Double-well systems isomerization

Gray-Rice Theory Versus Reactive Island Theory Isomerization in Double-Well Systems Isomerization in a Triple-Well System Isomerization of 3-Phospholene Isomerization of HCN — CNH Isomerization of Cyclobutanone (C4H6O)... 

Consider the rate constants for isomerization in symmetric and asymmetric double-well systems predicted by the several theories discussed above. The two-well potential for coupled x and y DOFs is given by... 

It is generally admitted that skeletal transformations of hydrocarbons are catalyzed by protonic sites only. Indeed good correlations were obtained between the concentration of Bronsted acid sites and the rate of various reactions, e g. cumene dealkylation, xylene isomerization, toluene and ethylbenzene disproportionation and n-hexane cracking10 12 On the other hand, it was never demonstrated that isolated Lewis acid sites could be active for these reactions. However, it is well known that Lewis acid sites located in the vicinity of protonic sites can increase the strength (hence the activity) of these latter sites, this effect being comparable to the one observed in the formation of superacid solutions. Protonic sites are also active for non skeletal transformations of hydrocarbons e g. cis trans and double bond shift isomerization of alkenes and for many transformations of functional compounds e.g. rearrangement of functionalized saturated systems, of arenes, electrophilic substitution of arenes and heteroarenes (alkylation, acylation, nitration, etc ), hydration and dehydration etc. However, many of these transformations are more complex with simultaneously reactions on the acid and on the base sites of the solid... 

Isomerization Rate Constants for Symmetric Double-Well Potential Systems Defined in Table XIV... 

HYNES - You emphasized using ideas and techniques from near equilibrium kinetics to understand far from equilibrium phenomena. Have you considered now going back in the other direction For example, can you visualize a molecular system (probably more complex than say a simple isomerization) for which the double well plus Poisson noise far from equilibrium problem you described might apply ... 

As a first step of this work, we wanted to verily if the predictions of the previous theoretical study on the prototype system (PC) [24] were vahd for BMPC, as well. For this aim we theoretically analysed the pathways leading from tram to (2-3 and 3-4) mono-cA isomers and explored, in addition, the possibility of concerted isomerizations at two C-C bonds (taking the 2-3, 4-5 double isomerization as an example). 

Photochemical electrocycltc ring-closure in a 4-electron system works well for many acyclic dienes (2.17) and related cyclic systems 12.18). The situation with conjugated trienes is more complex, and they can act as 6-electron systems (2.19) leading to cydohexa-1,3-dienes, or as 4-electron systems (2.20) giving cyclobutenes. In addition they can undergo other photochemical reactions such as geometrical isomerization about the central double bond Iwhich must be c/s if a 6-electron electrocydic ring-closure is to take place). 

The reverse migrations, i.e. the thermal isomerization of olefins to carbenes, have been well established to occur if the system involves the significantly twisted double bonds. Although no evidence of this isomerization was found for acyclic vinylsilanes, Conlin and coworkers first observed the isomerization of a-methylenesilacyclobutane 8 to a mixture... 

In 1953, G. D. Searle and Co. patented a related compound, norethynodrel. This steroid is also an active contraceptive when taken orally. This fact is not at all surprising to an experienced organic chemist because it is well known that a CC double bond such as the one in norethynodrel is readily isomerized into conjugation with a carbonyl group. This acid-catalyzed isomerization occurs via an enol intermediate, and the equilibrium favors the more stable, conjugated compound. The acidic conditions in the human gastric system are quite sufficient to accomplish the transformation of norethynodrel to norethindrone. It seems that chemical reactions do not care much about patents ... 

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