Not understanding Fischer projections

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Discussion Overview

The discussion revolves around the interpretation of Fischer projections, specifically addressing the representation of bonds in these diagrams. Participants explore the conventions used in depicting molecular structures, particularly in the context of D glucose and the confusion arising from the presence of diagonal bonds in the illustrations.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the accuracy of a Wikipedia statement regarding Fischer projections, noting the presence of diagonal bonds in a D glucose illustration despite the claim that all bonds should be horizontal or vertical.
  • Another participant suggests that the Wikipedia article is poorly written and proposes that it should clarify that only bonds between chiral centers are depicted as horizontal or vertical lines.
  • Some participants mention that there are competing conventions regarding how Fischer projections are drawn, including whether to depict terminal aldehydes and how to represent all bonds.
  • A later reply expresses understanding after the clarification about the focus on chiral centers, indicating that the explanation helped resolve their confusion.

Areas of Agreement / Disagreement

Participants generally agree that the Wikipedia article lacks clarity, but multiple competing views regarding the conventions of Fischer projections remain unresolved.

Contextual Notes

The discussion highlights limitations in the Wikipedia article's explanation, particularly regarding the assumptions about which bonds are represented in Fischer projections. There is also a lack of consensus on the best practices for drawing these projections.

ppppparker
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This is what's confusing me.
Wikipedia says that "All bonds are depicted as horizontal or vertical lines."
Then it shows a picture of D glucose chain with diagonal bonds. (the double bond and the hydrogen).
Why is it drawn with diagonal bonds if its supposed to be only vert or horiz bonds?
thanks for any help
 
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Hi ppppparker:

It would help if you post a link to the Wikipedia article, and you include the exact text from the article you want to ask about.

Regards,
Buzz
 
ppppparker said:
Wikipedia says that "All bonds are depicted as horizontal or vertical lines."
Then it shows a picture of D glucose chain with diagonal bonds. (the double bond and the hydrogen).
Why is it drawn with diagonal bonds if its supposed to be only vert or horiz bonds?
Because the Wikipedia article on Fischer projections is poorly written. It should say something to the effect of "All relevant bonds between chiral centers are depicted as horizontal or vertical lines." There are a few competing conventions for Fischer projections (Do you draw out the terminal aldehyde or just write it as CHO? Do you draw all bonds as horizontal or vertical, or just the ones to chiral centers?), but the important takeaway is that at the very least, the bonds between chiral centers are drawn as horizontal or vertical lines. This is the purpose of Fischer projections: to provide a shorthand for showing stereochemistry of molecules (like sugars) with a large number of chiral centers.

EDIT: Here's the link in question.
 
TeethWhitener said:
Because the Wikipedia article on Fischer projections is poorly written.
Hi TeethWhitener:

I have to agree with you that the article is poorly written. Your explanation is much clearer. Perhaps you might enter a comment on the talk page and suggest how the article might be improved. I have found that this does not often help, but sometimes it does.

Regards,
Buzz
 
"All relevant bonds between chiral centers are depicted as horizontal or vertical lines."

that makes total sense to me now. I see why textbook was explaining on and on about chirality now. thanks.
i thought that I must be missing something really dumb.
 

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