Dynamic NMR spectroscopy of three 2,2'-dialkyl/aryl-1-picrylhydrazines in liquid solution.
We have studied and compared the proton nuclear magnetic resonance spectra of a series of three 2,2'-di(alkyl/aryl)-1-(2,4,6-trinitrophenyl)hydrazines at 500 MHz in liquid toluene-d(8), with a view to learning details of the internal conformation changes taking place, as a function of temperature. Herein "alkyl" denotes 'methyl', and "aryl" denotes 'phenyl'. The synthesis and characterization of 2-phenyl,2'-methyl-1-picrylhydrazine is reported. One goal of the present study was to afford a comparison with the oxidation products, i.e., the three corresponding hydrazyl free radicals - which show striking differences. All the hydrazine molecules in liquid solution occur as interconverting enantiomorphic pairs (atropisomers). Advanced techniques for obtaining the relevant activation energies and pseudo-thermodynamic parameters (Arrhenius and Eyring) have been utilized, and these parameters are listed and discussed. The three hydrazines turn out be very similar with respect to their internal dynamics.
Brown
K C
KC
Department of Chemistry, University of Saskatchewan, Saskatoon, SK, Canada.
El-Bermani
M
M
Weil
J A
JA
D005609:Free Radicals / Q000737:chemistry; D006834:Hydrazines / Q000737:chemistry*; D007202:Indicators and Reagents / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008962:Models, Theoretical; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010851:Picrates / Q000737:chemistry; D012996:Solutions / Q000737:chemistry*; D013816:Thermodynamics
D005609:Free Radicals; D006834:Hydrazines; D007202:Indicators and Reagents; D010851:Picrates; D012996:Solutions; C005858:picric acid