Propene results

The addition of a large excess of bis(cj-alkenyl)zinc compounds to the TiC -catalyzed polymerization of propene resulted in an increased polymer yield, but a reduction in the molecular weights of the polymers.64 This suggests that the diorganozinc compounds are both co-catalysts and chain-transfer agents in this polymerization. The catalyst activity decreased in the order bis(3-butenyl)zinc < bis(7-octenyl)zinc < chlorodiethylaluminum. Bis(7-octenyl)zinc was co-polymerized with propene to afford hexylzinc side chains, whose zinc-carbon moieties were converted to vinyl groups by the addition of allyl bromide. 

In rats, 40% propene caused light anesthesia with no other toxic symptoms within 6 hours 55% propene for 3-6 minutes or 70% propene for 1-3 minutes produced deep anesthesia with no additional central nervous system disturbances. Animal experiments with cats have shown no toxic signs when anesthesia was induced at concentrations of 20-31% however, 70% propene resulted in a drop in blood pressure and an increased pulse rate, and an unusual ventricular ectopic beat occurred at concentrations ranging from 50% to 80%. 

Referring to the discussions presented in Chapter 5 regarding the relative stabilities of carbocations (and hyperconjugation), we are reminded that tertiary carbocations are more stable than secondary carbocations, which, in turn, are more stable than primary carbocations. Since, as shown in Scheme 7.9, protonation of propene results in cationic character at both a secondary carbon and a primary carbon, a greater presence of cationic character on the secondary site is expected compared to the primary. This allows... 

The formal substitution of one methyl, chloro or hydroxyl group at the allylic position of propene results into the reachvity order 1-butene > allyl chloride > aUyl alcohol. Methyl substitution on butenes also produces the expected ordering 2-methyl-2-butene > 2-methyl-l-butene > 3-methyl-1-butene (Table 18.8). 

In the case of compounds in Class 2, the elfect of the addition of increasing amounts of substances such as propene is important, for it is often found that although the addition of small amounts of propene results in a substantial decrease in the rate of decomposition of the compound, with further addition the rate attains a constant value which is unaltered by the presence of even very large amounts of propene i.e., a condition of maximal inhibition is attained. Inhibitors such as propene presumably act by replacing an active radical R with a relatively unre-active species, such as the resonance-stabilised allyl radical... 

Murphy et al. (3A17) reported that exposure of guinea pigs to low concentrations of acrolein (propenal) resulted in an increase in total respiratory flow resistance plus decreased respiratory rates and increased tidal volume. 

The copolymerization of ethene with a variety of other alkenes or dienes was also studied. The copolymerization of supercritical mixtures of ethene and propene (120-220 °C and 1000-1500 bar) was catalyzed by the silyl-bridged bis-(tetrahydroindenyl)zirconocene catalyst 19 and MAO at a metallocene concentration of 6 X 10 mole fraction and an Al Zr ratio of 22000 [92]. With a 50 50 mixture of SCC2H4 and scCsHg, the resulting polymer had only 8% incorporation of propene. Increasing concentrations of propene resulted in... 

It is self-evident that the concentration of the monomers has an influence on their copolymerization behavior. High concentrations of the nonpolar olefin such as ethene or propene results in higher polymerization activities due to the inaeased incorporation of these monomers. °° Hence, the incorporation level of the polar monomer is accordingly low. To achieve high incorporation rates of the polar comonomer, low concentrations of the nonpolar monomer have to be chosen, which in turn results in low polymerization activities due to the higher stetic demand of the aluminum-protected functionalized monomers. 

When these four (or three) contributions are summed for a molecule such as propene, we have the themial correction to the energy G3MP2 (OK). The result is G3MP2 Energy in the G3(MP2) output block. To this is added PV, which is equal to RT for an ideal gas, in accordance with the classical definition of the enthalpy... 

In Chapter 2 the Diels-Alder reaction between substituted 3-phenyl-l-(2-pyridyl)-2-propene-l-ones (3.8a-g) and cyclopentadiene (3.9) was described. It was demonstrated that Lewis-acid catalysis of this reaction can lead to impressive accelerations, particularly in aqueous media. In this chapter the effects of ligands attached to the catalyst are described. Ligand effects on the kinetics of the Diels-Alder reaction can be separated into influences on the equilibrium constant for binding of the dienoplule to the catalyst (K ) as well as influences on the rate constant for reaction of the complex with cyclopentadiene (kc-ad (Scheme 3.5). Also the influence of ligands on the endo-exo selectivity are examined. Finally, and perhaps most interestingly, studies aimed at enantioselective catalysis are presented, resulting in the first example of enantioselective Lewis-acid catalysis of an organic transformation in water. 

