View source for Glyceraldehyde

{{Chembox
| Verifiedfields = changed
| Watchedfields  = changed
| verifiedrevid  = 477396994
| Name           = Glyceraldehyde
| ImageFile      = Glyceraldehyde v2.svg
| ImageSize      = 150px
| ImageName      = Glyceraldehyde
| ImageClass     = skin-invert
| ImageFile1     = D-Glyceraldehyde 2D Fischer.svg
| ImageSize1     = 100px
| ImageName1     = D-glyceraldehyde
| ImageClass1    = skin-invert
| IUPACName      = Glyceraldehyde<ref>https://iupac.qmul.ac.uk/BlueBook/P10.html#t1002</ref>
| SystematicName = 2,3-Dihydroxypropanal<br>
{{sm|d}}-''glycero''-Triose<ref>https://iupac.qmul.ac.uk/BlueBook/P10.html#t1002</ref>
| OtherNames     = Glyceraldehyde<br />Glyceric aldehyde<br/>Glyceral
| Section1       = {{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo =56-82-6
| CASNo_Comment = (racemic)
| CASNo1_Ref = {{cascite|correct|CAS}}
| CASNo1 = 453-17-8
| CASNo1_Comment = (R)
| CASNo2_Ref = {{cascite|correct|CAS}}
| CASNo2 = 497-09-6
| CASNo2_Comment = (S)
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII =  DI19XSG16H 
| UNII_Comment = (racemic)
| UNII1_Ref = {{fdacite|correct|FDA}}
| UNII1 = 41A680M0WB
| UNII1_Comment = (R)
| UNII2_Ref = {{fdacite|correct|FDA}}
| UNII2 = GI7U82BL5A
| UNII2_Comment = (S)
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL =
| PubChem = 751
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 731
| SMILES = O=CC(O)CO
| InChI = 1/C3H6O3/c4-1-3(6)2-5/h1,3,5-6H,2H2
| InChIKey = MNQZXJOMYWMBOU-UHFFFAOYAU
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C3H6O3/c4-1-3(6)2-5/h1,3,5-6H,2H2
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = MNQZXJOMYWMBOU-UHFFFAOYSA-N
| SMILES2 = OCC(O)C=O
 }}
| Section2       = {{Chembox Properties
| Properties_ref = <ref>''Merck Index'', 11th Edition, '''4376'''</ref>
| C=3 | H=6 | O=3
| Density = 1.455 g/cm<sup>3</sup>
| MeltingPtC = 145
| BoilingPtC = 140 to 150
| BoilingPt_notes = at 0.8 mmHg
 }}
}}

'''Glyceraldehyde''' ('''glyceral''') is a [[triose]] [[monosaccharide]] with [[chemical formula]] [[Carbon|C]]<sub>3</sub>[[Hydrogen|H]]<sub>6</sub>[[Oxygen|O]]<sub>3</sub>. It is the simplest of all common [[aldose]]s. It is a [[sweet]], colorless, [[crystal]]line [[solid]] that is an intermediate compound in [[carbohydrate]] [[metabolism]]. The word comes from combining [[glycerol]] and [[aldehyde]], as glyceraldehyde is glycerol with one [[alcohol group]] oxidized to an aldehyde.<ref name=MOTW/>

== Structure ==
Glyceraldehyde has one [[chirality (chemistry)|chiral]] center and therefore exists as two different [[enantiomer]]s with opposite optical rotation:

* In the [[Absolute configuration#By relative configuration: D- and L-|{{smallcaps all|D/L}} nomenclature]], either {{smallcaps all|D}} from Latin ''Dexter'' meaning "right", or {{smallcaps all|L}} from Latin ''Laevo'' meaning "left"
* In the [[Absolute configuration#By absolute configuration: R- and S-|R/S nomenclature]], either R from Latin ''Rectus'' meaning "right", or S from Latin ''Sinister'' meaning "left"

