Type II ionic compounds

Type II Ionic compounds with metals (usually transition metals) that form cations with various charges... 

The basic form for the names of Type II ionic compounds is to have the name of the metal cation first, followed by the charge of the metal cation (in parentheses, using Roman numerals), and finally the base name of the non-metal anion with -ide attached to the end. 

In the ionic compounds considered previously (Type I), the metal involved forms only a single type of cation. That is, sodium forms only Na", calcium forms only Ca, and so on. However, as we will see in more detail later in the text, many metals can form more than one type of positive ion and thus form more than one type of ionic compound with a given anion. For example, the compound FeCli contains Fe " ions, and the compound FeCla contains Fe " ions. In cases such as these, the charge on the metal ion must be specified. The systematic names for these two iron compounds are iron(II) chloride and iron(III) chloride, respectively, where the Roman numeral indicates the charge of the cation. 

The second type of ionic compotmd (sometimes called Type II) contains a metal with a charge that can differ in different compounds. In other words, the metal in this second type of ionic compound can form more than one kind of cation (depending on the compound). Iron, for instance, has a 2+ charge in some of its compounds and a 3+ charge in others. Additional examples of metals that form more than one type of cation are listed in Table 5.4. Such metals are usually (but not always) found in the transition metals section of the periodic table ( Figure 5.13). However, some transition metals, such as Zn and Ag, form cations with the same charge in all of their compounds, and some main group metals, such as Pb and Sn, form more than one type of cation. 

Type II. These compounds have free volume behaviour at high temperatures and Arrhenius behaviour at low temperatures, with lower values of ionic conductivity. The Arrhenius law is expressed as follows ... 

The photochemical reaction that has been most thoroughly investigated from the ionic chiral auxiliary point of view is the well-known Norrish/Yang type II reaction. One example, taken from the work of Patrick, Scheffer, and Scott [36], deals with derivatives of 7-methyl-7-benzoylnorbornane-p-car-boxylic acid (37a, Scheme 8). This compound was treated with a variety of optically pure amines to afford the corresponding 1 1 salts (37b), and in an... 

This second class of five-membered heterocyclic meso-ionic compounds is represented by the type formula 14 20. So far, only eight representatives (Table II) of type B have been described, whereas acceptable combinations of the groupings a, b, c, d, e, and f derived from suitably substituted carbon, nitrogen, oxygen, or sulfur atoms lead, in principle, to 84 possibilities. However, not all these 84 possible structures are necess y well based because valence tautomerism (see Section VI) might well be associated with thermodynamic preference for the acyclic covalent valence isomer (46) rather than the cyclic meso-ionic alternative (20). 

One hundred and forty-four meso-ionic heterocycles of type A (13, 19) and 84 meso-ionic heterocycles of type B (14, 20) are possible. The numbers of these two types which are now known (Table I type A, 44 representatives) and (Table II type B, 8 representatives) encourage us to put forward the proposal that the term meso-ionic should in future be restricted to five-membered heterocycles belonging to type A (13, 19) and type B (14,20). This clear restriction upon the use of the term meso-ionic has obvious advantages. It still embraces 228 different classes of heterocycles with a common structural characteristic, and the many types of meso-ionic compounds included in the authoritative review by Ohta and Kato " are included. Needless to say, the restriction upon the definition of the term meso-ionic to five-mem red heterocycles of type A and type B still includes, for example, benz derivatives such as the compounds 67, 71, 110, 123, 133, 151, 206, 209, 226, 255, and 258. 

The host-guest and ionic chiral auxiliary approaches have been most intensively applied for solid-state asymmetric induction. A number of achiral organic compounds could be converted into chiral compounds in high enantioselectivities. However, all the photoreactions in themselves are well-known intramolecular photoreactions photocyclization, [2 + 2] photocyclization, Norrish type II photo-cyclization, di-ir-methane photorearrangement and photoisomerization. New types of asymmetric photoreactions have never been reported. 

Type II binary ionic compounds with the metal possessing more than one type of cation... 

Type I and II binary compounds are neutral, ionic compounds that contain two parts a cation and an anion. When a metal is the cation and a nonmetal is an anion, the following rules are used ... 

Some stable ionic compounds are capable of bonding to a certain number of molecules of water per formula unit. Thus, copper(II) sulfate forms the stable CuS04-5H20, with five molecules of water per CUSO4 unit. This type of compound is called a hydrate. The name of the compound is the name of the anhydrous (without... 

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