Neopentanoic acid, trimethylacetic acid
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|Molar mass||102.132 g/mol|
|Melting point||35 °C (95 °F; 308 K)|
|Boiling point||163.7 °C (326.7 °F; 436.8 K)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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- (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. Pivalic acid is also economically recovered as a by-product from the production of semi-synthetic penicillins like ampicillin and amoxycillin.
It was originally prepared by the oxidation of pinacolone with chromic acid and by the hydrolysis of tert-butyl cyanide. Convenient laboratory routes proceed via t-butyl chloride via carbonation of the Grignard reagent and by oxidation of pinacolone.
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.
Pivalic acid is sometimes used as an internal chemical-shift standard for NMR of aqueous solutions. While DSS is more commonly used for this purpose, the minor peaks from protons on the three methylene bridges in DSS can be problematic. On a 1H NMR spectrum at 25°C and neutral pH, pivalic acid gives a singlet at 1.08 ppm.
Like most carboxylic acids pivalic acid is a mild irritant and only weakly toxic (oral LD50 = 900 mg/kg for rats).
- Wilhelm Riemenschneider "Carboxylic Acids, Aliphatic" in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a05_235.
- Friedel and Silva, Ber. 6, 146, 826 (1873).
- Butlerow, Ann. 165, 322 (1873).
- S. V. Puntambeker, E. A. Zoellner, L. T. Sandborn, and E. W. Bousquet (1941). "Trimethylacetic acid from tert.- Butyl Chloride". Org. Synth.; Coll. Vol. 1, p. 524
- L. T. Sandborn and E. W. Bousquet (1941). "Trimethylacetic acid from Pinacolone". Org. Synth.; Coll. Vol. 1, p. 524