Search

Es werden die spezifischen Geschwindigkeitskonstanten der alkalischen Solvolyse von p-substituierten Dimethyl-phenyl-silanen in Athanol/Wasser gemessen und mit fruheren Ergebnissen an entsprechend substituierten Triphenyl-silanen verglichen. Induktiver und mesomerer Effekt der Aryl-Gruppe auf die Reaktionsgeschwindigkeit werden abgeschatzt. Specific rate constants of the alkaline solvolysis of p-substituted dimethyl-phenyl silanes in ethanol/water are determined and compared with former results of correspondingly substituted triphenyl silanes. The inductive and mesomeric effect of the aryl group on the reaction velocity are estimated.

The work described here forms part of a study of the relationship between absolute reaction velocity and its temperature coefficient in systems of the type Solid 1 → Solid 2 + Gaseous Product, and of the influence of the gaseous product upon the velocity. Preliminary Experimental Considerations . Rate measurements in heterogeneous systems of this kind are subject to certain difficulties which necessitate an extensive examination of the special circumstances of the reaction before much significance can be attributed to the absolute magnitude of an observed rate. It will be convenient to discuss these difficulties in terms of a dissociating salt hydrate, S1 . n H 2 O → S 2 . n 2 H 2 O + ( n 1 ─ n 2 )H 2 O, in which it is supposed that no solid solution is formed. It is assumed that the course of the reaction is being followed by direct measurement on a spring-balance of the weight change of the solid due to loss of the gaseous product.

It has been experimentally determined that the velocity of reaction between nitrogen and calcium carbide at high temperatures is not directly proportional to the nitrogen-pressure, but there exists the following relation: (Remark: Graphics omitted.) \oindentwhere P denotes the pressure, K and α certain constants depending upon temperature and other conditions of the reaction.It has also been found that the higher the temperature the greater is the effect of pressure-increase to the velocity of reaction, though the effect of the pressure-increase becomes smaller at higher pressures. At lower pressures the velocity of the reaction is nearly proportional to the pressure.

1. Assumed as monomolecular reaction, the velocity of the decom-position of potassium monochloracetate in aqueous solutions is measured, K_25°=0.837×10^-6 and K_30°=3.21×10^-62. The velocities of the following reactions are measured, CH2CLCOOK+KOH = CH2OHCOOK+KCL K_20°=0.227×10^-4, K_25°=0.521×10^-4 and K_30°=1.23×10^-4 CH2CLCOONa+NaOH=CH2OHCOONa+NaCl K_25°=0.381×10^-4, K_30°=0.704×10^-4 and K_35°=2.18×10^-4The velocity constant of potassium salt is larger than that of sodium salt. 3. The reaction velocity of potassium monochloracetate with potassium hydroxide is retarded by the presence of another salt (i.e. KNO3).

A diffusion model based on the simultaneous interdiffusion and reaction between alternate slabs of reactants is used to simulate the data of Vassilatos and Toor. After slab sizes are chosen to fit the conversion data for very rapid reactions in a stoichiometric mixture, reasonably good predictions are obtained of the effect of stoichiometry and reaction velocity constant on conversion. The results are close to the predictions of Kattan and Adler's stochastic mixing model, and the similar behavior of these disparate models implies that conversion is insensitive to the details of the mixing.

Purified soluble tyrosinase isolated from the melanosomes of Harding-Passey mouse melanoma was incubated with L-dopa. The reaction velocity of the tyrosinase thus incubated decreased significantly. There was an inverse linear relationship between the concentration of dopa in the preincubation mixture and the reaction velocity of the tyrosinase which remained. The experimental results obtained were similar to what had been observed in melanosomes. 64 Cu-exchanged tyrosinase or 11 C-amino-acid-labeled tyrosinase were incubated with L-dopa; the reaction mixture was centrifuged after varied incubation times, and the radioactivity of the obtained supernatant was determined. The time courses of the disappearance of labeled tyrosinase from the reaction systems indicated that soluble tyrosinase combined with the products of the dopa-tyrosinase reaction and precipitated out with them. Thus tyrosinase was excluded from the reaction systems. The experimental results obtained suggest that the decrease of tyrosinase activity is due to the binding of tyrosinase with reaction products, probably at the active site, and to the disappearance of the tyrosinase molecule from the reaction system.

The influences of temperature and aldehyde concentration over the reaction velocity in acetalizing PVA fibre with acrolein and the reaction velocity depending upon the diffusion velocity of reagent into fibre were sought. The degrees of swelling, tenacities and elongations of the fibres were measured, and found that this kind of treatment is of no use for particular improvement of mechanical properties of the fibre.

