Nuclear Magnetic Resonance Spectra of Pyrazines

The nuclear magnetic resonance spectra of simple heterocycles, including pyrazines, to about 1970 have been described by Batterham (1494), and these data are not discussed further here. 

Proton magnetic resonance techniques have been used for the measurement of rates of hydrogen-deuterium exchange of pyrazine (in CHsOD-CHsONa at 164.6 ) (591) for a study of protonation of pyrazine (1472) for analysis of the reaction mixture from quatemization of 2-substituted pyrazines with methyl iodide (666) for elucidation or confirmation of the structures of alkylpyrazines obtained by alkylation of pyrazines with aldehydes and ketones in the presence of a solution of an alkali or alkaline earth metal in liquid ammonia, or a suspension of these metals in other solvents (614) for a study of changes in chemical shifts produced on ionization of 2-methyl and 2-amino derivatives of pyrazine in liquid ammonia (665) for characterization of methoxymethylpyrazines (686) for the determination of the position of the A -oxide function in monosubstituted pyrazine V-oxides and the analysis of V-oxidation reactions (838) for a study of the structure of the cations of fV-oxides of monosubstituted pyrazines (1136) and for the determination of the structure of the products of peroxyacetic and peroxysulfuric acid iV-oxidation of phenyl- and chlorophenylpyrazines (733b). 

Benzylic coupling in substituted methylpyrazines (687) and the influence of side chain alkyl substitution on benzylic coupling constants (1500) have been examined. On the basis of the methyl replacement technique, within its inherent limitations, the para-benzylic coupling appeared to be rr-electron transmitted. 

Nuclear magnetic resonance parameters of disubstituted pyrazines have been correlated with chemical structures (867). The coupling constants of 2,3. 2,5-, and 2,6-disubstituted pyrazines were found to be 2.5-3.0, 1.1-1.4, and OHz, respectively, and the values were not influenced by the kind of substituents (867). Methyl-methyl proton spin-spin coupling constants in 2,5- and 2,6-dimethyl-pyrazines have been determined (1502). 

The and N relaxation rates and the deuterium quadrupole coupling constant for pyrazine have been reported (1503) but the motion of this molecule could not be analyzed. N-H Spin coupiings in pyrazine methiodides have been determined (704). 

---