Antara

If A transforms to B by an antara-type process (a Mdbius four electron reaction), the phase would be preserved in the reaction and in the complete loop (An i p loop), and no conical intersection is possible for this case. In that case, the only way to equalize the energies of the ground and excited states, is along a trajectory that increases the separation between atoms in the molecule. Indeed, the two are computed to meet only at infinite interatomic distances, that is, upon dissociation [89]. 

Antara Chemicals, BIOPAL VRO-20 Brochure, General Aniline and Eibn Corp., New York, 1958. 

Examples of nonionic surfactants are Emulphor ON and the Igepals (both Antara Chemicals), and Triton X-100 (Rohm Haas Company). 

A. Order [1,7] 1 +j supra/retention antara/inversion antara/retention antara/inversion... 

B. Order [i, j] i + j supra/supra supra/antara antara/antara ... 

For a successful cycloaddition to take place, the terminal tt lobes of the two reactants must have the correct symmetry for bonding to occur. This can happen in either of two ways, called supra facial and antara facial. Suprafacial cycloaddjtions take place when a bonding interaction occurs between lobes on the same face of one reactant and lobes on the same face of the other reactant. Antarafacial cycloadditions take place when a bonding interaction occurs between lobes on the same face of one reactant and lobes on opposite faces of the other reactant (Figure 30.8). 

Antara path products, loop construction, butene... 

Subscripts s and a are used to indicate a supra and an antara process respectively. Suprafacial, suprafacial (s, s) approach of two polyenes is normally sterically suitable for efficient orbital overlap. The vast majority of concerted additions involves the s, s approach. 

The antara-supra processes, even if less studied than the more common supra-supra reactions are frequently encountered in recent works on cycloaddition reactions and confirm in their turn the utility of orbital symmetry considerations. 

A G bond is considered to be involved in a cycloaddition in a supra manner if configuration is either retained or inverted at both of its termini in the course of the reaction. The retention of the configuration at one terminus and the inversion at the other will indicate an antara addition. 

The all cis. cyclobutane will yield only a cis alkene. Configuration is retained (or inverted) at both termini of the two o bonds involved, the reaction is a supra-supra process as in A. In B a cis alkene and a trans alkene are formed. Thus at both the termini of one G bond the configuration is retained only at one terminus and not at the other. The process will be supra-antara. 

C. David Sherrill, Antara Dutta, Micah L. Abrams, and John S. Sears... 

Abrams, Micah L., 75 Boese, A. Daniel, 183 Bytautas, Laimutis, 103 De Proft, Frank, 183 Dutta, Antara, 75 Fan, Peng-Dong, 37 Geerlings, Paul, 183 Gill, Peter M. W., 27 Hunt, Katharine L. C., 169 Klopper, Wim, 1 Kowalski, Karol, 37 Krylov, Anna I., 89 Kiimmel, Stephan, 13 Levchenko, Sergey V., 89 Lynch, Benjamin J., 153... 

Woodward und Hoffmann 8 a) verwenden die Bezeichnungen suprafacial und antarafacial von lat. supra — uber. .. bin, fiber. . . himveg (wohin), Sanskrit antara = der andere, lat. facies = Gestalt, Figur, Gesicht, engl. face = Flache. 

Brand Name(s) Antara, Lipidil Supra, Lofibra, Tricor, Triglide Chemical Class Fibric acid derivative... 

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