Structural aspects of the hydrolysis products of metal alkoxides and metal trialkylsilyloxides

1969 ◽  
Vol 47 (22) ◽  
pp. 4101-4111 ◽  
Author(s):  
J. W. Lorimer ◽  
D. E. G. Jones
Keyword(s):  
Metal Oxide ◽  
Complex Structure ◽  
Theoretical Models ◽  
Degree Of Polymerization ◽  
Average Degree ◽  
Degree Of Hydrolysis ◽  
Special Cases ◽  
Plausible Mechanism ◽  
Branched Chains ◽  
Structural Aspects

The average degree of polymerization [Formula: see text] depends on the average degree of hydrolysis [Formula: see text] as[Formula: see text] over a large range of [Formula: see text] for all metal oxide alkoxides and oxide trialkylsilyloxides that have been formed by hydrolysis and examined in solution. A number of general theoretical models are developed which permit quantitative interpretation of the parameters a and b. Mixtures of linear or branched chains in proportions governed wholly or partly by the degree of polymerization of the unhydrolyzed alkoxide can explain all the data on oxide alkoxides in solution in their corresponding alcohol, and the model leads to a plausible mechanism for disproportionation. Similar models with more complex structure can be involved in the metal oxide trialkylsilyloxides. Heterogeneity in the composition of the repeating units or in the number of metal–oxygen–metal bridges between successive repeating units can also be significant for both oxide alkoxides and oxide trialkylsilyloxides. Models involving cyclic chains are possible, but steric effects make them improbable in many cases. Mixtures of chains with equal average degrees of hydrolysis for each type of chain have been assumed in previous analyses, but are shown to be special cases of the more general model.

METAL OXIDE TRIALKYLSILYLOXIDE POLYMERS (POLYTRIALKYLSILOXANOMETALLOXANES): PART I. TITANIUM OXIDE TRIMETHYLSILYLOXIDE POLYMERS

1963 ◽  
Vol 41 (3) ◽  
pp. 629-635 ◽  
Author(s):  
D. C. Bradley ◽  
C. Prevedorou-Demas
Keyword(s):  
Molecular Weight ◽  
Metal Oxide ◽  
Titanium Oxide ◽  
Degree Of Polymerization ◽  
Average Degree ◽  
Degree Of Hydrolysis ◽  
Controlled Conditions

Tetrakis-(trimethylsilyloxy)-titanium Ti(OSiMe3)4 has been hydrolyzed under controlled conditions in dioxane. The initial products of hydrolysis undergo facile disproportionation, e.g. 3Ti2O(OSiMe3)6 → 4Ti(OSiMe3)4 + polymeric Ti2O3(OSiMe3)2. Molecular weight determinations were made on the titanium oxide trimethylsilyloxide polymers (polytrimethylsiloxanotitanoxanes) obtained by thermal disproportionation. Structures have been suggested for the polymers on the basis of the variation of number-average degree of polymerization with the degree of hydrolysis.

METAL OXIDE ALKOXIDE POLYMERS: PART I. THE HYDROLYSIS OF SOME PRIMARY ALKOXIDES OF ZIRCONIUM

1961 ◽  
Vol 39 (7) ◽  
pp. 1434-1443 ◽  
Author(s):  
D. C. Bradley ◽  
D. G. Carter
Keyword(s):  
Metal Oxide ◽  
Zirconium Oxide ◽  
Structural Models ◽  
Degree Of Polymerization ◽  
Degree Of Hydrolysis ◽  
Zirconium Alkoxides ◽  
Hydrolysis Of

Ebulliometric studies have been made on the hydrolysis of some zirconium alkoxides, Zr(OR)4 where R = Et, Prn, Bui, and Bun. The variation of the degree of polymerization of the zirconium oxide alkoxides so produced was determined as a function of the degree of hydrolysis. The results are interpreted in terms of structural models based on octahedrally 6-co-ordinated zirconium.

METAL OXIDE ALKOXIDE POLYMERS: PART II. THE HYDROLYSIS OF TANTALUM PENTAETHOXIDE

1961 ◽  
Vol 39 (9) ◽  
pp. 1818-1826 ◽  
Author(s):  
D. C. Bradley ◽  
H. Holloway
Keyword(s):  
Metal Oxide ◽  
Tantalum Oxide ◽  
Structural Models ◽  
Degree Of Polymerization ◽  
Degree Of Hydrolysis ◽  
Oh Groups ◽  
Infrared Studies ◽  
Hydrolysis Of ◽  
Considerable Range ◽  
Characteristic Manner

The hydrolysis of tantalum pentaethoxide has been studied in boiling benzene and in boiling ethanol. Soluble tantalum oxide ethoxides were obtained over a considerable range of hydrolysis. Infrared studies suggest that Ta—OH groups are absent in these products. Ebulliometric studies have shown that the number-average degree of polymerization varies with the degree of hydrolysis in a characteristic manner and this has been quantitatively explained in terms of fundamental structural models based on octahedrally 6-co-ordinated tantalum.

