Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Dimethylaniline, determination

The electron transfer pathway has been examined by analyzing relative reactivities of 4-X-substituted A,A-dimethylanilines, determined by competitive kinetics the reactivities span a wide reactivity range of 25 (from X = NO2 to X = MeO) and can be fitted to the Rehm Welter equation [90] for electron-transfer reactions (Eq. 2) ... [Pg.1596]

Kaplan and Thornton (1967) determined secondary kinetic isotope effects in two 8 2 displacement reactions, one of which involved quatemi-zation of N,N-dimethylaniline and N,N-dimethyl-eig-aniline with methyl p-toluenesulphonate (CHgOTs). The reactions were carried out in... [Pg.19]

Here again the disadvantage was the pyridine requirement in equation (a). The more readily accessible dimethylaniline can be used in place of pyridine in reaction (a), thus effecting a considerable economy for large-scale work.4 We found also that the production of a faint yellow coloration, due to a slight excess of chlorine, is probably a better indication of the end-point of the reaction (b) than is the determination of the increase in weight of the reactants. [Pg.57]

Table 29.3 Cognate Determination of N, N, Dimethylaniline in Official Pharmaceutical Substances... Table 29.3 Cognate Determination of N, N, Dimethylaniline in Official Pharmaceutical Substances...
An interesting question then arises as to why the dynamics of proton transfer for the benzophenone-i V, /V-dimethylaniline contact radical IP falls within the nonadiabatic regime while that for the napthol photoacids-carboxylic base pairs in water falls in the adiabatic regime given that both systems are intermolecular. For the benzophenone-A, A-dimethylaniline contact radical IP, the presumed structure of the complex is that of a 7t-stacked system that constrains the distance between the two heavy atoms involved in the proton transfer, C and O, to a distance of 3.3A (Scheme 2.10) [20]. Conversely, for the napthol photoacids-carboxylic base pairs no such constraints are imposed so that there can be close approach of the two heavy atoms. The distance associated with the crossover between nonadiabatic and adiabatic proton transfer has yet to be clearly defined and will be system specific. However, from model calculations, distances in excess of 2.5 A appear to lead to the realm of nonadiabatic proton transfer. Thus, a factor determining whether a bimolecular proton-transfer process falls within the adiabatic or nonadiabatic regimes lies in the rate expression Eq. (6) where 4>(R), the distribution function for molecular species with distance, and k(R), the rate constant as a function of distance, determine the mode of transfer. [Pg.90]

Dimethylaniline is both a manufacturing impurity in bupivacaine and since it is formulated in injections a possible breakdown product, although hydrolysis of amides is much slower than hydrolysis of esters. The BP uses a spectrophotometric method to assay for this impurity but GC provides a more sensitive and specific method for this determination. [Pg.229]

To determine the influence of the degree of exchange on zeolite activity, studies were done on samples la, 2a, and 4a (degree of NH4+ exchange 90%). Results of spectroscopic investigations on the adsorption of iV,2V-dimethylaniline in samples la, 2a, and 4a showed that only sample 4a is as active in the dark as sample 3 after pretreatment at 350°, 450°, and 550°C. Samples la and 2a appeared to be inactive in the dark. Photoirradiation of samples la and 2a yielded almost the same results as for samples 1 and 2 except for a slight increase in intensity of the spectral bands for the former samples. [Pg.250]

HNMR data have been used to determine the structure of certain unusual products obtained in the reaction of chlorohydroxypyrimido[4,5-c]pyridazines with phosphorus oxychloride and N,N-dimethylaniline (71CPB1849). NMR has also been used in the structure... [Pg.335]

The breaking of the carbon-oxygen bond and the attachment of the 7- carbon atom to the ortho position must be simultaneous, and this step, rather than the enolization of the hydrogen, must be the rate-determining step. If the latter were the slow step, the reaction would be speeded up by dimethylaniline, and this is not observed. The cyclic mechanism accounts for the occurrence of inversion. [Pg.16]

A relative of 12 has been prepared by Sanders, van der Plas, and coworkers [64], Triad 13 features an N,A-dimethylaniline-type donor and an anthraquinone acceptor. These moieties are linked to the ortho positions of the porphyrin aryl groups, and this leads to a folded conformation for the molecule, as determined from NMR studies. Both the free base and zinc derivatives of 13 were prepared. The folded conformation might be expected to facilitate electron transfer among the components of the triad, and while this could enhance the quantum yield of the initial charge separated state, it might unfavorably affect the yield of the final D+-P-QT state and its lifetime. Unfortunately, photochemical or spectroscopic studies were not reported. [Pg.123]

In an attempt to address the PCET versus HAT issue, Shearer, Karlin, and coworkers investigated the mechanism of dimethylaniline oxidations by [ Cu(MePy2) 2(02)] + (10, Figure 12). Here, the complexes are not pure peroxo or bis-/u.-oxo complexes, but instead are mixtures. The R -para pyridyl ligand donor substituent produces more of the bis-/u.-oxo tautomer as the R group is made more electron donating (7-30% bis-/u.-oxo). Based upon comparisons of both infra- vs intermolecular KIEs and KIE profiles of para-substituted dimethylaniline oxidations (R-DMA, Figure 12), it was determined that both PCET and HAT reactions occur. For the more easily oxidizable R-DMAs, a PCET reaction is preferred, while for the more difficult to oxidize R-DMAs a HAT pathway is favored. Also, it was observed that the more bis-/tr-oxo isomer that is in solution, the more likely it is that a HAT reaction will occur. [Pg.939]

The s pT a of five weak electrolytes of different chemical nature (butylamine, A,A-dimethylaniline, phenol, and benzoic acid) in 50% methanol/water at 20-50°C were determined by Castells et al. [108], and the values are shown in Table 4-15. The effect of temperature was the greatest for the basic compound butylamine, and a lesser effect was observed for the weaker bases pyridine and A,/V-dimethylaniline and the weakly acidic phenol. [Pg.195]


See other pages where Dimethylaniline, determination is mentioned: [Pg.354]    [Pg.88]    [Pg.118]    [Pg.36]    [Pg.567]    [Pg.102]    [Pg.164]    [Pg.447]    [Pg.448]    [Pg.263]    [Pg.723]    [Pg.76]    [Pg.630]    [Pg.207]    [Pg.212]    [Pg.630]    [Pg.555]    [Pg.311]    [Pg.244]    [Pg.67]    [Pg.178]    [Pg.39]    [Pg.349]    [Pg.303]    [Pg.104]    [Pg.115]    [Pg.43]    [Pg.437]    [Pg.220]    [Pg.107]    [Pg.337]    [Pg.422]    [Pg.97]    [Pg.137]   


SEARCH



Dimethylaniline

© 2024 chempedia.info