2.4- Dihydroxy-6- benzoic structure

Figure 14.6 Structures of some commonly used MALDI matrices (a) 2,5-dihydroxy benzoic acid (DHB), (b) a-cyano-4-hydroxy-cinnamic acid, and (c) sinapinic acid (SA). Combination of these acidic MALDI matrices with organic bases leads to the formation of ionic liquid matrices.

The increase in acid strength due to hydrogen bonding of this type is even more marked in 2,6-dihydroxy benzoic acid (Ka = 5 x io 2) in which the stability of the ion is increased by the contribution of the structures ... 

Chemical Name 2-[(7-Chloro-4-quinolinyl)amino] benzoic acid 2 3-dihydroxy-propyl ester Common Name Glycerylaminophenaquine Structural Formula ... 

The Stock in trade of structure theory was explaining otherwise mysterious cases of isomerism. In the first fascicle of his textbook (1859), Kekul6 offered a structural explanation for one case of aromatic isomerism, namely, benzoic acid and salicylous acid. In Kekulean terms the two substances were "metamers," or what we now call ordinary structural isomers. But subtler sorts of isomerisms were showing up in the aromatic realm. Even before structure theory appeared on the scene, chemists had recognized many cases of isomerism among double-substituted benzene two distinct dihydroxy benzenes, two distinct ni-trophenols, two distinct nitrobenzoic acids, two distinct aminobenzoic acids, two distinct chlorobenzoic acids, and two distinct hydroxyben-zoic acids. Kekule mentioned the last of these in 1859, and declared what he called "oxybenzoic acid" to be an "isomer in the narrower sense" (i.e., a nonstructural isomer) of salicylic acid. He commented that there must be some unknown difference in the composition of the "atomic groups that are assumed as radicals in their formulas." ... 

Other Names Fluorescein 3, 6 -Dihydroxyfluoran 3, 6 -Fluorandiol 3,6-Dihydroxyspiro [xanthene-9,3 -phthalide] 9-(( -Carboxyphenyl)-6-hydroxy-3-isoxanthenone Benzoic acid, 2-(6-hydroxy-3-oxo-3H-xanthen-9-yl)- C.I. 45350 1 C.I. Solvent Yellow 94 D and C Yellow No. 7 D C Yellow No. 7 Fluorescein acid Japan Yellow 201 Japan Yellow No. 201 NSC 667256 Resorcinolphthalein Solvent Yellow 94 Yellow fluorescein CA Index Name Spiro[isobenzofuran-l(3H),9 -[9H]xanthen]-3-one, 3, 6 -dihydroxy-CAS Registry Number 2321-07-5 Merck Index Number 4159 Chemical Structure... 

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