A numerical study is made of the interaction of a detonation wave having finite reaction velocity with a rarefaction wave of different intensity which approaches it from the rear, for the Zeldovich-Neumann-Doring (ZND) model with a single irreversible reaction A → B. It is found that, for a fixed value of the parameter characterizing the initial supercompression (depending on the activation energy and the heating value of the mixture), the considered interaction leads either to a gradual relaxation of the detonation wave and its transition to the Chapman-Jouguet (CJ) regime, or to the development of undamped oscillations.

Synopsis The thermodynamics of irreversible processes as developed by Onsager, De Groot and others has been applied to the case of thermal effusion of a fluid consisting of two isomers with a finite velocity of transformation. More general formulae than those of De Groot, Jansen and Mazur have been obtained, by considering the velocity of transformation to be different in the two chambers on account of the difference in temperature. Application of these results to liquid Helium II is discussed, and their importance in the study of chemical equilibria pointed out.

Puffersalze uben einen spezifischen Einflus auf die Redoxreaktion Rongalit/H2O2 aus. So verlauft die Reaktion in Acetatpuffer etwa viermal schneller als in Citratpuffer. Auch die durch dieses Redoxsystem initiierte Polymerisation von Acrylnitril zeigt qualitativ die gleiche Abhangigkeit. The redox reaction between sodium formaldehyde sulfoxylate and H2O2 is influenced specifically by the buffer salts employed. Thus the reaction velocity in acetate buffer is four times faster than in a citrate buffer. The polymerization of acrylonitrile initiated by the above redox system shows qualitatively the same dependence.

1. In a previous report, one of the authors* estimated the necessary activation energy E of the baking reation of resin finishing as approximately 16_??_18kcal/mol, based on data derived from commercial products. The activation energy E and frequency factor A of the reaction presented in this report are calculated by using our experimental measurements. For this purpose, we have made two series of experiments: a) baking of resin on clean glass plates, and b) baking of resin on cotton fabrics.2. Our experimental results fully agreed with the following equation of unimolecular reaction: where a: Unreacted part of resin i.e. in 70°C water soluble part at z=0 by Kyeldhal method. a-x: do. at z=z (min.) k: Reaction velocity constant at temp. T°K z: Baking time (min.) z0: Waiting time (min.)3. In all the experiments, the reaction velocity constant k fully agreed with the Ahrrenius equation: ln k=A+(-E/RT) where R: gas constant.4. From the said results, the activation energy E and frequency factor A are culculated as follows: for series a) E 8.82kcal/mol, A 2, 178 10-1 min. for series b) E 18.85kcal/mol, A 1, 012 10-1 min.5. We have further made cumulative baking at various temperatures and have found that experimental results agreed with the cumulative reaction equation:6. We conclude from the great difference of the activation energy E in the above two series, that in series a) only reaction between resin components occurs, whereas in series b) reaction between resin components and cellulose predominates.

The reactions between hydrogen chloride and α-, β-, and γ-butylene have been investigated in both the liquid and gaseous states. The effect of temperature and concentration of the reactants on the reaction velocities was studied and the reaction products were examined. In the liquid state the γ-isomer reacts rapidly, the α- much more slowly and the β- slowest of all. In the gaseous state at atmospheric pressure only γ-butylene shows a measurable reaction which is bimolecular and probably heterogeneous. The liquid reactions were found to be homogeneous. Where possible the freezing-point curves of the systems were determined in order to ascertain the extent of molecular compound formation. The results obtained bear out the conclusions arrived at from previous work on the effect of molecular attraction upon reaction velocity, and indicate the existence of a catalytic factor peculiar to the liquid state. Suggestions as to the mechanism of such a catalysis are offered.

The purification and properties of a Na+- and K+-activated ATPase from ox brain is described. The enzyme preparation is characterized by a high purity and a low content (< 1%) of Mg++-stimulated ATPase.

ナトリウムアマルガムによるアクリロニトリルの水素化二量化反応について検討した。二酸化炭素ガスで反応液のpHを調節しながら,ジオキサン溶媒中のアクリロ8トリル水溶液にナトリウムアマルガムを接触させて反応を行なった。アマルガム中のナトリウムの反応速度はその濃度に比例する0次反応であることが明らかになった。反応液中にトリメチルフェニルアソモ8ウム塩のような第4級アンモニウム塩を添加すると,反応速度が増加し,同時にアクリロニトリルの水素化二量体であるアジポユトリルへの選択率が上る。しかし,触媒の有無は反応の活性化エネルギーに変化を与えず,いずれも約3kcal/molNaであることがわかった。触媒としては,4級アンモニウム塩,ヒ素塩,ホスフィソ化合物などが有効であるが,特に4級アンモニウム塩中の一つの基がフェニルまたはシクロヘキシルのような立体的な大きさを持つことが効果のあることが認められた。また(CH3)3RNBr型触媒について検討した結果,Rが直鎖アルキルの場合,Rの炭素数が6～9に触媒効果の最低値があること,Rが環状物の場合,フェエルでもシクロヘキシルでも強い触媒作用を持つことが明らかになった。これらの検討の結果から水素化二量化反応における触媒の作用機構について,アクリロニトリルと触媒の相互作用を仮定して考察を行なった。

