Alkene chain length

Whereas various studies have been published dealing with new water-soluble ligands and their effects on the hydroformylation of higher alkenes, only little data are available in the academic literature on the Rh-TPPTS catalyst system, especially without any additives. This section will provide some information on the effect of various reaction parameters (pressure, P/Rh ratio, rhodium concentration, alkene chain length, etc.) in the two-phase hydroformylation of higher alkenes... 

The relationship between alkene chain length and melting point is described in Sectwn 12.1. 

A palladium complex with cyclodextrin modified with propionitrile and benzoylnitrile groups 73-74 was active in Wacker oxidation of higher 1-alkenes (Experiment 11-4, Section 11.7), and its activity was much higher than the activity of a catalj ic system prepared as a mixture of cyclodextrin and the palladium complex owing to the cooperative substrate binding and to the increase in the stability constant of the catalyst-substrate complex. As in hydroformylation, the catalyst was more active in the reaction with an aromatic substrate, styrene, than with linear alkenes [59,210-211], The catalyst activity depended on the 1-alkene chain length and was maximum for 1-heptene. 

DiisononylPhthalate andDiisodeeylPhthalate. These primary plasticizers are produced by esterification of 0x0 alcohols of carbon chain length nine and ten. The 0x0 alcohols are produced through the carbonylation of alkenes (olefins). The carbonylation process (eq. 3) adds a carbon unit to an alkene chain by reaction with carbon monoxide and hydrogen with heat, pressure, and catalyst. In this way a Cg alkene is carbonylated to yield a alcohol a alkene is carbonylated to produce a C q alcohol. Due to the distribution of the C=C double bond ia the alkene and the varyiag effectiveness of certain catalysts, the position of the added carbon atom can vary and an isomer distribution is generally created ia such a reaction the nature of this distribution depends on the reaction conditions. Consequendy these alcohols are termed iso-alcohols and the subsequent phthalates iso-phthalates, an unfortunate designation ia view of possible confusion with esters of isophthaUc acid. 

The composition of AOS and IOS is determined by the choice of the olefin feedstock, by the way the feedstock is sulfonated and by manufacturing conditions. As will be shown later, the structural parameters such as hydrophobe chain length and branching, the ratio of alkene- to hydroxyalkanesulfonate, and (for AOS) the mono disulfonate ratio determine the physicochemical properties of AOS and IOS these in turn determine the performance of AOS and IOS in their end formulations. 

Additional evidence came from the finding that sex pheromone production could be stimulated in male houseflies that do not normally produce detectable sex pheromone components. Male houseflies were found to have longer chain alkenes, Z9-27 H,but did not have Z9-23 H. Implantation of ovaries into male houseflies resulted in a change in hydrocarbon biosynthesis such that the longer chain alkenes were not made but rather they produced the shorter chain length Z9-23 H [240]. Likewise, injection of 20-hydroxyecdysone into males induced sex pheromone production in a dose-dependent manner. These studies demonstrated that males possess the biosynthetic capability to produce sex pheromone, but normally do not produce the 20-hydroxyecdysone necessary to induce sex pheromone production. Males became an excellent model in which to study the hormonal regulation of pheromone biosynthesis in the housefly. 

It is now superflous to point out the renewed interest for the Fischer-Tropsch (F-T) synthesis (j) i. . the conversion of CO+H2 mixtures into a broad range of products including alkanes, alkenes, alcohols. Recent reviews (292.9k ) emphasized the central problem in F-T synthesis1 selectivity or more precisely chain-length control. 

In order to investigate the effect of chain length of alkenes upon acidity and aggregation, Thiele and Streitwieser probed the equilibrium acidity of a series of polyenes using UV VIS-spectroscopy in THF at 25 °C Ph(CH=CH) CH2Ph (n = 1, DP3 n = 2, DP5 n = 3, DP7 n = 4, DP9)70. The equilibrium acidity was determined using the transmetallation reaction of equation 3 with Cs+ as the counterion. The results were consistent with... 

