketone product (even though in a lab setting you would observe the tertiary alcohol product).

Offline AWK

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 6509
  • Mole Snacks: +468/-79
  • Gender: Male
Re: synthesis of a phenyl cyclopentyl ketone
« Reply #3 on: March 11, 2008, 05:36:36 AM »
Benzaldehyde is also a cheap reagent
AWK

Offline kriggy

  • Chemist
  • Sr. Member
  • *
  • Posts: 1313
  • Mole Snacks: +111/-15
Re: synthesis of a phenyl cyclopentyl ketone
« Reply #4 on: April 10, 2019, 02:27:15 AM »
Rico, true.  However, I get the feeling this is early organic course where such things may not be taken into consideration.  Furthermore, this is probably a book question and I'm pretty certain that with the specification of 1 molar equivalent the answer they are trying to drive at is the ketone product (even though in a lab setting you would observe the tertiary alcohol product).

It is indeed taken into consideration in our early organic course :) It is IMO wrong to skip this kind of stuff and dont consider it.

@Portugal: RICO explained it quite well, you have more options than just acid chloride, you can use weinreb amide for example or do it differently with use of Friedel-Crafts acylation

Sponsored Links