Chapter 15
α-Carbon Chemistry: Enols, Enolates, and Enamines
Reattività degli Enoli
Enols are a class of compounds where a hydroxyl group is attached to a carbon–carbon double bond, which implies that it is a vinyl alcohol. A ...
Reattività degli ioni enolato
Enolate ions are formed by the acid–base reaction of a carbonyl compound with a base. This leads to deprotonation of the α hydrogen atom, ...
Tipi di enoli ed enolati
Aldehydes and ketones form enols, although only about 1% of the enol is present at the equilibrium for simple monocarbonyl compounds. The enol form is ...
Convenzioni del Meccanismo Enolato
When a carbonyl compound is treated with a strong base, the α position gets deprotonated to give a resonance-stabilized intermediate called an ...
Formazione regioselettiva di enolati
As depicted in the figure below, the unsymmetrical ketones can form two possible enolates: less substituted or more substituted enolates. Usually, ...
Effetti stereochimici dell'enolizzazione
The chiral α-carbon of the carbonyl compound is the stereocenter of the molecule. As shown in the figure below, when such a carbonyl compound ...
α-alogenazione catalizzata da acido di aldeidi e chetoni
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first ...
α-alogenazione di aldeidi e chetoni promossa da basi
α-Halogenation of aldehydes and ketones is a reaction involving the substitution of α hydrogens with halogens in the presence of a base. ...
Alogenazione multipla di metilchetoni: reazione di aloformio
A method involving the transformation of methyl ketones to carboxylic acids using excess base and halogen is called the haloform reaction. It begins with ...
α-alogenazione dei derivati dell'acido carbossilico: panoramica
Unlike aldehydes and ketones, carboxylic acids do not readily participate in α halogenation reactions via enols or enolate intermediates. However, ...
α-Bromurazione degli acidi carbossilici: reazione di Hell-Volhard-Zelinski
The method to achieve α-brominated carboxylic acids using a mixture of phosphorus tribromide and bromine is known as the ...
Reazioni dei composti α-alocarbonilici: sostituzione nucleofila
Nucleophilic substitution in α-halocarbonyl compounds can be achieved via an SN2 pathway. The reaction in α-haloketones is generally carried out ...
Nitrosazione degli Enoli
The nitrosation reaction is one of the methods of preparing 1,2-diketones. The enol tautomer of the starting ketone reacts with sodium nitrite in ...
Formazione del legame C-C: Panoramica sulla condensazione aldolica
Aldol condensation is an important route in synthetic organic chemistry used to generate a new carbon–carbon bond under basic or acidic conditions. ...
Reazione di addizione aldolica catalizzata da basi
As depicted in Figure 1, base-catalyzed aldol addition involves adding two carbonyl compounds in aqueous sodium hydroxide to form a β-hydroxy ...
Reazione di addizione aldolica catalizzata da acido
The aldol reaction of a ketone under acidic conditions successfully forms an unsaturated carbonyl as the final product instead of an aldol. The ...
Disidratazione degli aldoli a epale: condensazione aldolica catalizzata da basi
This lesson delves into the aldol condensation catalyzed by bases, where aldols undergo dehydration to enals. As shown in Figure 1, the β-hydroxy ...
Disidratazione degli aldoli a enoni: condensazione aldolica catalizzata da acido
As shown in Figure 1, under acidic conditions, the β-hydroxy ketone undergoes dehydration via an E1 elimination reaction to form an enone.
Figure 1. ...
Reazione aldolica intramolecolare
Intramolecular aldol reaction occurs in dicarbonyl compounds such as dialdehydes, diketones, and keto-aldehydes. The dicarbonyl compounds possess more ...
Scissione del legame C-C: reazione retro-aldolica
The reverse of the aldol addition reaction is called the retro-aldol reaction. Here, the carbon–carbon bond in the aldol product is cleaved under ...
