Nitrogen-15 couplings

According to eq. (3.15), the magnitude of one-bond car bon-13 —nitrogen-15 coupling constants correlates with the product of s characters of the hybrid orbitals overlapping in the C-N bond [135] ... 

Table 3.12. Carbon-13 —Nitrogen-15 Coupling Constants of Selected Organic Compounds. ...

Two-bond carbon-carbon or carbon-nitrogen-15 coupling constants of cumulenes are only available for allene (II) (157) and ethyl diazoacetate (254) (94b). 

Two-bond proton-nitrogen-15 coupling constants in diazocompounds may be assumed to follow qualitatively trends observed for VC Ca-Ha) in allenes. Such an example is found for C NH) in diazomethane (42) (158) and ethyl diazoacetate (254) (94b). In 254 V( NH) is more positive than in 42, comparable to the situation in allene and allenecarboxylic acid ester. 

The three-bond proton-nitrogen-15 coupling constants in diazocompounds seem to be rather insensitive to substituent effects as is also the case for the three-bond carbon-proton couplings in allenes (54,65). 

Obviously, with a range of only 0.04 V available very few species are thermodynamically stable. However, both the hydrogen couple and the nitrogen couple usually exhibit overvoltages of 1 V, so that in acid solutions the practical range of potentials for solutes is from 4-1.0 to — l.OV. Similarly in basic solutions the practical range... 

Durme, J. P., Murray, J. W., Aufdenkampe, A., Blain, S. and Rodier, M. (1999). Silicon-nitrogen coupling in the equatorial Pacific upwelling zone. Glob. Biogeochem. Cycles 131,715-726. 

No alteration of the nitrogen couplings was observed when spinach b f complex was treated with dibromothymoquinone (DBMIB) (8) or bovine mitochondrial membranes with undecylhydroxybenzothiazol (UHDBT) (87), although these inhibitors cause shifts in the EPR spectra of the Rieske cluster therefore, the changes of the EPR spectra... 

In the upper spectrum the nitrogen couples to two phosphorus nuclei to give a triplet, while in the lower spectrum there is a large (43.4) one-bond coupling to give a doublet, each line of which is in turn split into a triplet. 

Table 4. Nitrogen coupling constants A and Q3 for planar copper and silver complexes (data from Rist and Hyde16 in MHz)...

Table 15.1. Nitrogen coupling constants of aquo-myoglobin (data from Scholes et al.240,241 and Mun et al.242) in MHz)...

Recently, the radical cation of PBN has been characterized by matrix spectroscopy and its reactivity has been studied by fast spectroscopic methods (Zubarev and Brede, 1994), and found to conform to the behaviour deduced from the OsCU and TBPA + studies. y-Radiolysis of PBN in a glassy matrix of isobutyl chloride or Freon-113 (CF2C1CFC12) at 77 K produced an intensely green glass containing PBN +, the epr spectrum of which had an anisotropic nitrogen coupling constant Ay = 2.75 mT and gy = 2.0037. Tlie mechanism of the radiolysis reaction is well established (Neta, 1976) and involves the formation of solvated electrons (e ), which add to the matrix species and produce chloride ion, and positive holes (h+) which eventually come to rest at the matrix component of lowest Ip (Symons, 1997), in this case PBN (see reactions (30) and (31)). 

Thus the radicals produced add to the initial molecule of a trap giving spin adducts. The nitrogen coupling constants of these spin adducts lie in the ESR regions of 1.4-1.5 and 0.7-0.8 mT (Torsell 1970, Janzen 1971, Lagercrantz 1977). 

TABLE 14. Values and signs of some experimentally determined nitrogen coupling constants of oximes ... 

Cationic polymerization of 4-membered imines (IUPAC azetidines) generally follows the same patterns as the aziridines [Matyjaszewski, 1984a,b Muhlbach and Schulz, 1988]. Imines are generally unreactive toward anionic polymerization presumably because of the instability of an amine anion (which would constitute the propagating species). The exception occurs with V-acylaziridines as a result of the electron deficiency of the nitrogen coupled with the highly strained 3-membered ring. 

This view has been challenged by Mac et al. who detected only four sets of nitrogen couplings and assigned them to one monomeric Chi a + forming the primary donor.209 In their model the observed changes of spin densities are interpreted within the hybrid orbital model.203 The data have recently been critically reviewed.187... 

M. Pietrzak et al., 13C detected scalar nitrogen-nitrogen couplings across the intramolecular symmetric NHN hydrogen bond of proton sponge. J. Am. Chem. Soc. 123,4338 1339 (2001)... 

In simple aliphatic nitriles, when the length of the chain increases, the nitrogen coupling remains very close to a limit value — 3.8 MHz — obtained for the longest molecules studied. 

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