Question #ae5bd
1 Answer
You look at the formula as if you are wrapping it around a cylindrical tube.
Explanation:
You look at the formula as if you are wrapping it around a cylindrical tube.
The Fischer projection of glucose is
Look at any two adjacent chiral carbon atoms. Those two atoms are in the plane of the paper.
The horizontal bonds are coming out of the paper.
The carbon atoms have a tetrahedral geometry, so the vertical bonds to groups 1 and 4 must be behind the plane of the paper.
When you have a longer vertical chain, any two adjacent atoms are in the plane of the paper.
The two atoms directly above and below them are behind the plane of the paper, and the carbon chain has a completely eclipsed conformation.
You keep the same orientation as you move up and down the chain.
The chain is arch-shaped, as if it you wrapped around a cylindrical tube.
When you flatten the structure onto the surface of the cylinder, you get the Fischer projection of the molecule.
So C-1 is behind the plane of the paper, and the C-5 OH group is in front.
