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Very often, cis–trans stereoisomers contain double bonds or ring structures. In both cases the rotation of bonds is restricted or prevented. [4] When the substituent groups are oriented in the same direction, the diastereomer is referred to as cis, whereas when the substituents are oriented in opposing directions, the diastereomer is referred to as trans.
[4] A meso isomer need not have a mirror plane. It may have an inversion or a rotoreflexion symmetry such as S 4. For example, there are two meso isomers of 1,4-difluoro-2,5-dichlorocyclohexane but neither has a mirror plane, and there are two meso isomers of 1,2,3,4-tetrafluorospiropentane (see figure).
For example, despite having chiral gauche conformers that belong to the C 2 point group, butane is considered achiral at room temperature because rotation about the central C–C bond rapidly interconverts the enantiomers (3.4 kcal/mol barrier). Similarly, cis-1,2-dichlorocyclohexane consists of chair conformers that are nonidentical mirror ...
Cis-1,4-Di-tert-butylcyclohexane has an axial tert-butyl group in the chair conformation and conversion to the twist-boat conformation places both groups in more favorable equatorial positions. As a result, the twist-boat conformation is more stable by 0.47 kJ/mol (0.11 kcal/mol) at 125 K (−148 °C) as measured by NMR spectroscopy .
The descriptors cis (Latin, on this side of) [2] and trans (Latin, 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 substitution pattern with only two residues.
In practice polyisoprene is commonly used to refer to synthetic cis-1,4-polyisoprene, made by the industrial polymerisation of isoprene. Natural forms of polyisoprene are also used in substantial quantities, the most important being "natural rubber" (mostly cis-1,4-polyisoprene), which is derived from the sap of trees. Both synthetic ...
1,2-Dichloroethylene or 1,2-DCE is the name for a pair of organochlorine compounds with the molecular formula C 2 H 2 Cl 2. The two compounds are isomers, each being colorless liquids with a sweet odor. It can exist as either of two geometric isomers, cis-1,2-dichloroethene or trans-1,2-dichloroethene, but is often used as a mixture of the two ...
These groups can be cis or trans. Other isomers of cyclohexanedicarboxylic acid are known, but the 1,4- isomers are of greatest interest, perhaps because they are obtainable from a commodity chemical. Specifically, hydrogenation of terephthalic acid affords the title compound: [1] C 6 H 4 (CO 2 H) 2 + 3 H 2 → C 6 H 10 (CO 2 H) 2.