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Dehydrocondensation reaction

Takakura, K., Toyota, T, and Sugawara, T. (2003). A novel system of self-reproducing giant vesicles. J. Am. Chem. Soc., 125, 8134-8140. See also Takakura, K Toyota, T, Yamada, K., et al. (2002). Morphological change of giant vesicles triggered by dehydrocondensation reaction. ChemLett., 31,404-5. [Pg.296]

In 1962, Lesbre and Satge360 discovered that the dehydrocondensation reaction of trialkylgermane and carboxylic acids could be catalyzed by copper powder. For instance, the reaction of Bu3GeH and MeCOOH gave B GeOOCMe in 60% yield. [Pg.21]

Figure 1 show hydrogen conversions for dehydrocondensation at different temperatures of catalysts. It has been found that catalytic dehydrocondensation reaction displays the second order. Dehyd-rocondensation reaction rate constants are determined, and catalytic dehydrocondensation activation energies are calculated /, act = 28.1 -28.5 kJ/Mole. As a consequence, for anhydrous caustic potash and platinum hydrochloric acid application as the catalyst activation energies are almost the same. [Pg.170]

Figure 1. The hydrogen liberation rate in dehydrocondensation reaction of l,5-dihydride-l,5-dimethyltetraphenylcyclotetrasiloxane with 1,5-dihydroxy- 1,5-dimethyltetraphenylcyclotetrasiloxane, where 1 - at 40°C 2 - at 30°C 3 - at 20°C (with KOH as the catalyst). Figure 1. The hydrogen liberation rate in dehydrocondensation reaction of l,5-dihydride-l,5-dimethyltetraphenylcyclotetrasiloxane with 1,5-dihydroxy- 1,5-dimethyltetraphenylcyclotetrasiloxane, where 1 - at 40°C 2 - at 30°C 3 - at 20°C (with KOH as the catalyst).
Dehydrocondensation reaction proceeds according to the following scheme [111, 112,114] ... [Pg.202]

It is shown that the temperature coefficient of this dehydrocondensation reaction equals y=1.5. From the dependence of the reaction rate constants logarithm on reverse temperature, the activation energy of the reaction was calculated, which equals Ea = 32.55 kJ/mol. For copolymers N°7 and 9 (Table 16), quantitative values of Mn, Mco, Mz and Mco/ Mn were determined by gel permeation chromatography methods, which equal Mn=1.05-1.62xl04 and Mco-1.69-1.98/ 104 polydispersion degrees, D, of copolymer N 7 and 9 (Table 16) equal —1.46 and 1.22, respectively. [Pg.203]

The catalysed reaction of the dehydrocondensation of a,co-bis(trimethylsiloxy) ethylhydridsiloxanes with hydroxyorganocyclosiloxanes in the presence of an alkaline metal catalyst has been investigated and organosiloxane copolymers with various amounts of cyclic fragments in the side chain has been obtained. Dehydrocondensation reaction order, rate constants and activation energy were measured. [Pg.141]

As can be seen from Figure 6.23 with the increase of temperature from 40 to 60 °C, the hydrogen conversion increases from 65 to 80%. The dehydrocondensation reaction... [Pg.170]

X 10, Kgo OQ 2.85 X 10. From the dependence of the logarithm of the reaction rate constants on the reverse temperature (Figure 6.26), the activation energy of dehydrocondensation reaction was calculated as 51.5 KJ/mole. It was found that for each increase in temperature of about 10 °C, the reaction rate constant increases approximately -1.7 times. [Pg.172]

Self-reproducing giant vesicles, consisting of a vesicular boundary based on a bis ammonium imine bolaamphiphile together with 5 mol% of cholesterol as stabihzer, were studied by the group of Sugawara. The product of a dehydrocondensation reaction between amphiphilic aldehyde and... [Pg.3149]

Pyrolysis. Benzene undergoes thermal dehydrocondensation at high temperatures to produce small amounts of biphenyls and terphenyls (see Biphenyl AND terphenyls). Before the 1970s most commercial biphenyl was produced from benzene pyrolysis. In a typical procedure benzene vapors are passed through a reactor, usually at temperatures above 650°C. The decomposition of benzene iato carbon and hydrogen is a competing reaction at temperatures of about 750°C. Biphenyls are also formed when benzene and ethylene are heated to 130—160°C ia the presence of alkaH metals on activated AI2O3 (33). [Pg.40]

