Cis Alkene Synthesis
Cis Alkene Synthesis - Related Videos
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...
02:24
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
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2023
Introduction Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate. Thermodynamic Stability Catalytic hydrogenation reactions help evaluate the relative thermodynamic stability of hydrocarbons. For example, the heat of hydrogenation of acetylene is −176 kJ/mol, and that of ethylene is −137 kJ/mol. The higher exothermicity associated with...
02:02
Cis-regulatory Sequences
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2020
Cis-regulatory sequences are short fragments of non-coding DNA that are present on the same chromosomes as the genes that they regulate. These fragments serve as binding sites for transcriptional regulators, proteins that are responsible for controlling gene transcription and differential gene expression across cell types in eukaryotes. Cis-regulatory sequences can be close to the gene of interest or thousands of bases away in the DNA sequence; however, those sequences that are further away are...
08:19
Quantitative Comparison of cis-Regulatory Element (CRE) Activities in Transgenic Drosophila melanogaster
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Cited by 15 •
2011
Phenotypic variation for traits can result from mutations in cis-regulatory element (CRE) sequences that control gene expression patterns. Methods derived for use in Drosophila melanogaster can quantitatively compare the levels of spatial and temporal patterns of gene expression mediated by modified or naturally occurring CRE variants.
08:56
Synthesis of a Borylated Ibuprofen Derivative Through Suzuki Cross-Coupling and Alkene Boracarboxylation Reactions
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Cited by 1 •
2022
The present protocol describes a detailed benchtop catalytic method that yields a unique borylated derivative of...
FAQs
In the alkyne route, hydrogen adds syn, meaning both hydrogen atoms approach the same face of the triple bond. This stereochemical delivery directs formation of the cis alkene rather than an unspecified mixture of arrangements. The resulting geometry matters because it changes molecular shape and can influence how the alkene reacts.
A poisoned palladium catalyst, such as Lindlar’s catalyst, reduces the alkyne only partially. Catalyst deactivation limits the process after the alkene forms, preventing substantial further reduction to an alkane. This control is essential because the desired product retains the carbon-carbon double bond while acquiring the targeted stereochemical arrangement.
Partial hydrogenation establishes the alkene geometry by adding hydrogen syn across an existing alkyne and stopping at the alkene stage. Z-selective olefination instead establishes the corresponding same-side arrangement during carbon-carbon bond formation. These approaches therefore control stereochemistry at different points: one modifies a pre-existing multiple bond, while the other forms the alkene.
The process begins with an alkyne and uses hydrogen in the presence of a poisoned palladium catalyst. Syn addition converts the triple bond into an alkene, while catalyst deactivation limits additional reduction. The essential outcome is partial rather than complete hydrogenation, allowing the reaction to stop before an alkane becomes the main target.
Chemists choose this approach when the relative placement of substituents around the double bond is important to the target molecule. Cis alkene synthesis supports preparation of pharmaceuticals, natural products, agrochemicals, and functional materials. In each case, controlling geometry can help preserve the molecular shape and reactivity required for the intended compound.
The cis arrangement provides stereochemical information about the three-dimensional shape of an alkene-containing molecule. Because molecular shape can strongly influence reactivity, selecting a cis-forming strategy helps chemists design compounds with a specific structural relationship between substituents. This consideration connects alkene synthesis directly to broader stereochemical planning in chemistry.