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Definition
| The carbon atom adjacent to a carbonyl group |
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Term
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Definition
| The hydrogen atom on an α carbon. Also called α proton |
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Definition
| An alkene alcohol that is formed by tautomerism of an aldehyde or ketone, which has the general formula: R2C=C(OH)R' |
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Definition
| An α-hydrogen that is lost and regained through keto-enol tautomerism, thus losing its stereochemistry in the process |
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Definition
| The resonance-stabilized anion formed by deprotonating the α carbon atom adjacent to a carbonyl group, or by deprotonating the hydroxyl group of an enol tautomer |
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Definition
| Constitutional isomers that are easily interconverted; keto and enol tautomers differ in the position of a hydrogen atom and are rapidly interconverted in the presence of an acid or base |
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Definition
| Process by which two isomers are interconverted by the movement of an atom or a group (usually a hydrogen atom); in the presence of an acid or base, keto and enol tautomers are in equilibrium: RCH2COR' → RCH=C(OH)R'. Also called tautomerization |
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Term
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Definition
| Replacement of a hydrogen atom on the α carbon atom of a carbonyl compound by some other group |
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Definition
| Diastereomers that differ in configuration at only one stereogenic center |
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Definition
| Compound formed by replacing three hydrogen atoms in methane, CH4 , with halogen atoms to form CHX3 |
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Definition
| The reaction of a methyl ketone with a halogen and base to produce a carboxylate ion, RCOO‾, and a haloform, CHX3 |
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Definition
| A chemical test for methyl ketones, which react with iodine, I2 , and base (usually aqueous NaOH) to produce a precipitate of iodoform, CHI3 , which is a yellow solid |
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Definition
| A reaction in which a nucleophile adds to a substrate containing a polar multiple bond between carbon and a heteroatom (such as a carbonyl or nitrile group); the nucleophile attacks the δ+ carbon, which initially forms an alkoxide ion intermediate that subsequently attacks an electrophile (such as H+ ). |
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Term
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Definition
| A compound that is both an aldehyde (or ketone) and an alcohol; most aldols are β-hydroxy aldehydes or β-hydroxy ketones |
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Term
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Definition
| An acid- or base-catalyzed nucleophilic addition of the enolate of an aldehyde (or ketone) to the carbonyl carbon atom of an aldehyde (or ketone) to produce an aldol (β-hydroxy aldehyde or β-hydroxy ketone). Also called aldol addition reaction |
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Term
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Definition
| An aldol addition reaction followed by dehydration to produce an α,β-unsaturated aldehyde or α,β-unsaturated ketone, which is catalyzed by an acid, or by a base with heat |
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Definition
| A reaction that joins two molecules, with the loss of water or an alcohol. Also called a dehydration synthesis reaction when water is lost |
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Definition
| A base-catalyzed conversion of an aldol into an aldehyde (and/or ketone); the reverse of an aldol addition reaction |
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Definition
| An alkene aldehyde, which is usually conjugated, such as an α,β-unsaturated aldehyde, R2C=CHCHO |
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Term
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Definition
| An alkene ketone, which is usually conjugated, such as an α,β-unsaturated ketone, R2C=CHCOR |
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Term
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Definition
| An aldol addition reaction between two different aldehydes or ketones; this reaction is practical only when one reactant has no α hydrogen. Also called crossed aldol addition reaction |
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Term
| Crossed aldol condensation |
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Definition
| A crossed aldol addition reaction followed by dehydration to produce an α,β-unsaturated aldehyde or α,β-unsaturated ketone; only practical when one reactant has no α hydrogen |
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Term
| Claisen-Schmidt condensation |
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Definition
| A base-catalyzed aldol condensation of an aromatic aldehyde with a ketone (or aliphatic aldehyde) to produce an α,β-unsaturated ketone (or α,β-unsaturated aldehyde). |
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Definition
| An intramolecular aldol condensation of a dicarbonyl compound, usually a keto aldehyde, to form a five- or six-membered ring. |
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Term
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Definition
| Nucleophiles capable of reacting at two different nucleophilic sites |
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Definition
| The most stable enolate formed from an unsymmetrical ketone, which has the more highly substituted double bond; it is favored by use of a weak base in a protic solvent |
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Term
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Definition
| The enolate formed fastest from an unsymmetrical ketone, which usually has the least substituted double bond; it is favored by use of a very strong, sterically hindered base, such as LDA (lithium diisopropylamide), in an aprotic solvent, such as an ether like THF (tetrahydrofuran) or DME (dimethoxyethane). |
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Term
| Lithium diisopropylamide (LDA) |
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Definition
| A very strong, sterically hindered base, ( i-C3H7 )2N‾ Li+ , whose conjugate acid has pKa = 38 |
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Term
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Definition
| A crossed aldol reaction is forced to occur between a ketone enolate and an aldehyde by first deprotonating the ketone with LDA (lithium diisopropylamide), then slowly adding the aldehyde; if the ketone is unsymmetrical, then it will be selectively deprotonated by LDA at the less substituted α carbon to form the kinetic enolate |
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Term
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Definition
| A reaction in which a lithium enolate is selenated with benzeneselenyl bromide, then the α-selenyl ketone is converted to the α,β-unsaturated carbonyl by reaction with hydrogen peroxide |
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Term
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Definition
| An addition reaction in which two groups add to adjacent atoms in a conjugated system, which is fast and under kinetic control; in α,β-unsaturated carbonyl compounds, a nucleophile adds to the carbonyl carbon and the carbonyl oxygen is protonated. Also called simple addition |
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Term
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Definition
| An addition reaction in which two groups add to atoms that bear a 1,4-relationship in a conjugated system, which is energetically favored and under thermodynamic control; in α,β-unsaturated carbonyl compounds, a nucleophile adds to the β carbon and the carbonyl oxygen is protonated. Also called conjugate addition |
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Term
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Definition
| Base-promoted conjugate addition (1,4-addition) of a resonance stabilized carbanion nucleophile, such as a deprotonated active hydrogen compound (Michael donor), to an electrophilic conjugated double bond, such as an α,β-unsaturated carbonyl compound (Michael acceptor). Also called Michael reaction or Michael condensation |
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Term
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Definition
| Formation of a new six-membered ring, an α,β-unsaturated cyclic ketone, by the Michael addition of a cyclohexanone derivative to a methyl vinyl ketone derivative, followed by an intramolecular aldol condensation |
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