Reaction with Further Electrophiles of Group IVA (Sl,Ge,Sn). IV-Silylated aziridines can be prepared from ethyleneimine by amination of chlorosilanes in the presence of an HC1 acceptor, by dehydrocondensation with an organosilicon hydride or by cleavage of a silicon—carbon bond in 2-furyl-, 2-thienyl-, benzyl-, or allylsilanes in the presence of an alkali metal catalyst (262—266). N-Silylated aziridines can react with carboxylic anhydrides to give acylated aziridines, eg, A/-acetylaziridine [460-07-1] in high yields (267). At high temperatures, A/-silylaziridines can be dimerized to piperazines (268). Aldehydes can be inserted... [Pg.9]

Hydrosilatrane (49) reacts readily with alcohols and phenols in boiling xylene (equation 62). The process is catalyzed by sodium alkoxides or phenoxides304. As the acidity of the phenols decreases, the dehydrocondensation rate increases. An opposite tendency is observed for nucleophilic substitution by alkoxide ions. In this case the steric effect of the bulky alcohol plays a more important role than the electronic effect in governing the reaction rate. [Pg.1486]

In 1957, Anderson found that perfluoroalkanoic acids dehydrocondense with Et3GeH without catalyst to give Et3GeOOCR (R = CF3, C2F5, C3F7), whereas the reaction did... [Pg.20]

Dehydrocoupling (also referred to as dehydrocondensation) provides a versatile route to the synthesis of E-E bonds. The generalized dehydrocoupling reaction is shown in Eq. (1). [Pg.364]

Comparison of Catalytic Dehydrocondensation/Hydrosilation Reactions of CH2=C(Me)CH2OH in the Presence of Rh and TI-Based Catalysts... [Pg.393]

Trimethylsilane undergoes an interesting self-dehydrocondensation in the presence of Ru(H)3(SiMe3)(PMe3)3 as catalyst.119 The products of this reaction are a mixture of oligo(carbosilanes) [Eq. (21)] ... [Pg.398]

To increase the level of catalytic dehydrocondensation at the final stage of the reaction, the reaction products were heated up to 80°C during 3-4 hours. General scheme of dehydrocondensation proce-eding is as follows [16, 25] ... [Pg.170]

During catalytic dehydrocondensation of 1,7-dihydrideorganocyclohexasiloxane with 1,4-bis(hyd-roxydimethylsilyl)benzene in the presence of potassium hydroxide, the reaction order, rate constants and activation energy were determined. Catalytic dehydrocondensation is the second order reaction. Some physical and chemical parameters of low-molecular copolymers are shown in Table 16. [Pg.203]

Different authors tried to perform directly the hydrosilylation of unprotected sugars. It would avoid time-consuming protection-deprotection steps. It would avoid also the risk of equilibration of the silicone backbone occuring under the acid or basic deprotection conditions. Usually the sugar hydroxyl groups react with hydrosilanes to form silylethers, namely Si-O-C bonds in the presence of a hydrosilylation catalyst. This dehydrocondensation side reaction has to be controlled in order to avoid cross-linking, by using selected solvents and catalysts. [Pg.186]

In amodel reaction, S tadler et al. have successfully hydrosily lated 1 -ally loxy-2, 3-propanediol using THF or toluene as solvents and dichloro-dicyclopentadienyl-platinum(II) as catalyst, at 70°C (Fig. 5). The reaction was quantitative and no side-reactions, either dehydrocondensation or other reactions, were observed [12]. [Pg.186]

To obtain non-ionic siloxane surfactants, Wersig et al. [11] performed the hydrosilylation of a non-protected oUgoethoxylated but-2-yne dialcohol. Dioxane was applied as solvent, hexachloroplatinic acid as the reaction s catalyst at 100°C. The difference between the activation energies of dehydrocondensation and the triple bond hydrosilylation reactions can be increased by the use of an appropriate solvent, such as dioxane. The selectivity toward hydrosilylation has also been explained by the protective association of hydroxyl groups in coiled POE chains. Thus, in this case the hydrosilylation reaction has been carried out successfully without any protection. [Pg.187]


See other pages where Dehydrocondensation reaction is mentioned: [Pg.75]    [Pg.24]    [Pg.169]    [Pg.203]    [Pg.24]    [Pg.59]    [Pg.168]    [Pg.169]    [Pg.170]    [Pg.172]    [Pg.203]    [Pg.75]    [Pg.24]    [Pg.169]    [Pg.203]    [Pg.24]    [Pg.59]    [Pg.168]    [Pg.169]    [Pg.170]    [Pg.172]    [Pg.203]    [Pg.9]    [Pg.116]    [Pg.79]    [Pg.858]    [Pg.116]    [Pg.97]    [Pg.19]    [Pg.23]    [Pg.42]    [Pg.50]    [Pg.59]    [Pg.60]    [Pg.90]    [Pg.198]    [Pg.19]   
See also in sourсe #XX -- [ Pg.168 , Pg.172 ]




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Dehydrocondensation

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