Acetonitrile (CH3C≡N) is deprotonated by very strong bases.

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Question

Acetonitrile (CH3C≡N) is deprotonated by very strong bases.

Write resonance forms to show the stabilization of the carbanion that results.

Accepted Answer

Hey everyone, let's do this. It says it's a beauty run night trial is a weakly acidic compound and can only be deep protein ated using a very strong base draw the resonance structures to show the stability of the resulting carb an ion. So the problem mentions acidity. So what do we know about a strong acid? A strong acid will deep protein eight really easily. Right acids want to donate that hydrogen. So in order for something to dip renate easily. That means the ion that is formed when it's deep predominated or say the conjugate base will be very stable. So what would make that ion stable? Having a lot of resonance forms? Okay, so when we draw our resonance structures, it's saying to show the stability of the carbon ion, we do that by showing how many resonance forms it can form. For lack of better word. Alright, so let's see what is happening here. So we have a methyl group over here, a methyl group over here, a night trial group and then a carbon next to that nitrile group with one hydrogen. So, which of these hydrogen is going to be depreciated by our base? Well, it'll be the alpha hydrogen at the carbon that's alpha to the nitrile group. Right, so the base is going to grab that hydrogen and don't forget about the electrons that are bonding the carbon and hydrogen together. Right, those electrons will go onto this carbon. Okay, so I'm gonna draw the arrow for the products and sort of continue it down here. Okay, so we'll have our h bonded to our base. Right? And then let's see what our carbon ion looks like. So we have CH three falling into that carbon bonded to another method group. And now remember the electrons came down from that hydrogen onto this carbon. So there's going to be a lone pair bonded to that night trial group. So this carbon has 2468 electrons, but it also has a formal charge, right? There's 12345 electrons touching it. And carbon likes to have four. Right? So four minus five is negative one. So that carbon is going to have that negative charge there. So let's see what we can do from here. In terms of resonance. My left arrow never looks as good as the right. So I see a charge next to some pi bonds. Right, So I'm gonna draw the electrons going down towards this carbon because this carbon is between two electron dense groups. So it's going to have a partial positive charge and these electrons can move out of the way onto that nitrogen. So let's draw that out. So now we have a double bond to that carbon and now that carbon is double bonded to the nitrogen. So the nitrogen will have two lone pairs. So that carbon that had the negative charge now is happy, right? It's touching four electrons. And now this nitrogen has 123456 electrons touching it. So that negative charge has moved over to the nitrogen. Right. Is there anything else we could do here? No. Right. If we went back the other way, that would be the same resonance structure. Okay, so this compound has two resonance structures, but sort of like the problem says it's weakly acidic, Right? Two resonance structures is not very many. So that's why it has a weak acidic strength. Okay. It doesn't have a lot of resonance which doesn't make it very stable, which will make it not deep resonate very easily, which is why it's weakly acidic. I hope this video is helpful and thanks for watching.

Acetonitrile (CH3C≡N) is deprotonated by very strong bases. Write resonance forms to show the stabilization of the carbanion that results.

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