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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: pallidol on August 23, 2015, 12:49:06 AM

Title: Methylation product
Post by: pallidol on August 23, 2015, 12:49:06 AM
Dear guys.

i would like to ask regarding my work. I did my reaction and and the column chromatography gave me three fractions . For fraction 1 and 2 the NMR are just fit enough. But i have problem
for the fraction 3.

From NMR, all the signal compatible to the structure A. Somehow during writing the mechanism it does seems not make sense otherwise i suggest the structure B as the product.

Could anyone give a suggestion regarding this matter.tq
Title: Re: Methylation product
Post by: phth on August 23, 2015, 04:34:54 AM
May sound simple, but I would take an IR or #3.  Secondly, I would try this procedure K3PO4+18-crown-6 instead of NaOH. DOI: 10.1021/ie060899e    Ind. Eng. Chem. Res. 2007, 46, 3016-3023
Title: Re: Methylation product
Post by: Dan on August 24, 2015, 02:04:38 AM
I can't think of a reasonable mechanism for the oxidative dimer you posted.

It would help if post your NMR spectra, do you have MS?
Title: Re: Methylation product
Post by: pallidol on August 24, 2015, 02:29:22 AM
I only have NMR spectrums and have not do the MS analysis yet due to the instrument problem.
I attach here 1H, 13C and DEPT NMR spectrum. I have done HMQC and it just good enough to fit my structure-assumption of fraction 3(A).

tq for your concern. ;)
Title: Re: Methylation product
Post by: Dan on August 24, 2015, 03:24:44 AM
I have an idea of what it is. I could be wrong, but:

Hint 1: Start by adding the enolate form of your starting material to the keto form of your starting material
Hint 2: I think the formula of the product is C23H22N2O3
Title: Re: Methylation product
Post by: pallidol on August 24, 2015, 04:08:04 AM
I loss one O group?
Title: Re: Methylation product
Post by: Dan on August 24, 2015, 07:34:31 AM
Yes I think so (dehydration).
Title: Re: Methylation product
Post by: pallidol on August 24, 2015, 11:09:31 AM
yes i have tried to suggest the structure as a lactone unit and also in a spiro compound, but it seems none of it works.
Title: Re: Methylation product
Post by: pallidol on August 25, 2015, 12:46:43 AM
ok now i think i got the structure. But please correct me if i am wrong. It is quite close to the NMR of the chemdraw expectation.
Title: Re: Methylation product
Post by: Dan on August 25, 2015, 02:33:09 AM
Yes, that's what I think it is - via aldol condensation followed by methylation.
Title: Re: Methylation product
Post by: pallidol on August 25, 2015, 02:48:26 AM
ok thanks a lot Mr Dan for the help. I am gonna run GC-MS within this two days to confirm it. I will update the result.

very much appreciate of your help.  ;)
Title: Re: Methylation product
Post by: pallidol on August 27, 2015, 05:14:37 AM
i have done my GC-MS and there are several peak with the same molecular weight appear start from 28-30 minutes.

So I am pretty sure this is the structure. But somehow i am gonna analysis it using hr-ms within this two weeks.