Forster acidities

The Forster acidity, ApfC, may be found with the aid of the Forster cycle (Fig. 

Lauble, H., Miehlich, B., Forster, S. et al. (2002) Crystal structure of hydroxynitrile lyase from Sorghum bicolor in complex with the inhibitor benzoic acid a novel cyanogenic enzyme. Biochemistry, 41, 12043-12050. 

Forster, A.C., Mclnnes, J.L., Skingle, D.C., and Symons, R.H. (1985) Non-radioactive hybridization probes prepared by the chemical labeling of DNA and RNA with a novel reagent, photobiotin. Nucleic Acid Res. 13, 745-761. 

The Forster cycle method is quite simple, which explains why it has been extensively used. One of the important features of this cycle is that it can be used even in cases where the equilibrium is not established within the excited-state lifetime. However, use of the Forster cycle is difficult or questionable when (i) two absorption bands overlap (ii) the electronic levels invert during the excited-state lifetime (usually in a solvent-assisted relaxation process) (iii) the excited acidic and basic forms are of different orbital origins (electronic configuration or state symmetry) and (iv) the changes in dipole moment upon excitation are different for the acidic and basic forms. 

Conventional absorptiometric and fluorimetric pH indicators show a shift of band positions in absorption and emission spectra between the protonated and deprotonated forms. This feature allows the spectroscopic measurement of the acid dissociation constant in the ground state, Ka, and also the evaluation of the dissociation constant in the excited state, Ka (Eq. (5.5)), from the Forster cycle under the assumption of equivalent entropies of reaction in the two states.<109 112)... 

For the determination of the dissociation constant in the excited state, several methods have been used the Forster cycle,(109 m) the fluorescence titration curve/113 the triplet-triplet absorbance titration curve,014 but all involve the assumption that the acid-base equilibrium may be established during the lifetime of the excited state, which is by no means a common occurrence. A dynamic analysis using nanosecond or picosecond time-resolved spectroscopy is therefore often needed to obtain the correct pK a values.1(n5)... 

Diazo esters can also be prepared from glycine esters by treatment with nitrous acid [966] or with alkyl nitrites. Further methods include the oxidation of hydrazones, oximes (Forster reaction), and semicarbazones, the base-induced... 

Ethylazidobenzamide or N(/3-Azido-ethyl)-benzamide, CeHs CO,NH.CH2-CHa(Ns) mw 190.21, N 29.46% oil explodes violently on contact with coned sulfuric acid. It can be prepd from benzoyl chloride and J-azido-ethylamine in the presence of NaOH (Refs 1 2) Refs 1) Beil. 9, (97) 2) M.O. Forster Be S.H. 

In some cases, data obtained through the Forster cycle show similar inconsistencies, depending on whether absorption or emission is used. It may well be that either the equilibrium structure in the excited state is very different from the unrelaxed Franck-Condon one, or that 0-0 frequencies are too poorly estimated. It seems, therefore, that the most reliable results are those generated by method (3). This method has been applied to the study of carbazole (3) acidity in its S, state (85MI5). 

Phyllanthus virgatus Forster Xi Ye Zhu Chi Cao (whole plant) Vitamin C, amino acids.57 Treat heptitis, cold, fever, blood vomitting, diarrhea. 

Bayer BL, Forster W Actions of prostaglandin precursors and other unsaturated fatty acids on conduction time and refractory period in the cat heart. Br J Pharmacol 1979 66 191-195. 

According to A. J. Balard, hypochlorous acid produces some chloric acid with the alkali chlorides F. Forster and F. Jorre say that hypochlorous acid and alkali chloride form alkali chlorate 3H0Cl-(-NaCl=NaC103-(-3HCl, and free... 

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