Der alkalische Starke-Abbau wird durch laufende Messungen der Jodsorption verfolgt. Der Vf. stellt fest, das der Mechanismus und die Geschwindigkeit des Abbaus bei Gegenwart und Abwesenheit von Sauerstoff unterschiedlich sind. Die Messung der wahrend des Abbaus noch vorhandenen Glucosid-Bindungen ergibt, das die Starke-Degradation eine Reaktion 1. Ordnung ist. Die Aktivierungswarme des Abbaus und der Oxydation wird berechnet. Behaviour of Starch in Alkali-Media II: The Alkali-Degradation of Starch The alkali-degradation of starch has been followed by iodsorption measurements. The authors establish that the mechanism of degradation of starch in the presence of oxygen is different from that in the absence of oxygen. The reaction velocity measurements on the basis of the glycosides still unaffected during the degradation reaction show that it is a first order reaction. The authors have calculated the heat of activation of the degradation and oxidation.

In order to elucidate the curing reaction of epoxy resin, the effects of solvent, amine and epoxy compound for reaction of a monofunctional epoxy compound (phenylglycidylether and others) and the secondary amine (di-nbutylamine and others) have been investigated from the standpoint of velocity of reaction.The result indicated that the velocity of reaction was generally greater in a solvent having polar nature than in non-polar solvent.Especially, the alcoholic hydroxyl showed a tendency to accelerate the reaction by the concerted reaction.As to the effect of amines, the greater the steric hindrance effect of amines, the smaller was the reaction velocity constant.Among epoxy compounds, phenylglycidylether and isopropylglycidylether showed greater reaction velocity constant than styrene oxide and propylene oxide.The reaction velocity constant of n-butylamine (difunctional, primary amine) and phenylglycidylether in the first stage was 2-2.5 times greater than the second stage.Although there was some differences in reaction velocity constant by the kinds of amines and solvents, an activation eneryg was around 13-14 kcal/mol and approximately the same result was obtained.

The kinetics of the Co(III) reaction with NH 2 OH in various media was studied spectrophotometrically with regard to the possible analytical use of Co(III). The results of measurements in media of 3–8 M HClO 4 and 0.1–1 M HSO − 4 in 3 M HClO 4 can be summarized as follows: 1. The reaction was found to be first order with respect to Co(III) and of zero order with respect of NH 2 OH. 2. The reaction velocity increases linearly with increasing concentrations both of HClO 4 and of HSO − 4 3. The reaction velocity also increases linearly with increasing Co(II) concentration and it is possible to achieve a higher reaction rate in this way than by the addition of HSO − 4 . 4. This behaviour can be explained either by assuming hydrogen bonding between Co 3+ aq and Co 2+ aq which makes the electron transfer easier in some systems, or by formation of a more reactive complex between Co(III) and Co(II) than the simple Co(III) ion.

A method for the determination of enzyme kinetic constants Vm, Km, and Ki in a histochemical system has been devised. As a substitute for the reciprocal of the reaction velocity, the times necessary to reach a fixed amount of end product (the initial visible color) in a tissue site at various substrate concentrations are plotted, according to the method of Lineweaver and Burk, against the reciprocal of the substrate concentrations. The technique as applied to trypsin-like esterase and amidase activities in human mast cells indicates that a single enzyme or closely related enzymes in this site are responsible for the hydrolysis of both the amide and ester substrates and that typical trypsin substrates act as competitive inhibitors of their hydrolysis. Parallel biochemical studies were performed to evaluate the effect of certain aspects of the experimental histochemical method on a purified homospecific enzyme. The relative kinetic constants derived by the histochemical method afford a further means of characterizing enzymic activity in a histochemical system.

