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Alitretinoin. For organic molecules with multiple double bonds, it is sometimes necessary to indicate the alkene location for each E or Z symbol. For example, the chemical name of alitretinoin is (2E,4E,6Z,8E)-3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexenyl)nona-2,4,6,8-tetraenoic acid, indicating that the alkenes starting at positions 2, 4, and 8 are E while the one starting at position 6 is Z.
More complex alkenes may be named with the E–Z notation for molecules with three or four different substituents (side groups). For example, of the isomers of butene , the two methyl groups of ( Z )-but-2 -ene (a.k.a. cis -2-butene) appear on the same side of the double bond, and in ( E )-but-2-ene (a.k.a. trans -2-butene) the methyl groups ...
But-2-ene is an acyclic alkene with four carbon atoms. It is the simplest alkene exhibiting cis/trans-isomerism (also known as (E/Z)-isomerism); that is, it exists as two geometric isomers cis-but-2-ene ((Z)-but-2-ene) and trans-but-2-ene ((E)-but-2-ene). It is a petrochemical, produced by the catalytic cracking of crude oil or the dimerization ...
Bromine has a higher CIP priority than chlorine, so this alkene is the Z isomer. In principle, cis–trans notation should not be used for alkenes with two or more different substituents. Instead the E–Z notation is used based on the priority of the substituents using the Cahn–Ingold–Prelog (CIP) priority rules for absolute
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.
The prefix form is "carbamoyl-". e.g., HCONH 2 methanamide, CH 3 CONH 2 ethanamide. Amides that have additional substituents on the nitrogen are treated similarly to the case of amines: they are ordered alphabetically with the location prefix N : HCON(CH 3 ) 2 is N , N -dimethylmethanamide, CH 3 CON(CH 3 ) 2 is N , N -dimethylethanamide.
The (E)/(Z) selectivity is often poor with semistabilized ylides (R 3 = aryl). [17] To obtain the (E)-alkene for unstabilized ylides, the Schlosser modification of the Wittig reaction can be used. Alternatively, the Julia olefination and its variants also provide the (E)-alkene selectively.
Over short time scales, the E-alkene is favored because the attack from the less bulky side is preferred, but over longer times, the more stable (bulky methyl and phenyl groups on opposite sides) Z-alkene is preferred. Though the E-alkene is initially formed, it isomerizes to the Z-alkene through a carbocation intermediate the stems from ...