2- N coupling

Both T and E are expressed in tenns of two-electron integrals (i,j m.,n ) coupling the virtual spin orbitals... 

Charge number of electrochemical reaction n Coupling constant, direct dipolar AB... 

The possibility offered by new instruments to obtain N NMR spectra using natural abundance samples has made " N NMR spectroscopy a method which holds no interest for the organic chemist, since the chemical shifts are identical and the signal resolution incomparably better with the N nucleus (/ = ) than with " N (/ = 1). H- N coupling constants could be obtained from natural abundance samples by N NMR and more accurately from N-labelled compounds by H NMR. Labelled compounds are necessary to measure the and N- N coupling constants. 

In the presence of proton-donative organic solvents (alcohols), aliphatic amines do not react with diazonium, whereas aromatic amines form mainly triazenes and also para-aminoazo compounds, which subsequently interact slowly with an excess of diazo reagent via N-coupling and form disazo derivatives. 

H N coupling constants, often measured in H NMR using labeled compounds, are discussed together with N NMR (Section VI,D). Taking into account that H NMR data are now present in every paper dealing explicitly or implicitly with tautomerism, only a few articles are documented in this section. 

The solution of boundary value problems depends to a great degree on the ability to solve initial value problems.) Any n -order initial value problem can be represented as a system of n coupled first-order ordinary differential equations, each with an initial condition. In general... 

Cyanoisopropyl radicals (15) undergo unsymmetrical C-N coupling in preference to C-C coupling.11 1 The preferential formation of the ketenimine is a reflection of the importance of polar and steric influences.1"1 However, the ketenimine is itself thermally unstable and a source of 15, thus the predominant isolated product is often from C-C coupling. 

Preferential C-N coupling is also observed for oligomeric radicals (Scheme 5.9).117 A ketenimine (21) is the major product from the reaction of the "dimeric" MAN radical 18 with cyanoisopropyl radicals (15). Only one of the two possible ketcnimincs was observed a result which is attributed to the thermal lability of ketenimine 19. If this explanation is correct then, although C-N coupling may... 

An interesting improvement from the classical treatment of the bond under stress was proposed by Crist et al, [101], Considering the chain as a set of N-coupled Morse oscillators, these authors determined the elongation and time to failure as a function of the axial stress. The results, reported in Fig. 20, show a decreasing correlation between the total elastic strain before failure and the level of applied force with the chain length. To break a chain within some reasonable time interval (for example <10-3s) requires, however, the same level of stress (a0.7 fb) as found from the simpler de Boer s model. 

The high reactivity of heterocyclic diazonium ions in azo coupling reactions is the reason why in some cases the primary diazotization products cannot be isolated. For example, diazotization of 2-methyl-5-aminotetrazole (2.14) directly yields the triazene 2.15, i. e., the N-coupling product, since the intermediate diazonium ion is reactive enough to give the N-coupling product with the parent amine even under strongly acidic conditions (Scheme 2-8 Butler and Scott, 1967). 

In intramolecular N-coupling the diazonio group interacts with a nitrogen-containing substituent in the ortho-position of the aromatic ring. This is the cause of the difficulties in the diazotization and bisdiazotization of 1,2-diaminobenzene (6.45,... 

Cd +/n couples. Film composition was altered by changing the concentra-... 

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