Kinetics of Methylation

The kinetic method may be conveniently illustrated by reference to the methylation of the trans (2-H,9a-//)-2-methylquinolizidine (116) (Fig. 8) because this gives rise to an 50 50 mixture of the two methiodides.134 The basic expression required for the analysis of this system is that worked out for conformationally mobile systems in general by Eliel and by Winstein and Holness.3,1690 If c(l — x) and cx denote the concentrations of the transfused and cis-fused conformers of the methylquinolizidine at equilibrium, 

The rates of formation of the trans-fused and cis-fused methiodides are given by 

Values of k for the trans-(2-H,9a-H)-2-methylquinolizidine, quinolizidine, and the locked hexahydrojulolidines are shown in Table IX, and this gives a K of 0.0087 (AG° at 25°C = 2.8 kcal mol- ) for the frans-2-methylquino-lizidine. 

An attempt was made to extend this result to an estimation of K for the quinolizidine equilibrium. For the 2-methyl compound 116 discussed above, there is a difference of one gauche-butane (gb) interaction between the cis- and trans-fused conformers 116 and 117 compared with a difference of three such interactions between the quinolizidine conformers 118 and 119. This gives AG° at 25°C for quinolizidine as 2.8 + 2gb = 2.8 + 1.6 = 4.4 kcal mol-This value is uncertain because even groups remote from 

Pseudo First-Order Rate Constants Ik) for Methiodide Formation in Acetonitrile Solution1343 

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Cheng Y-W and Dunbar R C 1995 Radiative association kinetics of methyl-substituted benzene ions J. Rhys. Chem. 99 10 802-7... 

A study of the polymerization kinetics of methyl methacrylate, in the presence of PBN, and of molecular-mass properties of the obtained polymers shows that the systems react by the pseudoliving mechanism (699). In the first stages of the polymerization process, PBN reacts with oligomeric radicals, forming stable nitroxyl radical-spin adducts A-, see Scheme 2.207. 

The kinetics of methyl methacrylate (MMA) polymerization in ethyl acetate/water two phase systems was described as being more well-behaved ( ). Using hexadecylpyridinium chloride (HPC) as the phase transfer catalyst, Rp was found to be approximately first order in MMA concentration. In support of a typical phase transfer mechanism, it was found that... 

Estimates of the kinetics of methyl loss from energy-selected CztHg" species have been made by calculation.23 The hydride transfer from alkanes to carbenium ions in the gas phase is calculated to involve a species with a symmetric potential well, which is different from the situation in superacid or zeolite media.24 A correlation between the charge on a carbon and the in-plane tensor component of its 13 C chemical shift has been observed for a number of simple cationic and anionic species.25 High-level calculations... 

Solvent effects including 2-methyl-l,3-dioxepane (MDOP), as a solvent, on the propagation kinetics of methyl acrylate (MMA) have been investigated using the PLP-SEC technique (PLP = pulse laser polymerization) <2005MI267>, and the composition of dioxolane-dioxepane copolymers has been studied by IR and differential scanning calorimetry (DSC) <2004PB349>. 

Rehfinger A, Hoffmann U. Kinetics of methyl tertiary butyl ether liquid-phase synthesis catalyzed by ion exchange resin. I. Intrinsic rate expression in liquid-phase activities. Chem Eng Sci 1990 45 1605-1617. 

Absorption of purines and pyrimidines by cestodes occurs by a combination of passive diffusion and mediated transport. In H. diminuta, purine and pyrimidine uptake is very complex and seems to involve at least three carrier systems (Table 6.9), two of which appear to bind several substrate molecules simultaneously (631). Pyrimidine transport was thought to involve allosteric regulation because the relation between initial uptake and substrate concentration was sigmoidal. However, more recent work (890) has indicated that the sigmoidal kinetics of pyrimidine transport in H. diminuta is an isotope effect, obtained only when 2-14C-labelled pyrimidines were used absorption kinetics of methyl-l4C- and 3H-labelled pyrimidines were hyperbolic. Nucleosides (thymidine, uridine, adenosine and guanosine) are absorbed by H. diminuta, H. citelli and H. microstoma via a specific sodium-dependent, mediated system involving at least two carriers (347). Interestingly, the mechanism displays a diurnal periodicity in H. diminuta (616, 617). 

