Spin coupling constants carbon-nitrogen

Table 7.67 Nitrogen-15 to Carbon-13 Spin Coupling Constants 7.116...

Fig. 3. First derivative electron spin resonance spectra. (A) ESR spectrum of an unpaired electron. (B) ESR spectrum of an unpaired electron interacting with a nitroxide resulting in a nitrogen hyperfine coupling constant aN. (C) ESR spectrum of an unpaired electron interacting with a H nucleus and a l4N nucleus as is typical for PBN radical adducts. (D) ESR spectrum of an unpaired electron interacting with the l3C nucleus, the H nucleus and the 14N nucleus of the trichloromethyl radical adduct of PBN, where the carbon tetrachloride was labeled with 13C.

A recent study related to the structure of chlorodimethylformiminium chloride and chlorotetramethylformamidinium chloride showed that both compounds are completely in the polar form as evidenced by spin-spin coupling between the olefinic proton in the former, which appears at lower field, and the N-methyl protons, which are at higher field. Likewise, the carbon-13-proton coupling constant indicated a positive charge on the nitrogen ( ). 

The values of the hyperfine coupling constants are collected in Table 1. Because the hfs constants for aromatic protons are proportional to the spin densities at the adjacent carbon atoms through the McConnell relation,8 these values provide a clear-cut picture of the spin density distribution within the molecular framework of radical cation l+ The hfs constants for the nitrogen atoms should reflect, besides the spin density at the nitrogen atom itself, the spin density at the adjacent atoms as well as the nature of their bonds to the nitrogen.7... 

Fig. 10.92. The expected ESR spectra of the spin adducts formed by pentamethyl-nitrosobcnzene (10.21) (a) an ESR spectrum of tertiary carbon radical-spin adduct (b) an ESR spectrum of a secondary carbon-spin adduct and (c) an ESR spectrum of a primary carbon radical-spin adduct. The coupling constants of a hydrogen and nitrogen, are denoted Uh and respectively [2012].

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