Reactivity, of aluminum

Aluminum compounds such as AlMe3 are well known to be highly air and moisture sensitive due to the strength of the Al-O bond (—350kjmol-1) versus the Al-C bond (—255 kj mol-1). Complete oxidation of 1ml of A1Mc3 in ambient air can produce a fireball 3 ft in diameter. Recent studies under controlled conditions have produced a better understanding of the reactivity of aluminum alkyls. 

Control of the ROP of lactones was improved by using aluminum alkoxides instead of their anionic counterpart, as witnessed by the increase of the selectivity factor p, as shown for instance in Table 3 in the case of the polymerization of sCL. The lower reactivity of aluminum alkoxides compared to their anionic counterparts is shown by the decrease in the rate of propagation of the polymerization (A p). 

A variety of chelate complexes of Al3+ with N and/or O donor atoms are known through stability constant data.7,8 Their formation illustrates several aspects of A1 coordination chemistry. Chelates and other multidentate ligand systems provide a means of regulating the reactivity of aluminum compounds. For example, A1 alkoxides can be converted to amino alcohol derivatives to confer water solubility and a degree of hydrolytic stability on otherwise water-sensitive materials. 

Violante, A., Ricciardella, M., Del Gaudio, S. and Pigna, M. (2006) Coprecipitation of arsenate with metal oxides nature, mineralogy, and reactivity of aluminum precipitates. Environmental Science and Technology, 40(16), 4961-67. 

The reaction conditions generally seem to be more critical with aluminum chloride than with stannic chloride. Yields, perhaps as a result, are more often hard to duplicate. These facts are doubtless due in part to the greater reactivity of aluminum chloride and to the difficulty commonly experienced in obtaining samples of this reagent which do not vary in catalytic effect. A pronounced influence of the grade of the aluminum chloride already has been mentioned. 

The acidity of aluminum halides and the relatively moderate reactivity of aluminum enables surface film free aluminum electrodes to be obtained in several types of nonaqueous electrochemical solutions, as discussed in the next section. 

We have recently conducted a series of mass-selected experiments, employing the GIB-MS technique on the reactivity of aluminum oxide ions with CO. These experiments were motivated by a recent condensed-phase study where gold particles supported on alumina were found to be highly active in the oxidation of CO [85]. Alumina is an ideal catalyst support material due to its high mechanical... 

Figure 2. Reactivity of aluminum clusters toward D2. (a) Time-of-flight mass spectrum of bare Al and their deuterium addition products. Dashed trace—reference spectrum in which He only is pulsed into reactor, solid trace—Dj/He mixture is used, (b) Relative rate constants of Al (n = 2-14) toward chemisorption of Dj obtained from data such as that presented in (a). (From Cox et al. )...

In older applications of aluminum species in the Friedel-Crafts reaction ADC 3 (X = C1, Br, I) have been used as catalysts [6], Effects of covalently-attached strongly electron-withdrawing groups on the reactivity of aluminum(III) were investigated. The tris(triflate) catalyst Al(OTf)3 was originally devised by Olah and coworkers (Scheme 6.74) [96]. As expected, tris(trifryl)imide catalyst 102 had more pronounced catalytic efficiency, because of its greater Lewis acidity (Scheme 6.75) [97]. 

In order to enhance the reactivity of aluminum porphyrins (J ) especially towards C02 in the copolymerization with epoxide (Equation 4), the effect of addition of an amine or phosphine as a possible sixth ligand to the aluminum porphyrin was examined. The enhancement in reactivity by the addition of a tertiary amine such as N-methyl-imldazole was actually observed for the epoxlde-C02 reaction. The product, however, was a cyclic carbonate (JO), not a linear copolymer. On the other hand, J he addition of trlphenylphosphlne was very effective in the formation of an alternating copolymer from epoxide and... 

Inoue et al. have developed photochemical carboxylation of ketones by the virtue of photo-enhanced nucleophilic reactivities of aluminum porphyrin complexes. Treatment of [(TPP)AlNEt2l with aromatic ketones produces the corresponding porphinatoaluminum enolate products,... 

The reactivity of aluminum hydrides toward organomercurials decreases" LiAlH > HjAl NMej. The reaction of AI hydrides with alkenylmercurials gives alkenyl aluminums " ... 

Towle SN, Bargar JR, Brown GE Jr, Parks GA (1999b) Sorption of Co(II) on metal oxide surfaces II. Identification of Co(II)(aq) adsorption sites on (1-102) and (0001) surfaces of a-Al203 by grazing-incidence XAFS spectroscopy. J Colloid Interface Sci 217 312-321 Trainor TP (2001) X-ray Scattering and X-ray Absorption Spectroscopy Studies of the Structure and Reactivity of Aluminum Oxide Surfaces. Ph.D. Dissertation. Department of Geological Environmental Sciences, Stanford University, Stanford, CA, USA Trainor TP, Brown GE Jr, Parks GA (2000) Adsorption and precipitation of aqueous Zn(II) on alumina powders. J Colloid. Interface Sci 231 359-372... 

K. Kmel, T. Kosmac, Reactivity of aluminum nitride powder in dilute inorganic acids, J. Am. Ceram. Soc., 83 (2000) 1375-1378. 

The thermal decomposition characteristics of micron-sized aluminum powder and potassium perchlorate mixtures were studied with thermal analytical techniques by Pourmortazavi and coworkers [108]. The results showed that the reactivity of aluminum powder in air increases as the particle size decreases. Pure aluminum with 5 pm particle size has a fusion temperature of about 647 °C, but for 18 pm powder this temperature is 660 °C. Pure potassixun perchlorate has an endothermic peak at 300 C corresponding to a rhombic-cubic transition, a fiision temperature around 590 °C and decomposes at 592 °C. DTA curves for an AI5/KCIO4 (30 70) mixture show a maximum peak temperature for thermal decomposition at 400 °C. Increasing the particle size of aluminum powder increases the ignition temperature of the mixture. The oxidation temperature is increased by increasing the aluminum content of the mixture. 

An approximate gage for the reactivity of aluminum with various oxides is the difference between the equivalent heats of formation of aluminum oxide (66 kcal) and the oxide to be reduced If this difference exceeds 40 kcal (as is the case for PbO, Bi Og, CuO, and Pb02)... 

Reactivity of Aluminum Enolates and Application in Organic Synthesis. 293... 

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