Question

For the α anomer of a D-sugar, the anomeric hydroxyl in a Haworth projection a. has an upward projection (on the same side as the terminal CH₂OH group). b. has a downward projection (on the opposite side from the terminal CH₂OH group). c. may be either up or down, it depends on the individual sugar. d. is non-existent; anomers are a consideration only in Fischer projections.

Answer 1

Answer:

The correct option is: b. has a downward projection (on the opposite side from the terminal CH₂OH group).

Explanation:

The Haworth Projection depicts the three-dimensional cyclic structure of the monosaccharides.

The monosaccharide, D-glucose predominantly exists in the pyranose form and is known as D-glucopyranose. The D-glucopyranose has two anomeric forms: α- and the β- form and the carbon-1 (C-1 ) is known as the anomeric carbon.                

In the Haworth projection of α-D-glucopyranose, the hydroxyl group of anomeric carbon is projected in the downward direction. Whereas, the terminal CH₂OH group on the carbon-5 (C-5), is projected in the upward direction. Therefore, they are on the opposite sides of the plane of ring.