Question

What is the maximum number of stereo isomers that can be written for aldo-pentose?

Answer 1

There are eight possible stereoisomers of the aldopentoses.

Explanation:

The general structure of an aldopentose is

We see that the molecule has three chiral carbons.

The maximum number of stereoisomers is `2^n`, where `n` is the number of chiral carbons.

Since `n = 3` and `2^3 =8`, there are eight possible aldopentoses.

Here are the structures of four of the aldopentoses.

The other stereoisomers are the four L-aldopentoses: the mirror images of the D-aldopentoses shown above.