{{Short description|Class of chemical compounds}} [[File:Aldonic Acid 1.png|thumb|The skeletal structure of an aldonic acid, gluconic acid (top), and its aldose, glucose (bottom).]] '''Aldonic acids''' are sugar acids with the general chemical formula, HO<sub>2</sub>C(CHOH)<sub>n</sub>CH<sub>2</sub>OH. They are obtained by oxidizing the aldehyde (-CHO group) of an aldose to form a carboxylic acid (-COOH group).<ref>{{Cite book |url=https://goldbook.iupac.org/ |title=The IUPAC Compendium of Chemical Terminology: The Gold Book |date=2019 |publisher=International Union of Pure and Applied Chemistry (IUPAC) |editor-last=Gold |editor-first=Victor |edition=4 |location=Research Triangle Park, NC |language=en |doi=10.1351/goldbook.a00212}}</ref> Aldonic acids are generally found in their ring form. However, these rings do not have a chiral carbon at the terminal end bearing the aldehyde, and they cannot form R−O−R′ linkages between different molecules.<ref>{{Cite journal |last1=Sartori |first1=Suélen Karine |last2=Diaz |first2=Marisa Alves Nogueira |last3=Diaz-Muñoz |first3=Gaspar |date=2021-03-26 |title=Lactones: Classification, synthesis, biological activities, and industrial applications |url=https://www.sciencedirect.com/science/article/pii/S0040402021001009 |journal=Tetrahedron |volume=84 |article-number=132001 |doi=10.1016/j.tet.2021.132001 |issn=0040-4020|url-access=subscription }}</ref>
The nomenclature of aldonic acids and their lactones is based on replacing the suffix "-ose" with "onic acid" or "onolactone". Hence, D-glucose is oxidized to D-gluconic acid and D-gluconolactone.<ref>{{Cite book |last=Robyt |first=John F. |title=Essentials of carbohydrate chemistry |date=1998 |publisher=Springer |isbn=978-0-387-94951-2 |series=Springer advanced texts in chemistry |location=New York}}</ref>
==Inventory== Sugar acids are white, water-soluble solids. They tend to dehydrate to the lactone derivative, often before they can be melted. All are chiral and, at least in nature, enantiopure.
{| class="wikitable" |+ Some Aldonic Acids |- ! Compound !! RN !! melting point (C) !! parent sugar |- | L-Threonic acid || 7306-96-9 || 143 || threose |- | D-Ribonic acid || 642-98-8 || 143 || ribose |- | D-Xylonic acid || 526-91-0 || - || xylose |- | D-Arabinonic acid || 488-30-2 || 135-136 || arabinose |- | D-Lyxonic acid || 526-92-1 || - || lyxose |- | Gluconic acid || 526-95-4 || 131 || glucose |- | D-Gulonic acid || 526-97-6|| - || gulose |- | D-Galactonic acid || 576-36-3 ||- || galactose |- |D-Mannonic acid<ref>{{cite journal |doi=10.1016/j.carres.2006.05.023 |title=Enzymatic synthesis of aldonic acids |date=2006 |last1=Pezzotti |first1=F. |last2=Therisod |first2=M. |journal=Carbohydrate Research |volume=341 |issue=13 |pages=2290–2292 |pmid=16806132 }}</ref>||642-99-9|| 74-76|| mannose |- |L-Idonic acid||1114-17-6||-||idose |- |}
==Synthesis==
=== Oxidation by bromine and water === Aldonic acids are most commonly prepared by the oxidation of the sugar with bromine and water under neutral pH.<ref>{{Cite journal |last=Isbell |first=Horace S. |date=March 1962 |title=Oxidation of aldoses with bromine |journal= Journal of Research of the National Bureau of Standards, Section A |volume=66A |issue=3 |pages=233–239 |doi=10.6028/jres.066a.023 |issn=0022-4332 |pmc=5310681}}</ref> [[File:Bromine Ox Final.png|thumb|center|603x603px|The reaction mechanism of bromine and water being used to oxidize the aldehyde group of an aldose.]]
===Strecker reaction=== Alternatively, they arise by homologation of an aldose using the Strecker reaction.<ref>{{Cite journal |date=1956 |title=d-gulonic-y-lactone |journal=Organic Syntheses |language=en |volume=36 |page=38 |doi=10.15227/orgsyn.036.0038 |issn=0078-6209}}</ref> Cyanide in ammonia reacts with an aldose to produce an intermediate, which is then reacted with a hydronium ion to form an aldonic acid.
