Secondary reactions method

Yields of greater than 60% are obtained (46). This method has been used for the commercial production of OF2 (8). The NaOH concentration, however, must be kept low to avoid the loss of product by a secondary reaction ... 

A variation of this method involves the conversion of the amine into the amine hydrochloride prior to treatment with phosgene. This method has the advantage of producing generally cleaner products by retarding the secondary reaction of the free amine with carbamoyl chloride. 

Clearly the accurate measurement of the final (infinity time) instrument reading is necessary for the application of the preceding methods, as exemplified by Eq. (2-52) for the spectrophotometric determination of a first-order rate constant. It sometimes happens, however, that this final value cannot be accurately measured. Among the reasons for this inability to determine are the occurrence of a slow secondary reaction, the precipitation of a product, an unsteady instrumental baseline, or simply a reaction so slow that it is inconvenient to wait for its completion. Methods have been devised to allow the rate constant to be evaluated without a known value of in the process, of course, an estimate of A is also obtainable. 

The amount of heat released during a reaction is proportional to the amount of substance involved but the relationship is complicated in enzyme studies by secondary reactions. Although the use of entropy constants means that calorimetry theoretically does not require standardization, in many instances this will be necessary. The initial energy change can often be enhanced, giving an increase in the sensitivity of the method. Hydrogen ions released during a reaction, for instance, will protonate a buffer with an evolution of more heat. 

The liquid and solid products of the reaction were collected and measured after the head of the cylinder had been removed, the liquid products being drawn off into a measuring vessel and the solid products scraped out and weighed. Since secondary reactions might take place as soon as the air struck the products, the material collected might not be identical with that immediately resulting from the reaction however, no better method appears to have been devised... 

Synthesis of well defined functionalized (- telechellc or multifunctional-) macromolecules Is an Important task for polymer chemists. The polymers with P0(0R)2, - Si(0R)3, -OH, - . .. functional groupslrS. are produced In limited quantities. The need for polymeric materials possessing specific properties has led to a renewed Interest Is functional polymers, especially if the initial material Is a common hydrocarbon polymer. One of the techniques that we use in our laboratory to prepare these new molecules Is based on anionic processes. This anionic technique is best suited to control the length of the chains prepared and to obtain samples with low polydlsperslty. Although the functionalization of carbanionic sites with various deactivating reagents Is easier than with other methods because of the long lived species, It Is still necessary to carefully control the deactivation reaction to prevent secondary reactions. 

With the FTIR spectroscopic method, these free radical reactions cannot be studied individually under completely isolated conditions since competing side reactions and also secondary reactions involving the molecular products must be taken into account. These mechanistic complications can be greatly reduced by appropriate selection of the method of free radical generation, as described in Section II.B. In general, to minimize the occurrence of secondary reactions, the conversion of the molecular reactants, and consequently the product yields, have to be kept as small as is permissible in order to obtain accurate concentration measurements. Also, the reaction time required for such chemical analysis must be kept as short as possible to minimize photochemical and heterogeneous losses of labile products. 

The addition of a base, typically ammonia, to mixtures of transition metal halides and alcohols allows the synthesis of homoleptic alkoxides and phenoxides for a wide range of metals. Anhydrous ammonia was first used in the preparation of titanium alkoxides where the reaction is forced to completion by the precipitation of ammonium chloride.41 Although useful for the synthesis of simple alkoxides and phenoxides of Si, Ge, Ti, Zr, Hf, V, Nb, Ta and Fe, as well as a number of lanthanides,42-47 the method fails to produce pure /-butoxides of a number of metals.58 Presumably, secondary reactions between HC1 and Bu OH take place. However, mixing MC14(M = Ti, Zr) with the Bu OH in the presence of pyridine followed by addition of ammonia proves successful, giving excellent yields of the M(OBul)4 complexes.59... 

The mass spectrometric method has the advantage of permitting direct detection of initially formed radicals, since under the experimental conditions, secondary reactions are minimized. However, precise quantitative data are difficult to obtain, owing to the difficulty in controlling experimental parameters in this particular reaction system. 

One of the common methods for studying the interaction of radicals with retarders is to decompose an initiator, such as azofsobutyronitrile, in the presence of an additive and to carry out product analysis. If the solutions are dilute and if several rather similar products are formed, quantitative analysis by conventional methods is exceedingly difficult especially if only part of the initiator is allowed to decompose in order to minimise the importance of secondary reactions. Problems of this sort can be solved by the method of isotope dilution analysis if labelled reagents are used. 

The development of immunoassays for the detection of food components and contaminants has progressed rapidly in the last few years [7]. Antibodies against almost all the important food residues compounds are currently available. Classical immunochemical methods such as immunodiffusion and agglutination methods for food analyses generally involve no labeled antigen or antibody. Concentration of the antigen-antibody complex is estimated from the secondary reaction that leads to precipitation or agglutination. These methods are not sensitive, are subject to... 

The primary polyphosphazene synthesis processes discussed above provide access to an enormous variety of different macromolecules. Yet further structural diversity can be achieved by carrying out modification reactions on the organophosphazene polymers produced in these primary rections. Secondary reactions are particularly important for the preparation of polymers with functional units in the side group structure, species that would be difficult or impossible to produce by the primary synthesis methods. 

The data may be obtained from calorimetric methods usually employed for the study of secondary reaction and thermal stability as DSC, Calvet calorimetry, and adiabatic calorimetry. 

---