Pivalic acid

Pivalic acid
IUPAC name Dimethylpropanoic acid
Other names Neopentanoic acid, trimethylacetic acid
Identifiers
CAS number	75-98-9 Y
PubChem	6417
ChemSpider	6177 Y
ChEBI	CHEBI:45133 Y
ChEMBL	CHEMBL322719 Y
Jmol-3D images	Image 1
SMILES O=C(O)C(C)(C)C
InChI InChI=1S/C5H10O2/c1-5(2,3)4(6)7/h1-3H3,(H,6,7) Y Key: IUGYQRQAERSCNH-UHFFFAOYSA-N Y
Properties
Molecular formula	C5H10O2
Molar mass	102.132 g/mol
Density	0.905 g/cm3
Melting point	35 °C
Boiling point	163.7 °C
Related compounds
Related compounds	neopentyl alcohol neopentane
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Pivalic acid is a carboxylic acid with a molecular formula of (CH₃)₃CCO₂H. This colourless, odiferous organic compound is solid at room temperature.

Preparation

Industrial route

Pivalic acid is prepared by “hydrocarboxylation” of isobutene via the Koch reaction:

(CH₃)₂C=CH₂ + CO + H₂O → (CH₃)₃CCO₂H

Such reactions require an acid catalyst such as hydrogen fluoride. tert-Butyl alcohol and isobutyl alcohol can also be used in place of isobutene. Globally, several million kilograms are produced annually.^[1]

Laboratory methods

It was originally prepared by the oxidation of pinacolone with chromic acid^[2] and by the hydrolysis of tert-butyl cyanide.^[3] Convenient laboratory routes proceed via t-butyl chloride via carbonation of the Grignard reagent^[4] and by oxidation of pinacalone.^[5]

Applications

Relative to esters of most carboxylic acids, esters of pivalic acid are unusually resistant to hydrolysis. Some applications result from this thermal stability. Polymers derived from pivalate esters of vinyl alcohol are highly reflective lacquers. The pivaloyl (abbreviated piv or pv) group is a protective group for alcohols in organic synthesis.

Safety

Like most carboxylic acids pivalic acid is a mild irritant and only weakly toxic (oral LD₅₀ = 900 mg/kg for rats).

References

1. ^ Wilhelm Riemenschneider “Carboxylic Acids, Aliphatic” Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a05_235.
2. ^ Friedel and Silva, Ber. 6, 146, 826 (1873).
3. ^ Butlerow, Ann. 165, 322 (1873).
4. ^ S. V. Puntambeker, E. A. Zoellner, L. T. Sandborn, and E. W. Bousquet (1941), "Trimethylacetic acid from tert.- Butyl Chloride", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1p0524 ; Coll. Vol. 1: 524 
5. ^ L. T. Sandborn and E. W. Bousquet (1941), "Trimethylacetic acid from Pinacolone", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1p0524 ; Coll. Vol. 1: 524