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Topic: Theoretical question - solvents  (Read 1699 times)

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Offline Cantacoxinha

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Theoretical question - solvents
« on: February 14, 2017, 04:56:25 PM »
I have three brief questions:

-why is nitromethane listed as a polar protic solvent on the Wikipedia article "Protic solvent"? I.e. why is it protic?

-with regard to organic synthesis, in particular the reactions proceeding via electrophilic substitution, what is the benefit of using solvents with high dielectric constant? I've been reading a couple of papers where it was stated that "acetonitrile was a solvent of choice... ...due to high dielectric constant". In general, when do we use high dielectric constant solvents in organic synthesis (apart from microwave synthesis)?

-why exactly is sulfuric acid a strong acid? I very well understand the common answer "because it is highly dissociated in water etc...", but I'm curious what intrinsically makes it (or any other strong oxoacid as nitric, perchloric etc.) a strong proton donor?

Offline wildfyr

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Re: Theoretical question - solvents
« Reply #1 on: February 14, 2017, 07:07:04 PM »
1. In the wikipedia article "solvent" nitromethane is listed under polar aprotic. While the proton on nitromethane is pretty acidic, I wouldnt consider it a protic solvent. its a typo.

2. High dialectric constant essentially means its highly polar. Or more specifically, highly polarizable.

3. The way I like to think about bronstead-lowry acids is "how happy would this molecule be if it lost a proton and became an anion?" sulfuric acid has the 3 oxygen atoms with which to form resonance structures with if it loses a proton and becomes an anion, so it is quite happy to give away a proton.

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