Base-catalysed decomposition

The formation of oligomeric silicon chlorides SixCly from 1 with Si2Cl6 [1] might be due to base -catalysed decomposition of intermediate Me3Si-SiCl3 (a known compound), which would be the product of an anionic trichlorosilylation of the trimethylsilyl group of silylphosphane 1. 

Furthermore, although the intercepts k kiK/k- ) and the slope (kikjK/k-i) are equally influenced by the dimerization constant K in equation 28, this does not imply that they should show the same effect on changing the solvent. According to the dimer mechanism , it could be expected that the base catalysed decomposition of the transition state SB2, measured by Ag, should be more depressed by small additions of protic solvents than the spontaneous decomposition measured by Ag. Indeed, the overwhelming evidence on the classical base catalysis by amines shows that usually Ag is more important in aprotic than in protic solvents1. 

Nevertheless, the results observed for the reactions of o- and p-11 uoronitrobenzenes with propylamines demonstrate that (a) the dichotomy is not only observed when comparing primary with secondary amines (b) the origin is not due to primary steric effects (c) when there is no artho-n. m group the decrease in rate for the bulky amine is greater (d) the diminution in rate is due to an inhibition effect in the base-catalysed decomposition. 

In the reaction of the phenylacetonitrile carbanion with thiocyanates, a major side reaction leads to the formation of the dialkyl disulphides, as a result of the base-catalysed decomposition of the thiocyanate. This side reaction is reported to be insignificant in the reactions of the other carbanions. Phenylacetonitrile reacts with 1,2-ethanyl bisthiocyanate to produce 2-cyano-2-phenyl-1,3-thiolanes [52] under conditions analogous to those used for the synthesis of the thioethers (Scheme 4.12). 

A high carbon monoxide pressure ( 5 atmos.) favours the formation of the butane. Possible mechanisms for its formation include homolytic cleavage of the benzyl-cobalt tetracarbonyl complex and recombination of the radicals to generate 2,3-diphenylbutane and dicobalt octacarbonyl, or a base-catalysed decomposition of the benzylcobalt tetracarbonyl complex (Scheme 8.4). The ethylbenzene and styrene could arise from the phenylethyl radical, or from the n-styrene hydridocobalt tricarbonyl complex. 

Grob-type fragmentations induced by nucleophilic attack of Nhfr on the carboxyl group of quaternary /J-aminoaldcliydes and jS-aminoketones (119) have been reported (Scheme 14)." /V-(2-lmino-1 -oxopropyl)glycinc is fonned as an intennediate in the base-catalysed decomposition of (A -X)-Ala-Gly.100... 

Example the acid- and base-catalysed decomposition of nitramide... 

The base-catalysed decomposition of nitramide (3 in Scheme 1.4) is of special historical importance as it was the reaction used to establish the Bronsted catalysis law. The reaction has been studied over manyyears and considerable evidence indicates that the decomposition... 

The deactivation of the catalyst could arise from base-catalysed decomposition of copper-coordinated DBAD by BuOK in the absence of added alcohol. 

The first-order rate constant for the base-catalysed decomposition of diacetone alcohol increases rapidly when Pr4N+OH" is added, less rapidly when Me4N+OH is added, and decreases on addition of KOH. The conclusion that the variation in rate constant stems from the effects of the added cation is confirmed by observing that, at a fixed concentration of KOH, added Et4N+I- increases and added KI decreases the rate constant (Halberstadt and Prue, 1952). More recently, Hibbert and Long (1972) observed that the rate constant for the water-catalysed detritiation of t-butylmalononitrile at 298 K... 

The principle of microscopic reversibility requires the same direction for protonation or deprotonation. Base catalysed decomposition of the sulphone in (95)... 

Base-catalysed decomposition of 4,4-dimethyl-3-tosylhydrazone (various products, according to reaction conditions) J. F. Biellmann AND J. P, PkTE, Bull. Soc. Chim. France, (1967) 675. 

Acid and base catalysed decomposition of NHj NOj has already been des cribed by Hammett [45] who also mentioned earlier works such as that of Br nsted and Pedersen [46] ... 

A wide examination of the base-catalysed decomposition of NH2NO2 was given by Kresge and co-workers (48, 49J. They suggested two parallel decomposition pathways ... 

Because of the difficulties of purification and handling, many of the results for diazoalkanes have been obtained from reactions in which the diazo compound is not the starting material but in which it may reasonably be supposed to be an intermediate. Most popular in this respect has been the base-catalysed decomposition of arylsulphonyl-hydrazones of aliphatic aldehydes and ketones, a reaction which was first investigated by Bamford and Stevens (1952). Because the reaction... 

A rather different approach has been made by Kirmse and Rinkler (1962) who used the base-catalysed decomposition of nitrosoalkylureas as a source of aliphatic diazoalkanes. Because the reaction could be carried out at room temperature and below, it was possible to study the behaviour of diazoalkanes in methanol as solvent, thereby allowing straightforward analysis of the products of the reaction with the solvent... 

Table 2 shows rate constants for the base-catalysed decomposition of nitramide at 25 Graph the data for logZ g versus pAL, with and without the statistical correction and comment briefly on your result. What would happen to the correlation if a shorter range of pA /" values (say between 8 and 11) were employed ... 

D.S. Kemp and M.L. Casey, Physical Organic Chemistry of Ben-zisoxazoles. II. Linearity of the Bronsted Free Energy Relationship for the Base-Catalysed Decomposition of Benzisoxazoles, J. Am. Chem. Soc., 1973, 95, 6670. 

When all the variant reagents have similar structures each will have identical p and q values (for example alkyl phosphate dianions all have p - and q = 3). The slope, (3, will be identical using both treatments but the intercepts will differ. The statistically uncorrected Bronsted graph is illustrated in Figure 17 for the base-catalysed decomposition of nitramide. 

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