1. I. The reduction of riboflavin by dithionite was followed, using a rapid mixing apparatus, over a range of concentration, acidity and temperature. 2. 2. The time-course of reduction of riboflavin in the presence of excess dithionite was found not to be of exponential form, but of approximately linear form. Evidently the reaction is complex. 3. 3. In sufficiently dilute riboflavin solutions, the initial reaction velocity was directly proportional to riboflavin concentration. Under these conditions, the Q10 was approximately 2.0. 4. 4. In sufficiently concentrated riboflavin solutions, the initial reaction velocity became nearly independent of riboflavin concentration. 5. 5. An intermediate was found by its absorption in the infra-red. The maximum amount of intermediate formed was proportional to the square of the riboflavin concentration. The intermediate was only detected in sufficiently concentrated riboflavin solutions. Smaller amounts of intermediate were formed at higher temperatures. 6. 6. The mechanism of the reaction is discussed.

(1) A method for calculating both reaction velocity and activation energy in the case when the reaction has been carried out in the thermal separation column of Clusius and Dickel has been described. (2) The method has been applied to the polymerisation reaction of acetylene previously investigated by the present authors. (3) It has been found that the calculated heat of activation is slightly smaller than our preliminary value, but larger than the directly observed value by Taylor and van Hook, and that the calculated velocity constants are several times larger than those hitherto have been observed.

The velocity with which oxygen dissociates from its combination with hæmoglobin, and the factors upon which the velocity-constant of this reaction depends, have already been investigated by us in some detail in the second of the present series of papers (1). Since then we have been engaged in a similar inquiry into the velocity of the reverse reaction,i. e., the combination of oxygen with reduced hæmoglobin. The scope of the investigation, which we are now about to describe, was as follows:— (α) To determine the order of the reaction between oxygen and hæmoglobin (see p. 663). (β) To compare the value of the velocity-constant for the combination of O2+ Hb ______________________________________________________ the velocity-constant for the dissociation of O2.Hb→ with the value of the equilibrium-constant of the reaction as determined from the dissociation curve. (γ) To study the effect of (i)pH(ii) temperature, (iii) light, and (iv) salt content upon the velocity of the reaction between O2and hæmoglobin. The general methods adopted were similar to those used in studying the rate of dissociation of oxyhæmoglobin. One solution (I) consisted of water containing a considerable quantity of oxygen in solution, whereas the other solution (II) consisted of reduced hæmoglobin. These were driven by separate jets into the mixing chamber of the reaction velocity apparatus (2 and 3), and after mixing travelled steadily with known velocity down the observation tube. Spectroscopic observation of the ratio of oxyhæmoglobin to reduced hemoglobin concentration at various points of the tube, together with a knowledge of the rate of linear flow and of the total amount of (i) oxygen and (ii) hæmoglobin in unit volume of the mixed solution, gave us all the data required for the measurement of the velocity of the reaction.

Summary. 1 Esperiments carried out with low thrombin concentrations show that sera of different species under similar conditions inactivate different quantities of thrombin. 2 The course of the thrombin inactivation by sera of 12 mammalian species, during the initial phase, is calculnted. 3 Sera of horse, cattle, rabbit, sheep and goat absorb thrombin, and the fermentative inactivation has A constant velocity during the initial phase. Another group of sera (rat, mice, dog, guinea-pig, pig, hedpehog) shows no absorption, the inactivation is more rapid. and the reaction velocity is not constant.

1. 1. The variation of the Michaelis constant (Km and the maximum reaction velocity (V) with pH for the reaction of hemoglobin with human, canine and porcine pepsins was studied. 2. 2. At pH 2 the Km's were found to be 6 · 3 × 10−4 M, 10 × 10−4 and 1 · 1 × 10−4 M, respectively, for human, canine and porcine pepsins. 3. 3. The similarity between human and canine pepsins permits valid comparisons of these enzyme activities in molar terms, and porcine pepsin appears to be a reasonable gravimetric standard for such studies.

Cyanuric chloride and methanol react at low temperature without addition of alkali such as NaHCO3 and give (4)(See part (I);similarly in the case of (1), (2).and On.The reason is that the reaction of (2) or (3) with methanol is accelerated by the acid and this is explained by comparing the reaction velocity of (1), (2), and (3) with methanol in the presence or absence of HC1.On the other hand, the alkalis used in the reaction with methanol are divided into two of the following: i) Kinds of slowing the reaction such as NaHCO3 andCaCO3 than without the addittion of alkali, and ii) kind of giving mor vigorous acceleration such as NaOH.i) acts as an acid-removing agent and prevents rapid formation of B and C (See part (I)), it is a controlling agent for proceeding of stepwise reaction of A, B and C, and it is suitable for syntheses of (2) and (3).ii) has a tendency of accelerating the reaction of alcohol and it is suitable for synthesis of (4).