The rate also decreases with an increase in the chain length of the alkene molecule (hex-l-ene > oct-1-ene > dodec-l-ene). Although the latter phenomenon is attributed mainly to diffusion constraints for longer molecules in the MFI pores, the former (enhanced reactivity of terminal alkenes) is interesting, especially because the reactivity in epoxidations by organometallic complexes in solution is usually determined by the electron density at the double bond, which increases with alkyl substitution. On this basis, hex-3-ene and hex-2-ene would be expected to be more reactive than the terminal alkene hex-l-ene. The reverse sequence shown in Table XIV is a consequence of the steric hindrance in the neighborhood of the double bond, which hinders adsorption on the electrophilic oxo-titanium species on the surface. This observation highlights the fact that in reactions catalyzed by solids, adsorption constraints are superimposed on the inherent reactivity features of the chemical reaction as well as the diffiisional constraints. 

The limitations of hydroformylation reactions in water are the same as those of hydrogenation reactions, i.e. the poor solubility of the substrates (see Section 8.2.1). While aqueous-organic biphasic hydroformylation works well for alkenes with chain lengths up to C7, the solubility of longer chain alkenes is too low for viable processes. Although simple alkenes are poorly soluble, many functional alkenes have solubilities in water that are sufficiently high to avoid mass transfer problems, but at the same time this can impede separation. 

Example The observed KER values and also peak shapes may change dramatically as Eor decreases. Here, the chain length of a leaving alkene increases with an increase of the reacting alkyl substituent. Nevertheless, the mechanism of the reaction - McLafferty rearrangement of immonium ions (Chap. 6.7) - remains unaffected. [58]... 

Other typical reactions of carbenium ions are alkene loss, provided sufficient chain length is available (Chap. 6.6.1), and dehydrogenation in case of the smaller ions such as ethyl, propyl, or butyl ion (Chap. 6.2.4.). 

Particularly interesting is the reaction of enynes with catalytic amounts of carbene complexes (Figure 3.50). If the chain-length between olefin and alkyne enables the formation of a five-membered or larger ring, then RCM can lead to the formation of vinyl-substituted cycloalkenes [866] or heterocycles. Examples of such reactions are given in Tables 3.18-3.20. It should, though, be taken into account that this reaction can also proceed by non-carbene-mediated pathways. Also Fischer-type carbene complexes and other complexes [867] can catalyze enyne cyclizations [267]. Trost [868] proposed that palladium-catalyzed enyne cyclizations proceed via metallacyclopentenes, which upon reductive elimination yield an intermediate cyclobutene. Also a Lewis acid-catalyzed, intramolecular [2 + 2] cycloaddition of, e.g., acceptor-substituted alkynes to an alkene to yield a cyclobutene can be considered as a possible mechanism of enyne cyclization. 

Cyclic olefins and diolefins form much more aerosol than 1-alkenes that have the same number of carbon atoms (for example, cyclohexene 1-hexene, and 1,7-octadiene 1-octene). The same effect of chain length and double-bond position is observed for diolefins (1,7-octadiene > 1,6-heptadiene > 1,5-hexadiene, and 1,7-octadiene 2,6-octadiene). Heavier unsaturated cyclic compounds, such as indene and terpenes, form even more aerosol. 

Solubility of the reactants and products in the catalyst-containing aqueous phase is another factor to be considered. The solubility of >C3 terminal olefins rapidly decreases with increasing chain length [7] as shown in Table 4.3. The solubihty data in the middle colunm of Table 4.3 refer to room temperature, therefore the values for ethene through 1-butene show the solubility of gases, while the data for 1-pentene through 1-octene refer to solubihties of liquids. For comparison, the solubihties of hquid propene and 1-butene are also shown (third colunm), these were calculated using a known relation between aqueous solubihty and molar volume of n-alkenes [60]. 

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