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The cis isomer is already in the correct geometry in its most stable conformation; therefore, it eliminates easily. The repulsion between an axial t -butyl group and hydrogen atoms in the 1,3-diaxial position is so strong that the cyclohexane ring will revert to a twisted boat conformation.
trans-1,3-Disubstituted cyclohexanes are like cis-1,2- and cis-1,4- and can flip between the two equivalent axial/equatorial forms. [ 2 ] 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.
In the Benson heat of formation group additivity dataset, cis isomers suffer a 1.10 kcal/mol stability penalty. Exceptions to this rule exist, such as 1,2-difluoroethylene, 1,2-difluorodiazene (FN=NF), and several other halogen- and oxygen-substituted ethylenes. In these cases, the cis isomer is more stable than the trans isomer. [10]
An example of interactions within a molecule that would lead to steric strain, leading to a shift in equilibrium from boat to chair, is the interaction between the two methyl groups in cis-1,4-dimethylcyclohexane. In this molecule, the two methyl groups are in opposing positions of the ring (1,4-), and their cis stereochemistry projects both of ...
The cis isomer can adopt various conformations, the most stable one being shaped like a ribbon. [1] The most stable conformation of trans-cyclooctene is shaped like the 8-carbon equivalent of the chair conformation of cyclohexane. Longer cycloalkene rings such as the ten-carbon cyclodecene also occur as cis and trans isomers.
3 I. (Similar procedures can give cis,trans isomers of 1,4-cyclooctadiene and 1,5-cyclooctadiene). [2] In addition, a photochemical method exists for the direct cis–trans isomerisation. Although this equilibrium strongly favours the more stable cis form, the reaction can be driven towards the trans form by trapping with silver ions. [11] [12]
Clar's rule states that for a benzenoid polycyclic aromatic hydrocarbon (i.e. one with only hexagonal rings), the resonance structure with the largest number of disjoint aromatic π-sextets is the most important to characterize its chemical and physical properties. Such a resonance structure is called a Clar structure. In other words, a ...
A copper chromite catalyst is usually used industrially. [1] The cis/trans ratio of the CHDM is affected by the catalyst. [2] Byproduct of this process are 4-methylcyclohexanemethanol (CH 3 C 6 H 10 CH 2 OH) and the monoester methyl 4-methyl-4-cyclohexanecarboxylate (CH 3 C 6 H 10 CO 2 CH 3, CAS registry number 51181-40-9). [3]