Coupling constants thiazole

Concerning N-magnetic resonance, Boejesen et at. (113) have measured the following coupling constants on a sample of thiazole enriched in this isotope ... 

Experimental confirmation of the metal-nitrogen coordination of thiazole complexes was recently given by Pannell et al. (472), who studied the Cr(0), Mo(0), and W(0) pentacarbonyl complexes of thiazole (Th)M(CO)5. The infrared spectra are quite similar to those of the pyridine analogs the H-NMR resonance associated with 2- and 4-protons are sharper and possess fine structure, in contrast to the broad, featureless resonances of free thiazole ligands. This is expected since removal of electron density from nitrogen upon coordination reduces the N quad-rupole coupling constant that is responsible for the line broadening of the a protons. 

The 13C-H spin coupling constants of thiazole have been determined on samples with 13C natural abundance or on samples specifically enriched in the 2-, 4- or 5-positions (Table 8). The 13C chemical shifts of benzothiazole are reported in Table 9. 

NMR study of nitrothiazoles has been the subject of few number of works [525, 530-540], The proton chemical shifts of about 30 thiazole derivatives including 5-nitrothiazole and 2-nitrothiazole are presented in [536], The authors have found the coupling constants between H-2 and II-4 in most 5-substituted thiazoles to be negligible with the exception of 5-nitrothiazole and 5-thiazolecarboxylic acids [536], The change in the H-4 chemical shifts of the 2-substituted 5-nitrothiazole fragment enables the ratio of isomeric products of the reaction of 5-nitrothiazole 2-(T,3 -dicarbonyl) derivatives with hydrazine and hydroxylamine to be established (Scheme 3.8) [537],... 

TABLE 1-39. COUPLING CONSTANTS Jch (Hz) IN THIAZOLE AND SOME OF ITS DERIVATIVES A. Jc-H Couplings... 

TT-Electron densities, correlation with proton chemical shift, of alkylthiazoles, 344 of phenylthiazoles, 345 Electronic charges, of thiazole, 31 of aminothiazoles, 44 of chlorothiazoles, 44 of methylthiazoles, 40 Electronic effects, of 5-substituents on quaternization, 390 Electronic paramagnetic resonance, 84 coupling constants for nitrothiazoles, 84 coupling constants for 2-thiazolyl radical, 84... 

Nitrothiazole, 576 preparation of, 577 reduction of, 577 ring opening reaction, 577 Nitrothiazoles, chemical shift, proton, 68 coupling constants in EPR, 84 ionization potential, 5 2 reduction of, 381 ultraviolet absorption, 48 Nuclear magnetic resonance, 66 of alkyl thiazoles, 342 of aryl thiazoles, 342 correlation with theoretical calculations, 70... 

JCH coupling constants in thiazoles, 78 JHH coupling constants, in methylthia-zoles, 75 in thiazoles, 74... 

J j 5N-H coupling constants in thiazole, 81 JNH coupling constants of thiazole, 80 line width of thiazole lines, 80 of monosubstituted thiazoles, 68 proton chemical shifts, of alkylthiazoles, 342... 

TABLE 1-34. PROTON CHEMICAL SHIFTS AND COUPLING CONSTANTS J OF THIAZOLE IN VARIOUS SOLVENTS AT INFINITE DILUTION (20 C) (235)... 

The C-H coupling constants can also be used to calculate interorbital and internudear angles. For thiazole, very precise results have been... 

When the coupling is across a tricoordinate carbon atom involved in a delocalized 7t-electron system, the absolute value of 2/(15N-C-H) may increase to as much as 16 Hz. (le) In the review period, the signs of such coupling constants have been determined as negative for formamide, (144) pyrrole, (146, 154, 155) pyrazole, thiazole, pyridine and pyridazine (155) as well as for some azinium ions. (151) The latter afford another example of the decrease in the absolute value of the coupling constant upon protonation of the nitrogen lone pair (Table XXXIII) [79], [80]. 

Hz and J s 67.7 Hz for the less aromatic isoxazole. Similarly, J45 for thiazole (62.1 Hz) is closer to that of benzene than that of J45 for oxazole (70.8 Hz). This model is interesting, but other factors, including geometry, contribute to these coupling constants. 

Conformational analysis of 1,3-thiazolidines and other thiazole derivatives has been carried out by NMR methods (see Section 3.06.3.6.1). Thus, the analysis of the coupling constants of the H NMR spectra <74JA1465> permitted to postulate envelopes with either C-4 or C-5 as the flap atom and with the 2-substituent anti to the flap as the predominant conformations (Equation (2)). 

---