ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The oxidation of γ-MnOOH (manganite) in oxygen and its disproportionation in HNO3 lead topotactically to β-MnO2. The oxidation of synthetic α-MnOOH (groutite) in oxygen depends on its cristallite size; finely divided crystals oxidise rapidly to Mn5O8 which usually is stable but yields β-MnO2 by further oxidation. Larger crystals of disperse synthetic α-MnOOH are topotactically transformed to γ-MnO2. In HNO3 α-MnOOH disproportionates into γ-MnO2 and Mn2+. Though strictly topotactical, the reaction α-MnOOH → γ-MnO2 is not single-phase as might be expected. The discontinuity in the function: JAHN-TELLER distortion vs. reaction rate, may simply be interpreted as the crosspoint of two different functions attributed to the crystal species α-MnOOH and γ-MnO2, respectively. This distortion confirms the presence of Mn3+ in manganite and nsutite. The wide variety of possible X ray powder patterns of the phase γ-MnO2 is explained by the superposition of, (i) cristallite size broadening, (ii) intergrowth structure effects on the profile, and (iii) BRAGG angle shifts due to substitution of part of Mn4+ by Mn3+.
Additional Material:
18 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19690520815
Permalink