Oxyanions, naming

As indicated in Scheme 3-13, replacing the isopropoxide counterions with less basic oxyanions, namely, commercially available 3,5-di-/< r/-butylsalicylic acid, will lead to new catalyst 30, which shows very good results for the asymmetric aldol addition of alkyl acetate to ketene acetals (Scheme 3-13). 

Oxyanion Formula Oxyanion Name Oxyacid Formula Oxyacid Name... 

What is an oxyanion How is a series of oxyanions named (Give an example.)... 

First, identify the oxyanion present. The first word of an oxyacids name consists of the root of the oxyanion and the prefix per- or hypo- if it is part of the name, and a suffix. If the oxyanions name ends with the suffix -ate, replace it with the suffix -ic. If the name of the oxyanion ends with the suffix -ite, replace it with the suffix -ous. NO3, the nitrate ion, becomes nitric. 

The formula for an acid can also be derived from the name. It is helpful to remember that all binary acids contain hydrogen and one other element. For oxyacids—acids containing oxyanions—you will need to know the names of the common oxyanions. If you need to review oxyanion names, see Table 7.9 in the previous chapter. 

Acid Formula Acid Name Oxyanion Name Oxyanion Formula... 

An oxyanion is a polyatomic ion that contains oxygen. An oxyacid is an acid that contains hydrogen and an oxyanion. To name such an acid, first write a form of the root of the name of the oxyanion. If the oxyanion name ends in -ate, name the acid by adding the suffix -ic to the root. If the oxyanion name ends in -ite, name the acid by adding the suffix -ous to the root. Then add the word acid. 

Oxyanions consist of an atom of an element plus some number of atoms of oxygen covalently bonded to it. The name of the anion is given by the name of the element with its ending changed to either -ate or -ite. In some cases, it is also necessary to add the prefix per- or hypo- to distinguish all the possible oxyanions from one another. For example, there are four oxyanions of chlorine, which are named as follows ... 

Other elements have similar sets of oxyanions, but not all have four different oxyanions. You should learn the names of the seven ions ending in -ate for the most common elements. These are the most important oxyanions. (Use the rules given above for remembering the others.) These ions are presented in Table 6-5. Note that the ones with central atoms in odd periodic groups have odd charges and those in even periodic groups have even charges. 

Note that not all the possible oxyanions of these elements exist. If the name and formula are not given in Table 6-5, the ion is not known. If you learn the seven ions that end in -ate plus the meaning of the ending -ite and the prefixes, you will be able to write formulas for 20 oxyanions. You may double this number of names by learning an additional rule in Sec. 6.4. Note from Table 6-5 that for each central element, all ions present have the same charge. 

The oxyanion containing Zn2+, Zn022-, is known as a zincate, and it equivalent to Zn(OII)42, which is named as the tetrahydroxozincate(II) anion (see Chapter 16). From these reactions, it is clear that ZnO can react as either an acidic or basic oxide and it is therefore known as an amphoteric oxide. In essence, there are some oxides that are clearly acidic, some that are dearly basic, and some that are in between. There is, in fact, a continuum of acid-base character for the oxides of elements that is shown in Figure 9.2. 

The arrangement of S965, H746, and the oxyanion hole suggests that the classical steps of peptide-bond hydrolysis follow the sequence of the trypsin-like serine proteases, namely the formation of the tetrahedral adduct, the acyl-enzyme complex, and hydrolysis. Tricorn has been shown to exhibit both tryptic and chymotryp-tic specificities (Tamura et al. 1996a). The X-ray structure reveals that specificity for basic PI residues is conferred by D936 which is provided by the diad-related subunit (see Figures 10.9 and 10.10). 

The oxyanions OH-, SO2- and NOj coordinate strongly. The two first named have a considerable tendency to give polymeric structures. A rare single crystal X-ray determination is that of Na4Yb(0H)7-2.5H20, mentioned in Section 39.2.4.1. It shows octahedral coordination of the Yb3+ ion.251... 

Oxoanions (also called oxyanions) contain one element in combination with oxygen. Many common polyatomic anions are oxoanions that end with the suffix -ate. If an element has two possible oxoanions, the one with the element at a lower oxidation state ends with -ite. This anion will also usually have less oxygen per atom. Additional oxoanions are named with the prefix hypo- if they have a lower oxidation number than the -ite form and the prefix per- if they have a higher oxidation number than the -ate form. 

Only one other substituent is capable of stabilizing trityl cations more effectively than amino or dimethylamino groups namely, the oxyanion substituent O . The stabilization of the trityl cation form of the dianion of the indicator dye phenolphthalein depends on the presence of two such substituents ... 

Note in Table 2.5 that several series of anions contain an atom of a given element and different numbers of oxygen atoms. These anions are called oxyanions. When there are two members in such a series, the name of the one... 

Elements in the same family often form oxyanions of the same general formula. The anions are named in a similar fashion. What are the names of the oxyanions of selenium and tellurium Se042", Se032-, Te042, Te032 ... 

The mesoionic compounds 2 (also named l,3-dithiolylium-4-olates or l,3-dithiolium-4-olates) and 3 (also named 1,3-dithiolylium-4-thiolates or 1,3-dithiolium-4-thiolates) are described by canonical structures 2,3a-e, of which those with an oxyanion or a thioxyanion 2a and 2b, are presumably most representative. 

Stereochemical control in 0-alkylative /3-glycosylation relies on the kinetic anomeric effect [110] namely, that the oxyanion derived from a reducing sugar is more reactive in its 8-ori-ented form 71B than the corresponding a-anion 71A which should be more abundant. This tactic has met with partial success in cases of reactive substrate [111] (O Scheme 38). For example, reaction of 72 with a primary triflate in THF in the presence of NaH afforded the 8-glycoside in 62% yield. 

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