Halohydrin Cyclization
Halohydrin Cyclization - Related Videos
02:41
Formation of Halohydrin from Alkenes
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2025
An alkene, such as propene, reacts with bromine in the presence of water to yield a halohydrin. Halohydrins contain a halogen and a hydroxyl group attached to adjacent carbons. When the halogen is bromine, it is called a bromohydrin, while a chlorohydrin has chlorine as the halogen. Halohydrin formation commences when the π electrons of the alkene react with electrophilic bromine to form a bridged intermediate called a bromonium ion. Water, acting as a nucleophile, uses a lone pair of...
01:13
Intramolecular Claisen Condensation of Dicarboxylic Esters: Dieckmann Cyclization
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2023
Dieckmann cyclization is an intramolecular Claisen condensation of diesters. The reaction occurs in the presence of a base and generates a cyclic β-ketoester as the final product. Commonly, 1, 6 and 1, 7-diesters are preferred substrates for the reaction since the generated five, and six-membered cyclic β-keto esters are particularly more stable. In the reaction, α carbon connected to one end of the ester ends serves as an enolate nucleophile after losing its proton to the base. The carbonyl...
10:14
Synthesis and Purification of Iodoaziridines Involving Quantitative Selection of the Optimal Stationary Phase for Chromatography
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Cited by 3 •
2014
A protocol for the diastereoselective one-pot preparation of cis-N-Ts-iodoaziridines is described. The generation of diiodomethyllithium, addition to N-Ts aldimines and cyclization of the amino gem-diiodide intermediate to iodoaziridines is demonstrated. Also included is a protocol to rapidly and quantitatively assess the most appropriate stationary phase for purification by chromatography.
08:28
An Overview of bGDGT Biomarker Analysis for Paleoclimatology
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2023
Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst Throughout this series of videos, natural samples were extracted and purified in search of organic compounds, called biomarkers, that can relate information on climates and environments of the past. One of the samples analyzed was sediment. Sediments accumulate over geologic time in basins, depressions in the Earth into which sediment flows through the action of fluid (water or air), movement, and gravity. Two main types...
09:42
Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes
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Cited by 17 •
2016
Channels for the transportation of water molecules in enzymes influence active site solvation and catalysis. Herein we present a protocol for the engineering of these additional catalytic motifs based on in silico computer modeling and experiments. This will enhance our understanding of the influence of solvent dynamics on enzyme catalysis.
FAQs
Deprotonation converts the alcohol into an alkoxide, a substantially more effective nucleophile for the ring-closing substitution. Because the nucleophile and the carbon bearing the halogen are connected within the same molecule, the alkoxide can attack that neighboring center directly. Successful cyclization therefore depends on generating and maintaining access to the reactive alkoxide under basic conditions.
The alkoxide attacks the carbon attached to the halogen from the side opposite the leaving group, producing the characteristic inversion associated with substitution at that center. Consequently, the starting halohydrin’s three-dimensional arrangement influences the epoxide product. Stereochemical analysis must focus especially on the carbon undergoing displacement rather than treating ring formation as a nonselective process.
Halohydrin Cyclization is influenced by the substrate’s structure, the ability of the halogen-containing group to leave, and how readily the alcohol can become an accessible alkoxide. These factors determine whether intramolecular attack can compete successfully with unproductive pathways. A substrate that restricts alkoxide access or contains a poor leaving group may give a less favorable outcome.
The essential sequence begins with a vicinal halo alcohol and a basic environment. Base removes the alcohol proton, creating the alkoxide, which then attacks the adjacent carbon bearing the halogen. Displacement of the leaving group closes the three-membered epoxide ring. The procedure is therefore organized around enabling deprotonation followed by intramolecular substitution.
This approach connects a readily defined halohydrin arrangement directly to an epoxide through ring closure, making it useful when the substrate already places the alcohol and halogen on neighboring carbons. The resulting epoxide can then serve as a versatile intermediate for preparing alcohols, ethers, amines, and other functionalized molecules in subsequent synthesis.
The epoxide records both connectivity and stereochemical information from the cyclization. Its formation shows that the alkoxide reached the neighboring halogen-bearing carbon, while inversion at that carbon reflects the substitution pathway. Examining the product can therefore help relate the starting halohydrin’s structure to reaction success and clarify how substrate stereochemistry shaped the synthetic outcome.