Question

In the fischer projection of D-glucose, what is the penultimate carbon and why?

Answer 1

In a Fischer projection of a monosaccharide, the penultimate carbon is the next-to-last carbon or alternatively, the last stereogenic carbon. For D-sugars, this carbon is depicted with hydrogen on the left and hydroxyl on the right.

Step-by-step explanation:

A Fischer projection is a two-dimensional representation of a three-dimensional molecule. It is commonly used to depict monosaccharides and amino acids. In a Fischer projection of a monosaccharide, the penultimate carbon is the next-to-last carbon or alternatively, the last stereogenic carbon. For D-sugars, this carbon is depicted with hydrogen on the left and hydroxyl on the right. This notation is used to differentiate between L- and D- carbohydrates. L- and D- carbohydrates are enantiomers, which means they are non-superimposable mirror images of each other.

Answer 2

The penultimate carbon in the Fischer projection of D-glucose is the second-last carbon from the bottom, and it is the chiral center that determines if the sugar is a D- or L- form, with the OH group on the right in the case of D-glucose.

Step-by-step explanation:

In the Fischer projection of D-glucose, the penultimate carbon is the second-last carbon from the bottom of the projection. This carbon is special because it determines the D- or L- configuration of the sugar. If the hydroxyl group (-OH) attached to this carbon is on the right side, the sugar is designated as D-glucose, and if it is on the left, it is L-glucose. D-glucose is a D sugar because the OH group on the fifth carbon atom, which is the penultimate carbon in this context, is on the right side. This designation is an essential convention in carbohydrate chemistry, helping in the identification and differentiation of sugars.