Accelerators organic-based

Decomposition Hazards. The main causes of unintended decompositions of organic peroxides are heat energy from heating sources and mechanical shock, eg, impact or friction. In addition, certain contaminants, ie, metal salts, amines, acids, and bases, initiate or accelerate organic peroxide decompositions at temperatures at which the peroxide is normally stable. These reactions also Hberate heat, thus further accelerating the decomposition. Commercial products often contain diluents that desensitize neat peroxides to these hazards. Commercial organic peroxide decompositions are low order deflagrations rather than detonations (279). 

The solvent process involves treating phthalonitrile with any one of a number of copper salts in the presence of a solvent at 120 to 220°C [10]. Copper(I)chloride is most important. The list of suitable solvents is headed by those with a boiling point above 180°C, such as trichlorobenzene, nitrobenzene, naphthalene, and kerosene. A metallic catalyst such as molybdenum oxide or ammonium molybdate may be added to enhance the yield, to shorten the reaction time, and to reduce the necessary temperature. Other suitable catalysts are carbonyl compounds of molybdenum, titanium, or iron. The process may be accelerated by adding ammonia, urea, or tertiary organic bases such as pyridine or quinoline. As a result of improved temperature maintenance and better reaction control, the solvent method affords yields of 95% and more, even on a commercial scale. There is a certain disadvantage to the fact that the solvent reaction requires considerably more time than dry methods. 

Aldol reactions using phosphoramides as organocatalysts The organic base-catalyzed asymmetric intermolecular aldol reaction with ketone-derived donors can be successfully applied to the construction of aldol products with two stereogenic centers [82-86]. Trichlorosilyl enolates of type 51 have been used as nucleophiles. Such enolates are strongly activated ketone derivatives and react spontaneously with several aldehydes at —80 °C. A first important result was that in the aldol reaction of 51 catalytic amounts of HMPA led to acceleration of the rate of reaction. After screening several optically active phosphoramides as catalysts in a model reaction the aldol product anti-53 was obtained with a diastereomeric... 

The replacement of an aryl halogen atom by the cyano group can be accomplished by the action of anhydrous cuprous cyanide at 150-250° with or without an organic base (usually pyridine) as a promoter or solvent (Rosenmund-von Braun nitrile synthesis). The reaction is autocatalytic and may be accelerated by the addition of small amounts of a nitrile and Copper sulfate. Typical laboratory procedures are found in the syntheses of a-naphthonitrile (90%) and 9-cyanophenanthrene (87%). The adaptation of the process to commercial practice has been discussed. ... 

Besides the researches on the triethoxysilane hydrolysis on the silica surface which were discussed earlier [45,46], there are studies [56,69,74] concentrating upon the chemical reactions of HSi(OC2H5)3 with silanol groups. It was established by Petrova, Tertykh, and Pavlov [56] that this chemical reaction is accelerated not only in the presence of organic bases but also in the case of the introduction of hydrogen chloride into the reaction volume. The possible causes of the catalytic effect of electron- and proton-donors on the proceeding of chemical reactions in a silica surface layer has been discussed in more detail in our monograph [1]. 

Essentially, the OIT value quantitatively describes a lifetime of a composite (or actually any organic-based) material during its accelerated oxidation in pure oxygen at an elevated temperature, such as 190°G. For example, for unstabilized (without added antioxidants) WPG materials the OIT can be as low as 0.3-0.5 min. The lifetime of such WPG boards in the South (Arizona, Texas, Florida) can be as low as only several months. The lifetime in this context is a time period by the end of which the consumer can see there is something wrong with the deck and calls for help. In real terms, the deck owner contacts with the manufacturer and tiles a warranty claim. 

Organic bases such as tetraalkylammonium hydroxides, tertiary amines, and phosphines [46,49,52-54] were employed as additives to improve the activity and selectivity of platinum catalysts in the oxidation of L-sorbose to 2-keto-L-gulonic acid (2-KLG). Rate acceleration was attributed to a beneficial effect of the amine on the hydration of the intermediate aldehyde. The selectivity enhancement obtained with hexamethylenetetramine (HMTA) was attributed to a steric effect involving a complex between HMTA and L-sorbose via hydrogen bonding [52] (see Section 9.3.3.2). 

The reaction between an epoxy resin and an anhydride is rather sluggish. In commercial practice, the curing is accelerated by the use of organic bases to catalyze the reaction. These are usually tertiary amines such as a-methylbenzyl-dimethylamine and butylamine. The tertiary amine appears to react... 

Uses primary standard for acids accelerator for the vulcanization of rubber for use with thiazoles and sulfanamides complexing agent in the detection of metals and organic bases A... 

Organocatalysis is basically the reactions require an organic-based metal free catalyst in order to accelerate chemical reactions, and provide operational simplicity and low toxicity [1-3]. Owing to the metal free organic compotmds contaminant, organocatalysts attracted much attention in many fields of green chemistry associating food, pharmaceutical, and cosmetic industries [4]. 

There has been continued interest in developing an organic-based accelerator. Ramachandran and coworkers studied the effect of o, m, and p-nitrobenzoic acids on the hydration of tricalcium silicate.The m and p nitrobenzoic acids acted as accelerators. The acceleratory effect was attributed to the complex formation between the organic compound and the C-S-H phase on the surface of the tricalcium silicate phase. 

The addition of fully hydrated CAC to hydrating CAC systems can reduce setting times significantly. This behavior, also observed in portland cement systems, can be attributed to a nucleation mechanism.Set acceleration can also occur with the addition of dilute solutions of sodium, potassium and lithium salts, or organic bases, e.g., triethanolamine. 

One of the most dramatic examples of catalysis of organic reactions by coordinating the substrate to a metal center was provided by the 10 -fold acceleration of base hydrolysis of acetonitrile when coordinated to ruthenium(III) in [Ru(NH3)5(MeCN)]. Now the very much less dramatic acceleration of base-independent hydrolysis by the [Ru(NH3)5] moiety has been examined, for benzonitrile and 1-adamantyl cyanide as well as for acetonitrile. Rate constants and activation parameters and AS were determined. They are similar for all three compounds, indicating a close similarity of mechanism. " ... 

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