Abstract
The title compound, C20H22O3, was formed in the reaction between 2,4,6-tri-methyl-benzoic acid and N,N-diiso-propyl-ethyl-amine in the presence of 1,3-di-chloro-1,3-bis-(di-methyl-amino)-propenium hydrogen dichloride, and was recrystallized from diethyl ether solution. It is the first exclusively alkyl-substituted benzoic anhydride to have been structurally characterized. The asymmetric unit consists of a half mol-ecule, the other half of which is generated by twofold rotation symmetry; the dihedral angle between the symmetry-related aromatic rings is 54.97 (3)°. The geometric parameters of the aromatic ring are typical of those for 2,4,6-tri-methyl-phenyl substituted groups. The C=O and C-O bond lengths are 1.1934 (12) and 1.3958 (11) Å, respectively, and the angle between these three atoms (O=C-O) is 121.24 (9)°. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds and C-H⋯π inter-actions. The packing features wavy chains that extend parallel to [001].
Highlights
The title compound, C20H22O3, was formed in the reaction between 2,4,6trimethylbenzoic acid and N,N-diisopropylethylamine in the presence of 1,3dichloro-1,3-bis(dimethylamino)propenium hydrogen dichloride, and was recrystallized from diethyl ether solution
The asymmetric unit consists of a half molecule, the other half of which is generated by twofold rotation symmetry; the dihedral angle between the symmetry-related aromatic rings is 54.97 (3)
Benzoic anhydrides have traditionally been used in synthetic organic chemistry for the preparation of aromatic esters, amides and carboxylic acids
Summary
Benzoic anhydrides have traditionally been used in synthetic organic chemistry for the preparation of aromatic esters, amides and carboxylic acids. The synthesis of the compound we report here, 2,4,6-trimethylbenzoic anhydride (common name: mesitoic anhydride), was first published in 1941, where it was formed in the reaction between (2,4,6-trimethylphenyl)sodium and 2,4,6-trimethylbenzoic acid in the presence of pyridine (Fuson et al, 1941). Several new approaches for the syntheses of symmetric acid anhydrides, including the title compound, have been reported The most recent report involves the in situ generation of a Vilsmeier–Haack reagent for the coupling of symmetric carboxylic acids (McCallum & Barriault, 2015).
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