Author Topic: Grignard Reagent  (Read 3652 times)

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  • Guest
Grignard Reagent
« on: December 10, 2003, 11:43:00 PM »
How difficult is Grignard Reagent in using and preparing?


  • Guest
« Reply #1 on: December 10, 2003, 11:48:00 PM »
What have you smoked? You asked that last week in

Post 475089

(ADDkid: "Benzyl cyanide Propose Mech", Methods Discourse)

Edit: Ok, editing your post huh... In what unit do you want the difficulty expressed? Please specify your question some more...


  • Guest
Really sorry about that, that was truly and...
« Reply #2 on: December 11, 2003, 12:10:00 AM »
Really sorry about that, that was truly and accident. How diffcult is ether to dry.  Should one just distill ether from engine starter, or make.  If one wanted to react this R-MgBr compound with CO2, would dry ice be a must, or could one use CO2 from the little metal canisters.
                 Thanks       ADDkid


  • Guest
« Reply #3 on: December 11, 2003, 12:33:00 AM »
Well, I'm not sure if the ether isolated from a home synthesis or from starting gas is pure enough for use in a grignard reaction. To dry the ether, you need something along the lines of sodium or at least molecular sieves, drying with MgSO4 etc is not enough.

If you use CO2 gas instead of dry ice, I think you will have a lot of problems adding the correct amount, as well as blowing oxygen into the solution by mistake - not to mention the spattering of leading a high-pressured gas into a solution.


  • Guest
« Reply #4 on: December 11, 2003, 05:26:00 AM »
Another method of drying ethyl ether is in

Post 247216

(lugh: "Re: Drying Ether With NaOH", Chemistry Discourse)
; for preparing ether, the catalytic method of Senderens is rather facile:

Catalytic dehydration of aliphatic alcohols, in the vapor phase, in the presence af pumice soaked with sulfuric and phosphoric acids. JEAN-BAPTISTE SENDERENS. Compt. rend. 192, 1335-7(1931); cf. C. A. 24, 4256.-The vapors of MeOH, EtOH, PrOH, iso-PrOH and iso-BuOH were passed through an electrically heated tube contg. a porcelain boat with pumice soaked with 50-2° Be. H2SO4. The last 3 alcohols. gave re­sults similar to those obtained with NaHSO4. EtOH and MeOH were dehydrated, yielding Et20 and Me20, resp., the former at 135° in theoretical yield and the latter in greater quantity than that produced with Al2O2 at 300°. S. considers this method preferable to that generally used for the synthesis of Et2O. At 140° some C2H4 was also produced. After 8 days of operation at 8 hrs. per day, the contents of the boat appeared to be unaltered and the tube was dry. The pumice has an influence on the course of the reaction, for without it a black liquid was formed. Substitution of H2P04 for H2SO4 gave C2H4 at 180-5°, but the activity is very much less than that of H2SO4 and less than that of H2PO4 in Iiquid-phase operations.

Comptes Rendus 192(22), 93-95 (1931)

50 to 52° Baume is equal to 63-65% H2SO4.

A high yield Grignard carboxylation was published by Ivanoff:

Bull. Soc. Chim. France 287-296 (1925)



  • Guest
The chemistry of... pumice?
« Reply #5 on: December 11, 2003, 01:48:00 PM »
Is this the igneous rock sold for removing calloused skin?  How often is this used in chemistry and how does it work?


  • Guest
Volcanic Glass
« Reply #6 on: December 11, 2003, 05:30:00 PM »
Pumice is volcanic glass, so if you don't live near a volcano, you might want to visit your local pharmacy  ;)  As the abstract clearly states, the pumice is soaked in the acid, and the alcohol vapor is passed through it, the pumice promotes the reaction. If you want to know more about pumice, you'll have to research it yourself, SWIL thought this was an elegant way to make ether for bees, since it's yield is quantitative, the ether produced is rather pure, and the materials are rather easy to find  ;)  Eliminating the boat seems feasible, just put some glass wool in the bottom of the reaction tube, fill it with the treated pumice, heat it with nichrome wire, and boil ethanol through it into a still head, condenser and receiving flask  ;D  Senderens did it for eight consecutive days, which should provide enough ether for most bees' needs  :P