Effective boron compounds

Boron. The principal materials used are borax [1303-96-4] sodium pentaborate, sodium tetraborate, partially dehydrated borates, boric acid [10043-35-3] and boron frits. Soil appHcation rates of boron for vegetable crops and alfalfa are usually in the range of 0.5—3 kg/hm. Lower rates are used for more sensitive crops. Both soil and foHar appHcation are practiced but soil appHcations remain effective longer. Boron toxicity is not often observed in field appHcations (see Boron compounds). 

Inorganic boron compounds are generaHy good fire retardants (59). Bode acid, alone or in mixtures with sodium borates, is particularly effective in reducing the flammabHity of ceUulosic matetials. AppHcations include treatment of wood products, ceUulose insulation, and cotton batting used in mattresses (see Flame retardants). 

The reader will no doubt have realized that the y-hetero rearrangement is well-known, being none other than the familiar neighboring group effect. The a-hetero rearrangement is known for all of the elements mentioned but boron, aluminum, and silicon. Perhaps a suitably constituted boron compound would rearrange to a zwitterionic product as follows ... 

Boron rods provide an alternative wood preservative, which is considered safe for people and the environment. They are made of boron compounds that have been subjected to high temperatures to form water-soluble, glassllke rods. These rods are Inserted Into drilled holes In the wood, strategically positioned where decay is most likely the holes are then plugged to keep the rods In place. When the wood becomes wet, boric acid is released, which prevents fungal decay. Boron pastes have a similar effect. Manufacturers of boron rods are seeking to make these rods available for home use. 

With the development of CO 2 lasers, work on the infrared photochemistry of boron compounds is now appearing in the literature. Future woric on these compounds with UV laser sources is also expected. In this review the effect of radiation on boron compounds in the photon energy range 0.1 eV (CO2 laser) to 10.2 eV (H-a line) is examined. The range of tropics extends from the use of photochemical techniques for synthesis of new compounds to the production and isolation of reactive photochemical intermediates. The photochemistry of borazine is most extensively discussed. 

Interest in the photochemistry of boron compounds dates back as far as 1913 when Alfred Stock investigated the effects of light from a mercury vapor lamp on diboran 6) and on tetraboran 10). In the case of diborane(6) he commented UV light will also decompose B2H6. The volume of a sample in a quartz tube increased by 1/6 after 24 hours exposure to a mercury-arc lamp, and a pale yellow crystalline substance appeared. Stock also observed that B4H q decomposition to B2H is not noticeably influenced by sunlight. 

Linear polyethylene can further also be considered as polymethylene. Althoguh first prepared by the thermal decomposition of diazomethane,243 244 Meerwein should be credited to have prepared it by catalytic polymerization of diazomethane effected by boron compounds (esters, halides, alkyls)245-247 taking place with concomitant dediazotation ... 

Organic boron compounds reportedly have some antiknock effectiveness in addition to altering combustion-chamber deposit effects (35, 46). Other compounds showing antiknock properties have recently been reviewed (50). 

So far, only one detailed discussion of boron-11 nuclear magnetic resonance spectra of aminoborane systems has been reported 31>. It was found that the 1 lB chemical shifts of aminoborane systems can be described fairly well in terms of a set of additive substituent contributions. In consonance with earlier work on trisubstituted boron compounds 35> these contributions depend on the mesomeric effects of substituents rather than their electronegativity. 1,3,2-diazaboracycloalkanes can be considered as aminoborane derivatives and in the case of the known heterocycles the exocyclic boron substituent will govern primarily the boron chemical shifts and will do so by mesomeric effects. However, the available data are rather limited and it may be possible that additional factors must be considered. Steric effects appear to be negligible, however, since the heterocycles with either six or seven annular atoms have almost identical shifts (Table 5). 

Since the epoxidation step involves no formal change in the oxidation state of the metal catalyst, there is no reason why catalytic activity should be restricted to transition metal complexes. Compounds of nontransition elements which are Lewis acids should also be capable of catalyzing epoxidations. In fact, Se02, which is roughly as acidic as Mo03, catalyzes these reactions.433 It is, however, significantly less active than molybdenum, tungsten, and titanium catalysts. Similarly, boron compounds catalyze these reactions but they are much less effective than molybdenum catalysts 437,438 The low activity of other metal catalysts, such as Th(IV) and Zr(IV) (which are weak oxidants) is attributable to their weak Lewis acidity. 

Lack of space prevents descriptions of a number of additional types of boron compounds such as the numerous interstitial metallic borides, the subhalides (of type B2CI4), the organoboron compounds (such as B(CH3)3), and the boron-nitrogen addition compounds, many of which have been prepared by H. C. Brown to study the effects of structures on the stability of Lewis acid-base adducts. ... 

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