Irans-Decalin

PS-P(E/P) M = 48 and 80.38% Decane (selective for P(E/P)) irans-Decalin (neutral) and mixtures with decane Micellar D, RH and viscosity. Evidence for micellar association Viscometry, SLS, DLS Mandema ei at. (1979a, b)... 

In substituted irans-decalins, one of a pair of epimeric substitution products is necessarily axial and the other equatorial. In cfs-decalins, the possibility of inversion of the ring conformation permits an equatorial arrangement for each of a pair of epimers. If two or more substituents are present in m-decalin, there will be at least one axial group in some of the stereoisomers, and it then is necessary, when selecting the most stable conformation, to avoid conformations that show the effect seen in XVII, where an axial group is inside the L-shape and very close to three axial hydrogen atoms. 

That irans-decalin is more stable than cfs-decalin has been shown in various ways, - the reason for this being repulsions between the four hydrogen atoms inside the L-shape (shown in XVI). In [Pg.19]

Problem 4.21 Which isomer is more stable, irans-decalin or cis-decalin Explain. 

Fig. 28 Relaxation time tageing (squares) as a function of temperature of the solution from which the films were spun. The solid line represents the coil diameter of the individual polymer in solution, normalized by its diameter at the 0 temperature of PS in Irans-decalin (indicated by the vertical dotted line)...

Bond formation between C-2 and C-7 as well as C-6 and C-11 of famesane formally leads to the drimane basic skeleton of sesquiterpenes The accepted numbering system is derived from decalin and not from famesane. The parent hydrocarbon 5a,8a,9p,10p-drimane with irans-decalin as core stracture occurs in paraffin oil. 

There is an important difference between the cis- and irons-decalin systems with respect to their conformational flexibility. irans-Decalin because of the nature of the ring fusion, is inc able of ring inversion. ci5-Decalin is conformationally mobile and undergoes ring inversion at a rate only slightly slower than cyclohexane (AG = 12.3-12.4 kcal/mol)." The irons-decalin system than represents a conformationally locked system and can be used to determine the difference in stability and reactivity of groups in axial and equatorial environments. 

Two substituents of a cyclohexane ring (in ortho-position in the formulas below) can be either both on the same side of the plane of the ring (cis) or on opposite sides (Irans). The possibility of isomerism is retained even when the two substituents are connected by C atoms (see formula) to form a second ring. If this second ring is a six-membered ring then the compound is decalin, whose two isomers have been isolated (Hiickel). 

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