Proposed mechanisms for

According to the proposed mechanism for biological 0x1 dation of ethanol the hydrogen that is transferred to the coenzyme comes from C 1 of ethanol Therefore the dihydropyridme ring will bear no deuterium atoms when CD3CH2OH IS oxidized because all the deuterium atoms of the alcohol are attached to C 2... 

Lower alkanes such as methane and ethane have been polycondensed ia superacid solutions at 50°C, yielding higher Hquid alkanes (73). The proposed mechanism for the oligocondensation of methane requires the involvement of protonated alkanes (pentacoordinated carbonium ions) and oxidative removal of hydrogen by the superacid system. 

The proposed mechanism for producing ethanol [64-17-5] from butane involves -scission of a j -butoxy radical (eq. 38). The j -butoxy radicals are derived from j -butylperoxy radicals (reaction 14 (213)) and/or through some sequence involving reaction 33. If 25% of the carbon forms ethanol, over 50% must pass through the j -butoxy radical. Furthermore, the principal fate of j -butoxy radicals must be the P-scission reaction the ethoxy radical, on the other hand, must be converted to ethanol efficiently. 

A proposed mechanism for toughening of mbber-modifted epoxies based on the microstmcture and fracture characteristics (310—312) involves mbber cavitation and matrix shear-yielding. A quantitative expression describes the fracture toughness values over a wide range of temperatures and rates. 

Inhibitors are often iacluded ia formulations to iacrease the pot life and cute temperature so that coatings or mol dings can be convenientiy prepared. An ideal sUicone addition cure may combine iastant cure at elevated temperature with infinite pot life at ambient conditions. Unfortunately, real systems always deviate from this ideal situation. A proposed mechanism for inhibitor (I) function is an equUibtium involving the inhibitor, catalyst ligands (L), the sUicone—hydride groups, and the sUicone vinyl groups (177). 

Equation 22 gives the maximum theoretical obtainable chlorine dioxide from the disproportionation of HCIO,. Experimentally, differences in the stoichiometry have been reported. This is because the chloride formed in equation 21 can catalyze the reaction to form more chlorine dioxide as in equation 22. Proposed mechanisms for these reactions and the kinetics under various conditions have been described (16,108). 

Figure 5 Proposed mechanism for biosynthetie introduetion of bromine and ehlorine atoms into the Lcmrencia sesquiterpenoid nidifieine (24)...

Proposed mechanisms for the gaseous combustion processes which involve a series of chain reactions such as those for tire oxidation of hydrogen to form water vapour,... 

Phosphites are also believed to function, at least in part, in this way. Proposed mechanisms for the thio and phosphite compositions are shown in Figure 7.6. 

Electrolysis of 3,3-diphenylpropanoic acid in acetic acid-acetate solution gives the products shown below. Propose mechanisms for the formation of each of the major products. 

Fig. 27. Proposed mechanism for reaction of copper with untreated PMDA/ODA polyimide. Reproduced by permission of John Wiley and Sons from Ref. [33].

The proposed mechanism for the DD process is not intended to represent that of any actual catalytic reaction, but to simulate a generic bimolecular reaction. Monte Carlo simulations of the reaction mechanism described by Eqs. (21)-(25) have shown the existence of IPTs exhibiting a rich variety of critical behavior. 

The proposed mechanism for the Conrad-Limpach reaction is shown below. Condensation of an aniline with a 3-keto-ester (i.e., ethyl acetoacetate 5) with loss of water provides enamino-ester 6. Enolization furnishes 10 which undergoes thermal cyclization, analogous to the Gould-Jacobs reaction, via 6n electrocyclization to yield intermediate 11. Compound 11 suffers loss of alcohol followed by tautomerization to give 4-hydroxy-2-methylquinoline 7. An alternative to the proposed formation of 10 is ejection of alcohol from 6 furnishing ketene 13, which then undergoes 671 electrocyclization to provide 12. 

THF) at room temperature (Scheme 18) (95T8605). The proposed mechanism for this conversion involves the abstraction of H3 by basic attack of NaH to give an enolate anion, which, via ring opening, affords the 2(5//)-furanone 61 by a straightforward intramolecular nucleophilic acyl substitution (Scheme 18) (95T8605). 

