Propylene oxide, cleavage

Several conclusions are drawn from the product studies of the reactions of propylene oxide and isobutylene oxide in H O.23 In the acid-catalyzed hydrolysis of propylene oxide, cleavage of the secondary C-O bond is favored by a factor of 2-3 over cleavage of the primary C-O bond. In the acid-catalyzed hydrolysis of isobutylene oxide, cleavage of the tertiary C-O bond is highly favored (>99%). These results show that in acid-catalyzed epoxide hydrolysis, cleavage of the C-O bond leading to... 

Fatty acids, both saturated and unsaturated, have found a variety of applications. Brassilic acid (1,11-un-decanedicarboxylic acid [BA]), an important monomer used in many polymer applications, is prepared from erucic acid (Scheme 2), obtained from rapeseed and crambe abyssinica oils by ozonolysis and oxidative cleavage [127]. For example, an oligomer of BA with 1,3-butane diol-lauric acid system is an effective plasticizer for polyvinylchloride. Polyester-based polyurethane elastomers are prepared from BA by condensing with ethylene glycol-propylene glycol. Polyamides based on BA are known to impart moisture resistance. 

The alkyl iodides formed in the reaction are used to characterize the alkyl chain by GC. An alternative method is the cleavage with hydrogen bromide and GC of the alkyl bromides. A detailed discussion of the analytical techniques applicable to the analysis of the ethylene and propylene oxide content as well as the alkyl chain distribution has been made by Cross [311]. 

It not tertiary, the product yield is lowered by transfer of the carbinol hydride ion to the aldehyde to produce a new alkoxide and an enolate ion. Thus, propylene oxide, after reductive cleavage with LDBB and trapping with isobutyraldehyde or p-anisaldehyde, provided 5-methyl-2,4-hexanediol in 40-50% yield or 1-p-anisyl-1,3-butanediol in 44% yield, respectively (in both cases about equal mixtures of diastereoisomers were obtained). The cyclohexene oxide-derived dianion, when trapped with isobutyraldehyde, gave 2-(1-hydroxy-2-methylpropyl)cyclohexanol in 71% yield as a mixture of only partially separable isomers in the ratio 15 11 39 35. 

Excluding polymerizations with anionic coordination initiators, the polymer molecular weights are low for anionic polymerizations of propylene oxide (<6000) [Clinton and Matlock, 1986 Boileau, 1989 Gagnon, 1986 Ishii and Sakai, 1969 Sepulchre et al., 1979]. Polymerization is severely limited by chain transfer to monomer. This involves proton abstraction from the methyl group attached to the epoxide ring followed by rapid ring cleavage to form the allyl alkoxide anion VII, which isomerizes partially to the enolate anion VIII. Species VII and VIII reinitiate polymerization of propylene oxide as evidenced... 

The stereochemistry of ring-opening polymerizations has been studied for epoxides, episul-fides, lactones, cycloalkenes (Sec. 8-6a), and other cyclic monomers [Pasquon et al., 1989 Tsuruta and Kawakami, 1989]. Epoxides have been studied more than any other type of monomer. A chiral cyclic monomer such as propylene oxide is capable of yielding stereoregular polymers. Polymerization of either of the two pure enantiomers yields the isotactic polymer when the reaction proceeds in a regioselective manner with bond cleavage at bond 1. 

Polymerization of racemic propylene oxide proceeds differently depending on the initiator. Polymerization by potassium hydroxide or alkoxide proceeds with better than 95% regioselectivity of cleavage at bond 1, but the product is atactic [Tsuruta and Kawakami, 1989]. Both (R)- and (5)-propylene oxide react at the same rate as shown by the invariance... 

Levene and WaltilBM have studied the oourse of hydration of dextrorotatory propylene oxide in acid and in alkali. Acid-catjh /cd cleavage was found to involve Walden inversion at the optically stiiw center, whereas base-initiated ring opening was attended.by retention... 

Among alkyl-substituted ethylene oxides known to umletrn cleavage on treatment with sodium sulfite are propylene oxide, isobutylene oxide, 1,2-epoxybutane, 1,2-epoxyoctane, and 2,3-cpow-butane.1 75 These reactions with sodium sulfite constitute the bani-, ffrail analytical method developed by Swan1875 for the estimation <[Pg.179]

Propylene oxide, isobutylene oxide, and 2,3-epoxy bub uu J undergo cleavage readily on treatment with sodium azide (Eq. 7). 

