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Figured out the products and mechanism under basic conditions but still haven't figured out what happens with base! I have a mass spec of that product and its showing it formula mass to be around 255. Anyone know what happens or what it is?
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Re: Vanillin and Acetic Anhydride
Wed, May 7, 2008 - 7:06 PMSorry this might seem redundant because it is. I meant... what happens with ACID, not base... figured that out already. -
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Re: Vanillin and Acetic Anhydride
Wed, May 7, 2008 - 9:47 PMVanillin and acetic anhydride will form an ester with the hydroxy group (that gets you to M = 194) from there you are likely flying as a hemiacetal (sp, the carbonyl being converted into a hydroxy group and an acetic ester; in this case a high energy species that you might see on a mass spec) plus a proton; all of which gets you to M=255.
I suggest taking you product and doing a mild base extraction (pH 7-9), the product will be in the organic solvent without the hemiacetal (the parent mass = 194). Also take a NMR of the product before doing the base wash.
If you had oxidzed the carbonyl and formed an anhydride, the product mass would be 252 plus a proton for 253. -
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Re: Vanillin and Acetic Anhydride
Fri, May 9, 2008 - 3:36 PMCheck to see if you get a fragment at 123 ish or 165, If its 165 i think you'll know that one C2H3O group has been added to the ring rather than the aldehyde. most likely it would add to the phenol, but its possible for the acetyl group to add to the carbon at the 5 position( vanilin is 3-methoxy,4-hydroxy benzaldehyde right?). I believe in aqueous solution this is known to occur. Why? 'cause water will "surround" the anion of vanillin and render it a a bulky and poor nucleophile. You can draw a resonance structure (or intermediate whatever you want to call it) with a pair of electrons on the 5 position of the ring that can act as a nucleophile. What do you think troy, sound Plausible? Hope this helps :)
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