Double carbonate

In the longer carbon chains, two double carbon-carbon bonds may exist. Such molecules are called diolefins (or dienes), such as butadiene CH2 = CH - CH = CHj. 

The alkali metals of Group I are found chiefly as the chlorides (in the earth s crust and in sea water), and also as sulphates and carbonates. Lithium occurs as the aluminatesilicate minerals, spodimene and lepidolite. Of the Group II metals (beryllium to barium) beryllium, the rarest, occurs as the aluminatesilicate, beryl-magnesium is found as the carbonate and (with calcium) as the double carbonate dolomite-, calcium, strontium and barium all occur as carbonates, calcium carbonate being very plentiful as limestone. 

The carbonate minerals that comprise limestone ate calcite [13397-26-7] (calcium carbonate), which is easily the most abundant mineral type aragonite [14791-73-2] (calcium carbonate) dolomite [17069-72-6] (double carbonate of calcium and magnesium) andmagnesite [13717-31 -5] (magnesium carbonate). Individual limstone types ate further described by many common names (1). Some of this nomenclature is repetitious and overlapping. The following terms ate in common use in Europe and the United States. 

Basic zirconium carbonate reacts with sodium or ammonium carbonate solutions to give water-soluble double carbonates. The ammonium double carbonate is nominally NH4[Zr20(0H)2(C02)3]. These solutions are stable at room temperature, but upon heating they lose carbon dioxide and hydrous zirconia precipitates. 

In a study of zirconium double carbonates (205), a family of carbonates with C02 Zr ratios of 1, 1.5, 2, 2.5, 3, 3.5, and 4 1 were identified. None of these compounds combined with ammonia, confirming the absence of HCO7 ... 

The dry gas seal has one of two types of barrier seal (seal between the bearing and dry gas seal) either a labyrinth or single or double carbon rings. Normally the seal system includes provision to supply buffer gas to the barrier seal, also known as a separation seal. The gas to this seal is referred to as separation gas. One reason for choosing the carbon ring style bander seal is to keep the separation gas usage to a minimum. The gas is normally nitrogen. The basic control is by a direct-operated pres sure control valve. 

Polyisobutylene has a similar chemical backbone to butyl rubber, but does not contain double carbon-carbon bonds (only terminal unsaturation). Many of its characteristics are similar to butyl rubber (ageing and chemical resistance, low water absorption, low permeability). The polymers of the isobutylene family have very little tendency to crystallize. Their strength is reached by cross-linking instead of crystallization. The amorphous structure of these polymers is responsible for their flexibility, permanent tack and resistance to shock. Because the glass transition temperature is low (about —60°C), flexibility is maintained even at temperatures well below ambient temperature. 

Degree of unsaturation. Unsaturation accounts for the existence of carbon-carbon double bonds in resins. It is generally indicated by the bromine or iodine number. Both methods are based on the halogen addition to the double carbon-carbon bonds. Because the different reactivity of bromine and iodine, both numbers cannot be compared. The bromine or iodine number does not necessarily correlate with the reactivity of the resin, for instance in the ageing process. However, within a given resin series of the same structure, relative comparisons can be made. 

Rubber base adhesives can be used without cross-linking. When necessary, essentially all the cross-linking agents normally used in the vulcanization of natural rubber can be used to cross-link elastomers with internal double carbon-carbon bonds. A common system, which requires heat to work, is the combination of sulphur with accelerators (zinc stearate, mercaptobenzothiazole). The use of a sulphur-based cross-linking system with zinc dibutyldithiocarbamate and/or zinc mercaptobenzothiazole allows curing at room temperature. If the formulation is very active, a two-part adhesive is used (sulphur and accelerator are placed in two separate components of the adhesive and mixed just before application). 

Rubbers differ in their resistance to ozone. All the highly unsaturated rubbers (natural rubber, styrene-butadiene rubber, butyl rubber, nitrile rubber) are readily cracked while the deactivated double carbon-carbon bonds rubber (such as polychloroprene rubber) shows moderate ozone resistance. 

