Structure and Spectral Properties

It must be noted at this point that, when Szent-Gyorgyi initially isolated 1, he unfortunately called it hexuronic acid. In early 1933, he and Haworth39 proposed that the name be changed to ascorbic acid. In 1965, the trivial name L-ascorbic acid was recognized by the IUPAC-IUB Commission on Biochemical Nomenclature40 as an acceptable name for vitamin C. The systematic name for L-ascorbic acid is L-threo-hex-2-enono-l,4-lactone. In the past, scorbutamin, redoxon, vitamin C, cevitamic acid, and hexuronic acid have been used as names for 1. Throughout this article, the trivial name L-ascorbic acid will be used for 1. 

Shortly after the structure of L-ascorbic acid had been determined, several different syntheses were reported that provided further sup- 

Before proceeding to a discussion of the various syntheses of L-ascorbic acid, its chemical and physical properties will be sum- 

It has been proved by X-ray analysis that, in the solid state, 1 is the tautomer present, but the claim has been made that,68 in solution, L-ascorbic acid exists as 2. Structures 3,4, and 5 were readily eliminated by a study of the l3C-n.m.r. spectrum,88,87 and, on the basis of the chemical shifts of the carbon resonances for C-l, C-2, and C-3, and the known chemistry of L-ascorbic acid, 1 is favored over 2 in solution. Berger98 claimed that the proton-carbon-coupled spectrum of L-ascorbic acid is consistent only with structure 1. Ogawa and coworkers87 studied the conformation of L-ascorbic acid and L-ascorbic acid-5-d in deuterium oxide by 13C-n.m.r. spectroscopy, and concluded that, in 

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Two classes of charged radicals derived from ketones have been well studied. Ketyls are radical anions formed by one-electron reduction of carbonyl compounds. The formation of the benzophenone radical anion by reduction with sodium metal is an example. This radical anion is deep blue in color and is veiy reactive toward both oxygen and protons. Many detailed studies on the structure and spectral properties of this and related radical anions have been carried out. A common chemical reaction of the ketyl radicals is coupling to form a diamagnetic dianion. This occurs reversibly for simple aromatic ketyls. The dimerization is promoted by protonation of one or both of the ketyls because the electrostatic repulsion is then removed. The coupling process leads to reductive dimerization of carbonyl compounds, a reaction that will be discussed in detail in Section 5.5.3 of Part B. 

Recently, the structure and spectral properties of a well-known diiron Fe model complex ( ji-SCH2CH2CH2S)Fe2(CO)6 were reinvestigated by Darensbourg and coworkers (Lyon et al. 1999). Also the Fe2(CO)4(CN)2 derivative was prepared and investigated. The v(CO) and v(CN) bands of the latter complex best fitted those found for the reduced D. vulgaris [Fe] hydrogenase and hence the possibility of an Fe -Fe pair in the reduced enzyme was suggested by the authors. 

Farris, F.J., Weber, G Chiang, C.C., and Paul, I.C. 1978. Preparation, crystalline structure, and spectral properties of the fluorescent probe 4,4 -bis-l-phenylamino-8-naphthalenesulfonate. J. Am. Chem. Soc. 100 4469-4474. 

Figure 2. Structure and spectral properties of squarylium dyes synthesized in this work.

Special attention has been paid to the structure and spectral properties of heterocycles 92 and related systems in solution. The conformations of type 117 compounds were elucidated from their dipole moments [78JOM( 146)235 83JCS(P2)1109 85ZOB846], Some of the data are given in Table VII. 

More detailed information about structure and spectral properties of the nitrogenase Fe-clusters were obtained by a combination of physical methods. The structure suggested at that time and variation of spectra parameters is presented in Fig. 3.1, which was plotted on the basis of the data obtained in the works of Ohrme-Johnson s and Miinck s groups cited above. Subsequent investigations have confirmed the main parameters and added some important details. 

Structures and spectral Properties of the Redox-active Metal Sites... 

Taylor, M. S., Jacobsen, E. N. Highly enantioselective catalytic acyl-Pictet-Spengler reactions. J. Am. Chem. Soc. 2004, 126, 10558-10559. Kowalski, P., Mokrosz, J. L. Structure and spectral properties of P-carbolines. Part 9. New arguments against direct rearrangement of the spiroindolenine intermediate into P-carboline system in the Pictet-Spengler cyclization. An MNDO approach. Bull. Soc. Chim. Belg. 1997, 106, 147-149. 

Guha, S., and Nakamoto, K. 2005. Electronic structures and spectral properties of endohedral fullerenes. Coordination Chemistry Reviews 249, 1111-1132. 

Properties and Reactions of Ylidenemalononitriles, F. Freeman (1980). Dicyanomethylene compounds, their molecular structure and spectral properties, toxicity and analyses are reviewed. Various reactions like hydrolysis, oxidation and reduction, dimerizations, cyclizations, photochemistry and thermolysis are discussed. The review, which contains 380 references, also deals with unsaturated compounds, oxygen, nitrogen, phosphorous and sulfur compounds. 

Albani, J. R, 1998, Corelation between dynamics, structure and spectral properties of human ai-acid glycoprotein (orosomucoid) a fluorescence approach. Spectrochimica Acta Part A 54, 175-183. 

Oxazolium 5-Oxides (Munchnones) 4.2.2. Structure and Spectral Properties... 

Table 1. Structure and Spectral Properties of Triaryl-sulfonium Salts...

The radical anion is deep blue and is very reactive toward both oxygen and water, and must therefore be kept in an inert atmosphere. Many detailed studies on the structure and spectral properties of this and related systems have been carried out. Both ion pairing and coupling to give a diamagnetic dianion can occur reversibly for the simple aromatic ketyls, and the positions of the equilibria are strongly solvent-dependent ... 

Ishikawa, N. (2001). Electronic structures and spectral properties of double- and triple-decker phthalocyanine complexes in a localized molecular orbital view J. Porphyrins Phthalocyanines, 5, 87-101. 

Aluminosilicates are important as both inorganic compounds and as minerals and mineral glasses. Quantum mechanical calculations on cluster models for aluminosilicates can now accurately reproduce their energetic, structural and spectral properties. Species in glasses can be identified by matching their calculated spectral properties with experiment. More important, such calculations provide a framework for relating the structures and properties of inorganic aluminosilicates and their mineral coimterparts. 

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