Steric effects: the problem of their quantitative assessment and manifestation in the reactivity of hetero-organic compounds

Phosphorus (P) fixation is a global problem for soil fertility and negatively impacts agricultural productivity. This study characterizes P desorption of already fixed P by using KCl, KNO3, histidine, and malic acid as inorganic and organic compounds, which are quite common in soil. Goethite, gibbsite, and ferrihydrite, as well as hydroxide mixtures with varying Fe- and Al-ratio were selected as model substances of crystalline and amorphous Fe- and Al-hydroxides. Especially two- and multi-component hydroxide systems are common in soils, but they have barely been included in desorption studies. Goethite showed the highest desorption in the range from 70.4 to 81.0%, followed by gibbsite with values in the range from 50.7 to 42.6%. Ferrihydrite had distinctive lower desorption in the range from 11.8 to 1.9%. Within the group of the amorphous Fe-Al-hydroxide mixtures, P desorption was lowest at the balanced mixture ratio for 1 Fe: 1 Al, increased either with increasing Fe or Al amount. Precipitation and steric effects were concluded to be important influencing factors. More P was released by crystalline Fe-hydroxides, and Al-hydroxides of varying crystallinity, but desorption using histidine and malic acid did not substantially influence P desorption compared to inorganic constituents.

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The application of mass spectrometry to a quantitative characterisation of the electronic and steric effects in organic compounds—I: The transmission of substituent influence through the chain of conjugated double bonds

Organic Mass Spectrometry ◽

10.1002/oms.1210050903 ◽

1971 ◽

Vol 5 (9) ◽

pp. 1043-1048 ◽

Cited By ~ 15

Author(s):

B. M. Zolotarev ◽

L. A. Yanovskaya ◽

B. Umirzakov ◽

O. S. Chizhov ◽

V. F. Kucherov

Keyword(s):

Mass Spectrometry ◽

Organic Compounds ◽

Steric Effects ◽

Double Bonds ◽

Quantitative Characterisation ◽

Substituent Influence ◽

Electronic And Steric Effects

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ChemInform Abstract: PARTIAL MOLAL VOLUMES OF ORGANIC COMPOUNDS IN CARBON TETRACHLORIDE. 3. AROMATIC HYDROCARBONS: STERIC EFFECTS

Chemischer Informationsdienst ◽

10.1002/chin.197929189 ◽

1979 ◽

Vol 10 (29) ◽

Author(s):

F. SHAHIDI ◽

P. G. FARRELL ◽

J. T. EDWARD ◽

P. CANONNE

Keyword(s):

Carbon Tetrachloride ◽

Organic Compounds ◽

Aromatic Hydrocarbons ◽

Steric Effects ◽

Partial Molal Volumes ◽

Molal Volumes

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METALLO-ORGANIC COMPOUNDS CONTAINING METAL–NITROGEN BONDS: PART II. SOME DIALKYLAMINO DERIVATIVES OF Nb(V) AND Nb(IV)

Canadian Journal of Chemistry ◽

10.1139/v62-072 ◽

1962 ◽

Vol 40 (3) ◽

pp. 449-454 ◽

Cited By ~ 52

Author(s):

D. C. Bradley ◽

I. M. Thomas

Keyword(s):

Thermal Decomposition ◽

Organic Compounds ◽

The Other ◽

Considerable Reduction ◽

Steric Effects ◽

Niobium Pentachloride ◽

Alkyl Chains ◽

Steric Factors ◽

Nitrogen Bonds ◽

Derivatives Of

Reactions involving niobium pentachloride and lithium dialkylamides (LiNR2, where R = Me, Et, Prn, Bun) led to considerable reduction of niobium to Nb(IV) as the length of the alkyl chains increased. Nb(NMe2)5 was isolated by sublimation but distillation of the other products gave tetrakis-(dialkylamino)-niobium(IV) compounds. Steric factors are apparently responsible for the low stability of pentakis-(dialkylamino)-niobium(V) compounds. The smaller steric effects of —NMeBun and piperidino groups allowed the isolation of pentakis derivatives. The thermal decomposition of Nb(NMeBun)5 gave mainly Nb(NMeBun)4 with some BunN=Nb(NMeBun)3. Steric effects were also revealed in the replacement of —NMe2 groups in Nb(NMe2)5 by —NEt2 groups and in replacement of —NEt2 groups in Nb(NEt2)4 by piperidino groups.

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