Eis—trans isomerism

Examples of first-order reversible reaetions are gas phase eis-trans isomerization, isomerizations in various types of hydroearbon systems, and the raeemization of a and (3 glueoses. An example of a eatalytie reaetion is the ortho-para hydrogen eonversion on a niekel eatalyst. 

Both acids yield succinic acid, m.p. 185°, upon catalytic reduction (see Section 111,150), thus establishing their structures. Maleio and fumaric acids are examples of compounds exhibiting eis - trans isomerism (or geometric isomerism). Maleic acid has the cis structure since inter alia it readily yields the anhydride (compare Section 111,93). Fumario acid possesses the tram structure it does not form an anhydride, but when heated to a high temperature gives maleic anhydride. 

Catalyzed eis/trans isomerization of lipid double bonds in polyunsaturated fatty acids... 

For P123-templated nanocomposite films, a similar analysis was performed to evaluate the rate constants of the fast and the slow processes. The rate eonstants of the fast (ki) and the slow (k2) processes are 5.7 x 10 " s and 6.5 x 10 s respectively. Similar to those of Brij 56-templated nanocomposite films, the eis trans isomerization of P123-templated films is faster for k and is in the same order for k2-... 

Dinitro-tetrammino-cobaltic Salts, [Co(NH3)4(N02)2]It.—Two series of salts of this composition are known, the croceo-salts and the flavo-salts. The two are isomeric, and differ in colour and in method of preparation. They correspond to the isomeric series already described, the croceo-salts being the 1-, 6-, or trans-senes, and the flavo-salts the 1-, 2-, or eis-series. 

Asymmetric Michael addition to enoatesThe known conjugate addition of RCu BF, (8, 324-325) to a,/(-unsaturated carbonyl compounds4 proceeds with high chiral induction to trans- )-8-phenylmenthyl crotonate (2). Addition to the isomeric ei.v-crotonate (5) is less selective, but results mainly in the enantiomeric acid (6). 

Figure 10. Schematic potential energy curves accounting for the primary event in vision. I. Excited state of rhodopsin and bathorhodopsin. II. Ground state of rhodopsin and bathorhodop-sin. III. Ground state of the isolated PRSB chromophore. E] and E2 are estimated from the equilibrium constants IC = [rhodopsin]/ [11-cis retinal][opsin] < 10 and K2 + [bathorhodopsin]/[all-trans retinal][opsin] < 10"2, respectively. With E3 = 1 kcal, this leads to E4 = E2 + Ei - E3 > 13 kcal. The value estimated from thermal noise data in photoreceptors is E4 = 30 kcal. Note that according to the isomerization model (Section III-B-l-c),...

Keteniminium salt lb reacts with ( )-2-butene to give the /ran.Mctramethylcyclobutaniminium salt exclusively with d.r. (trans eis) >97 333a. Hydrolysis occurs with partial isomerization at the carbon a to the carbonyl group giving a transjeis mixture of 2,2,3,4-tetramethylcyclobu-... 

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