With a molar ratio of propylene glycol to H2O2 of 2.5, the selectivity to hydroxyacetone at 32% conversion of the glycol was 94%, and the selectivity based on H202 was 85%. Small amounts of acetic acid and formic acid were detected. The initial oxidation proceeds with high selectivity for the secondary alcohol group. Further oxidation affords oxidative cleavage products rather than pyruvic acid, as is observed when the oxidation of hydroxyacetone is carried out with 02 and noble metal catalysts. 

Acid cleavage of the diphenylmethyl group could be achieved under a variety of conditions e.g. i) 49% HBr, 100°, 45 min., ii) TFA/Anisole, reflux, 30 min. and the free aminophosphonous acid 8 then obtained by treatment of the hydrobromide salt with propylene oxide in ethanol, or simply by heating the trifluoro-acetates in ethanol. 

It has been found that the polymerisation of propylene oxide with catalysts characterised by an isolated metal atom surrounded by a porphyrin [49,50], Schiffs base [40,51] or calix[4]arene [41] moiety also proceeded by Cp—O bond cleavage. 

Studies of the regioselectivity of oxirane/carbon dioxide copolymerisation showed the polar effect exerted by the ring substituent, but not the bulkiness, to be the factor determining the direction of ring opening [231,232]. In the case of propylene oxide/carbon dioxide copolymerisation, C g—O bond cleavage... 

The results shown in Table 9.1.8 seem to indicate that the main reaction that takes place during poly(propylene oxide) pyrolysis Is the cleavage of C-0 bond and that there is very little C-C bond cleavage. Some elimination of water from the resulting alcohol is also possible. These reactions are shown below ... 

Tosyl iodide, which is easily prepared by the reaction of the sodium salt of p-toluenesulfinic acid with iodine, is a useful reagent for cleavage of vinylcyclopropanes, resulting in functionalized 5-iodopent-2-enyl sulfones (Table 6). ° Experimentally, a dichloromethane solution of the vinylcyclopropane was added to tosyl iodide and propylene oxide in dichloromethane at 40°C. The mechanism probably involved both free-radical and cationic intermediates, and was sensitive to solvent polarity. The resulting 5-iodopent-2-enyl sulfones were formed with Z configuration which enabled their use in subsequent base-catalyzed ring-closure reactions. 

In addition to the oxidation of propane and propylene, the following mode of oxidation over bismuth-containing mixed catalysts has been reported (i) oxidative coupling of hydrocarbons, (ii) ammo-oxidation of toluene and xylenes, (iii) oxygenation of alkanes and alkenes, (iv) oxidation of alcohols, and (v) oxidative cleavage of carbohydrates. Representative results are summarized in Scheme 5.12. 

The polymerization itself proceeds almost exclusively in the /3-cleavage manner. The results of end-group analysis showed that the addition of methoxide ion to propylene oxide preferred the /3-cleavage but in a less-specific way than that of the propagating oxide anion.95... 

One test of the latter hypothesis involves preparing a higher homologue, whose isomerization ought to yield characteristic products. To that end, the ditritiated w-propanol shown in Scheme 9 was synthesized and the neutral products from its /6-decay analyzed. Decay of the tritium at position 3 yields tritiated ethylene by cleavage of a carbon-carbon bond. Both propylene oxide and propionaldehyde are recovered as tritiated products from decay at position 2 in the presence of 0.5 bar trimethylamine, but no acetone is Protonated acetone would be expected among the thermal... 

The ion formed is sufficiently nucleophilic to attack the propylene oxide to cause cleavage as shown ... 

A ternary system that consists of a zirconocene dichloride, a trialkyl aluminum, and Ph3C+B(C6F5)4 has been developed by Chien et al. for ethylene and propylene polymerizations with superb activity. The use of excess of R3AI serves both to alkylate the dichloride precursor as well as to scavenge O2. H2O. and other protic impurities in the system. The entire activation process can be perceived as the initial in-situ alkylation of the zirconocene dichloride by the alkylaluminum, followed by subsequent oxidative cleavage of a Zr—R bond by Ph3C+ (eq 45). This... 

The interaction between l-[2-phenyl-2-methoxy] ethyl piperazine and 3-phenyl-3-methoxy propylene oxide in the presence of absolute ethanol at a temperature between 0-5°C gives rise to the formation of zipeprol. The reaction proceeds with the cleavage of epoxide ring to get converted to a secondary alcohol. 

The anionic polymerization of propylene oxide initiated by potassium alkoxide or hydroxide occurs predominantly (95%) by cleavage of the O-CH2 bond. For bulk polymerization at 80 °C, approximately 4% head-to-head placements occur. However, there is no stereocontrol in this alkoxide-initiated ring opening and the resulting polymer is nontactic [140]. 

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