Boron anomaly

In the past, the boron anomaly had generally been attributed to a rapid decrease in the relative proportion of BO4 groups at 15-20 molar percent alkali oxide. However, more recent NMR and NQR studies show that the concentration of BO4 groups continues to increase up to about 40 molar percent alkali oxide and then drops off to near zero by about 70 molar percent. This means that the boron anomaly does not correlate with a sudden disappearance of BO4 groups, as previously supposed. 

The boron anomaly does not occur for the glasses containing Al203 A20 =1 1, i.e., for the alkali aluminoborate glasses where alkali and AI2O3 share the same ratio. If the alumina content is increased, then the boron anomaly should occur for higher alkali oxide content. Anyhow, experimental studies indicate that the boron... 

Examination of this anomaly revealed that the carbon-carbon double bond was also reacting, producing a carbon-boron bond with loss of an equivalent of hydride. 

As such, nuclear contributions to the heat capacity due to the interaction between germanium crystalline electric field gradients and the quadrupole moments of boron nuclei could account for the observed onset of the Schottky anomaly. 

The results provide a clear indication of the importance of the change in hybridization between cyclopropane ( sp2 for the external bonds) and propane ( sp3). Electropositive groups prefer to be bonded to the more electron-withdrawing cyclopropane ring, whereas electronegative substituents prefer to be bonded to C2 of propane. The one anomaly in Table 3 is found with the BH2 substituent which leads to the most exothermic group transfer reaction. This is presumably a result of the interaction of the cyclopropane ring with the empty p orbital at boron. This type of interaction will be discussed in the next section. 

Adducts ofB(C6F5)3 that have been studied in detail either in solution or the solid state are collected in Table I along with selected solution NMR spectroscopic data and metrical parameters. In particular, both the nB NMR chemical shift35 and the separation between the resonances for the meta and para fluorine atoms in the 19F NMR spectrum109 are quite sensitive to the environment about the boron center and the strength of the LB-B(C6F5)3 interaction. Indeed, as shown in Fig. 1, a rough empirical correlation between these two NMR parameters is observed. Anomalies arise for two classes of LB more linear bases like nitriles or isonitriles that do not pyramidalize the boron center as severely and the RM1 adducts (M = Al, Ga). 

A. Bohg, Ethylene diamine-pyrocatechol-water mixture shows etching anomaly in boron-doped silicon, J. Electrochem. Soc. 118 401, 1971. 

The primary motivation for predicting the electrochemical properties of the coolant circuits of water-cooled nuclear power reactors has been that of explaining and predicting tenacious operating problems that include SCC and CF, mass transport of corrosion products and subsequent fouling of heat transfer surfaces, activity transport due to the movement of neutron-activated radionuclides from the core to out-of-core surfaces that are not shielded, and, in the case of PWRs, the axial offset anomaly (AOA). This latter phenomenon results from the deposition of boron... 

The two earliest reports of the COClj-BFj system are apparently contradictory the earlier [738a] claims that phosgene and boron(III) fluoride interact to form compounds (but does not identify these in any way), the later [1329] suggests that phosgene and boron(III) fluoride do not form a complex, even at temperatures as low as -120 C. However, a more detailed investigation [1329] resolved these anomalies. The phase diagram for the COClj-BFj system is illustrated in Fig. 9.1, and shows clear evidence for complex formation at compositions BF3.COCIJ (m.pt. -134.3 C) and BF3.2COCIJ (m.pt. -137.0 C) [1329]. 

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