URGENT: Reaction Mechanism; Anyone know?

[LJP07]

I need to have this mechanism for my report but I can't figure out the mechanism for the reaction, I need it done in the next 10 hours if possible. Thanks, here's the reaction equation:

 

Salicyclic Acid + H2SO4 + Acetyl Anhydride ---> Acetylsalicyclic Acid + H2O.

 

The lecturer said it was "Acid-Catalysed Ester Formation". so anyone any ideas would be greatly appreciated!!:)

[LaurieAG]

I need to have this mechanism for my report but I can't figure out the mechanism for the reaction, I need it done in the next 10 hours if possible. Thanks, here's the reaction equation:

 

Salicyclic Acid + H2SO4 + Acetyl Anhydride ---> Acetylsalicyclic Acid + H2O.

 

The lecturer said it was "Acid-Catalysed Ester Formation". so anyone any ideas would be greatly appreciated!!

 

Hi LJP07,

 

For a start Acetylsalicyclic Acid must consist of Salicyclic Acid + SO3 + Acetyl Anhydride.

[LJP07]

Well, so you are questioning 2 Departmental staff with Ph.D's in the area of Organic Chemistry, over 4 Demonstrating staff, and they are all wrong and you are right? This is only a reaction mechanism.

 

Anyhow, I have another one which might be simpler, but it doesn't look like there's any efficient organic chemists around here, here's the reaction:

 

Maleic Acid + HCL ---> Fumaric Acid.

This is acid catalysed isomerisation.

 

Anyone know?

 

Thanks.

[somebody]

its been a year since i had Ochem but the molecules look familiar and i am pretty sure if you open up a good organic chem book, it will help you out with mechanism.

 

Sorry this is not really an answer/good answer, but just a suggestion.

[LaurieAG]

Well, so you are questioning...

 

Are you talking to me?

[modest]

Maleic Acid + HCL ---> Fumaric Acid.

This is acid catalysed isomerisation.

 

Anyone know?

 

Sorry I didn't see this in time for your report.

 

You can’t rotate the double carbon bond in the center of maleic acid, but with a radical addition of Cl• it becomes a partial single bond that can be rotated - and so named - catalyzed isomerization.

 

I don't know well enough how to use latex to diagram this for you or if that's even possible with latex, but if you'd like I could use my scanner and show you the diagram.

 

As far as Acetylsalicyclic Acid - it is asprin. There are many medical or bio-chemistry sites on the internet that have very detailed descriptions of how to synthesize this with the reaction mechanism and all the other goodies.

 

Here is one - it has diagrams

 

a small excerpt:

The synthesis of aspirin is classified as an esterification reaction, where the alcohol group from the salicylic acid reacts with an acid (acetyl anhydride) to form an ester. Aspirin is commercially synthesized using a two-step process. First, phenol (generally extracted from coal tar) is treated with a sodium base which generates sodium phenoxide, which is then reacted with carbon dioxide under high temperature and pressure to yield salicylate, which is acidified, yielding salicylic acid. This process is known as the Kolbe-Schmitt reaction....

 

....Salicylic acid is then acetylated using acetic anhydride, yielding aspirin and acetic acid as a byproduct. It is a common experiment performed in undergraduate organic chemistry practicals, and generally tends to produce low yields due to the relative difficulty of its extraction from an aqueous state. The trick to getting the reaction to work is to acidify with phosphoric acid and heat the reagents under reflux with a boiling water bath for between 40 to 60 minutes.

 

-modest

[LJP07]

I just seen your post on my acid catalysed isomerisation but could you please either scan the mechanism with HCL for Maleic acid into fumaric acid because I need it in the next 2 hours maximum. I would really appreciate this,

 

tHANKS

[modest]

 

... looks right to me

 

-modest

[LJP07]

Why is there a Dot at the opposite carbon to the Chlorine in diagram 2? Is this supposed to represent an electron or a Positive Charge?

[modest]

Why is there a Dot at the opposite carbon to the Chlorine in diagram 2? Is this supposed to represent an electron or a Positive Charge?

 

It is more accurate to say that it represents a "valence hole" than a "valence electron". Have you worked with lewis dot diagrams?

[LJP07]

Yes, but I've never used them really in mechanisms, I'd just list the charge.

[modest]

Ok - same idea,

when the double carbon bond became single, it opened up a hole which is represented by the dot. Or, when the bottom carbon let go of the top carbon (because the top carbon took hold of the Cl - it left a hole in the bottom carbon. It is good practice to put the dot there.