Tetrolic acid

Tetrolic acid (2-butynoic acid) is a short-chain unsaturated carboxylic acid, described by the formula CH₃−C≡C−CO₂H. Salts and esters of tetrolic acid are known as tetrolates.

Tetrolic acid

Names
Preferred IUPAC name But-2-ynoic acid
Other names 2-Butynoic acid Butynoic acid
Identifiers
CAS Number	590-93-2
3D model (JSmol)	Interactive image
ChemSpider	61810 Y
ECHA InfoCard	100.008.815
PubChem CID	68535
UNII	W3AM9ANZ22 Y
CompTox Dashboard (EPA)	DTXSID4060444
InChI InChI=1S/C4H4O2/c1-2-3-4(5)6/h1H3,(H,5,6) Key: LUEHNHVFDCZTGL-UHFFFAOYSA-N
SMILES CC#CC(=O)O
Properties
Chemical formula	CH3C≡CCO2H
Molar mass	84.074 g·mol−1
Density	0.9641 g/cm3[1]
Melting point	78 °C (172 °F; 351 K)[1]
Boiling point	203 °C (397 °F; 476 K)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

History

The first reported synthesis^[2] of tetrolic acid is believed to be by German chemist Johann Georg Anton Geuther in 1871 as part of his work investigating the derivatives of ethyl acetoacetate.

Production

Tetrolic acid is manufactured^[3] on a commercial scale by treatment of propyne with a strong base (to form an acetylide), followed by carbon dioxide:

Scheme2

Strong bases such as n-BuLi^[4] and NaNH₂^[5] can be used.

Properties

Tetrolic acid is highly soluble in polar solvents (water, ethanol) and can be recrystallized from non-polar solvents (such as heptane, hexane or toluene). The compound is a white crystalline solid which can exist in two polymorphous crystalline forms.^[6]

The proton nuclear magnetic resonance (¹H-NMR) spectrum in deuterated dimethyl sulfoxide shows a characteristic singlet peak at 1.99 ppm corresponding to the –CH₃ protons.

Tetrolic acid sublimes at temperatures above 20°C, and should ideally be stored in a sealed container in a refrigerator.^[7]

Accelerated rate calorimetry (ARC) showed exothermic onset from 135 °C, precluding short-path distillation as a means of purification.^[7]