Germanates zwitterionic

From the theoretical point of view the greatest interest of amino adds is the possibility of the formation of dipole ions (a recent and more descriptive term than the German zwitterion ) by an internal rearrangement, or internal salt formation, according to the equilibrium... 

We saw in Sections 20.3 and 24.5 that a carboxyl group is deprotonated and exists as the carboxylate anion at a physiological pH of 7.3, while an amino group is protonated and exists as the ammonium cation. Thus, amino acids exist in aqueous solution primarily in the form of a dipolar ion, or zwitterion (German zwitter, meaning "hybrid"). 

C17-0120. In aqueous solution, amino acids exist as zwitterions (German for double ions ), compounds in which internal proton transfer gives a molecule with two charged functional groups. Use Lewis structures to illustrate the proton transfer equilibrium between the uncharged form of glycine (NH2 CH2 CO2 H) and its zwitterion form. 

Therefore, we can deduce that a-amino acids in solution at pH 7.0 exist as dipolar ions these are called zwitterions (German zwitter = hybrid) (see Section 13.1). 

When an amino acid is dissolved in water, it exists in solution as the dipolar ion, or zwitterion (German for hybrid ion ), shown in Figure 3-9. A zwitterion can act as either an acid (proton donor) ... 

The degree of TBP — RP distortions in the spirocyclic anionic and zwitterionic germanates (Section IV.B.3) is rather similar to that observed for the corresponding silicon analogues42 for a comparable set of ligands, although as a rule the structures of Si analogues are close to the TBP. 

The first representative of hexacoordinate germanium compounds with a Gcf sC. framework, the zwitterionic germanate 472, was recently synthesized (equation 83)925. 

Although we commonly write amino acids with an intact carboxyl (—COOH) group and amino (—NH2) group, their actual structure is ionic and depends on the pH. The carboxyl group loses a proton, giving a carboxylate ion, and the amino group is proto-nated to an ammonium ion. This structure is called a dipolar ion or a zwitterion (German for dipolar ion ). 

In this paper, we report on the synthesis and structural characterization of a series of related zwitterionic (molecular) spirocyclic X Si-silicates (mononuclear A, Si-silicon(IV) complexes) containing two bidentate l,2-diolato(2-) ligands derived from a-hydroxycarboxylic acids, such as glycolic acid, 2 methyllactic acid, benzilic acid, and citric acid. In addition, some analogous zwitterionic X Ge-germanates (mononuclear X Ge-germanium(rV) complexes) are described. Furthermore, we report on the synthesis and structural characterization of related zwitterionic x Si,X Si -disilicates (binuclear X Si-... 

Zwitterionic A. Ge-Germanates Containing Two Bidentate Diolato(2 ) Ligands Derived from a-Hydroxyearboxylic Acids... 

By analogy to the structures of the related zwitterionic VSi-silicates described in Chapter 2.1, the coordination polyhedron surrounding the germanium atom of the X, distorted trigonal bipyramid (Berry distortion [8] 11.4 %), in which the carboxylate oxygen atoms occupy the axial... 

Note that, as amino acids can both accept and donate protons, they can undergo an internal acid-base reaction and end up with both positive and negative charges on the same molecule, e.g. H3N CH(R)COO . This kind of ion is called a zwitterion, from the German meaning hermaphrodite or hybrid . It is this type of property that makes amino acids soluble in our stomach juices, and also ensures that they have high melting points. 

Since amino acids contain both an acidic and a basic group, they un( an intramolecular acid-base reaction and exist primarily in the torn, t dipolar ion, or zwitterion (German zwitter, "hybrid ) ... 

Summary The novel zwitterionic (molecular) spirocyclic X Ge-germanates lb-7b have been synthesized and characterized. Compounds lb-7b are germanium analogues of the already known zwitterionic Jt z-silicates la-7a (Ge/Si exchange). Syntheses and properties of the Si/Ge analogues are reported. In addition, the crystal structures of 4b and 5b-H20 are described. 

Over the past few years, a series of zwitterionic spirocyclic A, 57-silicates with an SiO C framework have been synthesized and structurally characterized [1]. The X A-silicates la-7a are typical examples of this particular type of compound (Fig. 1). In this paper, we report on the analogous zwitterionic spirocyclic A, Ge-germanates lb-7b (Fig. 1). 

As may be expected from their zwitterionic nature, the A, 5/-silicates la-7a and the X Ge-germanates lb-7b are high-melting crystalline solids All compounds are almost insoluble in unpolar solvents and exhibit very poor solubility in polar organic solvents. 

Zwitterions (the word is derived from the German for hybrid ion ) are ions that are electrically neutral overall but contain nonadjacent regions of pos-... 

Although the form of the amino add on the right in this equation is electrically neutral overall, il has a positively charged end and a negatively charged end. A molecule of this type is called a zwitterion (German for hybrid ion ). 

An interesting case is an amino acid, since it has on the same molecule a basic amino group and an acidic end. As shown in Scheme 8.14, the result is that the basic end will abstract the proton from the acidic end, and this process will generate the double ion form (called by chemists a zwitterion, which is a German word for a... 

Amino acids are well soluble in water, because they can appear in the form of a dipolar ion called, by the German word, Zwitterion. This ion can be considered as the product of self-protonation the amino group is protonated by the proton that comes from the carboxyl group. 

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