=== Oxidation by Benedict's and Fehling's reagents === Aldonic acids are the products of the oxidation of aldoses by Benedict's or Fehling's reagents.<ref>{{Cite journal |last1=Simoni |first1=Robert D. |last2=Hill |first2=Robert L. |last3=Vaughan |first3=Martha |date=April 2002 |title=Benedict's Solution, a Reagent for Measuring Reducing Sugars: the Clinical Chemistry of Stanley R. Benedict |journal=Journal of Biological Chemistry |volume=277 |issue=16 |pages=e5–e6 |doi=10.1016/s0021-9258(19)61050-1 |issn=0021-9258|doi-access=free }}</ref> Copper ions react with an aldose to form a red precipitate, Cu<sub>2</sub>O. [[File:Benedict's Final1.png|thumb|center|696x696px|The reaction scheme of an aldose being oxidized by the copper ions in a Benedict's reagent solution. The R group provided is an example of a sugar backbone.]]
===Natural synthesis=== Anaerobic bacteria can also perform dehydrogenation to produce aldonic acids.<ref name=":02" /> This is done by synthesizing enzymes that are able to selectively oxidize aldoses to their corresponding aldonic acid.
== Applications == In commercial settings, glucose, galactose, or arabinose are commonly oxidized to obtain aldonic acids.<ref name=":02">{{Cite journal |last1=Wieschalka |first1=Stefan |last2=Blombach |first2=Bastian |last3=Bott |first3=Michael |last4=Eikmanns |first4=Bernhard J. |date=March 2013 |title=Bio-based production of organic acids with C orynebacterium glutamicum |journal=Microbial Biotechnology |language=en |volume=6 |issue=2 |pages=87–102 |doi=10.1111/1751-7915.12013 |issn=1751-7915 |pmc=3917452 |pmid=23199277}}</ref> These products can then be used as the building blocks for preservatives, buffering agents, and other chemicals.<ref name=":02" /> As such, the use of aldonic acids for chemical applications is of growing interest to various industries.
Aldonic acids can be used as the natural starting materials to synthetic products<ref>{{Cite journal |last1=Mehtiö |first1=Tuomas |last2=Toivari |first2=Mervi |last3=Wiebe |first3=Marilyn G. |last4=Harlin |first4=Ali |last5=Penttilä |first5=Merja |last6=Koivula |first6=Anu |date=2016-09-02 |title=Production and applications of carbohydrate-derived sugar acids as generic biobased chemicals |url=https://www.tandfonline.com/doi/full/10.3109/07388551.2015.1060189 |journal=Critical Reviews in Biotechnology |language=en |volume=36 |issue=5 |pages=904–916 |doi=10.3109/07388551.2015.1060189 |pmid=26177333 |issn=0738-8551|url-access=subscription }}</ref> including polyesters and polyurethane.<ref name=":1">{{Cite journal |last1=Galbis |first1=Juan A. |last2=García-Martín |first2=M. de Gracia |last3=de Paz |first3=M. Violante |last4=Galbis |first4=Elsa |date=2016-02-10 |title=Synthetic Polymers from Sugar-Based Monomers |url=https://pubs.acs.org/doi/10.1021/acs.chemrev.5b00242 |journal=Chemical Reviews |language=en |volume=116 |issue=3 |pages=1600–1636 |doi=10.1021/acs.chemrev.5b00242 |pmid=26291239 |hdl=11441/154263 |issn=0009-2665|hdl-access=free }}</ref> The incorporation of these organic sugars into synthetic materials allow for a more renewable alternative to oil-based polymer synthesis,<ref name=":1" /> and increased structural durability within polymer chains.<ref name=":2">{{Cite journal |last1=Gregory |first1=Georgina L. |last2=López-Vidal |first2=Eva M. |last3=Buchard |first3=Antoine |date=2017-02-14 |title=Polymers from sugars: cyclic monomer synthesis, ring-opening polymerisation, material properties and applications |url=https://pubs.rsc.org/en/content/articlelanding/2017/cc/c6cc09578j |journal=Chemical Communications |language=en |volume=53 |issue=14 |pages=2198–2217 |doi=10.1039/C6CC09578J |pmid=28127607 |issn=1364-548X}}</ref>
== Properties == Aldonic acids are typically used in industrial applications for their ability to degrade naturally in the environment.<ref name=":1" /> This can be attributed to their affinity with water, as the polar bonds within the carboxylic acid group of aldonic acids allow them to interact with aquatic systems.<ref>{{Cite journal |last1=Morzyk-Ociepa |first1=Barbara |last2=Michalska |first2=Danuta |last3=Pietraszko |first3=Adam |date=January 2004 |title=Structures and vibrational spectra of indole carboxylic acids. Part I. Indole-2-carboxylic acid |journal=Journal of Molecular Structure |volume=688 |issue=1–3 |pages=79–86 |doi=10.1016/j.molstruc.2003.09.027 |bibcode=2004JMoSt.688...79M |issn=0022-2860}}</ref>
The structural diversity of aldonic acids also allow for various properties. Their ring formation creates an added layer of rigidity when integrated with other materials.<ref name=":2" />
==See also== *Aldaric acids *Uronic acids
==References== {{reflist}}
Category:Sugar acids