The proposed mechanism for the conversion of the furanone 118 to the spiro-cyclic lactones 119 and 120 involves electron transfer to the a -unsaturated methyl ester electrophore to generate an anion radical 118 which cyclizes on the /3-carbon of the furanone. The resulting radical anion 121 acquires a proton, giving rise to the neutral radical 122, which undergoes successive electron transfer and protonation to afford the lactones 119 and 120 (Scheme 38) (91T383). 

Scheme 2.1 Proposed mechanism for TMM [3+2 cycloaddition with an electron deficient olefin...

Scheme 5.1-42 Proposed mechanism for the formation of 2,3-diisopropyibenzo[b]furan.

A proposed mechanism for the oxidation of propylene to acrolein is by a first step abstraction of an allylic hydrogen from an adsorbed propylene by an oxygen anion from the catalytic lattice to form an allylic intermediate ... 

Draw the structures of the intermediate bromonium and cyclic caibocation, and propose mechanisms for all three steps. 

Treatment of tm s-2-chlorocyclohe anol with NaOH yields 1,2-epoxycyclohexane, but reaction of the cis isomer under the same conditions yields cyclohexanone. Propose mechanisms for both reactions, and explain why the different results arc obtained. 

One of the biological pathways by which an amine is converted to a ketone involves two steps (1) oxidation of the amine by N.AD+ to give an imine, and (2) hydrolysis of the imine to give a ketone plus ammonia. Glutamate, for instance, is converted by this process into a-ketoglutarate. Show the structure of the imine intermediate, and propose mechanisms for both steps. 

The step-growth polymer nylon 6 is prepared from caprolactam. The reaction involves initial reaction of caprolactam with water to give an intermediate open-chain amino acid, followed by heating to form the polymer. Propose mechanisms for both steps, and show the structure of nylon 6. 

One of the steps in the biosynthesis of uridine monophosphate is the reaction of aspartate with carbamoyl phosphate to give carbamoyl aspartate followed by cyclization to form dihydroorotate. Propose mechanisms for both steps. 

The polyurethane foam used for home insulation uses methanediphenyl-diisoevanate (MDI) as monomer. The MD1 is prepared by acid-cataly/ed reaction of aniline with formaldehyde, followed by treatment w ith phosgene COCl2- Propose mechanisms for both steps. 

Figure 11.2 Proposed mechanism for reductive activation of and DNA alkylation/crosslinking by FR66979.

Raushel, F. M., and Baldwin, T. O. (1989). Proposed mechanism for the bacterial bioluminescence reaction involving dioxirane intermediate. Biochem. Biophys. Res. Commun. 164 1137-1142. 

Many of the structures for MAH-modifled polyolefins that appear in the literature are wholly speculative, and are based on a proposed mechanism for the grafting reaction rather than an analysis of the reaction or reaction products. In early work, product characterization took the form of determining overall grafting levels by titration or IR spectroscopy. In more recent work, with the availability of... 

Still has also carried out mechanistic experiments9 3 from which he could deduce that the major reduction pathway is by attack of hydride ion at the sulphur atom. This conclusion was deduced from the fact that reduction with sodium borodeuteride-aluminium oxide gave a sulphoxide that had only incorporated about 25% mole equivalent of deuterium on to a methyl carbon atom bound to the sulphur atom. The mechanistic pathway for direct reduction is outlined in equation (38), whereas the pathway whereby deuterium could be incorporated is portrayed in equation (39). These reactions support the proposed mechanism for the hydride reduction of sulphones as outlined in Section III.A.l, namely that attack at sulphur by hydride ions may occur, but will be competitive with proton abstraction in cases when the attack at sulphur is not facilitated. 

FIGURE 1. Proposed mechanism for the disproportionation reaction of the arenesulfonyl radicals. 

FIGURE 2. Proposed mechanism for radical addition of some sulfonyl iodides79 (X = I) and Se-phenyl areneselenosulfonates80 (X = SePh) to ailenes. 

---