April 20, 2024, 03:31:47 AM
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Topic: How to determine if p-methoxycinnamic acid has the trans configuration?  (Read 3833 times)

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Offline Icey_cold

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Hi everybody~

I have a qns regarding p-methoxycinnamic acid.
How can we tell from a HMR spectrum of a p-methoxycinnamic acid has a trans configuration?

Appreciate if someone could enlightened me. :)


Offline discodermolide

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Re: How to determine if p-methoxycinnamic acid has the trans configuration?
« Reply #1 on: August 05, 2010, 12:37:07 PM »
examine the size of the coupling constants, usually small (<8Hz) are cis, large (>9 - upwards Hz) are trans.
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Offline Icey_cold

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Re: How to determine if p-methoxycinnamic acid has the trans configuration?
« Reply #2 on: August 07, 2010, 11:16:19 AM »
but I was given that the pair of doublet is centred at 6.4 ppm and 7.6 ppm. if this is the case, is there any way to prove that the product has trans or cis configuration?

Please advice.

Offline discodermolide

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Re: How to determine if p-methoxycinnamic acid has the trans configuration?
« Reply #3 on: August 07, 2010, 02:11:37 PM »
but I was given that the pair of doublet is centred at 6.4 ppm and 7.6 ppm. if this is the case, is there any way to prove that the product has trans or cis configuration?

Please advice.
Measure the coupling constant in Hz between the peaks of the individual doublets
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