Reazioni aldoliche incrociate: Panoramica
Crossed aldol addition is the reaction between two different carbonyl compounds under acidic or basic conditions. Here, both the carbonyl compounds ...
Reazione aldolica incrociata utilizzando basi deboli
This lesson deals with the crossed aldol reaction using weak bases. The self-condensation of an aldehyde having α hydrogen is prevented by adding it ...
Chetoni con aldeidi aromatiche non enolizzabili: condensazione di Claisen-Schmidt
Benzaldehyde, like formaldehyde, lacks an α hydrogen and cannot enolize to form an enolate. Hence, the reaction of benzaldehyde with a ketone in the ...
Reazione aldolica incrociata utilizzando basi forti: reazione aldolica diretta
The reaction between two different carbonyl compounds comprising α hydrogen in the presence of a strong base like lithium diisopropylamide (LDA) to ...
Condensazione aldolica con β-Dietrici: Condensazione di Knoevenagel
The Knoevenagel condensation is an aldol-type reaction involving the condensation of aldehydes or ketones with active methylene compounds such as ...
Esteri a β-chetoesteri: Panoramica sulla condensazione di Claisen
Regular Claisen condensation is a base-promoted reaction involving identical esters with two α hydrogens, condensing to produce β-ketoesters. It ...
Esteri in β-chetoesteri: meccanismo di condensazione di Claisen
Regular Claisen condensation involves the synthesis of β-ketoesters by combining identical ester molecules bearing two α hydrogens in the ...
Condensazione aldolica vs condensazione di Claisen
Aldol condensation is an acid or base-catalyzed condensation between aldehydes or ketones to give an α,ꞵ-unsaturated carbonyl compound. A ...
Condensazione Intramolecolare di Esteri Dicarbossilici: Ciclizzazione di Dieckmann
Dieckmann cyclization is an intramolecular Claisen condensation of diesters. The reaction occurs in the presence of a base and generates a cyclic ...
Composti β-dicarbonilici tramite condensazioni di Claisen incrociate
Crossed Claisen condensations are base-promoted reactions between two different ester molecules producing β-dicarbonyl compounds. The reaction ...
α-alchilazione di chetoni tramite ioni enolato
Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by ...
Fattori che influenzano la α-alchilazione dei chetoni: scelta della base
α-Alkylation of ketones is achieved in the presence of alkyl halides and a base. The reaction proceeds via the formation of an enolate ion followed ...
Alchilazione di β-chetoestere enolati: sintesi di esteri acetoacetici
Acetoacetic ester synthesis is a method to obtain ketones from alkyl halides and β-keto esters. The reaction occurs in the presence of an alkoxide ...
Alchilazione di enolati β-diester: sintesi di esteri malonici
Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.
The ...
Addizione coniugata a composti carbonilici α,β-insaturi
α,β-Unsaturated carbonyl compounds are molecules bearing a carbonyl and alkene functionality in conjugation with each other. The conjugation in ...
Addizione coniugata (1,4-addizione) vs addizione diretta (1,2-addizione)
α,β-Unsaturated carbonyl compounds with two electrophilic sites, the carbonyl carbon, and the β carbon, are susceptible to nucleophilic ...
Addizione coniugata di enolati: Addizione di Michael
The attack of a nucleophile at the β carbon of an α,β-unsaturated carbonyl compound is called conjugate addition. Conjugate addition ...
Cicloeseneni tramite l'addizione di Michele e la condensazione aldolica: l'annullamento di Robinson
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, ...
Sintesi di composti carbonilici α-sostituiti: la reazione dell'enammina della cicogna
α-Substituted ketones or aldehydes can be synthesized from enamines by the Stork enamine reaction, named after its pioneer Gilbert Stork. Enamines ...
Aldeidi non enolizzabili ad acidi e alcoli: la reazione di Cannizzaro
The Cannizzaro reaction is a base-promoted redox reaction producing a primary alcohol and a carboxylic acid from two molecules of a nonenolizable ...
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