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Pivalic anhydride | CAS 1538-75-6

A sterically hindered acid anhydride used for acyl chemistry and carboxyl activation, including published amidation through mixed anhydrides, where active reagent content and pivalic acid require separate attention.

CAS1538-75-6
Molecular formulaC10H18O3
Molecular weight186.25 g/mol

Product overview

Two pivaloyl groups joined by an anhydride oxygen define pivalic anhydride, also called trimethylacetic anhydride. The tert-butyl groups surrounding its acyl functions make it structurally different from smaller anhydrides such as acetic anhydride. Its role can extend beyond transfer of a pivaloyl group: published work uses it to activate other carboxylic acids for amidation. CAS 1538-75-6 therefore identifies a specific activation reagent, not pivalic acid or pivaloyl chloride. For qualification, the amount of intact anhydride should be established alongside free-acid content. Water and analytical sample preparation matter because anhydride consumption or hydrolysis changes the effective reagent charge used by the process.

Chemical identity

Chemical name
Pivalic anhydride
CAS number
1538-75-6
Molecular formula
C10H18O3
Molecular weight
186.25 g/mol

Application context

Published research describes pivalic anhydride-mediated amidation of carboxylic acids with N-alkyl anilines. The chemistry proceeds through activation associated with pivaloyl mixed anhydrides, allowing the chosen carboxylic acid fragment to form the amide. Pivalic acid is generated in the reported transformation. This distinction matters when defining the reagent: the desired product is not necessarily a pivalamide, and the anhydride serves as an activating partner. For buyers evaluating this application, an assay that differentiates usable anhydride from pre-existing pivalic acid is more informative than a nonspecific total acidity result. The required water and impurity limits should follow the selected reaction and workup.

Chemistry and synthetic role

The symmetric structure is tert-Bu–CO–O–CO–tert-Bu. Cleavage of the anhydride linkage can transfer acyl functionality or support mixed-anhydride formation with another acid.

Quality review

Measure intact anhydride

Agree a method that distinguishes the active anhydride from its parent acid.

Review pivalic acid separately

Pre-existing free acid changes the composition of the reagent charge and should have an agreed limit when relevant.

Control water and sampling

Use an analytical and handling approach suitable for an anhydride; confirm water criteria for the intended process.

Preparing a specification

Specify pivalic anhydride CAS 1538-75-6, anhydride assay, pivalic acid limit and water requirements. State whether the intended role is pivaloylation or activation of another carboxylic acid.

Packaging and storage

Packaging, closure and net weight are agreed for the selected grade, order quantity and destination. Confirm storage and transport requirements against the actual supplier SDS.

Documentation

Request a batch COA, specification, identity data and SDS. Confirm the availability of the analytical methods and any application-specific impurity results with the proposed supplier.

Procurement questions

Is it the same as pivaloyl chloride?

No. One is a symmetric anhydride and the other an acid chloride.

Does it always introduce a pivaloyl group into the target?

No. In mixed-anhydride chemistry it can activate another acid for coupling.

Why distinguish free acid from anhydride?

They represent different reactive compositions and are not equivalent on a reagent-charge basis.

Technical sources
  1. Trimethylacetic anhydride 143502Sigma-Aldrich
  2. Pivalic anhydride identityINERIS
  3. Base-free N-arylamide synthesis via pivaloyl mixed anhydrideOrganic & Biomolecular Chemistry / PubMed