Germane, protonated

The 1967 Nobel Prize in chemistry was shared by Manfred Eigen a German chemist who developed novel methods for measur ing the rates of very fast re actions such as proton transfers... 

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. 

German ED, Kuznetsov AM, Dogonadze RR (1980) Theory of the kinetic isotope effect in proton transfer reactions in a polar medium. J Chem Soc, Faraday Trans 2 76 1128-1146... 

The German chemist Liebig, in 1838, was the first to suggest mobile, replaceable, hydrogen atoms being responsible for acidic properties. Arrhenius extended the idea in 1887, when he said the hydrogen existed as a proton. 

The experimental germane PAq of 162.1 to 164.0 kcal mor is somewhat higher than our best estimate. The assumption that the experimental PAg is correct would lead to the conclusion that theory does a somewhat better job for germane than for protonated germane. However, the very recent study of Smith and Radom showed that the usual standard (PAq of isobutene) for the experimental determination of proton affinities may have to be corrected downwards by 2.4 to 4.8 kcal mol", which brings the theoretical PA<, close to the experimental value. ... 

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 proton affinity of CH3GeH3 is also unknown. An ab initio calculation144 at the Hartree-Fock level predicts that the structure of protonated methylgermane corresponds to a CH3GeH2+(H2) complex and that the proton affinity of CH3GeH3 is 22 klmol-1 higher than that of germane. 

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 ). 

Levich, V.G., Dogonadze, R., German, E., Kuznetsov, A.M., and Kharkats, Yu. I. (1970) Theory of homogeneous reactions involving proton transfer, Electrochem. Acta 15, 353-368. 

Figure 5-4 Schematic Representation of the Addition of Acid (HA) or Base (B") to an Isoelectric Protein. The isoelectric protein has equal numbers of positive and negative charges. The acid HA donates protons, the base B" accepts protons. Source Reprinted with permission from R. Hamm, Colloid Chemistry of Meat, 1972, Paul Parey (in German).

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