Xylose

Structural formula
Fischer projection , open-chain representation
General
Surname	Xylose
other names	Wood sugar
Molecular formula	C 5 H 10 O 5
Brief description	colorless, sweet-tasting needles or prisms
External identifiers / databases
CAS number 25990-60-7 (racemate) 58-86-6 ( D- shape) 609-06-3 ( L- shape) EC number 247-395-8 ECHA InfoCard 100.043.072 PubChem 644160 DrugBank DB09419 Wikidata Q66589603
properties
Molar mass	150.13 g · mol -1
Physical state	firmly
Melting point	154–158 ° C (both enantiomers)
solubility	well in water, soluble in pyridine and hot ethanol
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Xylose ( wood sugar , from ancient Greek ξύλον xylon , German , wood ' ) is a Aldo pentose , a type of sugar with five carbon - atoms and an aldehyde group as a functional group which, inter alia, in the hydrolysis of wood rubber with dilute acids is produced. The sugar substitute xylitol is made from it. In relation to sucrose , a 10% D -Xylose solution has a sweetness of 67%. Xylose is not broken down in the human organism and is excreted again in unchanged form. In medicine, xylose is therefore used to investigate gastric emptying and resorption processes in the intestine.

Stereochemistry

The term xylose stands for two enantiomers : D- xylose and L- xylose, which relate to each other like image and mirror image. The position of the hydroxyl group at C ₄ (the second lowest carbon atom) determines whether it is the D or the L enantiomer. In the Fischer projection , this points to the right in D -Xylose ( Latin : dexter, hence D ), in L -Xylose to the left (Latin: laevus, L ). Like other long-chain sugars , xylose can react intramolecularly to form a cyclic hemiacetal with five or six atoms in the ring. Due to the newly created chiral center, there are four isomers each for the ring forms of D - and L -xylose.

D -Xylose - spellings
Wedge formula	Haworth notation
	α- D -xylofuranose	β- D -xylofuranose
	α- D -Xylopyranosis	β- D -Xylopyranosis

The suffixes -pyranose and -furanose describe the similarity of the ring with the heterocycles pyran and furan .

At 20 ° C, D -xylose dissolved in water is, like D - glucose , 35% in the α-pyranose form and 65% in the β-pyranose form.

The CAS number for the open-chain, racemic xylose is 25990-60-7 . Each ring shape and each stereoisomer has its own CAS number:

	open- chain	Furanosis		Pyranosis
		α	β	α	β
D -Xylose	58-86-6	14795-83-6	37110-85-3	6763-34-4	2460-44-8
L -Xylose	609-06-3	41546-30-9	41546-29-6	7296-58-4	7322-30-7

Medical use

The D -Xylose Absorption Test can be used to test for malabsorption .

Web links

Commons : Xylose  - collection of images, videos and audio files

Wiktionary: Xylose  - explanations of meanings, word origins, synonyms, translations

Individual evidence

1. ↑ ^{a b c} Entry on xylose. In: Römpp Online . Georg Thieme Verlag, accessed on December 25, 2014.
2. ↑ L-Xylose data sheet from Sigma-Aldrich , accessed on May 12, 2017 ( PDF ).
3. ↑ Data sheet D-Xylose from Sigma-Aldrich , accessed on May 12, 2017 ( PDF ).
4. ↑ ^{a b} data sheet DL-Xylose at Sigma-Aldrich , accessed on October 16, 2016 ( PDF ).
5. ↑ Hans-Dieter Belitz, Werner Grosch and Peter Schieberle : Textbook of food chemistry . Springer, Berlin; 6th, completely revised edition 2008; ISBN 978-3-540-73201-3 ; P. 263.
6. ↑ Hans-Dieter Belitz , Werner Grosch and Peter Schieberle: Textbook of food chemistry . Springer, Berlin; 6th, completely revised edition 2008; ISBN 978-3-540-73201-3 ; P. 269.