Showing papers on "Reactivity (chemistry) published in 1968"
1,319 citations
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TL;DR: The apparent K(m) with respect to ATP and Mg(2+) of ATP-creatine phosphotransferase was observed to increase about tenfold on attachment of the enzyme to CM-cellulose, and to increase by only 23% on its attachment to p-aminobenzyl cellulose.
Abstract: 1. Purified ficin was chemically attached to CM-cellulose, and partially purified ATP–creatine phosphotransferase was chemically attached to both CM-cellulose and p-aminobenzylcellulose. 2. The apparent Km with respect to ATP and Mg2+ of ATP–creatine phosphotransferase was observed to increase about tenfold on attachment of the enzyme to CM-cellulose, and to increase by only 23% on its attachment to p-aminobenzylcellulose. 3. The reactivity of both ficin and ATP–creatine phosphotransferase with 5,5′-dithiobis-(2-nitrobenzoic acid) was observed to decrease on chemical attachment of these enzymes to water-insoluble derivatives of cellulose. With derivatives prepared from CM-cellulose, the extent of the reaction with 5,5′-dithiobis-(2-nitrobenzoic acid) was dependent on ionic strength, but with similar derivatives prepared from p-aminobenzylcellulose the extent of this reaction was independent of ionic strength. 4. The effect of diffusion and electrostatic interaction of charged enzyme substrates and charged enzyme supports on the apparent Km of a water-insoluble derivative of an enzyme is discussed. An equation is derived that satisfactorily describes the observed effects of these factors on the apparent Km.
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TL;DR: The electron-rich olefins are accordingly also excellent reducing agents as discussed by the authors, which is strengthened in enol ethers and enamines, and is particularly pronounced in tetramethoxyethylene and in tetraaminoethylenes.
Abstract: Olefins are normally preferentially attacked by electrophiles. This trend is strengthened in enol ethers and enamines, and is particularly pronounced in tetramethoxyethylene and in tetraaminoethylenes. These electron-rich olefins are accordingly also excellent reducing agents. In their reactivity, therefore, they behave as counterparts of tetracyanoethylene. This compound shares with the electron-rich olefins a strong tendency to undergo cycloadditions, the electron-rich olefins adding particularly readily to electrophiles.
103 citations
TL;DR: The relative reactivity of the substrates studied toward the microsomal hydroxylating system correlates well with their reactivity toward chemical reagents which cause electrophilic substitution: i.e., reactive or electron-rich rings act as the best substrates.
89 citations
TL;DR: Based upon a thermodynamic study of the accelerated oxidation of superalloys exposed in oxidizing environments containing minor quantities of sea salt, it was concluded that NaCl is necessary only to form Na2SO4.
Abstract: Based upon a thermodynamic study of the accelerated oxidation of superalloys exposed in oxidizing environments containing minor quantities of sea salt, it is concluded that (a) NaCl is necessary only to form Na2SO4, (b) Na2SO4 is formed by the reaction between NaCl and the oxides of sulfur, (SO2 and SO3) and (c) accelerated oxidation attack occurs only when Na2SO4 is present in the condensed form. Experimental verifications of the above conclusions is presented.
89 citations
86 citations
TL;DR: The effect of adding 20-50% H2 to active nitrogen has been studied at both 196 and 320° K in this paper, where the consumption of both nitrogen atoms and oxygen atoms was followed photometrically and the results yields a ration k8/k9-1.4± 0.1 at 320° k.
Abstract: The effect of adding 20–50 % H2 to active nitrogen has been studied at 196 and 320° K. At neither temperature is there a primary reaction but when the nitrogen atoms are partially titrated with nitric oxide at 320° K, a catalytic removal of atoms is induced involving the reactions : O + H2= OH + H (5), N + OH = NO + H (8), N + NO = N2+ O (1), O + OH = O2+ H (9), with (5) rate controlling. The consumption of both nitrogen atoms and oxygen atoms was followed photometrically and the results yields a ration k8/k9– 1.4±0.1 at 320° K. The rate constant k5 was (1.2 × 0.1)× 107cm3 mole –1 sec–1at 320° K in separate experiments. The role of H2 as a third body in the recombination reactions of nitrogen and oxygen atoms has been examined at 196° K where reaction (5) is unimportant.
