Acetoxy group explained

In organic chemistry, the acetoxy group (abbr. AcO or OAc; IUPAC name: acetyloxy^[1]), is a functional group with the formula and the structure . As the -oxy suffix implies, it differs from the acetyl group by the presence of an additional oxygen atom. The name acetoxy is the short form of acetyl-oxy.

Functionality

An acetoxy group may be used as a protection for an alcohol functionality in a synthetic route although the protecting group itself is called an acetyl group.

Alcohol protection

There are several options of introducing an acetoxy functionality in a molecule from an alcohol (in effect protecting the alcohol by acetylation):

• Acetyl halide, such as acetyl chloride in the presence of a base like triethylamine^[2]
• Activated ester form of acetic acid, such as a N-hydroxysuccinimide ester, although this is not advisable due to higher costs and difficulties.^[3]
• Acetic anhydride in the presence of base with a catalyst such as pyridine with a bit of DMAP added.^[4]

An alcohol is not a particularly strong nucleophile and, when present, more powerful nucleophiles like amines will react with the above-mentioned reagents in preference to the alcohol.^[5]

Alcohol deprotection

For deprotection (regeneration of the alcohol)

• Aqueous base (pH >9)^[6]
• Aqueous acid (pH <2), may have to be heated^[7]
• Anhydrous base such as sodium methoxide in methanol. Very useful when a methyl ester of a carboxylic acid is also present in the molecule, as it will not hydrolyze it like an aqueous base would. (Same also holds with an ethoxide in ethanol with ethyl esters)^[8]

See also

• Acetyl group
• Acetylation

Notes and References

1. Book: Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book) . . 2014 . Cambridge . 805 . 10.1039/9781849733069-00648 . 978-0-85404-182-4 . The systematic name ‘acetyloxy’ is preferred to the contracted name ‘acetoxy’ that may be used in general nomenclature..
2. Book: Ouellette, Robert J. . Organic Chemistry . Rawn . J. David . 2019 . 978-0-12-812838-1 . 2nd . 665-710 . 22 - Carboxylic Acid Derivatives . 10.1016/C2016-0-04004-4 . 2024-05-08 . https://www.sciencedirect.com/science/article/abs/pii/B9780128128381500220 . limited.
3. Book: Cali, Khasim . Odorant Binding and Chemosensory Proteins . Tuccori . Elena . Persaud . Krishna C. . 2020-08-19 . 2020 . Pelosi . Paolo . Methods in Enzymology . 642 . 435-468 . en . Chapter Eighteen - Gravimetric biosensors . 10.1016/bs.mie.2020.05.010 . 0076-6879 . 2024-05-08 . Knoll . Wolfgang . https://www.sciencedirect.com/science/article/abs/pii/S0076687920302329.
4. Book: Glycoscience Protocols (GlycoPODv2) . 2021 . Japan Consortium for Glycobiology and Glycotechnology . Nishihara . Shoko . Saitama (JP) . 37590565 . Angata . Kiyohiko . Aoki-Kinoshita . Kiyoko F. . Hirabayashi . Jun.
5. Wall . Leo A. . Pummer . Walter J. . Fearn . James E. . Antonucci . Joseph M. . 1963-09-01 . Reactions of polyfluorobenzenes with nucleophilic reagents . . en . 67A . 5 . 481 . 10.6028/jres.067A.050 . 0022-4332 . 5319811 . 31580596.
6. Book: Matyjaszewski, Krzysztof . Polymer Science: A Comprehensive Reference . Möller . Martin . . 2012 . 978-0-08-087862-1 . 8 . 37-76 . en . 8.03 - Photoresists and Advanced Patterning . 10.1016/B978-0-444-53349-4.00201-6 . https://www.sciencedirect.com/science/article/abs/pii/B9780444533494002016.
7. Howard . Kyle T. . Chisholm . John D. . 2016-01-02 . Preparation and Applications of 4-Methoxybenzyl Esters in Organic Synthesis . . en . 48 . 1 . 1–36 . 10.1080/00304948.2016.1127096 . 0030-4948 . 4989276 . 27546912.
8. Banyikwa . Andrew Toyi . Miller . Stephen E. . Krebs . Richard A. . Xiao . Yuewu . Carney . Jeffrey M. . Braiman . Mark S. . 2017-10-31 . Anhydrous Monoalkylguanidines in Aprotic and Nonpolar Solvents: Models for Deprotonated Arginine Side Chains in Membrane Environments . . en . 2 . 10 . 7239–7252 . 10.1021/acsomega.7b00281 . 2470-1343 . 6645140 . 31457300.