Pivalic acid is a
carboxylic acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...
with a molecular formula of (CH
3)
3CCO
2H. This colourless, odiferous
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...
is solid at room temperature. A common abbreviation for the pivalyl or pivaloyl group (''t''-BuC(O)) is Piv and for pivalic acid (''t''-BuC(O)OH) is PivOH.
Preparation
Industrial route
Pivalic acid is prepared by
hydrocarboxylation
Carbonylation refers to reactions that introduce carbon monoxide into organic and inorganic substrates. Carbon monoxide is abundantly available and conveniently reactive, so it is widely used as a reactant in industrial chemistry. The term carbon ...
of
isobutene
Isobutylene (or 2-methylpropene) is a hydrocarbon with the chemical formula . It is a four-carbon branched alkene (olefin), one of the four isomers of butylene. It is a colorless flammable gas, and is of considerable industrial value.
Productio ...
via the
Koch reaction:
:(CH
3)
2C=CH
2 + CO + H
2O → (CH
3)
3CCO
2H
Such reactions require an acid
catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
such as
hydrogen fluoride
Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock i ...
.
''tert''-Butyl alcohol and
isobutyl alcohol
Isobutanol (IUPAC nomenclature: 2-methylpropan-1-ol) is an organic compound with the formula (CH3)2CHCH2OH (sometimes represented as ''i''-BuOH). This colorless, flammable liquid with a characteristic smell is mainly used as a solvent either dire ...
can also be used in place of isobutene. Globally, several million kilograms are produced annually. Pivalic acid is also economically recovered as a byproduct from the production of semisynthetic penicillins like ampicillin and amoxycillin.
Laboratory methods
It was originally prepared by the oxidation of
pinacolone
Pinacolone (3,3-dimethyl-2-butanone) is an important ketone in organic chemistry. It is a colorless liquid and has a slight peppermint- or camphor- odor. It is a precursor to triazolylpinacolone in the synthesis of the fungicide triadimefon and ...
with
chromic acid
The term chromic acid is usually used for a mixture made by adding concentrated sulfuric acid to a dichromate, which may contain a variety of compounds, including solid chromium trioxide. This kind of chromic acid may be used as a cleaning mixtu ...
and by the hydrolysis of
''tert''-butyl cyanide. Convenient laboratory routes proceed via
''tert''-butyl chloride via carbonation of the
Grignard reagent
A Grignard reagent or Grignard compound is a chemical compound with the general formula , where X is a halogen and R is an organic group, normally an alkyl or aryl. Two typical examples are methylmagnesium chloride and phenylmagnesium bromide ...
and by oxidation of pinacolone.
:
Applications
Relative to esters of most carboxylic acids,
ester
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...
s of pivalic acid are unusually resistant to hydrolysis. Some applications result from this thermal stability. Polymers derived from pivalate esters of
vinyl alcohol
Vinyl alcohol, also called ethenol (IUPAC name; not ethanol), is the simplest enol. With the formula , it is a labile compound that converts to acetaldehyde. It is not a precursor to polyvinyl alcohol.
Synthesis
Vinyl alcohol can be formed by th ...
are highly reflective lacquers. The pivaloyl (abbreviated Piv or Pv) group is a
protective group
A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis.
In many ...
for
alcohol
Alcohol most commonly refers to:
* Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom
* Alcohol (drug), an intoxicant found in alcoholic drinks
Alcohol may also refer to:
Chemicals
* Ethanol, one of sev ...
s in
organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...
. Pivalic acid is sometimes used as an internal chemical shift standard for
NMR
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with ...
spectra 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. The
1H NMR spectrum at 25 °C and neutral pH is a singlet at 1.08 ppm. Pivalic acid is employed as co-catalyst in some of the Palladium catalyzed C-H functionalization reaction.
Alcohol protection
The pivaloyl group is used as a
protecting group
A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis.
In many ...
in
organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...
. Common protection methods include treatment of alcohol with pivaloyl chloride (PvCl) in presence of
pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a d ...
.
Alternatively, the esters can be prepared using pivaloic anhydride in the presence of
scandium triflate
Scandium trifluoromethanesulfonate, commonly called scandium triflate, is a chemical compound with formula Sc(SO3CF3)3, a salt consisting of scandium cations Sc3+ and triflate anions.
Scandium triflate is used as a reagent in organic chemistr ...
(Sc(OTf)
3) or
vanadyl triflate
The vanadyl or oxovanadium(IV) cation, VO2+, is a functional group that is common in the coordination chemistry of vanadium. Complexes containing this functional group are characteristically blue and paramagnetic. A triple bond is proposed to ...
(VO(OTf)
2).
Common deprotection methods involve hydrolysis with a base or other nucleophiles.
See also
*
Methyl pivalate
Methyl pivalate is an organic compound with the formula CH3O2CC(CH3)3. It is a colorless liquid, the methyl ester of pivalic acid
Pivalic acid is a carboxylic acid with a molecular formula of (CH3)3CCO2H. This colourless, odiferous organic compo ...
References
{{Reflist
Alkanoic acids
Tert-butyl compounds