Meyers reaction mechanism

Andres, J., Cardenas, R., Silla, E. and Tapia, 0. A theoretical study of the Meyer-Schuster reaction mechanism minimum-energy profile and properties of transition-state structures,. /. Am. Chem. Soc., 110 (1988), 666-672... 

Tapia, O., Lluch, J. M., Cardenas, R. and Andres, J. Theoretical study of solvation effects in chemical reactions. A combined quantum chemical/Monte Carlo study ofthe Meyer-Schuster reaction mechanism in water, J. Am. Chem.Soc., Ill (1989), 829-835... 

For preliminary communications and lecture, see G. A. Olah, Conference Lecture at the 9th Reaction Mechanism Conference, Brookhaven, New York, August 1962 Abstracts, 142nd National Meeting of the American Chemical Society (Atlantic City, NJ, 1962), p. 45 W. S. Tolgyesi, J. S. McIntyre, J. J. Bastien, and M. W. Meyer, p. 121 G. A. Olah, Angew. Chem. 75, 800 (1963) Rev. Chim. Rep. Populaire Roumaine 7, 1139 (1962) Preprints, Div. Petr. Chem., ACS 9(7), 21 (1064) Organic Reaction Mechanism Conference, Cork, Ireland, June 1964, Special Publications No. 19, Chemical Society, London, 1965. 

Mass spectra of the important explosives RDX, HMX, TNT, TNB and Tetryl were first briefly reported by Meyer (Ref 34) and later investigated in greater detail with high resolution and labeling techniques by Bulusu et al (Ref 45). Mass spectrometric studies of the photodecomposition of labeled dimethyl-nitramine (Ref 56) and the thermal decomposition of HMX and RDX (Refs 27 31) illustrate the application of these techniques to studies of reaction mechanism and bond dissociation processes. Nitroguanidines have only recently been investigated by Beynon (Ref 35)... 

Electrochemical methods can also be used for obtaining analytical information on porous materials. Voltammetric methods and related techniques have been largely used to acquire information on reaction mechanisms for species in solution phase, whereas impedance techniques have been extensively used in corrosion and metal surface studies. In the past decades, the scope of available methods has been increased by the development of the voltammetry of microparticles (Scholz et al., 1989a,b). This methodology, conceived as the recording of the voltammetric response of a solid material mechanically transferred to the surface of an inert electrode, provides information on the chemical composition, mineralogical composition, and speciation of solids (Scholz and Lange, 1992 Scholz and Meyer, 1994, 1998 ... 

Analogous in overall formula, but following a radical mechanism, is the Sand-meyer reaction, in which replacement of diazonium groups by CN , Cl , Br or N3 occurs in the presence of Cu salts. 

Lindstedt RP, Meyer MR A dimensionally reduced reaction mechanism for methanol oxidation. Proc Combust Inst 2002 29 1395-1402. 

These observations can be rationalized by a model in which an addition-elimination pathway is operative, with the overall stereoselectivity determined by the two steps (Scheme 8.4). The first step presumably involves initial complexation of organomagnesium 9 with oxazoline 8. The nitrogen lone pair would lie in the plane of the oxazoline and coordinate Mg. Furthermore, Mg is also coordinated to the methoxy leaving group. Although the mechanism of the Meyers reaction has not yet been elucidated computationally [20], it is assumed that chelate B is favored sterically over chelate A. The bulky isopropyl substituent favors attack of the nucleophile from the opposite face, leading to azaenolate 12. The oxazoline moiety not only induces chirality but also favors addition of the... 

On rare occasions, the reaction is first order in the aromatic structure and zero order in the nucleophile. This is reminiscent of an SnI reaction. This mechanism occurs with diazo-nium salts, where the leaving group is so good (N2) that it can depart without assistance, leaving behind an aryl cation that is trapped by a nucleophile (Eq. 10.115). The nucleophile can be water to make a phenol, or CuX salts that place the X group on the ring (the Sand-meyer reaction). The Sandmeyer reaction actually involves electron transfer, as we describe in a Connections highlight in Section 12.2.3. 

