Sciencemadness Discussion Board

Oxidation of simple sugars

UnintentionalChaos - 15-7-2008 at 19:32

Hopefully there is not some simple reference I am overlooking. At any rate, I am posting it in beginnings since it is a relatively simple question. I have a big bag of d-glucose (dextrose) and would like to oxidize it to gluconic acid, which is nothing more than changing the aldehyde group on the chain form to a carboxylic acid group. I have found information suggesting that hypoiodite is highly selective in this conversion, but I do not have any appreciable quantity of iodide or iodine to do this with. Has anyone come across or does anyone have suggestions for a suitable alternative method?

Largely, I would like to prepare calcium gluconate to make an antidote gel, which is a good thing to have around with the hydrofluoric acid I recently acquired, as well as have some other gluconate salts around for experiments.

EDIT: Here is one of the several references I have seen using hypoiodite. This seems also to be a relatively old analytical technique.
http://www.jbc.org/cgi/reprint/72/2/801.pdf

[Edited on 7-15-08 by UnintentionalChaos]

not_important - 15-7-2008 at 22:07

I think the use of iodine/hypoiodite is simply for the analytical application.
Quote:

When glucose is acted upon by chlorine water, bromine water, silver oxide, or dilute nitric acid, the aldehyde group is oxidized to carboxyl and a mono-basic acid results. CH2OH— (CHOH)4— CHO + О => CH2OH— (CHOH)4— COOH Gluconic acid Aldo-kexose Penta-hydroxy hexanoic acid.

A Textbook of Organic Chemistry By Joseph Scudder Chamberlain

U.S. patents 5132452 and 4843173, among others, use Pd-Bi and similar alloys to catalyse oxidize of glucose to gluconic acid using oxygen.
Quote:
An efficient oxidation of glucose to gluconic acid was performed using a porous gold(0) catalyst in a low-cost microreactor designed from Pyrex glass capillary tubing; compared with the conventional synthesis procedure this novel approach of using a capillary-microreactor offers a convenient and highly efficient means to optimise reaction conditions and catalytic activities.

http://www.rsc.org/publishing/journals/CC/article.asp?doi=b4...

And most likely not practical, using methylene blue
http://faculty.mansfield.edu/bganong/biochemistry/bluebott.h...

[Edited on 16-7-2008 by not_important]

UnintentionalChaos - 15-7-2008 at 22:47

See, that's exactly what I was looking for. Thanks not_important. I figured the hypoiodite was largely for the analytical potential but its a relatively mild oxidizer compared to say hypochlorite. Originally, I was looking at using a modified Fehling's solution/ Benedict's reagent but it would have been an ugly isolation of product. I've been looking around since I posted this and Im now thinking hypochlorite oxidation in mildly basic solution with catalytic bromide (forming Br2 and OBr-) is probably the way to go for cheap and easy purification

not_important - 16-7-2008 at 04:11

You'll want to chase down details, possibly in Ochem books from the late 19th to earlier 20th century, as I know oxidation of the hydroxyl groups can also occur.