Polymerization of methanal

Exercise 16-20 Write a reasonable mechanism for the polymerization of methanal in water solution under the influence of a basic catalyst. Would you expect base catalysis to produce any 1,3,5-trioxacyclohexane Why ... 

Applications to polymer chemistry have also been proposed. Interestingly. the adhesion toward itself. Al or stainless steel, of polythene or TeHon with epoxyresins adhesives is considerably improved by a glow discharge polymerization of methane (or etheiie. ethyne) on the polymer surface, CH4 giving the best results (33). Such a modification of polymer surfaces has also received attention within the scope of modifying poly mer membrane compatibility with blood for medical applications. Various o nic compounds (even CH4 > have been studied in this context, where an ultrathin layer (< 1000 is sufficient to alter blood compatibility 134). 

Figure 29.13 depicts the influence of conditions of plasma polymerization of methane on the decay rate constant, k in the relationship given by The... 

The first completely synthetic ion exchange resins were prepared by B. A. Adams and E. L. Holmes in 1935. The basis of their synthesis was the condensation polymerization of methanal (formaldehyde) with phenol or polysubstituted benzene compounds to give, after... 

Miyama, M. Yasuda, H. Direct current cathodic glow discharge polymerization of methane and butane. J. Appl. Polym. Sci. 1998, 70, 237-245. 

The plasma may induce the polymerization of a constituent of the gas phase and so cause deposition of a thin polymeric film, or primer, onto the substrate. Several workers have explored this route for depositing a primer, to which another polymer is subsequently adhered, or for depositing a protective coating directly onto a metal substrate [216-223]. For example, Nichols et al. [217] have deposited polymeric primer films, about 30 nm thick, from glow-discharge polymerization of methane tetrafluoroethylene or tetramethyl-disiloxane onto platinum wires. These primers were then coated with a few-micron-thick layer of either poly(p-xylylene) or poly(chloro-p-xylylene), which are good electrical insulators in thin-film applications provided this coating... 

The key initiation step in cationic polymerization of alkenes is the formation of a carbocationic intermediate, which can then interact with excess monomer to start propagation. We studied in some detail the initiation of cationic polymerization under superacidic, stable ion conditions. Carbocations also play a key role, as I found not only in the acid-catalyzed polymerization of alkenes but also in the polycondensation of arenes as well as in the ring opening polymerization of cyclic ethers, sulfides, and nitrogen compounds. Superacidic oxidative condensation of alkanes can even be achieved, including that of methane, as can the co-condensation of alkanes and alkenes. 

Fig. 1. Examples of temperature dependence of the rate constant for the reactions in which the low-temperature rate-constant limit has been observed 1. hydrogen transfer in the excited singlet state of the molecule represented by (6.16) 2. molecular reorientation in methane crystal 3. internal rotation of CHj group in radical (6.25) 4. inversion of radical (6.40) 5. hydrogen transfer in halved molecule (6.16) 6. isomerization of molecule (6.17) in excited triplet state 7. tautomerization in the ground state of 7-azoindole dimer (6.1) 8. polymerization of formaldehyde in reaction (6.44) 9. limiting stage (6.45) of (a) chain hydrobromination, (b) chlorination and (c) bromination of ethylene 10. isomerization of radical (6.18) 11. abstraction of H atom by methyl radical from methanol matrix [reaction (6.19)] 12. radical pair isomerization in dimethylglyoxime crystals [Toriyama et al. 1977].

A number of dihydroquinolines have been prepared by treating aniline derivatives with acetone or mesityl oxide in the presence of iodine. In these cases aromatization to the fully unsaturated quinoline would require the loss of methane, a process known as the Riehm quinoline synthesis. Such Skraup/Doebner-von Miller-type reactions are often low yielding due to large amounts of competing polymerization. For example, aniline 37 reacts with mesityl oxide to give dihydroquinolines 39, albeit in low yield. ... 

An interesting example of the application of the theory is a prediction of a new route to polyamantane by polymerization of -quinodi-methane 121h The first step would be n-n overlapping interaction. The HO and LU of quinodimethane are indicated in Fig. 7.40 a. The mode of n HO-LU interaction and the possible structure of polyamantane derived therefrom (Type I polymer) can be seen in Fig. 7.40b. On the other hand, the direction of the hybridization change would be controlled by the a-n interaction. The nodal property of n HO and a LU of the monomeric unit are as shown in Fig. 7.40 c, so that the hybridized states of carbon atoms might change into the form illustrated in Fig. 7.40d to lead to the Type II polymer. 

The interactions of dimethyl- and diethylzinc with bulky tris(hydroxyphenyl)methanes, Scheme 86, yielded, depending on the reaction conditions, a variety of alkylzinc alkoxides, featuring two-, three-, and four-coordinate zinc centers. These polynuclear compounds (Figure 63 shows the trinuclear ethylzinc derivative 136) are relatively poor catalysts for the co-polymerization of cyclohexene oxide and carbon dioxide.197... 

The product distribution frcm the Fischer-Tropsch reaction on 5 is shown in Table I. It is similar but not identical to that obtained over other cobalt catalysts (18-21,48, 49). The relatively low amount of methane production (73 mol T when compared with other metals and the abnormally low amount of ethane are typical (6). The distribution of hydrocarbons over other cobalt catalysts has been found to fit the Schulz-Flory equation [indicative of a polymerization-type process (6)]. The Schulz-Flory equation in logarithmic form is... 

Sherwood-Lollar et al. 1993,2002). In contrast to thermogenic hydrocarbons where higher hydrocarbons (ethane, propane, butane) are enriched in and D relative to methane, abiogenic alkanes may be depleted in C and D relative to methane. These depletion patterns relative to methane may be produced by polymerization reactions of methane precursors (Sherwood-Lollar et al. 2002). 

This is a major achievement, mainly due to Basset and his group, in surface organometallic chemistry because it has been thus possible to prepare single site catalysts for various known or new catalytic reactions [53] such as metathesis of olefins [54], polymerization of olefins [55], alkane metathesis [56], coupHng of methane to ethane and hydrogen [57], cleavage of alkanes by methane [58], hydrogenolysis of polyolefins [59] and alkanes [60], direct transformation of ethylene into propylene [61], etc. These topics are considered in detail in subsequent chapters. 

TABLE 2-4 Effect of Solvent on Molecular Weight in Polymerization of Bis(4-isocyanatophenyl)methane with Ethylene Glycol 1 ... 

A substantial difficulty in ethanol SR is a too rapid catalyst deactivation due to coking. This can occur by several reactions, such as methane decomposition (19) or the Boudouard reaction (20), but primarily the polymerization of ethylene is thought to cause the problems (21). Unlike the situation for methane SR, it appears that for ethanol SR the deactivation by coke formation is lower at high temperatures. 

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