{| class="wikitable" style="margin: 1em auto 1em auto"
|-
| align = "center"|
| align="center"| '''{{smallcaps all|D}}-glyceraldehyde'''<br />(''R'')-glyceraldehyde<br />(+)-glyceraldehyde
| align="center"| '''{{smallcaps all|L}}-glyceraldehyde'''<br />(''S'')-glyceraldehyde<br />(−)-glyceraldehyde
|-
| align = "center"| '''[[Fischer projection]]'''
| align = "center"| [[Image:D-Glyceraldehyde 2D Fischer.svg|87px|class=skin-invert-image|D-glyceraldehyde]]
| align = "center"| [[Image:L-Glyceraldehyde 2D Fischer.svg|100px|class=skin-invert-image|L-glyceraldehyde]]
|-
| align = "center"| '''[[Skeletal formula]]'''
| align = "center"| [[Image:D-glyceraldehyde-2D-skeletal.svg|150px|class=skin-invert-image|D-glyceraldehyde]]
| align = "center"| [[Image:L-glyceraldehyde-2D-skeletal.svg|150px|class=skin-invert-image|L-glyceraldehyde]]
|-
|}

While the [[optical rotation]] of glyceraldehyde is (+) for ''R'' and (−) for ''S'', this is not true for all monosaccharides. The stereochemical configuration can only be determined from the chemical structure, whereas the optical rotation can only be determined [[empirically]] (by experiment).

It was by a lucky guess that the molecular {{smallcaps all|D-}} geometry was assigned to (+)-glyceraldehyde in the late 19th century, as confirmed by [[X-ray crystallography]] in 1951.<ref>{{cite journal | doi = 10.1038/168271a0 | title = Determination of the Absolute Configuration of Optically Active Compounds by Means of X-Rays | date = 1951 | last1 = Bijvoet | first1 = J. M. | last2 = Peerdeman | first2 = A. F. | last3 = Van Bommel | first3 = A. J. | journal = Nature | volume = 168 | issue = 4268 | pages = 271–272 | bibcode = 1951Natur.168..271B }}</ref>

===Aqueous and concentrated solutions of glyceraldehyde===
The description above focuses on classification of isomers, but the glyceraldehyde is subject to a further complications: the tendency of hydroxy-aldehydes to exist as hydrates.  [[NMR spectroscopy|NMR measurements]] indicate that in aqueous solution, glyceraldehyde exists in a hydrate owing to this reaction:
:{{chem2|HOCH2CH(OH)CHO + H2O  <->  HOCH2CH(OH)CH(OH)2}}
The same study indicates that concentrated ("syrupy") forms of glyceraldehyde exist as dimers, indicating [[hemiacetal]] formation.<ref>{{cite journal |doi=10.1071/CH9801001 |title=The Composition of Reducing Sugars in Aqueous Solution : Glyceraldehyde, Erythrose, Threose |date=1980 |last1=Angyal |first1=SJ |last2=Wheen |first2=RG |journal=Australian Journal of Chemistry |volume=33 |issue=5 |page=1001 }}</ref>

== Nomenclature ==
In the [[Absolute configuration#By relative configuration: D- and L-|{{smallcaps all|D/L}} system]], glyceraldehyde is used as the configurational standard for carbohydrates.<ref>{{Cite web|date=2015-03-19|title=22.03: The D and L Notation|url=https://chem.libretexts.org/Courses/Purdue/Purdue%3A_Chem_26200%3A_Organic_Chemistry_II_(Wenthold)/Chapter_22._Carbohydrates/22.03%3A_The_D_and_L_Notation|access-date=2022-01-09|website=Chemistry LibreTexts|language=en}}</ref> Monosaccharides with an absolute configuration identical to (''R'')-glyceraldehyde at the ''last'' stereocentre, for example C5 in [[glucose]], are assigned the stereo-descriptor {{smallcaps all|'''D-'''}}. Those similar to (''S'')-glyceraldehyde are assigned an {{smallcaps all|'''L-'''}}. <!---Both {{smallcaps all|D}} and {{smallcaps all|L}}, should be [[Smallcaps all|small capital letters]].--->