Chang PBL, Young TM (2000) Kinetics of Methyl lert-Butyl Ether Degradation and By-Product Formation During UV/Hydro-gen Peroxide Water Treatment, Wat. Res. 

Subbaiah, G., Sethuram, B., Mahadevan, E. G., Rao, T. N. Kinetics of methylation of primary alkyl amine hydrochlorides with formaldehyde... 

The kinetics of methyl radical production on 1% Sr/La203 was also studied recently by Feng et al. The reaction apparatus used in their work consisted of a heated flow reactor coupled to a photoionization mass spectrometer. The experimental results were interpreted in terms of the simplest methyl radical production mechanism given by the reactions ... 

The kinetics of methyl ethyl ketone oxidation shows that two peroxides are formed [165], The rate coefficients for peroxide X (suggested to be CH3CH2COCH2OOH) are... 

SuNDBERG J, JONSSON S, Karlsson MO and OsKARSSON A (1999) Lactational exposure and neonatal kinetics of methyl mercury and inorganic mercury in mice. Toxicol Appl Pharmacol 154 160-169. 

M. Dogan, M. Alkan, Adsorption kinetics of methyl violet onto perlite , Chemosphere, 50, 517-528, (2003). 

A. Rehfinger, U. Hoffmann, Kinetics of Methyl Tertiary Butyl Ether Liquid Phase Synthesis Catalyzed by Ion Exchange Resin. I. Intrinsic Rate Expression in Liquid Phase Activities, Chem. Eng. Sci., 1990, 45,1605 1617. 

Figure 6.5 Photopolymerization and photo-cross-link kinetics of methyl methacrylate (MMA) in a PS/MMA (5/95) mixture in situ monitored by FT-IR at 25 °C. (Tasuku MU-RATA, Masters Dissertation, KIT, 2010.)...

Van Eijkeren ME, Thierens H, Seuntjens J, Goenthals P, Lemahieu I, Strijckmans K. Kinetics of [methyl-"C]thymidine in patients with squamous cell carcinoma of the head and neck. Acta Oncol 1996 35 737-741. 

For the methanolyses in MeCN at 25.0 °C of benzoyl chloride and 11 para- or mete-substituted derivatives (50), the kinetics of methyl ester (51) formation have... 

Fig. 14. Kinetics of methyl vinyl ketone in situ electiopoly-meiization for various monomer cones. 0.9 M 1.8 M ...

Buback M, Kowollik C. Termination kinetics of methyl methacrylate free-radical polymerization studied by time-resolved pulsed laser experiments. Macromolecules 1998 31 3211-3215. 

The initial stage of tetramethylene-a, -dimethyl acrylate (MB) monophase solutions polymerization was analyzed in papers [189,199], The characteristic viscosity of tetramethylene-a,o)-dimethyl acrylate q 5 centipoise. Polymerization was carried out in nonreactive oligomers with different viscosity in bis-(di-oxyethylenephthalate)-a,(D-diisobutyrate (IDF), (q 1000 centipoise) in trioxyethylene-a,(D-di-isobutyrate (TGI) (q 10 centipoise) and in full saturated analogue of tetramethylene-a, -dimethyl acrylate, tetramethylene-a,ra- di-isobutyrate (IB), (q 5 centipoise). The obtained results were compared with polymerization kinetics of methyl meta acrylate, dissolved in the same nonreactive oligomers. 

Stickler, M., Free-Radical Polymerization Kinetics of Methyl Methacrylate at Very High Conversions, A/aAromo/. Chem., 184, 2563-2579, 1983. 

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