Combined Implementation of Dynamic Rating-based Protection and Calculating the Average Degree of Polymerization for Power Transformers

2021 ◽  
Vol 141 (7) ◽  
pp. 528-534
Author(s):  
Kohei Ito ◽  
Mutsumi Aoki ◽  
Toru Amau ◽  
Tetsuo Otani ◽  
Tatsuya Ozawa ◽  
...  
Keyword(s):  
Degree Of Polymerization ◽  
Average Degree ◽  
Power Transformers

Nanostructured Metal Oxide Gas Sensor

2014 ◽  
pp. 1213-1253
Author(s):  
Jamal Mazloom ◽  
Farhad E. Ghodsi
Keyword(s):  
Metal Oxide ◽  
Gas Sensor ◽  
Recent Progress ◽  
Theoretical Models ◽  
Response Mechanism ◽  
Conduction Model ◽  
Hollow Nanostructures ◽  
Metal Oxide Gas Sensor ◽  
Semiconducting Metal Oxide ◽  
Nanostructured Metal

This chapter provides a review of recent progress in gas sensor based on semiconducting metal oxide nanostructure. The response mechanism and development of various methods to enhancement of sensing properties receives the most attention. Theoretical models to explain the effects of morphology, additives, heterostructured composite and UV irradiation on response improvement were studied comprehensively. Investigations have indicated that 1D nanostructured metal oxide with unique geometry and physical properties display superior sensitivity to gas species. Also, the proposed conduction model in gas sensor based on 1D Metal oxide is discussed. Finally, the response mechanism of hierarchical and hollow nanostructures as novel sensing materials is addressed.

scholarly journals Extraction and Characterization of Inulin-Type Fructans from Artichoke Wastes and Their Effect on the Growth of Intestinal Bacteria Associated with Health

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Zahraa Zeaiter ◽  
Maria Elena Regonesi ◽  
Sofia Cavini ◽  
Massimo Labra ◽  
Guido Sello ◽  
...  
Keyword(s):  
Intestinal Bacteria ◽  
Degree Of Polymerization ◽  
Average Degree ◽  
Globe Artichoke ◽  
Ethanol Precipitation ◽  
Long Chain ◽  
Simpler Method

Globe artichoke is an intriguing source of indigestible sugar polymers such as inulin-type fructans. In this study, the effect of ultrasound in combination with ethanol precipitation to enhance the extraction of long chain fructans from artichoke wastes has been evaluated. The inulin-type fructans content both from bracts and stems was measured using an enzymatic fructanase-based assay, while its average degree of polymerization (DP) was determined by HPLC-RID analysis. Results show that this method provides artichoke extracts with an inulin-type fructans content of 70% with an average DP between 32 and 42 both in bracts and in stems. The prebiotic effect of long chain inulins from artichoke extract wastes was demonstrated by its ability to support the growth of five Lactobacillus and four Bifidobacterium species, previously characterized as probiotics. Besides, we considered the possibility to industrialize the process developing a simpler method for the production of inulin-type fructans from the artichoke wastes so that the artichoke inulin preparation could be suitable for its use in synbiotic formulations in combination with different probiotics for further studies including in vivo trials.

THE MECHANISM OF DEGRADATION OF A CELLODEXTRIN BY MYROTHECIUM CELLULASE

1956 ◽  
Vol 34 (1) ◽  
pp. 488-494 ◽  
Author(s):  
D. R. Whitaker
Keyword(s):  
Degree Of Polymerization ◽  
Average Degree ◽  
Transfer Reactions ◽  
Mechanism Of Degradation ◽  
Specific Activities

A cellodextrin with a number-average degree of polymerization (D.P.) of 24 was hydrolyzed by Myrothecium cellulase in the presence of C14-labelled cellobiose. The specific activities of cellotriose and cellotetraose isolated at various stages of the hydrolysis were less than 20% of that of cellobiose isolated at the same time. It is concluded that transfer reactions involving cellobiose contributed little to the formation of cellotriose and cellotetraose. The ratio moles of cellotriose formed/mole of cellobiose formed was at least 0.7 and the corresponding ratio for cellotetraose at least 0.4. The number-average D.P. of the substrate decreased slightly during the hydrolysis. The results exclude a degradation of the substrate by cleavage of cellobiose units from the ends of its chains but are consistent with degradation by random cleavage.

Molecular design of supported metal oxide catalysts: An initial step to theoretical models

1993 ◽  
Vol 82 (2-3) ◽  
pp. 443-455 ◽  
Author(s):  
Israel E. Wachs ◽  
Goutam Deo ◽  
Michael A. Vuurman ◽  
Hangchun Hu ◽  
Du Soung Kim ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Molecular Design ◽  
Initial Step ◽  
Theoretical Models ◽  
Oxide Catalysts ◽  
Metal Oxide Catalysts ◽  
Supported Metal Oxide ◽  
Supported Metal
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