[lo2]

Hi there

I recently came across this reaction when solving some chemistry problems:


The teacher told us how the mechanism went, but I did not really get it. So I was hoping that someone in here would want to show me the mechanism.

I get that the first step is converting the cyanide into an amide, and from there into an ester, right?

[sjb]

Hi there

I recently came across this reaction when solving some chemistry problems:


The teacher told us how the mechanism went, but I did not really get it. So I was hoping that someone in here would want to show me the mechanism.

I get that the first step is converting the cyanide into an amide, and from there into an ester, right?

Unlikely, consider the leaving groups you'd need. Try using the acid first on the nitriles...

[lo2]

Yeah well I get that the CN group gets protonated, but I can not see what happens next. The nitrogen is now positive, so I guess it will react with the lone pair of oxygen. But I am not sure which oxygen it will react with, water or ethanol? Am I right about this?

[orgopete]

Yeah well I get that the CN group gets protonated, but I can not see what happens next. The nitrogen is now positive, so I guess it will react with the lone pair of oxygen. But I am not sure which oxygen it will react with, water or ethanol? Am I right about this?

Okay, now I understand the confusion.

Q: Which oxygen is more positive, H3O(+), H2O, or HO(-)?
A: Neither, they are all plus 8. What has changed is the number of protons added to the electrons surrounding the oxygen atoms.

The formal charge of a protonated nitrogen simply means the electrons are being pulled away form the nitrogen. It still has 10 electrons and so resists addition of more electrons, just as the oxygen above does. The solution is to use one of the electron pairs shared by the C≡N bond or draw a -C(+)=N-H resonance structure. That should give a new target for electron attack.

[lo2]

Ok thanks for the information! Well on the basis of that information I have now tried to make a mechanism, which I would like you to take a look at:



So what do you say about this?

(please note that I have not added lone pairs, as I did not know how to draw them, in the program I was using)

[lo2]

I would indeed be very glad, if somebody would take a look at my proposed reaction mechanism.

Is it correct? And if not where is the error(s)?

[discodermolide]

I would indeed be very glad, if somebody would take a look at my proposed reaction mechanism.

Is it correct? And if not where is the error(s)?

I think the imino ester is the intermediate, which then looses ammonia giving the ester.
The imino ester can be isolated. As far as I remember it can be used in an imidazole synthesis.

[orgopete]

There isn't any water.

Hint, ethyl chloride is a product.