Activation of acids

Catalytic amounts of I fCl4-AgC104 and Hf(OTf)4 are used for activation of acid halides and acid anhydrides for Friedel -Crafts acylation (Scheme 42) 178 the reactions of both reactive and unreactive aromatic substrates proceed smoothly in the presence of Hf(OTf)4. Furthermore, the Fries rearrangement179,180 and direct C-acylation of phenolic compounds181,182 take place using Hf(OTf)4. Formation of esters and Mannich-type reactions and allylation of imines have been also reported.152... 

Breen C, Zahoor FD, Madejova J, Komadel P (1997) Characterisation and catalytic activity of acid-treated, size-fractionated smectites. J Phys Chem B 101 5324-5331... 

Chatterjee, M. and Wu, S., 2001, Involvement of Fas receptor and not tumor necrosis factor-alpha receptor in ultraviolet-induced activation of acid sphingomyelinase. Mol. Carcinog. 30 47-55. 

Starek A. 1980a. [The influence of kerosene hydrocarbons on the activity of acid hydrolases of lymphocytes in rats.] Folia Med Cracov 22(3-4) 385-392. (Polish)... 

At low temperatures, the activity of acid catalysts in transesterification is normally fairly low and to obtain a sufficient reaction rate it is necessary to increase the reaction temperature to >170 °C. Therefore, sulfonic acid resins can be used in esterification reactions where they perform well at temperatures <120 °C and particularly in the pretreatment of acidic oils. Under these reaction conditions, acidic resins are stable. Poly(styrenesulfonic add), for example, has been used in the esterification of a by-product of a vegetable oil refinery with a 38.1 wt% acidity at 90-120 ° C and 3-6 atm. It was not deactivated after the first batch and maintained a steady catalytic performance in the next seven batches [22]. 

As a means to characterize the activity of acid catalysts, hexane cracking offers unique advantages and is best carried out at high temperature, such as 538°C, and low pressure. 

To reveal factors which influence activities of acid-base catalysts in alkylation and isomerization is the challenge to activity in this field. Q he greatest amount of work has been done in connection with the effect of para-selectivity, which is observed in alkylation of aromatic hydrocarbons on ZSM-5 type zeolites [1]. This effect has been explained by a number of authors either by the influence of diffusion factors [2,3] or by the isomerizing activity of the external surface of zeolite crystals [4]. In refs. [5,6] and especially in ref.[7] the para-selective effect of ZSM-5 type zeolites is shown to be due to decreasing their isomerizing activity becaiase of the decrease in the concentration of strong protic centres as a result of modifiers introduced. Para-selective effect is related to the action of chemical factors. However, in... 

Food consumption of adults decreased after day 16 accelerated development of pluteal stages all developmental stages had increased activities of acid phosphatase... 

Oral administration of di(2-ethylhexyl) phthalate at levels of 0, 250, 500 or 1000 mg/kg bw to adult albino rats for 15 days resulted in a significant decrease in sperm count in the epididymus and increased activity of P-glucuronidase, y-GT and lactate dehydrogenase and a decrease in the activity of acid phosphatase in the testes. The authors interpreted these findings as indicating germ-cell depletion and deterioration of the germinal epithelium in the testes (Parmar et al, 1986). 

Fixed Acid. The total acid (as tartaric) less the volatile acidity (as tartaric) is the fixed acidity. It is useful to make this calculation when one suspects activity of acid-reducing bacteria, as in the malo-lactic fermentation. 

Activation of Acids with Miscellaneous Coupling Reagents... 

The conclusion of Bernardi and Griffe (3) that the phosphodiesterase activity of acid DNase is an intrinsic property of the enzyme molecule has been recently challenged by Slor (46, 58), Swenson and Hodes (54), and Slor and Hodes (55), who claimed to have obtained a separation of the two activities. In fact, none of the reported results proves an actual separation of the two activities and constitutes an acceptable evidence against the two activities being carried by the same protein molecule. Some data suggest, however, that the phosphodiesterase activity may be inactivated preferentially by some treatments. In connection with the phosphodiesterase activity of acid DNase, see also Tables I and II in reference (56) and the related discussion (56a). 

In 1924, Martland et al. (1) reported on phosphatase activity in red blood cells. Roche later differentiated between the phosphatase of the red cells with pH optimum 6.0-6.2 and the phosphatase from white cells with optimum 8.8-9.0. Roche also showed that a-glycerophosphate was split more rapidly than -glycerophosphate by red cell extracts while the reverse was true of acid phosphatase activity in plasma (2). While studying the source of acid phosphatase activity in male urine, Kutscher and Wolberg discovered the very high activity of acid phosphatase in human prostate (3). This tissue was shown by Woodard to have one-thousand times the activity of extracts from bone, liver, and kidney (3a). Igarashi and Hollander crystallized the acid phosphatase of rat liver and showed that under certain conditions allosteric control of the activity could be demonstrated (4). 

Fig. 31. Catalytic activities of acidic Na or Cs salts of HjPW 204o as a function of Na or Cs content, (a) M = Na (O) dehydration of 2-propanol, (A) decomposition of formic acid, ( ) conversion of methanol, ( ) conversion of dimethyl ether, (b) M = Cs (O) dehydration of 2-propanol, ( ) conversion of dimethyl ether, (A) alkylation of 1,3,5-trimethylbenzene with cyclohexene. (From Refs. 46 and 128.)...

A large number of inorganic compounds can be used as the activators of acid-ion (anionic) activated lactam polymerization. The activator in anionic activated lactam polymerization not only increases the process rate, but also changes the structure and functionality of a polymer formed, and, as a result an activator can regulate the properties of the end-product.1... 

Inorganic Base-Promoted Activation of Acidic Organic Compounds... 

In mineral and synthetic engine oil formulations, hydrogen bond formation between anionic or molecular bases (A, B) and their conjugate acids HA or BH+, have a heavy impact on the activity of acids and their salts. For example, in mixtures of carboxylic acid with excess of sodium carboxylate in hydrocarbon and aprotic solvents, the activity of the acid is greatly decreased because of homoconjugation ... 

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