Diglycolic acid

Oxidation of diethylene glycol with concentrated nitric acid was described by A. Wurtz in 1861{{citation|surname1=A. Wurtz|periodical=Liebigs Ann. Chem.|title=Umwandlung des Aethylens zu complicirten organischen Säuren|volume=117|issue=1|pages=136–140|date=1861|language=German|doi=10.1002/jlac.18611170114

|url=https://zenodo.org/record/1427159}}

File:Diglycolsäure aus DEG.svg

In parallel, W. Heintz reported the synthesis of diglycolic acid from chloroacetic acid by heating with sodium hydroxide solution.{{citation|surname1=W. Heintz|periodical=Annalen der Physik|title=Ueber die Diglycolsäure (Paraäpfelsäure)|volume=191|issue=2|pages=280–295|date=1862|language=German|doi=10.1002/andp.18621910206

|url=https://zenodo.org/record/1423686}}

File:Diglycolsäure aus Monochloressigsäure.svg

In a version with barium hydroxide solution as an alkaline medium, diglycolic acid is obtained in 68% yield after acidification.{{citation|surname1=K.E. Füger|title=Synthese und katalytische Reduktion von Glykolsäure und Glykolsäureestern, Promotionsarbeit ETH Zürich|publisher=Juris-Verlag|date=1959|language=German|url=http://e-collection.library.ethz.ch/eserv/eth:33645/eth-33645-02.pdf

}}

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%.{{citation|surname1=C. Erk|periodical=Liebigs Ann. Chem.|title=Condensation of diglycolic acid dichloride with polyglycols, 5. An improved synthesis of cyclic polyether-esters by cyclization|volume=1991|issue=10|pages=1083–1084|date=1991|doi=10.1002/jlac.1991199101186

}} 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.{{Cite patent|country = US|number =4066691 |title =Process for the production of pure diglycolic acid by oxidation if diethylene glycol with nitric acid |pubdate =1978-1-3 |fdate =1976-9-8 |inventor =M. Schröder |assign=Chemische Werke Hüls AG}}

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.{{Cite patent|country = US|number =3879452 |title =Method for making diglycolic acid, dipropionic acid and the salts there

f |pubdate =1975-4-22 |fdate =1971-6-18 |inventor=G.E. Brown, Jr. |assign=Conen Corp.}} In the presence of a platinum catalyst, yields of 90% can be obtained by air oxidation.{{Cite patent|country = US|number =4256916 |title =Oxidation of polyethylene glycols to dicarboxylic acids|pubdate =1981-3-17 |fdate =1979-8-15 |inventor=D.L. Morris, W.J. Gammans, J.D. Holmes |assign=Eastman Kodak Co.}}

On a bismuth platinum contact catalyst, yields of 95% are to be achieved under optimized reaction conditions.{{citation|surname1=Y-Y. Zhang, Z.-Y. Liang, Y.-D. Zhang|periodical=Fine Chemicals|title=Preparation of Diglycolic Acid via Oxidation of Diethylene Glycol with Molecular Oxygen|date=May 2012|url=http://en.cnki.com.cn/Article_en/CJFDTOTAL-JXHG201205023.htm

}}

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%.{{Cite patent|country = US|number =3952054 |title =Process for preparing diglycolic acid|pubdate =1976-4-20 |fdate =1974-12-5 |inventor =C.Y. Shen |assign=Monsanto Co.}}

File:Diglycolsäure aus p-Dioxanon.svg

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.{{citation|surname1=W.M. Bruner, L.T. Sherwood, Jr.|periodical=Ind. Eng. Chem.|title=Diglycolic acid – a new commercial dibasic acid|volume=41|issue=8|pages=1653–1656|date=1949|doi=10.1021/ie50476a032

}}

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).{{Cite patent|country = US|number =3173888 |title =Diesters of diglycolic acid and vinyl chloride polymers plastized therewith|pubdate =1965-3-16 |fdate =1962-11-13 |inventor=P.T. von Bramer, R.M. Simons |assign=Eastman Kodak Co.}}

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.{{Cite patent|country = US|number =3639279 |title =Scale removal composition and method using salt of diglycolic acid and base at pH above 5|pubdate =1972-2-1 |fdate =1969-4-1 |inventor =T.R. Gardner, R.M. Lasater, J.A. Knox |assign=Halliburton Co.}}

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:{{Cite patent|country = US|number =5696178 |title =Absorbable polyalkylene diglycolates|pubdate =1997-12-9 |fdate =1996-7-22 |inventor=K. Cooper, A. Scopelianos |assign=Ethicon, Inc.}}

File:Synthese von Polyalkylenglycolaten.svg

{{Reflist}}

Category:Dicarboxylic acids

Category:Ethers