I was looking into purchasing some glucose to do some reduction experiments and to make some Tollens Reagent. But when I went to purchase some I got
hit with a bit of a quandary. I was not aware there were different kinds of glucose?
There were three different kinds offered and non were mentioned in the processes of the reactions I wanted to do.
I know what the anhydrous and monohydrate means but what one would be best for using the the aforementioned reactions?Magpie - 27-9-2011 at 13:00
Those must be reagent grade and are enantiomers. For a reducing sugar I would not waste my money on reagents, but instead just buy some fructose at
the health food store. Ozone - 27-9-2011 at 13:02
D or L nomenclature refers to the hydroxyl connected to the penultimate carbon in the chain. When laid out in a Fischer projection, this hydroxyl will
be right (D) or left (L). The consequences are real as your enzymes can't work with L sugars. In general, in nature we see D-sugars and L-amino acids.
Despite the names, D = dextrorotatory or L = laevorotatory, the designation in no way predicts optical rotation. For example, D-glucose rotates light
by about +53° and D-fructose by -92°. The designation was made originally for glyceraldehyde, for which it is accurate (eg. D = clockwise and L =
counterclockwise). These must also not be confused with R or S designations.
L-glucose is just as reductive (the aldehyde group is the same) it's just VERY much more expensive (and completely unnecessary).
I'd go with the anhydrous D-form (to make everything simple and more compatable with organic solvents/reagents). As a simple reducing agent, the
monohydrate is just as good, just be sure to account for the water to keep your stoichiometry straight.
When making aqueous solutions, be sure to stir rigorously and made small additions--otherwise, the anhydrous material will make a brick as it
hydrates. Saturation at rt is ~50 g solids/100g (aq).
Those must be reagent grade and are enantiomers. For a reducing sugar I would not waste my money on reagents, but instead just buy some fructose at
the health food store.
And what would you use the fructose for? It's not a reducing sugar. Glucose is cheap and works. I agree that buying reagent grade stuff would be a
waste of money but fructose would be an even bigger wasteScienceSquirrel - 28-9-2011 at 03:21
Glucose monohydrate is cheaply and readily available at most pharmacies, supermarkets and home brew shops.
It will be food or pharmacopia grade so will be pure enough for almoat all purposes. The monohydrate does not clump so much when added to water.
