3-Hydroxybutanal

In organic chemistry, 3-hydroxybutanal (acetaldol, aldol) is an organic compound with the formula CH₃CH(OH)CH₂CHO and the structure H₃C−CH(OH)−CH₂−CH=O. It is classified as an aldol (R−CH(OH)−CHR'−C(=O)−R") and the word "aldol" can refer specifically to 3-hydroxybutanal. It is formally the product of the dimerization of acetaldehyde (CH₃CHO). A thick colorless or pale-yellow liquid, it is a versatile and valuable intermediate with diverse impacts.^[2] The compound is chiral although this aspect is not often exploited.

3-Hydroxybutanal

Skeletal formula of 3-hydroxybutanal
Names
Preferred IUPAC name 3-Hydroxybutanal[1]
Other names Acetaldol 3-Hydroxybutyraldehyde beta-Hydroxybutyraldehyde β-Hydroxybutyraldehyde
Identifiers
CAS Number	107-89-1 (R/S) Y 117706-97-5 (R) Y 117706-98-6 (S) Y
3D model (JSmol)	Interactive image
ChemSpider	7609 (R/S) Y 18915429 (R) Y
ECHA InfoCard	100.003.210
EC Number	203-530-2
MeSH	3-hydroxybutanal
PubChem CID	7897 (R/S) 13061653 (R)
UNII	8C6G962B53 N
CompTox Dashboard (EPA)	DTXSID2050407
InChI InChI=1S/C4H8O2/c1-4(6)2-3-5/h3-4,6H,2H2,1H3 Y Key: HSJKGGMUJITCBW-UHFFFAOYSA-N Y InChI=1/C4H8O2/c1-4(6)2-3-5/h3-4,6H,2H2,1H3 Key: HSJKGGMUJITCBW-UHFFFAOYAI
SMILES CC(O)CC=O
Properties
Chemical formula	C4H8O2
Molar mass	88.106 g·mol−1
Appearance	colorless liquid
Density	0.98 g/mL
Boiling point	162 °C (324 °F; 435 K)
Related compounds
Related aldehydes	Glycolaldehyde Lactaldehyde
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Production

Acetaldehyde dimerizes upon treatment with aqueous sodium hydroxide:^[2]

2 CH₃CHO → CH₃CH(OH)CH₂CHO + H₂O

This is the prototypical aldol reaction.

Reactions and uses

Dehydration of 3-hydroxybutanal gives crotonaldehyde. Distillation of 3-hydroxybutanal is sufficiently forcing to effect this conversion:^[2]

CH₃CH(OH)CH₂CHO → CH₃CH=CHCHO + H₂O

Hydrogenation of 3-hydroxybutanal gives 1,3-butanediol:

CH₃CH(OH)CH₂CHO + H₂ → CH₃CH(OH)CH₂CH₂OH

This diol is a precursor to 1,3-butadiene, precursor to diverse polymers.

Polymerization of 3-hydroxybutanal is also spontaneous, but can be stopped with the addition of water.

Aldol has been used in making perfumes and in ore flotation.^[3]

Former or niche uses

It was formerly used in medicine as a hypnotic and sedative.^[4]

See also

• 4-Hydroxybutanal