Die Reaktionen der Radikale werden am Beispiel der Emulsionspolymerisation behandelt. Die Polymerisation beginnt mit einer meist kurzen Periode, in der Latexteilchen gebildet werden und lauft dann in den Latexteilchen mit den gleichen Elementarreaktionen (Start, Wachstum, Ubertragung, Abbruch) weiter wie in homogener Losung. Die Radikale treten einzeln von ausen in die Latexteilchen ein; dadurch erhalt man besonders ubersichtliche Verhaltnisse. Wachstums- und Abbruchskonstanten konnen, wie am Beispiel des Styrols und des Methylmethacrylats gezeigt wird, verhaltnismasig einfach bestimmt werden. Die Polymerisation verlauft von Anfang an in einer ziemlich konzentrierten Polymerenlosung. Bei fortschreitendem Umsatz wird als schnellste Reaktion zuerst die Abbruchsreaktion durch die Diffusion kontrolliert: die Abbruchsgeschwindigkeit nimmt ab und die Bruttoreaktionsgeschwindigkeit zu (Trommsdorffeffekt). Bei hohen Umsatzen gerat auch die Wachstumsreaktion unter Diffusionskontrolle: jetzt nimmt die Bruttoreaktionsgeschwindigkeit sehr schnell ab. Beim Methylmethacrylat ist der Effekt besonders stark. Aus den diffusionskontrollierten Geschwindigkeitskonstanten der Abbruchs- und der Wachstumsreaktion lassen sich nach einer Methode von Schulz die Diffusionskonstanten der Makroradikale und des Monomeren berechnen. Reactions of radicals are treated for the case of emulsion polymerization. Polymerization starts with a frequently short period during which latex particles are formed and proceeds in the latex particles with the same elementary steps (initiation, propagation, transfer, termination) as in homogeneous solution. Radicals enter the latex particles singly from the outside, and an exceptionally simple situation results from this. Rate constants for propagation and termination are relatively easily determined, as is shown in the cases of styrene and of methyl methacrylate. Initially the polymerization takes place in a fairly concentrated polymer solution. With progressive conversion the termination reaction, being the most rapid one, is the first to be diffusion-controlled. The termination velocity decreases and the overall reaction velocity increases (Trommsdorff effect). At high conversions the propagation reaction becomes likewise controlled by diffusion, and now there is a rapid drop in the gross reaction velocity. The effect is particularly marked for methyl methacrylate. According to a method due to Schulz, the diffusion constants of macroradicals and monomer can be calculated from the diffusion-controlled rate constants of termination and propagation reactions.

The reaction-velocity of hydrogen and oxygen at the surface of platinum in dependence on both gases was determined by measuring the change of pressure of the combustible gas. From the formula for the reaction-velocity could be inferred the way in which both gases were adsorbed at the solid surface.

The reaction of Al upon hydrochloric acid solution (1.5-4N) was investigated based upon the reaction velocity theory. The result is as follows:1. Al reacts on and dissolves in hydrochloric acid solution according to the following chemical equation:Al+3HCl=AlCl3+3/2H22. The dissolving reaction of Al in hydrochloric acid solution consists of the stages of primary and secondary dissolution. The former can be shortened or eliminated by a suitable pretreatment, and the latter becomes the main-part of the reaction.3. In 1.5-4N hydrochloric acid solution the first order reaction of Al will take place, under which the following reaction velocity equation will hold:d(Al)/dt∞dV/dt=3.11×102[HCl]⋅S⋅e-8200/1.986T(V∞-V)(see equation 5, page 357).From this equation, we can determine the life of Al in hydrochloric acid.4. The activation energy is 8200cal/mol; from this figure the reaction is regarded as a diffusion reaction.

The factors determining the rate of reactions between solids are discussed. When the solid phases are internally in equilibrium and when equilibrium also is established at the phase boundaries, the kinetics are given by the geometric dimensions of the system, the free energy decrease, and the mobility of the diffusing particles in the reaction product. These conditions are not fulfilled in most practical cases, the reactions being strongly dependent on topochemical factors. Topochemical imperfections in crystals and their influence on the reaction velocity are described, but the mechanism of reactions influenced by topochemical factors can only be found empirically. The way of approach is outlined for the case of spinel formation from zinc oxide and iron oxide.

Heparin cofactor material of M ~15,000 has been separated from Fraction I. Isolated systems containing heparin, cofactor, and thrombin exhibit a progressive, limited thrombin inactivation. Complications arise since reaction velocity, specific capacity of cofactor (units T/mg. C) and extent of reversibility (using protamine) are functions of cofactor concentration.