2-Nitrosopyridine, 1, 3-methyl-2-nitrosopyridine, 2, and 4-methyl-2-nitrosopyridine, 3, exist in org. solvents as monomer-azodioxy dimer equil. with the dimers predominating at ambient temps. In the case of compds. 1 and 3 only the Z-dimers co-exist with the monomers, whereas for compd. 2 both Z- (major) and E- (minor) dimers are present with the monomer. Variable temp. 1H NMR bandshape anal. and 2D-EXSY spectra of 1-3 provided thermodn. and kinetic data for the dissocn. equil. Z- (or E-) dimer .dblharw. 2 monomer, ΔH values being in the range 53-58 kJ mol-1 and ΔG ‡ (298.15 K) values in the range 70-82 kJ mol-1. An X-ray crystal structure of 1 identified the compd. as a Z-dimeric species with the two pyridine rings twisted by 62.7° and their heterocyclic N atoms pointing towards each other.
The solid-and the Solution-State Structures of 2-Nitrosopyridine and its 3- and 4- Methyl derivatives
MELE, Giuseppe Agostino;VASAPOLLO, Giuseppe;
2000
Abstract
2-Nitrosopyridine, 1, 3-methyl-2-nitrosopyridine, 2, and 4-methyl-2-nitrosopyridine, 3, exist in org. solvents as monomer-azodioxy dimer equil. with the dimers predominating at ambient temps. In the case of compds. 1 and 3 only the Z-dimers co-exist with the monomers, whereas for compd. 2 both Z- (major) and E- (minor) dimers are present with the monomer. Variable temp. 1H NMR bandshape anal. and 2D-EXSY spectra of 1-3 provided thermodn. and kinetic data for the dissocn. equil. Z- (or E-) dimer .dblharw. 2 monomer, ΔH values being in the range 53-58 kJ mol-1 and ΔG ‡ (298.15 K) values in the range 70-82 kJ mol-1. An X-ray crystal structure of 1 identified the compd. as a Z-dimeric species with the two pyridine rings twisted by 62.7° and their heterocyclic N atoms pointing towards each other.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
