Alpha Alkylation Ketones
Alpha Alkylation Ketones - Related Videos
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α-Alkylation of Ketones via Enolate Ions
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2025
Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the α carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the α carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the strong interaction...
01:10
Factors Affecting α-Alkylation of Ketones: Choice of Base
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2023
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 by nucleophilic substitution. The choice of base employed is essential as it is the key factor in determining the reaction outcome. The reaction involving bases like EtO− whose conjugate acid EtOH (pKa = 15.9) is stronger than the ketone (pKa = 19.2) results in an equilibrium mixture with higher ketone concentration. As a consequence, side reactions...
03:09
Identification of Unknown Aldehydes and Ketones - Concepts
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2020
Aldehydes and Ketones Aldehydes and ketones have a carbonyl group (C=O) as a functional group. A ketone has two alkyl or aryl groups attached to the carbonyl carbon (RCOR’). The simplest ketone is acetone, which has two methyl groups attached to the carbonyl carbon (CH3COCH3). An aldehyde is similar to a ketone, except that instead of two side groups connected to the carbonyl carbon, they have at least one hydrogen (RCOH). The simplest aldehyde is formaldehyde (HCOH), as it has two hydrogens...
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Identification of Unknown Aldehydes and Ketones - Student Protocol
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2020
Source: Lara Al Hariri and Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA DNPH Test for Aromatic Aldehydes and KetonesExpand In this lab, you'll use the DNPH test, the Tollens' test, and the iodoform test to identify two unknown aldehydes or ketones. You'll use butanone and benzaldehyde as known compounds to confirm that the tests are working as expected. You'll start the lab with the DNPH test, which relies on the reaction between 2,4-dinitrophenylhydrazine, or DNPH,...
02:45
Alkyl Halides
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2023
Structural Properties Alkyl halides are halogen-substituted alkanes wherein one or more hydrogen atoms of an alkane is replaced by a halogen atom such as fluorine, chlorine, bromine, or iodine. The carbon atom in an alkyl halide is bonded to the halogen atom, which is sp3-hybridized and exhibits a tetrahedral shape. Unlike alkyl halides, compounds in which a halogen atom is bonded to an sp2 -hybridized carbon atom of a carbon-carbon double bond (C=C) are called vinyl halides. Whereas aryl...
FAQs
The strong base removes an acidic hydrogen from the carbon next to the ketone, producing an enolate. This intermediate is central because it contains the carbon nucleophile that will form the new carbon–carbon bond. In practice, controlling enolate formation helps determine which substituted ketone is produced and supports selectivity during multistep organic synthesis.
The enolate carbon provides the reactive site for bond formation with an alkyl halide. Rather than merely activating the ketone, enolate formation creates a nucleophilic carbon that can participate in SN2 substitution. This mechanistic feature allows the reaction to convert an existing ketone framework into a more complex molecule bearing a new carbon substituent.
The alkyl halide supplies the alkyl group incorporated into the ketone product. After base-generated enolate formation, the enolate carbon reacts with this partner through an SN2 substitution, creating the new carbon–carbon bond. The identity of the alkyl halide therefore directly affects the structure of the substituted ketone obtained from the reaction.
Reaction conditions influence how effectively the enolate forms and which product pathway is favored. Because enolate chemistry governs the reactive carbon species, changes in conditions can affect regioselectivity, meaning the location at which substitution occurs, and can also increase or reduce competing reactions. Careful control is therefore important when planning a multistep synthesis.
A typical sequence begins by treating the ketone with a strong base, often lithium diisopropylamide, to remove the acidic alpha hydrogen. The resulting enolate is then exposed to an alkyl halide, allowing SN2 substitution at the enolate carbon. The outcome is a ketone with an added alkyl group and greater molecular complexity.
This carbon–carbon bond-forming method is useful when a synthesis requires a substituted ketone or needs to increase molecular complexity. Its products can serve in pharmaceutical, natural product, and materials synthesis. In chemistry research, understanding the associated enolate behavior helps investigators manage regioselectivity and limit competing reactions across multistep synthetic routes.