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Asymmetric hydrogenation is a chemical reaction that adds two atoms of hydrogen to a target (substrate) molecule with three-dimensional spatial selectivity.Critically, this selectivity does not come from the target molecule itself, but from other reagents or catalysts present in the reaction.
The rule states that with the addition of a protic acid HX or other polar reagent to an asymmetric alkene, the acid hydrogen (H) or electropositive part gets attached to the carbon with more hydrogen substituents, and the halide (X) group or electronegative part gets attached to the carbon with more alkyl substituents. This is in contrast to ...
Hydroformylation of an alkene (R 1 to R 3 organyl groups (i. e. alkyl-or aryl group) or hydrogen). In organic chemistry, hydroformylation, also known as oxo synthesis or oxo process, is an industrial process for the production of aldehydes (R−CH=O) from alkenes (R 2 C=CR 2).
Transfer hydrogenation usually occurs at mild temperature and pressure conditions using organic or organometallic catalysts, many of which are chiral, allowing efficient asymmetric synthesis. It uses hydrogen donor compounds such as formic acid, isopropanol or dihydroanthracene, dehydrogenating them to CO 2, acetone, or anthracene respectively. [1]
Alkenes are generally colorless non-polar compounds, somewhat similar to alkanes but more reactive. The first few members of the series are gases or liquids at room temperature. The simplest alkene, ethylene (C 2 H 4) (or "ethene" in the IUPAC nomenclature) is the organic compound produced on the largest scale industrially. [5]
In organic chemistry, the ene reaction (also known as the Alder-ene reaction by its discoverer Kurt Alder in 1943) is a chemical reaction between an alkene with an allylic hydrogen (the ene) and a compound containing a multiple bond (the enophile), in order to form a new σ-bond with migration of the ene double bond and 1,5 hydrogen shift.
For example, the addition of hydrogen to ethene has a Gibbs free energy change of -101 kJ·mol −1, which is highly exothermic. [11] In the hydrogenation of vegetable oils and fatty acids, for example, the heat released, about 25 kcal per mole (105 kJ/mol), is sufficient to raise the temperature of the oil by 1.6–1.7 °C per iodine number drop.
This is due to the abstraction of a hydrogen atom by the alkene from the hydrogen halide (HX) to form the most stable carbocation (relative stability: 3°>2°>1°>methyl), as well as generating a halogen anion. A simple example of a hydrochlorination is that of indene with hydrogen chloride gas (no solvent): [4]