Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Absolute values of the coupling constants ¹J(¹⁵N¹⁵N), ¹J(¹⁵NH) of six phenylhydrazones forming hydrogen bond, ²J(¹⁵N¹⁵NH) of four, and ⁴J(¹⁵NH) of two phenylhydrazones have been determined. Three coupling constants ¹J(¹⁵N¹⁵N) have been obtained from the nitrogen-15 monolabelled compounds by measuring the other nitrogen at natural abundance. The coupling constants ²J(¹⁵N¹⁵NH) have been measured with the nitrogen-15 doubly labelled compounds, because in the arrangement ¹⁵N¹⁴NH there exists a broadening of the proton signal due to nitrogen-14. Absolute values of the coupling constants ¹J(¹⁵N¹⁵N) of the phenylhydrazones forming hydrogen bond to the ester group are smaller ( 10.8 Hz) than those of the phenylhydrazones having hydrogen bond to carbonyl group ( 11.1 Hz). The coupling constants ²J(¹⁵N¹⁵NH) have a value 2.4 ± 0.2 Hz. The value of ¹J(¹⁵N¹⁵N) of 1-phenylazo-2-naphthalenol decreases with increasing content of hydrazone form. The values of ²J(¹⁵N¹⁵NH) of this compound are within 1.2 to 1.6 Hz.