Chemistry:Hexenuronic acid
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| Names | |
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| IUPAC name
(2S,3R,4S)-3,4-dihydroxy-2-[(2R,3R,4S,5R)-4-hydroxy-2,5-dimethoxyoxan-3-yl]oxy-3,4-dihydro-2H-pyran-6-carboxylic acid
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| Other names
4-deoxy-4-hexenopyranosyluronic acid
4-deoxy-beta-L-threo-hex-4-enopyranosyluronic acid | |
| Identifiers | |
3D model (JSmol)
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| Abbreviations | HexA |
| MeSH | C095263 |
PubChem CID
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| Properties | |
| C13H20O10 | |
| Molar mass | 336.293 g·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Hexenuronic acid (HexA) is a bicyclic organic compound with the formula C13H20O10.[1][2] It is an unsaturated sugar produced during the kraft process in the creation of wood pulp.[2]
Kraft process
During the kraft process, which is the turning of wood into wood pulp for papermaking, wood chips are treated with sodium hydroxide and sodium sulfide. Sodium hydroxide catalyzes the demethylation of 4-O-methyl-D-glucuronoxylan, which is found at the ends of the polysaccharide xylan.[2][1][3]
Hexenuronic acid decreases a wood's kappa number, which is a measure of bleachability of wood pulp, by 3-7.[3] It readily reacts with common wood pulp bleaching agents like ozone, peracetic acid, and chlorine dioxide.[2][1] Consequently, research has focused on ways to break down hexenuronic acid prior to bleaching to decrease dangerous waste products and costs.[3]
The main method of destroying hexenuronic acid is to treat the wood pulp post kraft processing with strong acids at high temperatures. HexA is hydrolyzed and broken down into aldehydes and alcohols like 2-furoic acid and 5-carboxy-2-furaldehdye.[3][2] This process has led to a 50% reduction in bleaching costs of the wood pulp in some cases.[2]
In microbes
Polysaccharide lyases (PL) are a type of enzyme that is found in numerous microorganisms including bacteriophages that break down parts of wood.[4] PL catalyzses β-elimination of uronic acid-containing polysaccharides into HexA.[4][5]
References
- ↑ 1.0 1.1 1.2 "Influence of the hexenuronic acid content on refining and ageing in eucalyptus TCF pulp". Bioresource Technology 101 (10): 3554–3560. May 2010. doi:10.1016/j.biortech.2009.11.105. PMID 20074936.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 "Influence of hexenuronic acids on us bleaching operations". TAPPI Journal 83 (11). November 2000. https://imisrise.tappi.org/TAPPI/Products/00/NOV/00NOV62.aspx.
- ↑ 3.0 3.1 3.2 3.3 "Hexenuronic acid removal from unbleached kraft eucalyptus pulp by peroxymonosulfuric acid". Journal of the Chilean Chemical Society 49 (4): 355–360. December 2004. doi:10.4067/S0717-97072004000400016. ISSN 0717-9707. http://www.scielo.cl/scielo.php?script=sci_abstract&pid=S0717-97072004000400016&lng=en&nrm=iso&tlng=en.
- ↑ 4.0 4.1 "Polysaccharide lyases". FEMS Microbiology Reviews 16 (4): 323–347. July 1995. doi:10.1111/j.1574-6976.1995.tb00179.x. PMID 7654407.
- ↑ "Black fungi and ants: a genomic comparison of species inhabiting carton nests versus domatia". IMA Fungus 13 (1): 4. March 2022. doi:10.1186/s43008-022-00091-5. PMID 35256015.
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