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Topic: Need help assigning R and S  (Read 3538 times)

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Offline helpme2

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Need help assigning R and S
« on: September 26, 2016, 09:50:16 PM »
Here is the molecule: http://imgur.com/1lleNn3

I can't solve it. The molecule doesnt have any wedges or dashes, therefore i have no idea where to even start!
« Last Edit: September 27, 2016, 01:31:13 PM by Borek »

Offline discodermolide

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Re: Need help assigning R and S
« Reply #1 on: September 27, 2016, 02:27:40 AM »
Try re-drawing it as a "flat molecule" like this
O[C@H]1C[C@@H](O)CCC1

maybe this will help? Ignore the chiral flag
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Offline AWK

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Re: Need help assigning R and S
« Reply #2 on: September 27, 2016, 02:54:15 AM »
Your projection is unambiguous. Wedges or dashes are not needed. Your drawing contains information which part is closer to you.
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Offline helpme2

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Re: Need help assigning R and S
« Reply #3 on: September 27, 2016, 02:55:46 AM »
Try re-drawing it as a "flat molecule" like this
O[C@H]1C[C@@H](O)CCC1

maybe this will help? Ignore the chiral flag

how did you know if the OH is wedged or dashed?

Offline helpme2

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Re: Need help assigning R and S
« Reply #4 on: September 27, 2016, 02:56:37 AM »
Your projection is unambiguous. Wedges or dashes are not needed. Your drawing contains information which part is closer to you.

Do you mind telling me what information that is?

Offline jasongnome

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Re: Need help assigning R and S
« Reply #5 on: September 27, 2016, 06:39:15 AM »
If you look at it, it looks 3-D and you can see what's coming towards you.

Do you have a MolyMod kit? Actually building the molecules so you havhis siorte a physical 3D form in front of you can really help with this sort of exercise.

Any of the top 3 on this page would be useful, as you can see they're not expensive.

https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=molymod
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Offline AWK

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Re: Need help assigning R and S
« Reply #6 on: September 27, 2016, 01:08:53 PM »
Your projection is unambiguous. Wedges or dashes are not needed. Your drawing contains information which part is closer to you.

Do you mind telling me what information that is?
This is projection analogous to Haworth. Ther lower part of ring is closer to us. Moreover, the line obscured is broken (see picture). It's mean this OH group is closer us.
AWK

Offline discodermolide

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Re: Need help assigning R and S
« Reply #7 on: September 28, 2016, 08:00:38 AM »
Try re-drawing it as a "flat molecule" like this
O[C@H]1C[C@@H](O)CCC1

maybe this will help? Ignore the chiral flag

how did you know if the OH is wedged or dashed?



In the 3D version both OH groups are "up" above the plane of the molecule hence in the "flat drawing they will be represented by wedges.
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Offline Vidya

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Re: Need help assigning R and S
« Reply #8 on: September 29, 2016, 12:14:19 AM »
from the molecule it is clear that it is cis conformation so when you a make an image as flat molecule you can put both the OH on the wedge or dash ..basically they are on the same side of the molecule.

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