D-galactose
- Diastereomer of D-mannose & D-glucose
- Epimer of D-glucose: only differ at C4
- Differs from D-mannose at C2 & 4 (diastereomer/not epimer)
Instructions for drawing D-galactose:
- Next to our drawing of D-mannose and D-glucose, draw a third vertical chain of six carbons and label the carbon atoms 1-6 from top to bottom.
- Add the carbonyl group and hydrogen to carbon 1 and the two hydrogens and hydroxyl group to carbon 6.
- To carbons 2 and 5, add a hydrogen atom on the left of the carbon and a hydroxyl group on its right.
- To carbons 3 and 4 do the opposite, add the hydroxyl group on the left and the hydrogen atom on the right.
- Indicate that this molecule is D-galactose, another simple sugar used in metabolism and in the formation of carbohydrates.
- Notice that D-galactose differs from D-mannose at carbons 2 and 4, making it a diastereomer but not an epimer.
- On the other hand, D-galactose only differs from D-glucose at carbon 4, making it a diastereomer and an epimer of D-glucose.