Search results
Results from the WOW.Com Content Network
There are two types of alpha-olefins, branched and linear (or normal). The chemical properties of branched alpha-olefins with a branch at either the second (vinylidene) or the third carbon number are significantly different from the properties of linear alpha-olefins and those with branches on the fourth carbon number and further from the start of the chain.
Straight-chain terminal alkenes, also called linear alpha olefins (LAO) or normal alpha olefins (NAO), are alkenes (olefins) having a chemical formula C n H 2n, distinguished from other alkenes with a similar molecular formula by being terminal alkenes, in which the double bond occurs at the alpha (α-, 1-or primary) position, and by having a linear (unbranched) hydrocarbon chain.
A 3D model of ethylene, the simplest alkene. In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. [1] The double bond may be internal or at the terminal position. Terminal alkenes are also known as α-olefins.
Terminal alkynes, like acetylene itself, are mildly acidic, with pK a values of around 25. They are far more acidic than alkenes and alkanes, which have pK a values of around 40 and 50, respectively. The acidic hydrogen on terminal alkynes can be replaced by a variety of groups resulting in halo-, silyl-, and alkoxoalkynes.
In organic chemistry, hydrovinylation is the formal insertion of an alkene into the C-H bond of ethylene (H 2 C=CH 2): CH 2 =CHR + CH 2 =CH 2 → CH 3 −CHR−CH=CH 2. The more general reaction, hydroalkenylation, is the formal insertion of an alkene into the C-H bond of any terminal alkene. The reaction is catalyzed by metal complexes.
In addition to terminal alkenes, tri- and tetrasubstituted alkenes have been used in RCM reactions to afford substituted cyclic olefin products. [32] Ring-closing metathesis has also been used to cyclize rings containing an alkyne to produce a new terminal alkene , or even undergo a second cyclization to form bicycles.
Metalation of terminal alkynes is a significant side reaction that occurs under these conditions. If metalation is desired, tertiary amine complexes of DIBAL-H are useful. [13] (5) The use of silyl acetylenes avoids the problem of competitive metalation of terminal alkenes.
A notable variant of the Huisgen 1,3-dipolar cycloaddition is the copper(I) catalyzed variant, no longer a true concerted cycloaddition, in which organic azides and terminal alkynes are united to afford 1,4-regioisomers of 1,2,3-triazoles as sole products (substitution at positions 1' and 4' as shown above).