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Cis and trans descriptors are not used for cases of conformational isomerism where the two geometric forms easily interconvert, such as most open-chain single-bonded structures; instead, the terms "syn" and "anti" are used. According to IUPAC, "geometric isomerism" is an obsolete synonym of "cis–trans isomerism". [2]
2-Hexyne can be semihydrogenated to yield 2-hexene or fully hydrogenated to hexane. [3] With appropriate noble metal catalysts it can selectively form cis-2-hexene. [4] 2-Hexyne can act as a ligand on gold atoms. [5] With strong sulfuric acid, the ketone 2-hexanone is produced. However this reaction also causes polymerization and charring. [6]
In organic chemistry, hexene is a hydrocarbon with the chemical formula C 6 H 12. The prefix "hex" is derived from the fact that there are 6 carbon atoms in the molecule, while the " -ene " suffix denotes that there is an alkene present—two carbon atoms are connected via a double bond .
In larger rings (8 or more atoms), cis–trans isomerism of the double bond may occur. This stability pattern forms part of the origin of Bredt's rule , the observation that alkenes do not form at the bridgehead of many types of bridged ring systems because the alkene would necessarily be trans in one of the rings.
The descriptors cis (lat. on this side of) [2] and trans (lat. over, beyond) [3] are used in various contexts for the description of chemical configurations: [4] [5] In organic structural chemistry, the configuration of a double bond can be described with cis and trans, in case it has a simple
Simple cis and trans isomers may be indicated with a prefixed cis-or trans-: cis-but-2-ene, trans-but-2-ene. However, cis- and trans- are relative descriptors. It is IUPAC convention to describe all alkenes using absolute descriptors of Z- (same side) and E- (opposite) with the Cahn–Ingold–Prelog priority rules (see also E–Z notation ).
Structures of the significant conformations are shown: chair 1, half-chair 2, twist-boat 3 and boat 4. When ring flip happens completely from chair to chair, hydrogens that were previously axial ( blue H in upper-left structure) turn equatorial and equatorial ones ( red H in upper-left structure) turn axial. [ 3 ]
E–Z configuration, or the E–Z convention, is the IUPAC preferred method of describing the absolute stereochemistry of double bonds in organic chemistry.It is an extension of cis–trans isomer notation (which only describes relative stereochemistry) that can be used to describe double bonds having two, three or four substituents.