Glyceraldehyde

Structural formula
Fischer projection , open-chain representation
General
Surname	Glyceraldehyde
other names	Glyceraldehyde Glyceronaldehyde 2,3-dihydroxypropanal Glyceral
Molecular formula	C 3 H 6 O 3
Brief description	colorless powder
External identifiers / databases
CAS number 367-47-5 56-82-6 [ DL - (±) -Glyceraldehyde] 453-17-8 [ D - (+) - glyceraldehyde] EC number 200-290-0 ECHA InfoCard 100,000,264 PubChem 751 ChemSpider 731 DrugBank DB02536 Wikidata Q423211
properties
Molar mass	90.08 g mol −1
Physical state	firmly
density	1.46 g cm −3 ( D , L shape)
Melting point	145 ° C
boiling point	140–150 ° C (1.1 hPa )
solubility	30 g l −1 (in water at 18 ° C) good in ethanol , bad in diethyl ether
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 .

Glyceraldehyde is a sweet-tasting chemical compound that forms a crystalline solid when anhydrous. It belongs to the group of sugars and within this to the subgroup of trios . Since it contains a center of chirality, there are two enantiomers . If “glyceraldehyde” is mentioned in this text or in the scientific literature without any additional name ( prefix ), it is usually D -glyceraldehyde. In terms of its molecular structure, it is the simplest conceivable simple sugar . The physiological importance of the compound is great, as it is a basic metabolic substance from which the cell is able to produce many other substances. With C ₃ H ₆ O _3, glyceraldehyde has the same empirical formula as the structurally isomeric dihydroxyacetone .

Special historical significance in stereochemistry

Glyceraldehyde plays a special role in the history of science , since an agreement that concerned this compound could also specify the configuration (i.e. the spatial arrangement of the substituents) of other chiral molecules.

Without knowing the actual spatial arrangement of the hydroxyl groups on the glyceraldehyde, the following was agreed: the glyceraldehyde enantiomer that rotates linearly polarized light to the right was assigned the configuration D ( D stands for dexter , Latin for right ). Accordingly, it was assumed that the hydroxyl group at the chiral center points to the right in the Fischer projection. ( For details: see Fischer projection ) . The glyceraldehyde enantiomer, which rotates linearly polarized light to the left, was arbitrarily assigned the L configuration . One could have chosen the assignment the other way around, because the absolute configuration and the direction of rotation can just as easily differ from one another (example: L -lactic acid rotates linearly polarized light to the right.)

With this agreement, the configuration of other chiral molecules could be specified: the compound to be tested (e.g. lactic acid) was converted into glyceraldehyde by chemical reactions without changing the configuration at the center of chirality. If the resulting compound turned linearly polarized light to the left, it was known that by convention it was L- glyceraldehyde. From this it could be concluded that the starting compound also had the L configuration, since the chemical reactions were carried out with retention of the configuration (e.g. L -lactic acid).

Only after the introduction of the X-ray structure analysis could the actual configuration be verified experimentally. It was found that the assignment (levorotatory glyceraldehyde → L configuration, dextrorotatory glyceraldehyde → D configuration) was chosen coincidentally in accordance with the Fischer projection.

properties

Structural formula of glyceraldehyde-3-phosphate (deprotonated)

Glyceraldehyde and a derivative - glyceraldehyde-3-phosphate - are widespread; they are key substances in cell metabolism .

Molecular structure and optical properties

Glyceraldehyde is an optically active compound with a center of chirality on the middle carbon atom. Depending on the spatial arrangement of the substituents at this center of chirality, there are two compounds, the molecules of which behave like an image and a mirror image. As is usual with sugars, the two enantiomers are usually referred to as D- glyceraldehyde and L -glyceraldehyde , in accordance with the Fischer projection . The Cahn-Ingold-Prelog convention gives ( R ) -glyceraldehyde for D-glyceraldehyde or ( S ) -glyceraldehyde for L-glyceraldehyde. L -glyceraldehyde turns linearly polarized light to the left, while D -glyceraldehyde turns to the right.

Structural formulas of glyceraldehyde

	L -glyceraldehyde ( S ) -glyceraldehyde	D -Glyceraldehyde ( R ) -glyceraldehyde
Fischer projection
Wedge formula

Chemical properties

The aldehyde group (-CHO)  can be oxidized to the carboxy group (-COOH) by suitable oxidizing agents . The compound changes into glyceric acid .

Glyceraldehyde isomerized with base catalysis in the Lobry-de-Bruyn-Alberda-van-Ekenstein rearrangement both to dihydroxyacetone and from the D form to the L form. There is therefore an equilibrium reaction between D - and L -glyceraldehyde and the non-chiral dihydroxyacetone. In the following figure, the residue - R stands for the group –CH ₂ –OH:

Accordingly, glyceraldehyde-3-phosphate is also in equilibrium with dihydroxyacetone phosphate. The establishment of equilibrium in the cell is catalyzed by certain enzymes.

Manufacturing

Glyceraldehyde can most easily be produced by catalytic umpolung of formaldehyde.

In the laboratory, like its isomer dihydroxyacetone , it can be prepared by oxidizing glycerol with hydrogen peroxide and an iron salt as a catalyst. Dihydroxyacetone and glyceraldehyde can be separated due to their different solubilities in water.

proof

The aldehyde group of glyceraldehyde can be detected using the Fehling's test , the Tollens test or the Schiff's test .

Individual evidence

1. ↑ ^{a b c} Entry on glyceraldehyde. In: Römpp Online . Georg Thieme Verlag, accessed on June 1, 2014.
2. ↑ ^{a b c} The Merck Index . An Encyclopaedia of Chemicals, Drugs and Biologicals . 14th edition, 2006, ISBN 978-0-911910-00-1 , p. 774.
3. ↑ Data sheet DL-Glyceraldehyde, ≥90% (GC) from Sigma-Aldrich , accessed on February 15, 2013 ( PDF ).
4. ↑ Axel Schunk, CCC, Univ. Erlangen, 09/1999: Cross- linked chemistry: R, S nomenclature. Retrieved January 28, 2018 . 
5. ↑ Patent DE4212264A1 : Process for the catalytic production of condensation products of formaldehyde. Released on 1992 . ‌

Web links

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