Polar Protic, Polar Aprotic and Non-Polar Solvents
Key Questions
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Answer:
Non-polar solvents are non-polar molecules that can be used as solvent.
Explanation:
Non-polar solvents are any non-polar molecules that can be used as a solvent.
Example:
Hexane, pentane, heptane, etc.
Carbon tetrachlorideCCl4 .
Dr. Hayek
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4
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Oct 3 2015
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Here's an example.
Let's hypothetically react
Li(+)[(CH2)3CH3](−) (commonlyBuLi ) with acetone. Normally,BuLi is a fantastic nucleophile due to lithium's lewis acid characteristics.
) If you solvate
BuLi in the optimal amount of ethanol (commonlyEtOH ), you have now in solution, before anything happens,BuLi ,EtOH , and acetone.Acetone:
) What would most likely happen is that since
BuLi has such a high nucleophilicity, instead of reacting with acetone all the time, there is a good chance it would also steal a proton fromEtOH .At that point,
BuLi would become butane, which is clearly nonreactive as a poor nucleophile. Then,EtO− forms and it becomes a potential nucleophile to attack acetone (but less often, as it's a worse nucleophile).At this point, you may realize that you now have a situation where:
BuLi grabs a proton and loses its reactivity, allowingEtO− to be an additional nucleophile (there's still someBuLi leftover)BuLi attacks acetone and the reaction proceeds toEtOH protonating the tetrahedral intermediate to form a tertiary alcohol.
The result then is a mixture of the butane,
EtOH , acetone, the tertiary alcohol, and the product of the mechanism whereEtO− attacks acetone. Ideally you don't want a mixture that you'd have to separate and purify later. If you got a pure product, that's what you should want.So naturally, it's a good idea, for example, to not use a protic solvent when using an anionic nucleophile, because it may actually deactivate the nucleophile.
Truong-Son N.
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1
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Jul 11 2015