Cis Diol Formation
Cis Diol Formation - Related Videos
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...
02:02
Cis-regulatory Sequences
0 Views •
2023
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.
02:37
Disubstituted Cyclohexanes: cis-trans Isomerism
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2023
Depending upon the different spatial orientation of the substituents, the disubstituted cycloalkanes exhibit two types of stereoisomers. The cis isomers have the substituents on the same side of the ring, whereas the trans isomers have the substituents on the opposite sides. These stereoisomers exhibit different physical properties and cannot be interconverted without breaking the carbon-carbon bonds. In cyclohexane, the substituents can occupy different positions generating distinct isomers.
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...
FAQs
The key stereochemical event is syn addition, meaning both oxygen-containing groups are delivered to the same face of the alkene. Because the two new carbon–oxygen bonds form together through the same reaction pathway, their relative orientation is preserved when the intermediate is converted into the product. This stereospecificity distinguishes the transformation from processes that can produce mixed orientations.
Osmium tetroxide reacts with the alkene to generate a cyclic intermediate containing both newly introduced oxygen atoms. Hydrolysis then breaks this intermediate and releases the vicinal diol. This sequence explains why the oxidation is organized rather than two unrelated substitutions, and why the relationship between the hydroxyl groups reflects the original face of alkene addition.
An alkene can be approached from either face, but syn addition places both oxygen atoms on the face selected during the reaction. The resulting product therefore records the stereochemical course of alkene oxidation. This relationship makes the transformation useful not only for installing neighboring hydroxyl groups, but also for analyzing or preserving stereochemical information in organic molecules.
Cold, dilute potassium permanganate provides a related route to the same type of neighboring hydroxyl-group arrangement. Osmium tetroxide is described through formation of a cyclic intermediate followed by hydrolysis, whereas permanganate is presented as an alternative reagent system for the oxidation. The comparison is useful when identifying the reaction class and its stereochemical outcome rather than treating the reagents as unrelated processes.
A typical sequence begins by exposing the alkene to an oxidant, such as osmium tetroxide, so that oxygen adds across the double bond and forms a cyclic intermediate. Hydrolysis follows to release the diol. When the alternative permanganate approach is used, the specified conditions are cold and dilute, which supports the related oxidation described for this conversion.
The reaction is useful when a synthesis requires two neighboring oxygen-containing functional groups with a defined relative orientation. The resulting diol can serve as an intermediate in further synthetic planning, including work relevant to organic and medicinal chemistry. Its stereospecific character also helps chemists determine alkene stereochemistry while carrying out a purposeful functional-group transformation.