Cation dynamic studies in n-propylammonium chloride, CH3(CH2)2NH3Cl, by NMR

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Journal titleThe Journal of Chemical Physics
Pages39673971; # of pages: 5
Subjectactivation energies; phase transitions; protons; magnetic resonance; nuclear magnetic resonance
AbstractPulsed and continuous wave protonmagnetic resonance techniques have been used to study the low and room temperature modifications of CH3(CH2)2NH3Cl (n-propylammonium chloride or PACl) and CH3(CH2)2ND3Cl (d 3-PACl) over the temperature region 77 °K to ∼ 346 °K. The proton static spin–lattice relaxation time (T 1) and second moment data in the ordered low temperature phase are consistent with a model where only CH3 and CH3+NH3 + group rotation about their three-fold axes take place in d 3-PACl and PACl, respectively. At each temperature the methyl group rotation is faster than that of NH3 + and the respective activation energies are 2.4 (±0.15) and 3.7 (±0.2) kcal/mole for CH3 and NH3 + rotation. For the room temperature phase of both salts relatively fast chain rotation about their long chain axis with independent CH3 +NH3 + group rotation was found from second moment analysis. The activation energy obtained for this motion from the T 1 data is 2.5 (±0.2) kcal/mole. The reported phase transition exhibits an appropriate discontinuity in the T 1 curve at 186±2 °K and seems to be associated with the dynamic disorder. The reorientations and phase transitions in the corresponding modifications of the n-alkylammonium chloride series is discussed in the light of our results and other published data.
Publication date
AffiliationNational Research Council Canada
Peer reviewedYes
NRC number17611
NPARC number21275091
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Record identifierb7c7ac6b-3408-4fec-bafd-21b3cba5e3a2
Record created2015-05-07
Record modified2016-05-09
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