D-glucose: from Fischer projection, via 3D glucopyranose, to Haworth projection.

Maitland Jones 2nd Ed., section 23.1

A thought experiment visualised

The relation between the Fischer projection of D-glucose and the 3-dimensional structure of the beta-D-glucopyranose ring is shown here in the form of a 40 structure animation.
The starting structure resembles the Fischer projection: the carbon chain is vertical, the aldehyde at the top, and the horizontal bonds pointing towards you (in agreement with the definition of the Fischer projection).
the four oxygen positions that define the type of sugar. The stereochemical position of the violet OH group determines the D type of sugar. It is this oxygen that attacks the carbonyl group and ends up in the ring.
colour.
Zoom structure with Shift-LeftMouseButton

animation rate 1  2  3  5 

To compare stereo-isomers of cyclic compounds, only the relative positions of the substituents matter. The flexibility of the ring doesn't affect cis or trans relations between substituents. Therefore Haworth introduced a projection in which the ring is made flat, and the substituents are pointing either up or down.

The next animation shows the relation between the 3D structure of glucopyranose and the Haworth projection. Try to align the structure as in the drawing on the right. Note how the alternating up/down (trans/trans) positions of the substituents stick out clearly now.

Questions

Note: Although the questions are in English, you may answer them in Dutch...
  1. At which stage (conformation number) it is decided whether alpha or beta glucopyranose is formed? Why?

  2. In pyranose sugars other than glucose, at least one hydroxyl group ends up in an axial position. Which one (#) is it in galactose?

  3. What would be the main characteristic of substituent positions in L-glucopyranose?

  4. What would be the first step in the reverse reaction, the (acid catalyzed) opening of the pyranose ring?

Fill in your name(s) (compulsory!):

and your answers!

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