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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: nickbar on February 11, 2016, 06:18:11 AM

Title: Reaction mechanisms...
Post by: nickbar on February 11, 2016, 06:18:11 AM

Hi there!!! I want to learn three mechanisms for some organic reactions for a presentation during my postgraduate studies...

1) (https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fs15.postimg.org%2Fo2lyrcqln%2Ftriaz.jpg&hash=42c1d2f1ee881cefa21b759f58eb122f50f165e5)

The mechanism begins by the nitrogen in the hydrazide attacking the carbonyl carbon on the amide. Then The negatively charged oxygen then abstracts two hydrogens from neighboring nitrogens in order for a molecule of water to be released maybe...

But whats the next step???

2)(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fs10.postimg.org%2Fkw99wqp3t%2Fsocl.jpg&hash=e24628b4f238dbb73213ee318ada8138dbe7d202)

In this reaction there is a sulfonic acid to react with a chlorosulfuric acid .
The first step may begins with the hydroxyle of sulfonic acid attacking to the hydrogen of the chlorosulfuric... But ..then????

Title: Re: Reaction mechanisms...
Post by: Babcock_Hall on February 11, 2016, 08:59:01 AM

It might help to draw out the reaction.  I am not sure that you have the first step of the mechanism of reaction 2 correct.  Is there anything else that could happen?

Title: Re: Reaction mechanisms...
Post by: nickbar on February 11, 2016, 02:34:24 PM

Quote from: Babcock_Hall on February 11, 2016, 08:59:01 AM

It might help to draw out the reaction.  I am not sure that you have the first step of the mechanism of reaction 2 correct.  Is there anything else that could happen?

Then it must be the opposite... The hydroxyle of the chlorosulfuric attacking the sulfur of the sulfonic acid...

Any suggestion?

Title: Re: Reaction mechanisms...
Post by: Babcock_Hall on February 11, 2016, 03:31:32 PM

Do you see a good leaving group?

Title: Re: Reaction mechanisms...
Post by: nickbar on February 12, 2016, 10:15:24 AM

If the hydroxyle of sulfonic acid attacking to the hydrogen of the chlorosulfuric, there is a H2O that can be a leaving group maybe...

(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fs8.postimg.org%2Fheu05vw0l%2F0004.jpg&hash=bcafb3c433de9652d5109209546e8eb68d4fa2b7)

Then the S of the anion could attack the S... Also at some point it can be the formation of  H2SO4 on the molecule which could leave as a leaving group... But how could it be???

Title: Re: Reaction mechanisms...
Post by: Babcock_Hall on February 12, 2016, 10:43:53 AM

I am not sure of the mechanism, but I have an idea.  What if the hydroxyl group attacked the sulfur atom of chlorosulfuric acid?  If chloride ion left, what would the intermediate look like?

Title: Re: Reaction mechanisms...
Post by: nickbar on February 13, 2016, 08:56:44 AM

Ok. Then we are here...


(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fs9.postimg.org%2Fdzcbbs1b2%2F0002.jpg&hash=b5792ee6d0f1a22580e70f52b4ff36ae4c232e8a)

Then the H2SO4 can be a leaving group but how could the chloride ion attack to the sulfonic part? 

Title: Re: Reaction mechanisms...
Post by: Babcock_Hall on February 13, 2016, 09:40:49 AM

The attack of a chloride ion on an intermediate bearing a good leaving group is hardly without precedent.  Consider thionyl chloride:  http://www.masterorganicchemistry.com/2015/03/20/pbr3-and-socl2/