Boron addition

In perhaps the most important technological observation, it was found that the reacted Ni3Al products have hardness values equivalent to cold-rolled or rapidly solidified NijAl containing boron additives. The hardness is notable in that the material contains a low density of dislocations. It is observed that crystallites are less than 10 nm in dimension. 

The synthesis in Scheme 13.37 also used a me,ro-3,4-dimethylglutaric acid as the starting material. Both the resolved aldehyde employed in Scheme 13.36 and a resolved half-amide were successfully used as intermediates. The configuration at C(2) and C(3) was controlled by addition of a butenylborane to an aldehyde (see Section 9.1.5). The boronate was used in enantiomerically pure form so that stereoselectivity was enhanced by double stereodifferentiation. The allylic additions carried out by the butenylboronates do not appear to have been quite as highly stereoselective as the aldol condensations used in Scheme 13.37, since a minor diastereoisomer was formed in the boronate addition reactions. 

Among the three subcategories, boronate compounds seemed to be the most efficient in coordinating with anions and enhancing lithium ion stability, although the number of electron-withdrawing substituents in boronate is only two. The authors thus inferred that the ability of these anion receptors to capture an anion depends not only on the electron-deficiency of the core atom but perhaps also on the steric hindrance presented by these substituents on the core. With only two substituents, the core of the boronates is obviously more exposed and therefore more easily accessible for an anion. The higher ion conductivity achieved by boronate additive therefore comes from the better balance between the electron-deficiency and steric openness of this compound as... 

The enantioselective addition of ally organometallics to carbonyls has become one of the workhorses of organic synthesis. Dennis Hall of the University of Alberta reports (J. Am. Chem. Soc. 125 10160, 2003) the scandium triflate catalysis chiral allylboronic acids become more effective tools. The best of these, the Hoffmann camphor derivative 2, adds to aldehydes under Sc(OTf), catalysis with excellent enantiomeric excess. The reaction works equally well for methallyl, and for the E and Z crotyl boronic acids. The crotyl derivatives react with the expected high diastereocontrol. A limitation to the boronate additions is that branched chain aldehydes give low yields. 

Ammonium Sulfate. Addition to the fused nitrite causes effervescence and ignition.3 Boron. Addition to the fused nitrite causes violent decomposition.4 Potassium Amide. Explosion occurs when mixture with potassium amide is heated under vacuum.5... 

AGR fuel is transported to Sellafield in skips which are placed inside lidded containers using a dry inlet facility shared with Magnox fuel in the FHP. The container provides criticality control by segregation so boron addition to the water is unnecessary. The design of the lid allows containers to be triple stacked. After a minimum of 180 days cooling the elements are dismantled. 

Figure 9 Enhancement of tensile elongation and change of fracture type of NisAl (with 24 at. % Al) by small boron additions. (Ref. 43. Reproduced by kind permission of Springer Science Business Media)...

Boron, addition to explosives 18 Boron compounds in rocket propellants 572.573 (111/311)... 

Wurtzite-type BN (wBN or yBN) is close to cubic BN in density and will transform to cubic BN above 55 GN/m and 1450°C. It will also convert to hexagonal BN below about 60GN/m and above 1000°C. wBN is a metastable form at pressures and temperatures where cBN is fabricated. The powder can be synthesized from graphitic or hexagonal BN by shock compression and an alkaline fusion technique. The effect of TiBa and boron additives on the transformation of wBN to cBN has been studied. TiBa shifts the formation region of cBN to higher temperatures while B shifts it to lower temperatures. wBN can be synthesized by static compression at pressures exceeding 5.5 GN/m and low temperatures or by shock compression . ... 

At present, this liquid-solid substitution approach has been extended to the secondary synthesis of zeolites containing Si, Fe, Sn, Ti, Cr, and other heteroatoms. An exception is that BF4 cannot be used for liquid-phase dealumination and boron-addition of zeolites to prepare boron-containing zeolites.[33] In the following galliation of NH4Y will be taken as an example to discuss the isomorphous substitution secondary synthesis technique. 

Unpublished results. The cataKtic hydroboration of 1-octyne with 7 in benzene in the presence of Pd(PPh,)4 (2 mol n) proceeds at room temperature to give a 4 96 mixture of Uoctenylborate favoring the terminal boron addition product. 

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