Which ether solvant must we ban when making grignard reagents?

  • Thread starter Thread starter duchuy
  • Start date Start date
  • Tags Tags
    Ether
AI Thread Summary
In the discussion, the focus is on the appropriate choice of solvent for reactions involving Grignard reagents. It is emphasized that Grignard reagents are extremely strong bases, capable of deprotonating compounds that are not typically acidic. Carbonyl solvents are discouraged due to their acidic alpha-protons and electrophilic nature. Instead, aliphatic ethers are recommended as they are polar enough to dissolve various organic compounds while remaining aprotic. Other potential solvents mentioned include acetonitrile and chlorinated hydrocarbons, which may also be acidic enough to be deprotonated by Grignard reagents. The importance of practical experimentation is highlighted, as the actual outcomes in the reaction flask ultimately determine the validity of theoretical considerations.
duchuy
Messages
79
Reaction score
3
TL;DR Summary
Ethers such as Et2O or THF are usually used as a solvant to do perform reactions with RMgX. But now i have to find which ether solvant to avoid.
Hi, I'm I supposed to find an ether with acidic hydrogens or a very strong electrophilic centre? I'm trying with acidic H but it doesn't seem to be working...
Please help me thank you!
 
Chemistry news on Phys.org
Grignard reagents can be viewed as extremely strong bases (sometimes analogous to a deprotonated alkane (Bruice), meaning a pKa of ~50) and can therefore deprotonate compounds that aren't normally considered "acidic".

For example, any carbonyl solvent is already a no-go as these usually contain acidic alpha-protons and are also electrophilic. Acetonitrile, di- and tri- chloromethane and similar compounds are probably acidic enough to be deprotonated by a Grignard reagent, as well as primary and secondary amines.

Aliphatic ethers are great because they are somewhat polar, which allows for them to dissolve a wide array of organic compounds (namely esters, aldehydes and ketones in the contenxt of Grignard reactions) while being entirely aprotic. In theory you could also use hydrocarbon solvents (pentane, hexane, heptane, etc.), but the solubility of your reagents may be very limited.

Can't vouch 100% for everything said here, I'm just using my chemical intuition. After all, whatever happens in the reaction flask decides what's true in this field.
 
It seems like a simple enough question: what is the solubility of epsom salt in water at 20°C? A graph or table showing how it varies with temperature would be a bonus. But upon searching the internet I have been unable to determine this with confidence. Wikipedia gives the value of 113g/100ml. But other sources disagree and I can't find a definitive source for the information. I even asked chatgpt but it couldn't be sure either. I thought, naively, that this would be easy to look up without...
I was introduced to the Octet Rule recently and make me wonder, why does 8 valence electrons or a full p orbital always make an element inert? What is so special with a full p orbital? Like take Calcium for an example, its outer orbital is filled but its only the s orbital thats filled so its still reactive not so much as the Alkaline metals but still pretty reactive. Can someone explain it to me? Thanks!!
Back
Top