==Synthesis and reactions==
Glyceraldehyde can be prepared from acetals of [[acrolein]] (CH<sub>2</sub>=CHCHO) in two steps, oxidation<ref>{{cite journal |doi=10.15227/orgsyn.011.0052 |title=dl-Glyceraldehyde Ethyl Acetal |journal=Organic Syntheses |date=1931 |volume=11 |page=52|first1=E. J. |last1=Witzemann|first2=Wm. |last2=Llloyd Evans|first3=Henry|last3=Hass|first4=E. F.|last4=Schroeder
 }}</ref> followed by hydrolysis of the acetal.<ref>{{cite journal |doi=10.15227/orgsyn.011.0050 |title=dl-Glyceraldehyde |journal=Organic Syntheses |date=1931 |volume=11 |page=50|first1=E. J. |last1=Witzemann|first2=Wm. |last2=Llloyd Evans|first3=Henry|last3=Hass|first4=E. F. |last4=Schroeder
 }}</ref> Its cyclohexylidene acetal can also be produced by oxidative cleavage of the bis(acetal) of [[mannitol]].<ref>{{cite journal |doi=10.15227/orgsyn.099.0363|title=Preparation of 1,2:5,6-Di-O-cyclohexylidene-D-mannitol and 2,3-Cyclohexylidene-D-glyceraldehyde |year=2022 |last1=Dhatrak |first1=N. R. |last2= Jagtap |first2=T. N.|last3= Shinde|first3=A. B. |journal=Organic Syntheses |volume=99 |pages=363–380 |s2cid=254320929 |doi-access=free }}</ref> Glyceraldehyde can also be synthesized through the partial oxidation of Glycerol, for example with a fenton type reagent.<ref>{{Cite journal |last=Zoltán |first=Köntös |date=2024-01-24 |title=Fenton oxidation of glycerin: A sustainable approach for byproduct treatment |url=https://journals.sagepub.com/doi/full/10.1177/17475198231226386 |journal=Journal of Chemical Research |language=EN |doi=10.1177/17475198231226386|doi-access=free }}</ref> 

Glyceraldehyde is a precursor to four-carbon sugars ([[tetrose]]s) via [[cyanation]] followed by hydrolysis of the cyanohydrin:<ref name=MOTW>{{cite web |title=Molecule of the Week: D-Glyceraldehyde |url=https://www.acs.org/molecule-of-the-week/archive/g/d-glyceraldehyde.html|publisher=C&E News|year = 2023}}</ref>
:{{chem2|HOCH2CH(OH)CH(OH)CN + 2 H2O -> HOCH2CH(OH)CH(OH)CO2H  +  NH3}}
:{{chem2|HOCH2CH(OH)CH(OH)CO2H + 2 H2 -> HOCH2CH(OH)CH(OH)CH2OH  +  H2O}}

== Biochemistry ==
The enzyme [[glycerol dehydrogenase (NADP+)|glycerol dehydrogenase (NADP<sup>+</sup>)]] has two substrates, [[glycerol]] and [[Nicotinamide adenine dinucleotide phosphate|NADP<sup>+</sup>]], and 3 products, D-glyceraldehyde, [[Nicotinamide adenine dinucleotide phosphate|NADPH]] and [[Hydron (chemistry)|H+]].<ref>{{Cite journal|last1=Kormann|first1=Alfred W.|last2=Hurst|first2=Robert O.|last3=Flynn|first3=T.G.|title=Purification and properties of an NADP+-dependent glycerol dehydrogenase from rabbit skeletal muscle|url=https://linkinghub.elsevier.com/retrieve/pii/0005274472909655|journal=Biochimica et Biophysica Acta (BBA) - Enzymology|year=1972|language=en|volume=258|issue=1|pages=40–55|doi=10.1016/0005-2744(72)90965-5|pmid=4400494}}</ref>

The interconversion of the phosphates of glyceraldehyde ([[glyceraldehyde 3-phosphate]]) and [[dihydroxyacetone]] ([[dihydroxyacetone phosphate]]), catalyzed by the [[enzyme]] [[triosephosphate isomerase]], is an intermediate step in [[glycolysis]].

== See also ==
* [[Stereoisomerism]]

==References==
{{Reflist}}

{{Carbohydrates}}
{{Fructose and galactose metabolic intermediates}}
{{Authority control}}

[[Category:Vicinal diols]]
[[Category:Trioses]]