Shaw concluded that hydrogenation of 3-alkyl-4-aminomethylene isoxazol-5-ones (184) in the presence of palladium catalyst resulted in the saturation of either the endocyclic double carbon-nitrogen bond or the exocyclic double C—C bond with the retention of the heterocyclic nitrogen-oxygen bond. Recent data reported by Kochetkov et al. on the properties, and in particular on hydrogenation, of isoxazolid-5-ones - indicate, however, that Shaw had probably ob-... 

Polymerisation involves either aidehydic carbonyl or the double carbon-carbon... 

Compounds of this type, listed in Table 9, are available by interaction of triallylboranes with certain polyyne derivatives of silicon and tin. Their formation involves 1,1- and 1,2-allylboration of triple and double carbon-carbon bonds. 

In a molecule such as formaldehyde, the bonding and non-bonding orbitals are localized (like the bonds) between pairs of atoms. Such a picture of localized orbitals is valid for the a orbitals of single bonds and for the n orbitals of isolated double bonds, but it is no longer adequate in the case of alternate single and double carbon-carbon bonds (in so-called conjugated systems). In fact, overlap of the n orbitals allows the electrons to be delocalized over the whole system (resonance... 

Aldehydes themselves are of little commercial interest, but they open a way to alcohols via hydrogenation, to carboxylic acids via oxidation, and to amines via reductive amination. Aldolization is the starting point for branched alcohols, carboxylic acids, and amines with a double carbon number. As an example of co-aldolization, the route to polyols is shown. All... 

Single and double carbon-carbon bond forming reactions, and metathesis (ROMP) reactions, can be used to produce polymers. However, many other... 

Alkanes are saturated hydrocarbons, i.e., no double carbon bonds. Examples are CH4, C2H6, CsHg, and C(n)H(2n+2). Alkenes have carbon-carbon double bonds such as ethene C2H4 and C(n)H(2n). 

Hydrogen is added to the carbon double bonds of unsaturated or polyunsaturated molecules where not all these double carbon bonds are used. This process changes unsaturated fats (liquids) to saturated fats (solids). 

Nickel carbonate forms many double salts, such as, Na2COs NiCOs IOH2O with alkali metal carbonates. However, such double carbonates usually are prepared by mixing an alkali metal or ammonium bicarbonate solution with a nickel salt solution, followed by crystallization. 

In contrast, in the SSH model, the electrical bandgap arises because of the alternation between single and double carbon-carbon bonds, a signature of the Peierls distortion in a ID system. When a perfect ID chain of equidistant carbon atoms is considered, the electronic structure resulting from the electronic coupling between the atomic Pz-orbitals is that of a half-filled n band, implying a metallic... 

Aromatic Various Ring strnctnres, based on the benzene ring, in which single and double carbon bonds alternate... 

Fusion Mixture. A mixt of Na and K carbonates used to fuse in sol substances of high mp s (such as ores) in order to render them soluble in die form of double carbonates. Fusion can also be achieved by heating insol... 

The thiocyanate is prepared in solution by adding ammonium thiocyanate, NPLjSCN to HC1 solutions of the chloride. Both basic and double carbonates are known. The former is precipitated from Sc3+ solutions by adding carbonate solutions, and is probably Sc(OH)CC>3 H O. The latter are obtained by the use of an excess of the soluble carbonate. Normal, basic, and double sulfates are known. The first exists in several degrees of hydration the second is obtained as Sc(0H)S04 - 2H2O. by treating the normal sulfate tetrahydrate with the hydroxide. The alkali double sulfates and alums are obtained by treating the sulfate solution with an excess of the alkali (or ammonium) sulfate solution. 

Both normal and mixed carbonates are known. The former is precipitated, as Y2(C03)3 3H O from Y31 solutions by alkali metal carbonates, which in excess dissolve the precipitate to form a soluble hydrated double carbonate. The oxy carbonate is also a double molecule, 3Y2(C(>3)3 2Y(OH>3, formed by action of CCU, upon the hydroxide. 

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