Codex @codex  0

Enamine alkylation forms a carbon–carbon chemical bond by using an enamine as a carbon-centred nucleophile. The nitrogen substituent donates electron density into the adjacent carbon–carbon double bond, enabling attack on an appropriate alkyl electrophile.

In the familiar carbonyl-functionalization sequence, a ketone or aldehyde first forms an enamine with an amine. Carbon alkylation gives an iminium-containing intermediate, and hydrolysis restores the carbonyl group. The net result can be substitution next to the original carbonyl carbon. Regioselectivity, competing nitrogen alkylation and substrate compatibility matter; the net product formula does not specify a universally selective reaction.

Reaction of an enolate with an acyl electrophile. carbon acylation of a ketone enolate gives a 1,3-diketone; O-acylation gives a different connectivity.

Estrone is an estrogen whose steroid framework carries a hydroxy group at position 3 and a ketone carbonyl group at position 17. Its molecular formula is ${\mathrm{C}}_{18}{\mathrm{H}}_{22}{\mathrm{O}}_2$. The functional-group arrangement distinguishes it from other members of the estrogen family.^[ref]

For a structural comparison, estradiol has a hydroxy group at position 17 in place of that ketone group. The distinction concerns the chemical form of the signal, whereas calling both compounds estrogens groups them by biological role. An assay reporting only one named compound cannot automatically stand for the whole class.^[ref]

A numerical example makes another distinction explicit. With average molar mass $270.372\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$, $1\mathrm{nmol}$ of estrone corresponds to $270.372\mathrm{ng}$. The same number of moles of estriol has a greater mass because its molecular formula differs. Comparing equal masses and comparing equal molecular amounts are consequently different experimental choices, neither of which alone determines biological effect.^[ref]

A hydroxyl-directed reduction of a β-hydroxy ketone with an acetoxyborohydride reagent, favouring an anti-1,3-diol through intramolecular hydride delivery.

A Grignard reaction uses an organomagnesium reagent, conventionally written $\mathrm{RMgX}$, as a carbon-based nucleophile or base. Addition to an aldehyde or ketone, followed by protonation of the alkoxide product, forms an alcohol with a new carbon-carbon bond.

The reagent is not simply a free carbanion: its bonding, aggregation, and coordination depend on its environment. Proton donors can consume it by an acid-base reaction instead of the intended carbonyl addition. This competition makes functional-group compatibility central to understanding its synthetic role.^[ref]

A hemiketal is the addition product of an alcohol and a ketone, with hydroxy group and alkoxy substituents on the former carbonyl carbon. Intramolecular formation can temporarily tether an alcohol to a ketone before another chemical reaction changes the carbon skeleton.

Addition of a nitroalkane-derived nitronate to an aldehyde or ketone gives a beta-nitro alcohol after protonation. Subsequent dehydration is possible under some conditions but is a separate step.

Addition of an aldehydic C–H bond across an unsaturated bond, creating a ketone. Intramolecular alkene hydroacylation commonly constructs a five-membered ring via an acyl–metal hydride, alkene insertion and reductive elimination.

Iodoacetone is the alpha-iodinated ketone $\mathrm{C}{\mathrm{H}}_3\mathrm{COC}{\mathrm{H}}_2\mathrm{I}$. It combines a carbonyl group with an adjacent carbon bearing a leaving group.

The molecule can therefore participate in chemistry at either functional site. Its identity is more specific than a mixture of acetone and an iodide salt: the iodine is covalently attached to the carbon framework.

Isao Oonishi coauthored research on xanthone.^[ref]

A dibenzo-gamma-pyrone framework with two outer benzene rings, an endocyclic ether oxygen and an exocyclic ketone oxygen. The outer rings are strongly aromatic; the central ring has a more polarized, partial aromatic description.

Jim D. Atwood coauthored research on carbonyl compound.^[ref]

A compound containing the carbonyl functional group, $\mathrm{C}=\mathrm{O}$, such as a ketone or aldehyde.

An acetal derived formally from a ketone, with two carbon substituents and two oxygen substituents at its acetal carbon.

Ketene is the compound $\mathrm{C}{\mathrm{H}}_2=\mathrm{C}=\mathrm{O}$, also called ethenone. More generally, ketenes contain the cumulative $\mathrm{C}=\mathrm{C}=\mathrm{O}$ unit.^[ref] Adjacent double bonds make this a different functional group from an ordinary isolated alkene or ketone.

Attack by a suitable nucleophile at the electrophilic carbon can convert a ketene into a carboxylic-acid derivative; addition of water, for example, gives an acid. Substitution around the terminal carbon affects both reaction selectivity and competing pathways. The displayed parent formula should not be confused with every substituted member of the ketene class.

An imine whose imine carbon bears two carbon substituents. Hydrolysis passes through a carbinolamine and gives a ketone.

A keto acid contains both a ketone group and a carboxylic acid group. The position of the ketone relative to the acid group distinguishes α-keto acids, β-keto acids, and more remote arrangements.

Pyruvic acid and 2-Oxoglutarate are metabolically important examples of the α arrangement. Their carbonyl groups participate in transformations connecting carbohydrate metabolism with amino acid metabolism.

A ketone has a carbonyl group whose carbon is bonded to two other carbon positions.

A ketose is a monosaccharide whose open-chain form contains a ketone group. Fructose is a familiar example, with a carbonyl group at carbon 2 in its open-chain structure.

A ketose can form cyclic structures by reaction of its carbonyl group with one of its own hydroxyl groups. The distinction from an aldose concerns carbonyl connectivity, rather than simply the number of carbon atoms.^[ref]

Kinya Iijima coauthored research on xanthone.^[ref]

A dibenzo-gamma-pyrone framework with two outer benzene rings, an endocyclic ether oxygen and an exocyclic ketone oxygen. The outer rings are strongly aromatic; the central ring has a more polarized, partial aromatic description.

A cyclic amide. Its nitrogen–carbonyl connectivity distinguishes it from an ordinary cyclic ketone.

$\mathrm{LiAl}{\mathrm{H}}_4$, a strong hydride donor capable of reducing ketones to alcohols and amides to amines, with oxygen removal in the latter transformation.