Which ether solvant must we ban when making grignard reagents?

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In summary, the conversation discusses the use of Grignard reagents as strong bases to deprotonate compounds that are not typically considered acidic. Aliphatic ethers are a preferred solvent due to their polarity and ability to dissolve a wide range of organic compounds. Hydrocarbon solvents can also be used, but may have limited solubility for the reagents. The information is based on chemical intuition and the outcome of the reaction will determine its validity.
  • #1
duchuy
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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!
 
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  • #2
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.
 

Related to Which ether solvant must we ban when making grignard reagents?

1. What is a Grignard reagent?

A Grignard reagent is a type of organometallic compound that is commonly used in organic chemistry reactions. It is made by reacting an alkyl or aryl halide with magnesium metal in an ether solvent.

2. Why is it important to ban certain ether solvents when making Grignard reagents?

Certain ether solvents can react with the Grignard reagent and cause unwanted side reactions. This can lead to low yields and impure products. Banning these solvents helps to ensure the success and purity of the reaction.

3. Which ether solvents should be avoided when making Grignard reagents?

Ether solvents that contain acidic protons, such as THF (tetrahydrofuran) and diethyl ether, should be avoided when making Grignard reagents. This is because they can react with the Grignard reagent and form undesired compounds.

4. Can other solvents be used instead of ether when making Grignard reagents?

Yes, other solvents such as diisopropyl ether, dioxane, and toluene can be used as alternatives to ether when making Grignard reagents. These solvents are less acidic and therefore do not react with the Grignard reagent.

5. Are there any safety concerns when working with Grignard reagents?

Yes, Grignard reagents are highly reactive and can react violently with water and other protic solvents. It is important to handle them with caution and follow proper safety protocols, such as wearing gloves and working in a well-ventilated area.

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