Glycine acid-base properties

Relationship between the Titration Curve and the Acid-Base Properties of Glycine A 100 mL solution of 0.1 m glycine at pH 1.72 was titrated with 2 m NaOH solution. The pH was monitored and the results were plotted on a graph, as shown at right. The key points in the titration are designated I to V. For each of the statements (a) to (o ), identify the appropriate key point in the titration and justify your choice. 

Relationship between the Titration Curve and the Acid-Base Properties of Glycine A 100 mL... 

Considerable attention has been devoted to the nature of the solvent effects (as determined in water and in various mixed solvents) on the ionic dissociations (and related thermodynamic quantities) and other acid-base properties of aliphatic zwitterionic compounds. Such investigations include studies of tricine in 50 mass % methanol-water (1), Bes in pure water and in 50 mass % methanol-water 2,3), glycine in 50 mass % monoglyme-water (4), and glycine in pure water and in 50 mass % methanol-water (5,6, 7). The numerous factors (8,9,10) which... 

Glycine, 1054, 1056, 1059 acetylation, 1063 acid-base properties, 1057-1061 electrostatic potential map, 1053 ethyl ester, 1079, 1080 Glycogen, 995... 

The addition of other deprotonated nucleophiles to vinyl ketone was further expanded recently to the synthesis of much more complex molecules. In 2006, the group led by Shibasaki reported on the concise synthesis of cylindricine C, a spirocychc molecule with numerous biological properties isolated from Clavelina cylindrical (Scheme 11.44). Glycine Schiff base 182 was found to react efficiently with enone 183. Catalyst 184 was the most effective for this transformation giving a good 82% ee at —40°C. Noteworthy, the process tolerated numerous functional groups such as the more substituted enone that was kept untouched. Remarkably, compound 185 could be transformed into the tricychc backbone 186 of cylindricine C by a tandem cych-zation in acidic conditions. 

Based on the properties of the side chains, the 20 amino acids can be put into six general classes. The first class contains amino acids whose side chains are aliphatic, and is usually considered to include glycine, alanine, valine, leucine, and isoleucine. The second class is composed of the amino acids with polar, nonionic side chains, and includes serine, threonine, cysteine, and methionine. The cyclic amino acid proline (actually, an imino acid) constitutes a third class by itself. The fourth class contains amino acids with aromatic side chains tyrosine, phenylalanine, and tryptophan. The fifth class has basic groups on the side chains and is made up of the three amino acids lysine, arginine, and histidine. The sixth class is composed of the acidic amino acids and their amides aspartate and asparagine, and glutamate and glutamine. 

Properties of a Buffer The amino acid glycine is often used as the main ingredient of a buffer in biochemical experiments. The amino group of glycine, which has a pKa of 9.6, can exist either in the protonated form (—NHjj) or as the free base (—NH2), because of the reversible equilibrium... 

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