THE OXIDATION OF BENZOYL-ORTHO-TOLUIDINE AT A BENZENE-WATER INTERFACE WITH SPECIAL REFERENCE TO THE TEMPERATURE COEFFICIENT OF THE REACTION RATE

1929 ◽  
Vol 51 (4) ◽  
pp. 965-974 ◽  
Author(s):  
Louis S. Kassel ◽  
Norwood K. Schaffer
Keyword(s):  
Special Reference ◽  
Temperature Coefficient ◽  
Reaction Rate ◽  
Water Interface

Mechanism of Rubber Vulcanization with Sulfur

1938 ◽  
Vol 11 (1) ◽  
pp. 107-130
Author(s):  
W. K. Lewis ◽  
Lombard Squires ◽  
Robert D. Nutting
Keyword(s):  
Natural Rubber ◽  
Temperature Coefficient ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Reaction Rate ◽  
Complex Behavior ◽  
Double Bonds ◽  
Irreversible Reaction ◽  
Sulfur Addition

Abstract THAT vulcanization of rubber with sulfur always involves a chemical reaction consisting in the addition of sulfur to the double bonds of the rubber molecule has been conclusively established (18, 28). The facts indicate that this addition of sulfur to rubber is an irreversible reaction (31). The temperature coefficient of the reaction is high, increasing about 2.65 fold per 10° C. at ordinary curing temperatures (31). Furthermore, the reaction is apparently exothermic (4, 24). It is noteworthy that catalysts are apparently necessary, since synthetic rubbers prepared from pure materials add sulfur slowly, if at all. The proteins and perhaps the resins in natural rubber undoubtedly serve as accelerators. The curves for combined sulfur vs. time of cure for typical mixes are shown in Figures 1 and 2. Figure 1 is taken from the data of Kratz and Flower (16); the composition and temperature of cure for this mix are shown in Cranor's Table I (9). Figure 2, curve 1, is from Table I of Eaton and Day (10), and curve 2 from data obtained in this laboratory (27, Table I). Superficial inspection of these curves shows extraordinary divergence of type. Figure 1 is a typical fadeaway curve, characteristic of most chemical reactions, where the reaction rate decreases with decreasing concentration of the reacting materials. Curve 1, Figure 2, is an entirely different type, where the rate of sulfur addition is constant until nearly 70 per cent of the initial sulfur has reacted. Curve 2, Figure 2, shows even more complex behavior. Again the rate is constant in the initial portions of the cure. However, following this period, the rate increases markedly but later falls off, approaching zero, to give an S-shaped eurve.

Experimental investigation and kinetic modeling of the negative temperature coefficient of the reaction rate in rich propane—oxygen mixtures

1997 ◽  
Vol 46 (12) ◽  
pp. 2006-2010 ◽  
Author(s):  
V. I. Vedeneev ◽  
L. B. Romanovich ◽  
V. Ya. Basevich ◽  
V. S. Arutyunov ◽  
O. V. Sokolov ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Temperature Coefficient ◽  
Kinetic Modeling ◽  
Reaction Rate ◽  
Negative Temperature Coefficient ◽  
Negative Temperature

scholarly journals A comparison of the activity of phosphatidylinositol phosphodiesterase against substrate in dispersions and as monolayers at the air-water interface

1975 ◽  
Vol 149 (1) ◽  
pp. 199-208 ◽  
Author(s):  
P J Quinn ◽  
Y Barenholz
Keyword(s):  
Reaction Rate ◽  
Substrate Surface ◽  
Phospholipid Bilayers ◽  
Initial Surface ◽  
Water Interface ◽  
Ph Optimum ◽  
Bivalent Ions ◽  
Rate Of Reaction ◽  
Air Water Interface ◽  
Zero Order Reaction

The activity of phosphatidylinositol phosphodiesterase, purified from rat brain, against substrate in three forms, (a) multibilayer liposomes, (b) single bilayer vesicles of phosphatidylinositol and (c) phosphatidylinositol oriented as monolayers at the air-water interface, was examined. The reaction rate was similar against the two substrate dispersions prepared with the same phospholipid concentration, although there was a large difference in substrate surface area available to the enzyme, and this similarity could not be accounted for by any differences in the microviscosity of the hydrocarbon region of the phospholipid bilayers. The reaction showed apparent zero-order reaction kinetics until about 10% of the substrate had been degraded, whereupon the rate decreased. The reaction against monolayers of phosphatidylinositol was linear throughout the entire digestion of the film, provided that more than 0.25 mg of enzyme was present in the subphase. The pH optimum was 6.6. Bivalent ions)Ca2+, Mg2+, Co2+, Ni2+ and Mn2+) facilitated enzyme penetration into substrate monolayers, but the enzyme was only activated by Ca2+ (optimal concentration, 1mM) and to a lesser extent by Mg2+. The reaction rate was independent of initial surface pressures of less than about 22mN·m-1 but at higher pressures the rate decreased. This decrease could be prevented by the addition of 10mol of octadecylamine/90mol of phosphatidylinositol to the substrate monolayer; the amine did not increase the rate of reaction in films of less than 22mN·m-1.

THE HOMOGENEOUS UNIMOLECULAR DECOMPOSITION OF GASEOUS ALKYL NITRITES: VII. A GENERAL DISCUSSION OF THE EFFECT OF CHEMICAL CONFIGURATION ON THE REACTION RATE

1936 ◽  
Vol 14b (7) ◽  
pp. 268-274 ◽  
Author(s):  
E. W. R. Steacie ◽  
S. Katz ◽  
S. L. Rosenberg ◽  
W. McF. Smith
Keyword(s):  
Special Reference ◽  
Experimental Evidence ◽  
Homologous Series ◽  
Reaction Rate ◽  
Progressive Increase ◽  
Point Of View ◽  
Unimolecular Decomposition ◽  
Alkyl Nitrites

A general discussion is given of the rate of unimolecular decomposition of an homologous series of compounds from the point of view of the Kassel theory. The experimental evidence is discussed with special reference to the decomposition of the alkyl nitrites. It is concluded that existing theories are unable to account for the progressive increase in rate as one ascends the homologous series.

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