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In allyl compounds, where the next carbon is saturated but substituted once, allylic rearrangement and related reactions are observed. Allyl Grignard reagents (organomagnesiums) can attack with the vinyl end first. If next to an electron-withdrawing group, conjugate addition (Michael addition) can occur.
A site adjacent to the unsaturated carbon atom is called the allylic position or allylic site. A group attached at this site is sometimes described as allylic. Thus, CH 2 =CHCH 2 OH "has an allylic hydroxyl group". Allylic C−H bonds are about 15% weaker than the C−H bonds in ordinary sp 3 carbon centers and are thus more reactive.
In contrast, the sp 2-hybridized carbon atoms resonate around 80 ppm in a region typical for alkyne and nitrile carbon atoms, while the protons of a CH 2 group of a terminal allene resonate at around 4.5 ppm — somewhat upfield of a typical vinylic proton.
The vinyl cation is a carbocation with the positive charge on an alkene carbon. Its empirical formula of the parent ion is C 2 H + 3.Vinyl cation are invoked as reactive intermediates in solvolysis of vinyl halides, [1] [2] as well as electrophilic addition to alkynes and allenes.
α,β-Unsaturated carbonyl compounds featuring a carbonyl conjugated to an alkene that is terminal, or vinylic, contain the acryloyl group (H 2 C=CH−C(=O)−); it is the acyl group derived from acrylic acid. The preferred IUPAC name for the group is prop-2-enoyl, and it is also known as acrylyl or simply (and incorrectly) as acryl. Compounds ...
At room temperature, acetaldehyde (H 3 CC(O)H) is more stable than vinyl alcohol (H 2 C=CHOH) by 42.7 kJ/mol. [3] Vinyl alcohol gas isomerizes to the aldehyde with a half-life of 30 min at room temperature.
The vinylogous enolate reacts at the terminal position of the double bond system (the γ-carbon), rather than the α-carbon immediately adjacent to the carbonyl, as would a simple enolate. Allylic electrophiles often react by vinylogous attack of a nucleophile rather than direct addition. Vinylogous aldol reaction. Cf. the simple aldol reaction.
Allyl alcohol is converted mainly to glycidol, which is a chemical intermediate in the synthesis of glycerol, glycidyl ethers, esters, and amines. Also, a variety of polymerizable esters are prepared from allyl alcohol, e.g. diallyl phthalate. [5] Allyl alcohol has herbicidal activity and can be used as a weed eradicant [9]) and fungicide. [8]