Acyl group

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Acyl
)
organyl substituent or hydrogen
in the case of R1)

In

phosphonic acids. In the most common arrangement, acyl groups are attached to a larger molecular fragment, in which case the carbon and oxygen atoms are linked by a double bond
.

Compounds

Well-known acyl compounds are the acyl chlorides, such as

formyl
).

Acylium cations, radicals, and anions

Resonance structures of acylium ion

Acylium ions are

Å (110-112 pm), which is shorter than the 112.8 pm of carbon monoxide and indicates triple-bond character.[3][4][5]

The carbon centres of acylium ions generally have a

mass spectra of ketones
.

Acylium ions are common reactive intermediates, for example in the

Friedel–Crafts acylation and many other organic reactions such as the Hayashi rearrangement. Salts containing acylium ions can be generated by removal of the halide from acyl halides
:

RC(O)Cl + SbCl5 → [RCO]+[SbCl6]−

Acyl radicals are readily generated from aldehydes by hydrogen-atom abstraction. However, they undergo rapid decarbonylation to afford the alkyl radical:[6]

RC(H)=O → RC•=O → R• + C≡O

Acyl

carbamoyl anion stable at these temperatures.[7]

In biochemistry

In biochemistry there are many instances of acyl groups, in all major categories of biochemical molecules.

Acyl-CoAs are acyl derivatives formed via fatty acid metabolism. Acetyl-CoA, the most common derivative, serves as an acyl donor in many biosynthetic transformations. Such acyl compounds are thioesters.

Names of acyl groups of

lysyl
.

Names of acyl groups of

ribonucleoside monophosphates such as AMP (5′-adenylic acid), GMP (5′-guanylic acid), CMP (5′-cytidylic acid), and UMP
(5′-uridylic acid) are adenylyl, guanylyl, cytidylyl, and uridylyl respectively.

In phospholipids, the acyl group of phosphatidic acid is called phosphatidyl-.

Finally, many

saccharides
are acylated.

In organometallic chemistry and catalysis

Main article: Transition metal acyl complexes

Acyl

alkyl bonds. Metal acyls also arise from reactions involving acyl chlorides with low-valence metal complexes or by the reaction of organolithium compounds with metal carbonyls. Metal acyls are often described by two resonance structures, one of which emphasizes the basicity of the oxygen center. O-alkylation of metal acyls gives Fischer carbene complexes.[8]

Nomenclature

The common names of acyl groups are derived typically by replacing the -ic acid suffix of the corresponding carboxylic acid's common name with -yl (or -oyl), as shown in the table below.

In the

hydrocarbyl group's systemic name (or the -oic acid suffix of the corresponding carboxylic acid
's systemic name) with -oyl, as shown in the table below.

The acyls are between the hydrocarbyls and the carboxylic acids.

The

aryl groups (benzyl
).

Corresponding
hydrocarbyl
group name
RC– 		Acyl group name
RC(O)– 		Corresponding carboxylic acid name
RC(O)O-H
common systematic common systematic common systematic
methyl
formyl
 methanoyl formic acid methanoic acid
ethyl acetyl ethanoyl acetic acid ethanoic acid
propyl propionyl propanoyl propionic acid propanoic acid
butyl butyryl butanoyl butyric acid butanoic acid
propenyl acrylyl or
acryloyl
 propenoyl acrylic acid propenoic acid
crotyl
 butenyl
crotonyl
 butenoyl crotonic acid butenoic acid
benzyl benzoyl benzoic acid

Acyl species

In acyloxy groups the acyl group is bonded to oxygen: R−C(=O)−O−R′ where R−C(=O) is the acyl group.

Acylium ions are

cations of the type R−C+=O ↔ R−C≡O+ and play an important role as intermediates in organic reactions[1] for example the Hayashi rearrangement
.

See also

References

  1. ^
    doi:10.1351/goldbook.A00123
  2. doi:10.1351/goldbook.A00129
  3. doi:10.1021/ja00771a031
    .
  4. doi:10.1039/B407654K
    .
  5. PMID 33826216
    .
  6. ISBN 978-0-470-46259-1
    .
  7. ISSN 0008-4042
    .
  8. ISBN 3-527-29390-6
    .

External links
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