Schmidt reaction experimental conditions

Schmidt RF (1924) Uber den Imin-Rest. Ber Dtsch Chem Ges 57(4) 704—706 Smith PAS (1948) The Schmidt reaction experimental conditions and mechanism. J Am Chem Soc 70(l) 320-323... 

This phenomenon has been observed by Abderhalden anpancreatic juice, and the extract of yeast, by Schmidt-Nielsen with rennet, by Horlow with ptyalin, by Shaklle and Meltzer with pepsin. The results, however, depend on experimental conditions imder which this shakin takes place. Duration and rapidity, the content of the liquid in enzyme, and the temperature play an important r61e in this% phenomenon. An active solution, introduced into a reaction tube and agitated for 2 minutes, can lose as much as 75 per cen.t of its activity. After 5 minutes the disappearance is almost ... 

The Curtius, Hofmann (see p. 267), and Schmidt (see p. 307) reactions are in that order decreasingly mild, decreasingly flexible, and increasingly expeditious. The last-named quality varies somewhat with the available starting material, whether the free acid or the ester. The Curtius reaction lends itself to the preparation of isocyanates, sym-and 08-ureas, amides, urethans, and amines at will, and provides a wide choice of experimental conditions. For synthetic purposes the Hofmann reaction can be used only to prepare sym-ureas, urethans, and amines directly, and halting the reaction at a desired intermediate is often not possible. The variety of experimental conditions is narrower and more limited. The Schmidt reaction on carboxylic acids or derivatives has been applied as a preparative method only to the production of amines although urethans and isocyanates have been prepared occasionally by this reaction, it can hardly be considered a preparative method for them. Amides can be prepared by the Schmidt reaction only from ketones. The choice of experimental conditions employable in the Schmidt reaction is narrow. 

Subsequent work by other research groups (see Schmidt and Bowman and references cited therein3) resulted in the development of improved computer models. The number of elementary reactions used was increased to 127. These additional reactions while they are unimportant under the range of conditions used in the Thermal DeNOx process, improve the model because they allow it to make predictions beyond this range. The adjustable parameters used in our model were replaced with experimentally determined rate constants. 

Traditionally, relative stabilities of carbocations have been derived from the comparison of the rates of solvolysis reactions following the SN1 mechanism, for which the designation Dm + An has recently been proposed [36], The comparison of solvolytic rate constants for substrates of a large structural variety is hampered by the fact that the published solvolysis rates refer to different solvents, different temperatures, and precursors with different leaving groups. Dau-Schmidt has, therefore, converted solvolysis rates of a manifold of alkyl chlorides and bromides to standard conditions, i.e., soiv of RC1 in 100% EtOH at 25° C (Scheme 6) [37]. Although from a theoretical point of view, ethanol is not an ideal solvent for observing unassisted SN 1-type reactions (nucleophilic solvent participation), it has been selected as the reference solvent because most available experimental data have been collected in solvents of comparable nucleophilicity, a fact which made conversions to 100% ethanol relatively unproblematic [38],... 

In order to calculate the conversion of a reaction the axial mixing coefficient has to be known. There are ample experimental data available. In principle, the axial mixing coefficient of a component A is determined by flow conditions and by the diffusivity of A, Generally speaking, the Bodenstein number for axial mixing is a function of the Reynolds and Schmidt numbers (for definitions see eq. 4.23) ... 

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