Question

What is the difference between an alpha and beta carbohydrate?

Answer 1

They differ in the orientation of the `"OH"` group at `"C-1"`.

Explanation:

When the straight-chain form of a carbohydrate like glucose closes to form a ring, it forms a new chiral centre at `"C-1"`.

This gives two different structures.

Their Haworth formulas are

Structure 1

and

Structure 2

To assign the α or β configurations to these forms, you look at the relative positions of `"C-6"` and the `"OH"` group on `"C-1"`.

In the α-form (Structure 1), the `"OH"` group on `"C-1"` is on the opposite side of the ring from `"C-6"`.

In the β-form (Structure 2), the `"OH"` group on `"C-1"` is on the same side of the ring as `"C-6"`.