Oxychloride bond

The oxychloride bond, a mixture of magnesium chloride and magnesium oxide, has had... 

Bond Type. Most bonded abrasive products are produced with either a vitreous (glass or ceramic) or a resinoid (usually phenoHc resin) bond. Bonding agents such as mbber, shellac, sodium siHcate, magnesium oxychloride, or metal are used for special appHcations. 

Chemically bonded basic bricks are blended much the same as burned brick mixes except that a bonding agent, eg, magnesium sulfate or magnesium chloride, is added to the mix as well as tempering water to form oxysulfates or oxychlorides. 

Cross-bonded starches can also be manufactured by reaction with trimetaphosphates (115), but these require more vigorous conditions than phosphoms oxychloride. Typically, a starch slurry and 2% trimetaphosphate salt react at pH 10—11 and 50°C for 1 h. 

Zirconium tetrachloride is instantly hydrolyzed in water to zirconium oxide dichloride octahydrate [13520-92-8]. Zirconium tetrachloride exchanges chlorine for 0x0 bonds in the reaction with hydroxylic ligands, forming alkoxides from alcohols (see Alkoxides, METAl). Zirconium tetrachloride combines with many Lewis bases such as dimethyl sulfoxide, phosphoms oxychloride and amines including ammonia, ethers, and ketones. The zirconium organometalLic compounds ate all derived from zirconium tetrachloride. 

Preparation of the oxime presents no problem, since there is little tendency for hydroxylamine to add to the double bond of the unsaturated system. A variety of acid catalysts has been used e.g., POCI3, BF3, p-ACNHC6H4SO2CI) to effect the rearrangement, and phosphorous oxychloride is the usual choice. 

Chloroquinazoline can be isolated, at best in 40% yield, by boiling 2-hydroxyquinazoline with phosphorus pentachloride in phosphorus oxychloride for 45 min, and attempts to improve this yield have proved fruitless. The yields are much higher when an aryl group is in position 4 w hich suggests an attack of the 3,4-double bond in 2-hydroxy- and 2-chloro-quinazolines by the chlorinating agent. 

The number of valence electrons in niobium oxychloride clusters decreases as the number of oxide hgands increases (Table 6.4). The compound Cs2LuNbi Cli70 has the VEC of 16 as found in most chloride clusters, suggesting that the presence of one oxide ligand per cluster does not tip the balance between the Nb-Nb bonding and Nb-L anti-bonding contributions to the a2u state. The VEC of most clusters... 

The three major types of oxysalt bonded AB cement are the zinc oxychloride, the magnesium chloride and the magnesium oxysulphate cements. The bases employed, therefore, are either zinc oxide or magnesium oxide, both of which readily undergo hydration in aqueous solution, behaving as M(OH)2 species and acting as a source of hydroxyl ions. They are thus both clearly bases in the Bronsted-Lowry sense. 

These cements were the earliest of the oxysalt bonded cements to be prepared (Sorel, 1855) and their chemistry has been the subject of numerous investigations over the years. There are considerable difficulties associated with such investigations. Not only does the cement contain a complex mixture of different crystalline precipitates but it is unaffected by boiling water and dissolves only slowly in strong acids. Consequently separation or analysis of any of the phases which may be present is difficult. Nonetheless, as early as 1925 at least 17 crystalline compounds were claimed to occur in the zinc oxychloride cement (Mellor, 1925). 

Molybdenum oxytetrachloride is a dark green crystalline compound with a melting point of 100 to 101°. Infrared absorption (KBr disk) has been used to establish the absence of OH- and H20 in verification of the anhydrous state. A broad band appears in the 970-em.-1 region and reveals molyb-denum-to-oxygen bonding. The oxychloride reacts with thoroughly dried Nujol so that satisfactory infrared spectra cannot be obtained with this as a dispersion medium. When exposed to light, molybdenum oxytetrachloride forms a brown film on the surface of the ampule. Since this film is not formed when the ampules are stored in the dark, molybdenum oxytetrachloride is concluded to be photosensitive. 

Partial hydrolysis of pentachlorides also leads to the formation of oxychlorides, which are useful intermediates that contain reactive PCI bonds. 

For the halogen-metal exchange reaction of bulkier halopyrimidines, steric hindrance retards the nucleophilic attack at the azomethine bond. As a consequence, halogen-metal exchange of 5-bromo-2,4-di-r-butoxypyrimidine (43) with n-BuLi could be carried out at -75 °C [20]. The resulting lithiated pyrimidine was then treated with n-butylborate followed by basic hydrolysis and acidification to provide 2,4-di-f-butoxy-5-pyrimidineboronic acid (44). 5-Bromopyrimidine 43 was prepared from 5-bromouracil in two steps consisting of a dehydroxy-halogenation with phosphorus oxychloride and an SnAt displacement with sodium r-butoxide. 

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