Pyrazole, dipole moment

Experimental values are collected in the McClellan book (B-63MI40400) and in a review on dipole moments and structure of azoles (71KGS867). Some selected values are reported in Table 3. The old controversy about the dipole moment of pyrazole in solution has been settled by studying its permittivity over a large range of concentrations (75BSF1675). These measurements show that pyrazole forms non-polar cyclic dimers (39) when concentration increases and, in consequence, the permittivity value decreases. 

Table 3 Experimental Dipole Moments of Pyrazoles and Indazoles at 25 °C...

H NMR, 5, 184 (B-73NMR165, B-76MI40402) Pyrazole, 3,4-dibromo-dipole moment, 5, 177 (71KGS867)... 

Indeed, in the speetrum of ethynylpyrazole 94, the triple bond appears at 2112 em and then in the speetrum of earbinol 95, as in other disubstituted aeetylenes, their frequeney inereases by about 100 em . Note that the high intensity of the 2112 em band of eompound 94 is likely to result from the elevated eleetron density at position 4 of the pyrazole ring and the resulting inerease in the dipole moment of the triple bond eonjugate to it. 

Pyrazole, 3-methyl-dipole moment, 5, 177 <75BSF1675> kinetic data, 6, 21 <73AJC1949>... 

Structure and reactivity of neutral pyrazole, its anion and its cation. 2.2 Structure and reactivity of substituted pyrazoles. 2.3 Structure and reactivity of indazoles. 2.4 Dipole moments Structural Methods. 3.1 X-Ray diffraction. 3.2 Microwave spectroscopy. 3.3 H NMR spectroscopy. 3.4 C NMR spectroscopy. 3.5 Nitrogen NMR spectroscopy 3.6 UV spectroscopy. 3.7 JR spectroscopy. 3.8 Mass spectrometry. 3.9 Photoelectron spectroscopy. 3.10 Electron spin resonance spectroscopy Thermodynamic Aspects. 4.1 Intermolecular forces. 4.2 Stability and stabilization. 4.3 Conformation and configuration Tautomerism... 

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