Electrophilic Alkenes
Electrophilic Alkenes - Related Videos
02:24
Introduction to Electrophilic Addition Reactions of Alkenes
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2023
The double bond in a simple, unconjugated alkene is a region of high electron density that can act as a weak base or a nucleophile. The filled π orbital (HOMO) of the double bond can interact with the empty LUMO of an electrophile. A bonding interaction occurs when the electrophile attacks between the two carbons; the electrophile then accepts a pair of electrons from the π bond and undergoes addition across the double bond, yielding a single product. Addition and elimination reactions can be...
02:20
Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
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2026
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others. The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
06:52
Ozonolysis of Alkenes
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2023
Source: Vy M. Dong and Zhiwei Chen, Department of Chemistry, University of California, Irvine, CA This experiment will demonstrate an example of an ozonolysis reaction to synthesize vanillin from isoeugenol (Figure 1). Ozonolysis of alkenes, an oxidation reaction between ozone and an alkene, is a common method to prepare aldehydes, ketones, and carboxylic acids. This experiment also demonstrates the use of an ozone generator and a low temperature (−78 °C) reaction. Figure 1. Diagram showing...
02:28
Electrophiles
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2023
This lesson explains the definition, classification, and characteristic features of an electrophile that are key features of nucleophilic substitution reactions. An analysis of their charge and orbital picture helps understand their reactivity for seeking electrons. Electrophiles can be classified into positive and neutral species. Other classes include free radicals and polar functional groups. While a positive electrophile, like a proton, reacts due to its vacant, low-energy 1s orbital, the...
02:29
Nomenclature of Alkenes
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2023
The IUPAC naming system for alkenes replaces -an- with -en- in the corresponding parent alkanes. Accordingly, a simple alkene replaces the -ane suffix of the alkane with -ene. As per the IUPAC rules, the longest carbon chain containing the maximum number of double bonds is identified as the parent chain and is numbered such that the doubly bonded carbon atoms receive the lowest possible numbers. The location of the double bond is indicated by the number of its first carbon atom. In branched...
FAQs
In a conjugate addition, the nucleophile forms a bond at the β-carbon rather than directly at the carbonyl carbon. This placement shifts electron density through the conjugated system and produces an anion whose charge is stabilized by the electron-withdrawing group. That stabilization helps explain why α,β-unsaturated systems serve as useful partners for nucleophilic bond formation.
Adjacent electron-withdrawing groups reduce electron density in the carbon-carbon double bond, making the alkene more receptive to nucleophilic attack. The same group can then stabilize the anion generated during addition. This combination of activation and intermediate stabilization distinguishes structures such as enones, acrylates, and nitroalkenes as important electrophilic reaction partners.
A useful prediction begins by identifying an electron-withdrawing group connected to the carbon-carbon double bond and locating the β-carbon within that conjugated arrangement. When these features are present, nucleophilic bond formation can occur at the β-position, while the resulting anion gains stabilization from the withdrawing group. This pattern supports assignment of possible conjugate-addition reactivity.
Planning starts by identifying the electron-withdrawing group, the β-carbon, and the nucleophile that will supply the new bond. The expected pathway is then evaluated by tracing nucleophilic attack at the alkene and considering stabilization of the resulting anion. This framework helps organize transformations involving enones, acrylates, or nitroalkenes without treating all alkenes as equivalent.
Their nucleophilic reactivity supports several synthetic objectives, including carbon-carbon bond formation and construction of heterocycles. Because the alkene provides a defined site for nucleophile attack and the withdrawing group stabilizes the resulting anion, these substrates can also enable selective modification of more complex molecules. Their value therefore extends beyond a single reaction type.
Enones, acrylates, and nitroalkenes illustrate how different electron-withdrawing groups can make a conjugated alkene an electrophilic reaction site. Studying these examples connects molecular structure with nucleophilic reactivity and helps chemists select substrates for carbon-carbon bond formation, heterocycle construction, or selective changes to complex molecular frameworks.