Alkyl cations coupling constants

A number of methods used to decide which type of cation is formed rely upon spectroscopic comparisons of protonated molecules with the methylation or alkylation products in general ([3] and [4], with Me or R instead of H). In alkylation products there is no mobility of the group R and the structure of the ion is thus fixed. There is no possibility of mobile tautomeric equilibria. The properties of the TT-electron system, which determines nmr coupling constants and ultraviolet/visible absorption (and, not quite... 

The 13C NMR shift in the ferf-pentyl cation [C2H5(CH3)2C+] 3 is at 813C 335.4, which is similar to the that of the ferf-butyl cation. The shift difference is much smaller than the 17 ppm found in the case of the related alkanes, although the shift observed is in the same direction. The 13C NMR chemical shifts and coupling constants 7C-h of C3 to Cg alkyl cations 1-13 are shown in Tables 3.2 and 3.3.95... 

It is of interest to compare the markedly different methyl coupling constants in the positive and negative ions of 9,10-dimethylanthracene with those found in neutral alkyl radicals. Various methods of comparison suggest that the value of 8-0 G for the cation is close to that expected if the proportionality constant is about equal to that for the... 

D. W. Clack, J. C. Evans, A. Y. Obaid, and C. C. Rowlands, The assignment of the hyperfine coupling constants for the pyridyl protons in aryl and alkyl A-substituted bipyridylium radical cations, Tetrahedron 39, 3615-3620 (1983). 

Table 3. 13C Jq-H coupling constants of the static C3 to Cg alkyl cations...

Parameters that Affect Diffusion-Limited Transport. Brown et aL varied the length of the alkyl chain of alkyl o-nitrophenyl ether membrane solvents and examined its influence on the proton-coupled transport of alkali metal cations by a crown ether derivative. By comparison of solvent characteristics, such as the dielectric constant, viscosity, and surface tension, they concluded that hexyl o-nitrophenyl ether is a better membrane solvent than NPOE (43), The effect of the solvent on the transport of NaC104 by carrier 4 has been studied by Visser et al (44), Transport parameters and were determined. A series of octyl phenyl ethers containing an electron withdrawing group (NO2, CN) of various positions on the phenyl ring were used. Data are presented in Table 5. 

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