TL;DR: In this paper, the relative reactivity of tris(trimethylsilyl)silyllithium (I) was investigated in an attempt to estimate the importance of (dπ-pπ) bonding involving two contiguous silicon atoms.
01 Jan 1968
TL;DR: In this paper, a comparative study of the reactivity of hydroxide and various alkoxide anions was made by determining percentage weight loss of poly(ethylene terephthalate) fiber.
Abstract: A comparative study of the reactivity of hydroxide and various alkoxide anions was made by determining percentage weight loss of poly(ethylene terephthalate) fiber. Regardless of the basicity of the anions, the order of reactivity was found to be hydroxide < tert-butoxide < sec-propoxide < methoxide < ethoxide. This observed order follows the nucleophilicity of the bases, and the relatively lower reactivity of sec-propoxide and tert-butoxide is assumed to be due to steric retardation during the equilibrium reactions.
TL;DR: It is found that reactions in which a functional group attached to a high polymer exhibits widely different reactivity to that in small molecules are often found.
Abstract: In discussing the reactivity of macromolecules, it is generally assumed that a functional group attached to a high polymer has a chemical reactivity similar to that which would be observed for such a group in small molecules1. This generalization may essentially be true, but we often find reactions in which a functional group attached to a high polymer exhibits widely different reactivity to that in small molecules.
TL;DR: In this paper, it is shown how minority-carrier reactions on the zinc oxide surface may lead to current doubling and use of this observation to study hole reactivity of reducing agents and to study free radical reactions.
TL;DR: The reaction of amine nucleophiles at the phosphorus center of mono-and di-anions of phosphate monoesters involves concerted displacement processes as discussed by the authors, and the reactivity depends strongly on the leaving group, but only weakly on the basicity of the nucleophile.
Abstract: The reactions of amine nucleophiles at the phosphorus centre of mono- and di-anions of phosphate monoesters involve concerted displacement processes. The reactivity of the dianions depends strongly on the leaving group, but only weakly on the basicity of the nucleophile, and for a sufficiently good leaving group the Bronsted coefficient is zero. Thus, substituted pyridines differing in basicity by more than eight powers of ten attack the dianion of 2,4-dinitrophenyl phosphate at the same rate. These reactions must lie close to the borderline between unimolecular and bimolecular processes. The reactions with the monoanions are sensitive to the basicity of the nucelophile, and also depend strongly on the leaving group. The reactivity of phosphate monoester monoanions is similar to that of the anions of the diesters, and both react readily with fluoride anion.
TL;DR: In this paper, an activity order of catalysts (the best is palladium on charcoal), a reactivity comparison of iodine, bromine and chlorine, and the influence of ortho, meta or para position in halogenobenzoic acids in relation to halogen-obenzenes and to several other halogen compounds are given.
Abstract: Sodium tetrahydroborate has a poor reduction capacity for the elimination of aromatic halogens. The addition of metal catalysts (in particular Pd, Co, Ni, Cu) accelerates this reaction to such an extent that even the rather stable aromatic chlorine can be exchanged by hydrogen at room temperature. An activity order of catalysts (the best is palladium on charcoal), a reactivity comparison of iodine, bromine and chlorine, and the influence of ortho, meta or para position in halogenobenzoic acids in relation to halogenobenzenes and to several other halogen compounds are given. Two preparative examples are described.
TL;DR: 4,5-dimethyl- and 4,5,6-trimethyl-3-pentadecyl- o -quinones, in which both of the normal sites for nucleophilic attack by the protein are blocked, do not react to any appreciable extent, while 3-pentadescyl-O -quinone is most reactive of all the compounds tested.
TL;DR: In this article, the authors studied the kinetics of the hydrolysis of methyl-, cyclohexyl-, and phenylphosphonates by sodium hydroxide in 50% water/dioxane.