Shifted homology

In comparing and contrasting the rare-earth and late-actinide hydride systems, it should be noted that a shifted homologous relationship exists for the metals, as shown in fig. 1. As noted by Johansson (1975) and discussed by Ward (1985b), the heavy actinide metals relate to the beginning of the rare-earth series, rather than to the direct... 

Fig. 1. Shifted homologous relationships between the lanthanide and actinide metals. The properties of Am through Es (metals without significant f-bonding) most closely mimic those for Pr through Eu the half-filled shell gives Cm some properties like Gd. After Ward et aL (1986).

Calculation can also explain why in some thiazole dyes vinyiene shift of the first two homologs is larger than the shift between higher members of the series, and also why wavelengths of absorption of nonsymmetrical dyes as calculated by the mean value rule differ from experimental data (6671. This deviation is caused by an interannular no-bond SS-interaction in the monomethine ion. 

Evans studied the influence of the position of the sulfate group on the CMC at 40°C for a large number of sodium alcohol sulfates [92]. The results are given in Table 10. From these results it is possible to determine the constants A and B of Eq. (11) at 40°C as shown in Table 11. Observation shows a slight constant decrease of the slope (B) of the lines as the sulfate group is shifted toward the middle of the chain whereas the values of A are almost constant for all homologous series. 

The fact that many 4 systems are paratropic even though they may be nonplanar and have unequal bond distances indicates that if planarity were enforced, the ring currents might be even greater. That this is true is dramatically illustrated by the NMR spectrum of the dianion of 83 (and its diethyl and dipropyl homologs). We may recall that in 83, the outer protons were found at 8.14-8.67 8 with the methyl protons at —4.25 8. For the dianion, however, which is forced to have approximately the same planar geometry but now has 16 electrons, the outer protons are shifted to about -3 8 while the methyl protons are found at 21 8, a shift of 258 We have already seen where the converse shift was made, when [16]annulenes that were antiaromatic were converted to 18-electron dianions that were aromatic. In these cases, the changes in NMR chemical shifts were almost as dramatic. Heat of combustion measurements also show that [16]annulene is much less stable than its dianion. 

Fig. 1. Amino acid sequence homology between the neonatal fast-twitch and slow-twitch skeletal muscle forms of the Ca -ATPase. The sequence of the slow Ca -ATPase is shown above the neonatal fast-twitch form, with nonhomologous amino acids indicated by asterisks. The sequence of the slow ATPase is shifted to the right by one residue at residue 505 to allow realignment after the difference in sequence length. Ml-MlO, membrane spanning regions S1-S5, stalk sectors Tl, T2, major tryptic cleavage sites P,...

The principal competing reactions to ruthenium-catalyzed acetic acid homologation appear to be water-gas shift to C02, hydrocarbon formation (primarily ethane and propane in this case) plus smaller amounts of esterification and the formation of ethyl acetate (see Experimental Section). Unreacted methyl iodide is rarely detected in these crude liquid products. The propionic acid plus higher acid product fractions may be isolated from the used ruthenium catalyst and unreacted acetic acid by distillation in vacuo. 

Shida and Hamill23 found that the positive and negative molecular ions of 1,3-butadiene and its homologs have similar absorption spectra. Band maxima of the anions are not sensitive to substituent alkyl groups, whereas those of the cations are red-shifted as the number of substituent methyl groups increases. In alcoholic matrices the butadiene anions abstract the alcoholic proton to form an allylic radical (equation 23), as was proven by ESR spectroscopy. 

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