Diglycolic acid
Diglycolic acid is an aliphatic dicarboxylic acid, its acidity is between the one of acetic acid and oxalic acid.[1] It is formed in the oxidation of diethylene glycol in the body and can lead to severe complications with fatal outcome.[2]
Preparation
Oxidation of diethylene glycol with concentrated nitric acid was described by A. Wurtz in 1861[3]
Diglycolsäure durch Oxidation von DEG
In parallel, W. Heintz reported the synthesis of diglycolic acid from chloroacetic acid by heating with sodium hydroxide solution.[4]
Diglycolsäure aus Monochloressigsäure
In a version with barium hydroxide solution as an alkaline medium, diglycolic acid is obtained in 68% yield after acidification.[5]
The yields of the described reactions are unsatisfactory for use on a technical scale.
The single-stage nitric acid process gives even in the presence of an oxidation catalyst (vanadium(V)oxide) yields of only 58-60%.[6] In a multi-stage process of nitric acid oxidation at 70 °C and multiple crystallization steps, evaporation of the residues and return of the diethylene glycol-containing mother liquor, product yields of up to 99% (based on diethylene glycol) can be achieved.[7]
The oxidation of diethylene glycol with air, oxygen or ozone avoids the use of expensive nitric acid and prevents the inevitable formation of nitrous gases.[8] In the presence of a platinum catalyst, yields of 90% can be obtained by air oxidation.[9]
On a bismuth platinum contact catalyst, yields of 95% are to be achieved under optimized reaction conditions.[10]
The oxidation of 1,4-dioxan-2-one (p-dioxanone, a lactone which is used as a comonomer in biodegradable polyesters with nitric acid or dinitrogen tetroxide) is also described with yields of up to 75%.[11]
Properties
Diglycolic acid is readily water-soluble and crystallizes from water in monoclinic prisms as a white, odorless solid. At an air humidity of more than 72% and 25 °C, the monohydrate is formed. The commercial product is the anhydrous form as free-flowing flakes.[12]
Application
Diesters of diglycolic acid with (branched) higher alcohols can be used as softeners for polyvinyl chloride (PVC) with comparable properties as di-n-octyl phthalate (DOP).[13]
Basic solutions of diglycolic acid are described for the removal of limescale deposits in gas and oil bores, as well as in systems such as heat exchangers or steam boilers.[14]
Diglycolic acid can be used as a diester component in homo- and copolymeric polyesters (so-called polyalkylene diglycolates) which are biocompatible and biodegradable and can be used alone or in blends with aliphatic polyesters as tissue adhesives, cartilage substitutes or as implant materials:[15]
References
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- ↑ <templatestyles src="Citation/styles.css"/>Template:Citation/make link, M. Schröder, "Process for the production of pure diglycolic acid by oxidation if diethylene glycol with nitric acid", published Script error: No such module "auto date formatter"., assigned to Chemische Werke Hüls AGScript error: No such module "Check for unknown parameters".
- ↑ <templatestyles src="Citation/styles.css"/>Template:Citation/make link, G.E. Brown, Jr., "Method for making diglycolic acid, dipropionic acid and the salts there f", published Script error: No such module "auto date formatter"., assigned to Conen Corp.Script error: No such module "Check for unknown parameters".
- ↑ <templatestyles src="Citation/styles.css"/>Template:Citation/make link, D.L. Morris, W.J. Gammans, J.D. Holmes, "Oxidation of polyethylene glycols to dicarboxylic acids", published Script error: No such module "auto date formatter"., assigned to Eastman Kodak Co.Script error: No such module "Check for unknown parameters".
- ↑ Script error: No such module "citation/CS1".
- ↑ <templatestyles src="Citation/styles.css"/>Template:Citation/make link, C.Y. Shen, "Process for preparing diglycolic acid", published Script error: No such module "auto date formatter"., assigned to Monsanto Co.Script error: No such module "Check for unknown parameters".
- ↑ Script error: No such module "citation/CS1".
- ↑ <templatestyles src="Citation/styles.css"/>Template:Citation/make link, P.T. von Bramer, R.M. Simons, "Diesters of diglycolic acid and vinyl chloride polymers plastized therewith", published Script error: No such module "auto date formatter"., assigned to Eastman Kodak Co.Script error: No such module "Check for unknown parameters".
- ↑ <templatestyles src="Citation/styles.css"/>Template:Citation/make link, T.R. Gardner, R.M. Lasater, J.A. Knox, "Scale removal composition and method using salt of diglycolic acid and base at pH above 5", published Script error: No such module "auto date formatter"., assigned to Halliburton Co.Script error: No such module "Check for unknown parameters".
- ↑ <templatestyles src="Citation/styles.css"/>Template:Citation/make link, K. Cooper, A. Scopelianos, "Absorbable polyalkylene diglycolates", published Script error: No such module "auto date formatter"., assigned to Ethicon, Inc.Script error: No such module "Check for unknown parameters".
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