Boron chemical properties

Chemical Properties. In addition to the reactions Hsted in Table 3, boron trifluoride reacts with alkali or alkaline-earth metal oxides, as well as other inorganic alkaline materials, at 450°C to yield the trimer trifluoroboroxine [13703-95-2] (BOF), MBF, and MF (29) where M is a univalent metal ion. The trimer is stable below — 135°C but disproportionates to B2O2 and BF at higher temperatures (30). 

Elements dissolved in boron influence its crystal structure. Dissolved impurities also influenee the physical and chemical properties of boron, especially the electrical properties, because boron is a semiconductor. Preparation of solid solutions in jS-rh boron requires a careful choice of crucible material. To avoid contamination, boron nitride or a cold, coinage-metal crucible should be used or the levitation or floating-zone melting techniques applied. 

The dodecahydrododecaborate anion, B H 2-, is termed unique with considerable justification. This ion and its perhalo derivatives, e.g., Bi2C1i22-, are the most symmetrical molecular aggregates known. The boron atoms occupy the vertices of a regular icosahedron and each is bonded terminally to a hydrogen atom all boron atoms are environmentally equivalent.7,8 This anion is the only known example of the 7 symmetry group.8 General spectral, physical, and chemical properties of Bx2Hi22-are detailed in a paper by Muetterties et al.9... 

Quite evidently, changing the structure of the aromatic carbene from BA to XA has a profound effect on AGST. There is a difference of more than lOkcalmol-1 in this physical property for these two structures. This difference, in turn, appears to control and determine the chemical properties of the carbenes. With the assumptions outlined earlier, this effect can be wholly attributed to a perturbation of the electronic character engendered by replacement of the boron in BA with the oxygen of XA. It will be seen shortly that these two carbenes represent extremes of a nearly continuously tunable range of carbene properties. 

Another early suggestion was that some of the fullerene carbon atoms could be replaced by another element such as nitrogen or boron.1811 Such heterofullerenes are envisaged to have strongly altered chemical properties in comparison to the all-carbon structures.1811 For example, as the substitution number of an electronegative element such... 

Scandium - the atomic number is 21 and the chemical symbol is Sc. The name derives from the Latin scandia for Scandinavia , where the mineral were found. It was discovered by the Swedish chemist Lars-Fredrik Nilson in 1879 from an ytterbium sample. In the same year, the Swedish chemist Per Theodore Cleve proved that scandium was Mendeleev s hypothetical element eka-boron , whose properties and position in the Period Table Mendeleev had previously predicted. 

Due to boron s unique structure and chemical properties, there are still more unusual compounds to be explored. 

Treatment of chromium (III) acetylacetonate with acetic anhydride and boron trifluoride etherate yielded a complex mixture of acetylated chelates but very little starting material. Fractional crystallization and chromatographic purification of this mixture afforded the triacetylated chromium chelate (XVI), which was also prepared from pure triacetylmethane by a nonaqueous chelation reaction (8, 11). The enolic triacetylmethane was prepared by treating acetylacetone with ketene. The sharp contrast between the chemical properties of the coordinated and uncoordinated ligand is illustrated by the fact that chromium acetylacetonate does not react with ketene. 

Jhe distribution of beryllium, boron, titanium, vanadium, chromium, cobalt, nickel, copper, zinc, gallium, germanium, tin, molybdenum, yttrium, and lanthanum in the principal coal-producing beds of the Interior Province has been studied by the U. S. Geological Survey. Data, methods of sampling, and analyses are discussed by Zubovic and others (II, 12). This chapter discusses the occurrence of 13 of these elements with respect to geological and geochemical environments of coal deposition and chemical properties of the elements. Zinc and tin are not included in this study because they were detected in only a few samples. 

One chemical property quoted in support of aromatic character is kinetic stability towards hydrolytic break-down. Many boron heterocycles have been stated to be more stable than expected for organoboranes. On the other hand, several saturated cyclic boron compounds are stable as well, suggesting that the cyclic structure itself is favorable. 

Borazine is isoelectronic with benzene, as B=N is with C=C, (Fig. 16.21). in physical properties, borazine is indeed a close analogue of benzene. The similarity of the physical properties of the alkyl-substituted derivatives of benzene and borazine is ever more remarkable. For example, the ratio of the absolute boiling points of the substituted borazines to those of similarly substituted benzene is constant. This similarity in physical properties led to a labeling of borazine as "inorganic benzene." This is a misnomer because tbe chemical properties of borazine and benzene are quite different Both compounds have aromatic rr clouds of electron density with potential for delocalization over all of the ring atoms. Due to the difference m electronegativity between boron and nitrogen, the cloud in borazine is "lumpy" because more electron... 

Mendeleev had determined some physical and chemical properties of elements before they were discovered and gave these unknown elements names such as eka-aluminum, eka-silicon, eka-boron, eka-cesium and eka-iodine. 

The first blank was filled in 1875. A French chemist discovered an element—gallium—that had all the properties Mendeleyev predicted for the space below aluminum. In 1879, a Swedish researcher discovered scandium, which looked and acted exactly how Mendeleyev said it would in its place below boron. In 1886, a German scientist discovered germanium, the element below silicon. Its chemical properties were almost exactly what Mendeleyev had predicted. 

However, the boron-11 nmr spectrum of (C4He)B2H4 116-117> clearly shows that it has structure 1 below, not structure a. Moreover, the chemical properties reported for (C4He)2B2H2 115> are not consistent with those of known tetraalkyl derivatives of diborane(6), e.g. at room temperature it does not hydroborate terminal olefins nor react with methanol. Brown and coworkers therefore proposed 114> structure 2 for (C4H6) 2B2H2. 

Some molecules containing boron (e.g. BF3) have an incomplete octet (only six electrons with B) and these effect the chemical properties of such compounds. 

Although Sc was difficult to isolate, its existence and several of its chemical properties were predicted in 1871 by Dmitri Mendeleyev, who called it ekaboron because of its expected similarity to boron. Lars Fredrik Nilson first isolated its oxide (scandia) while persuing the oxide of a different rare earth. 

Out of Russia came the patriarchal voice of a prophet of chemistry. There is an element as yet undiscovered. I have named it eka-aluminum. By properties similar to those of the metal aluminum you shall identify it. Seek it, and it will be found. Startling as was this prophecy, the sage of Russia was not through. He predicted another element resembling the element boron. He was even bold enough to state its atomic weight. And before that voice was stilled, it foretold the discovery of a third element whose physical and chemical properties were thoroughly described. No man, not even the Russian himself, had beheld these unknown substances. 

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