Not understanding Fischer projections

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In summary, the article on Fischer projections states that all relevant bonds between chiral centers are drawn as horizontal or vertical lines.
  • #1
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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  • #2
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
 
  • #3
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.
 
  • #4
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
 
  • #5
"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.
 

1) What is a Fischer projection?

A Fischer projection is a two-dimensional representation of a three-dimensional molecule, commonly used in organic chemistry. It shows the relative positions of different groups attached to a central carbon atom, with vertical lines representing bonds extending away from the viewer and horizontal lines representing bonds extending towards the viewer.

2) How do I know which way to draw a Fischer projection?

Fischer projections are typically drawn with the most oxidized group (such as a carbonyl or carboxyl group) at the top, and the least oxidized group (such as a methyl or methylene group) at the bottom. The horizontal lines should also be drawn on the same side of the vertical line, as this represents the group extending towards the viewer.

3) Can Fischer projections be rotated?

Yes, Fischer projections can be rotated 90 degrees clockwise or counterclockwise without changing the molecule's identity. However, flipping a Fischer projection (horizontally or vertically) would result in a different molecule.

4) How do I convert a Fischer projection into a 3D model?

To convert a Fischer projection into a 3D model, you can use a modeling kit or a molecular modeling software. Start by identifying the carbon atom in the center of the Fischer projection and then attach the appropriate groups to the correct positions. Remember to maintain the correct stereochemistry (i.e. wedges and dashes) when building the 3D model.

5) Why are Fischer projections used in organic chemistry?

Fischer projections are useful in representing complex molecules in a simple and concise manner. They also provide a clear visualization of the stereochemistry of a molecule, making it easier to determine the relationships between different groups. Additionally, Fischer projections are commonly used in organic chemistry reactions and can help predict the products of a reaction.

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