The most concentrated component in this complex equilibrium is methylene glycol (n = 1) with a formation equilibrium constant, K = 5 X 10 at 60°C. Studies on the NMR spectra of the glycol oligomers and the reaction mechanisms under acidic and basic conditions have been done. In an acidic medium the unique formaldehyde molecule takes the form of a carbonium ion, whereas in a basic medium it reacts through an ionic species generated from the diglycol molecular form. It was shown in an early NMR study by Woodbrey that if other hydroxyl groups are present, like on phenol or methanol, hemiacetals are formed. Raman and infrared spectra and other specific reactions are covered in Meyer and Walker. 

While all hyaluronidases can bring about the depolymerization of hyaluronic acid, the individual enzymes differ considerably in specificity, reaction mechanism, and the products of the catalyzed reaction (Meyer el al., 1960 Gibian, 1966). Apart from an enzyme from leech (an endo- glucuronidase) (Meyer el al., 1960), all other known hyaluronidases act upon the ondohexosarainide linkages. 

Rearrangement to an open chain imine (165) provides an intermediate whose acidity toward lithiomethylthiazole (162) is rather pronounced. Proton abstraction by 162 gives the dilithio intermediate (166) and regenerates 2-methylthiazole for further reaction. During the final hydrolysis, 166 affords the dimer (167) that could be isolated by molecular distillation (433). A proof in favor of this mechanism is that when a large excess of butyllithium is added to (161) at -78°C and the solution is allowed to warm to room temperature, the deuterolysis affords only dideuterated thiazole (170), with no evidence of any dimeric product. Under these conditions almost complete dianion formation results (169), and the concentration of nonmetalated thiazole is nil. (Scheme 79). This dimerization bears some similitude with the formation of 2-methylthia-zolium anhydrobase dealt with in Chapter DC. Meyers could confirm the independence of the formation of the benzyl-type (172) and the aryl-type... 

The diffusion coefficient corresponding to the measured values of /ch (D = kn/4nRn, is the reaction diameter, supposed to be equal to 2 A) equals 2.7 x 10 cm s at 4.2K and 1.9K. The self-diffusion in H2 crystals at 11-14 K is thermally activated with = 0.4 kcal/mol [Weinhaus and Meyer 1972]. At T < 11 K self-diffusion in the H2 crystal involves tunneling of a molecule from the lattice node to the vacancy, formation of the latter requiring 0.22 kcal/mol [Silvera 1980], so that the Arrhenius behavior is preserved. Were the mechanism of diffusion of the H atom the same, the diffusion coefficient at 1.9 K would be ten orders smaller than that at 4.2 K, while the measured values coincide. The diffusion coefficient of the D atoms in the D2 crystal is also the same for 1.9 and 4.2 K. It is 4 orders of magnitude smaller (3 x 10 cm /s) than the diffusion coefficient for H in H2 [Lee et al. 1987]. 

In this connection attention should be paid to the principally possible reaction sequence corresponding to the so-called RARP mechanism C. Y. Meyers, W. S. Matthews, L. L. Ho, V. M. Kolb and T. E. Parady in Catalysis in Organic Syntheses 1977 (Ed. G. V. Smith), Academic Press, New York, 1977, p. 197. 

Two other steric parameters are independent of any kinetic data. Charton s v values are derived from van der Waals radii/ and Meyer s values from the volume of the portion of the substituent that is within 0.3 nm of the reaction center. The V values are obtained by molecular mechanics calculations based on the structure of the molecule. Table 9.7 gives v and value.s for some groups. As can be seen in the table, there is a fair, but not perfect, correlation among the Ei, v, and values. Other sets of steric values, (e.g., and have also been proposed. ... 

Meanwhile, these chemicals—like chemical agents encountered at work or in hobbies or as pollutants in air, water, soil, or food—can also cause harm. Sometimes the known mechanisms of action permit us to predict the nature of toxicity to be expected. A meta-analysis of prospective studies from U.S. hospitals indicates that 6.7% of in-patients have serious adverse drug reactions 0.3% have fatal reactions (Lazarou et al., 1998). In fact, estimates of 40,000 to 100,000 deaths per year attributed to errors in medical care, primarily due to adverse reactions to pharmaceuticals, make this phenomenon a major cause of death in the United States (Meyer, 2000). A tremendous... 

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