Molecular dynamics in solid L-adrenaline by proton NMR.
Proton NMR measurements of the spectrum, second moment, spin-lattice relaxation time T1 and dipolar relaxation time T1D were carried out on polycrystalline L-adrenaline at 14 and 25 MHz between 55 and 400 K. Between 70 K and 250 K relaxation is dominated by C3 reorientation of the single methyl group in each molecule, characterized by an activation energy 8.3+/-0.3 kJ/mole. Below 70 K tunnelling assisted relaxation is significant, characterized by an excitation energy of 1.9+/-0.2 kJ/mole. Above 250 K an additional molecular motion becomes significant, with activation energy above 28 kJ/mole, attributed to conformational motion of the methylene group in the ethylamine side chain.
Andrew
E R
ER
Department of Physics, University of Florida, Gainesville 32611, USA.
Peplinska
B
B
Kempka
M
M
D004837:Epinephrine / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011522:Protons; D013696:Temperature; D013816:Thermodynamics
D011522:Protons; D004837:Epinephrine