In
organic chemistry, the acetoxy group (abbr. AcO or OAc;
IUPAC name: acetyloxy
), is a
functional group with the
formula
In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...
and the
structure
A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...
. As the ''-oxy'' suffix implies, it differs from the
acetyl group
In organic chemistry, acetyl is a functional group with the chemical formula and the structure . It is sometimes represented by the symbol Ac (not to be confused with the element actinium). In IUPAC nomenclature, acetyl is called ethanoyl, ...
() 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
In organic chemistry, acetyl is a functional group with the chemical formula and the structure . It is sometimes represented by the symbol Ac (not to be confused with the element actinium). In IUPAC nomenclature, acetyl is called ethanoyl, ...
.
Alcohol protection
There are several options of introducing an acetoxy functionality in a molecule from an alcohol (in effect protecting the alcohol by
acetylation
:
In organic chemistry, acetylation is an organic esterification reaction with acetic acid. It introduces an acetyl group into a chemical compound. Such compounds are termed ''acetate esters'' or simply '' acetates''. Deacetylation is the oppo ...
):
* Acetyl halide, such as
acetyl chloride in the presence of a base like
triethylamine
*
Activated ester form of acetic acid, such as a
N-hydroxysuccinimide ester, although this is not advisable due to higher costs and difficulties.
*
Acetic anhydride
Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CH3CO)2O. Commonly abbreviated Ac2O, it is the simplest isolable anhydride of a carboxylic acid and is widely used as a reagent in organic synthesis. It is a col ...
in the presence of base with a catalyst such as
pyridine with a bit of
DMAP added.
An alcohol is not a particularly strong
nucleophile
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...
and, when present, more powerful nucleophiles like
amines will react with the above-mentioned reagents in preference to the alcohol.
Alcohol deprotection
For deprotection (regeneration of the alcohol)
*
Aqueous base (pH >9)
* Aqueous acid (pH <2), may have to be heated
*
Anhydrous
A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achie ...
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)
See also
*
Acetyl group
In organic chemistry, acetyl is a functional group with the chemical formula and the structure . It is sometimes represented by the symbol Ac (not to be confused with the element actinium). In IUPAC nomenclature, acetyl is called ethanoyl, ...
*
Acetylation
:
In organic chemistry, acetylation is an organic esterification reaction with acetic acid. It introduces an acetyl group into a chemical compound. Such compounds are termed ''acetate esters'' or simply '' acetates''. Deacetylation is the oppo ...
References
{{DEFAULTSORT:Acetoxy Group
Functional groups