Chapman rearrangement

Written by J.A Dobado | Last Updated on September 15, 2025

Whis is Chapman rearrangement?

Mumm et al. reported the occurrence of a reaction in 1915, which was subsequently studied extensively by Chapman in the 1920s and 1930s. This reaction involves the thermal rearrangement of aryl imidates into N,N-diaryl amides and is commonly known as the Chapman rearrangement. It is occasionally referred to as the Beckmann-Chapman rearrangement as well.

The Chapman rearrangement follows approximately first-order kinetics and exhibits high yields when carried out in either polar or nonpolar solvents. However, the presence of polar solvents accelerates the reaction. Interestingly, the Chapman rearrangement can even take place in a solid state at a slower rate compared to its solution counterpart.

The Chapman rearrangement is classified as an intramolecular nucleophilic aromatic substitution, where the migration of the aryl ring attached to oxygen occurs in a stereospecific manner. The presence of ortho substituents on the aryl ring connected to the oxygen atom enhances the migration rate due to steric acceleration resulting from hindered rotation (SAHR) effect. This effect arises because free rotation restricts the formation of a four-membered ring in the transition state.

Moreover, it has been observed that the migration rate is increased by a para electron-donating group, while a para electron-withdrawing group (such as Cl or NO₂) decreases the reaction rate. The Chapman rearrangement has been utilized for the synthesis of substituted N-phenylanthranilic acids.

Notably, if the migrating aryl moiety possesses an α-acidic hydrogen at the ortho position, an “abnormal” Chapman rearrangement takes place.

References

• Mumm, O., Hesse, H. and Volquartz, H. (1915), Zur Kenntnis der Diacylamide. [To the knowledge of the diacylamides.] Ber. Dtsch. Chem. Ges., 48: 379-391. https://doi.org/10.1002/cber.19150480154
• CCLXIX.—Imino-aryl ethers. Part III. The molecular rearrangement of N-phenylbenziminophenyl ether
  A. W. Chapman, J. Chem. Soc., Trans., 1925, 127, 1992-1998
  DOI: 10.1039/CT9252701992
• Chapman, A. W. (1927). CCXXVII.—Imino-aryl ethers. Part V. The effect of substitution on the velocity of molecular rearrangement. Journal of the Chemical Society, 1743-1751. doi: 10.1039/JR9270001743
• LXXXIII.—A new method for preparing substituted diphenylamines
  A. W. Chapman, J. Chem. Soc., 1929, 569-572
  DOI: 10.1039/JR9290000569
• .Chapman, A. W., and Perrott, C. H. (1930). CCCXXIII.—Dynamic isomerism involving mobile hydrocarbon radicals. Part III. Some effects of substitution on the velocity of interchange and position of equilibrium of isomeric triarylbenzenylamidines. Journal of the Chemical Society, 2462-2468. doi: 10.1039/JR9300002462
• Chapman, A. W., and Howis, C. C. (1933). 197. Studies of the Beckmann change. Part I. The spontaneous rearrangement of oxime picryl ethers. Journal of the Chemical Society, 806-811. doi: 10.1039/JR9330000806
• Chapman, A. W. (1934). 337. Studies of the Beckmann change. Part II. The kinetics of the spontaneous rearrangement and solvent effects. Journal of the Chemical Society, 1550-1555. doi: 10.1039/JR9340001550
• Chapman, A. W., and Fidler, F. A. (1936). 108. Studies of the Beckmann change. Part IV. Some effects of substitution on the rate of rearrangement of ketoxime picryl ethers. A suggested mechanism of the transformation. Journal of the Chemical Society, 0, 448-453. doi: 10.1039/JR9360000448