Finally, in Chapter 5, micellar catalysis of Diels-Alder reactions is discussed. In view of the nonpolar nature of most Diels-Alder reactants, efficient micellar catalysis of this reaction was anticipated However, this has not been observed. The results for the Diels-Alder reaction between cyclopentadiene and substituted 3-phenyl-l-(2-pyridyl)-2-propene-l-one dienophiles, discussed in... 

Chapter 2 describes the results of the first detailed study of Lewis-acid catalysis of a Diels-Alder reaction in water. Substituted 3-phenyl-l-(2-pyridyl)-2-propen-l-one dienophiles (la-gin Scheme 1) were found to coordinate to Co, Cu" and Zn ions in aqueous solution. This process forms... 

The combination of sulfuric acid addition to propene followed by hydrolysis of the resulting isopropyl hydrogen sulfate is the major method by which over 10 lb of isopropyl alcohol is prepared each year m the United States... 

When propene is polymerized under free radical conditions the polypropylene that results IS atactic Catalysts of the Ziegler-Natta type however permit the preparation of either isotactic or syndiotactic polypropylene We see here an example of how proper choice of experimental conditions can affect the stereochemical course of a chemical reaction to the extent that entirely new materials with unique properties result... 

These acids (51) are organic molecules that contain a plurality of cyano groups and are readily ionized to hydrogen ions and resonance-stabilized anions. Typical cyanocarbon acids are cyanoform, methanetricarbonitrile (5) 1,1,3,3-tetracyanopropene [32019-26-4] l-propene-l,l,3,3-tetracarbonitrile (52) 1,1,2,3,3-pentacyanopropene [45078-17-9], l-propene-l,l,2,3,3-pentacarbonitrile (51) l,l,2,6,7,7-hexacyano-l,3,5-heptatriene [69239-39-0] (53) 2-dicyanomethylene-l,l,3,3-tetracyanopropane [32019-27-5] (51) and l,3-cyclopentadiene-l,2,3,4,5-pentacarbonitrile [69239-40-3] (54,55). Many of these acids rival mineral acids in strength (56) and are usually isolable only as salts with metal or ammonium ions. The remarkable strength of these acids results from resonance stabilization in the anions that is not possible in the protonated forms. 

Thermal decomposition of cis- and frans-3,6-dimethyl-3,4,5,6-tetrahydropyridazines affords propene, cis- and frans-l,2-dimethylcyclobutanes and 1-hexene. The stereochemistry of the products is consistent with the intermediacy of the 1,4-biradical 2,5-hexadienyl. The results indicate that thermal reactions of cyclic azo compounds and cyclobutanes of similar substitution proceed with similar stereospecificity when compared at similar temperatures 79JA2069). 

The important hydrocarbon classes are alkanes, alkenes, aromatics, and oxygenates. The first three classes are generally released to the atmosphere, whereas the fourth class, the oxygenates, is generally formed in the atmosphere. Propene will be used to illustrate the types of reactions that take place with alkenes. Propene reactions are initiated by a chemical reaction of OH or O3 with the carbon-carbon double bond. The chemical steps that follow result in the formation of free radicals of several different types which can undergo reaction with O2, NO, SO2, and NO2 to promote the formation of photochemical smog products. 

Interpretation of tiie ratio of capture of competing nucleophiles has led to the estimate that bromonium ions have lifetimes on the order of 10 s in methanol. This lifetime is about 100 times longer than fliat for secondary caibocations. There is also direct evidence for the existence of bromonium ions. The bromonium ion related to propene can be observed by NMR spectroscopy when l-bromo-2-fluoropropane is subjected to superacid conditions. The terminal bromine adopts a bridging position in the resulting cation. 

From this value and known C—H bond dissociation energies, pK values can be calculated. Early application of these methods gave estimates of the p/Ts of toluene and propene of about 45 and 48, respectively. Methane was estimated to have a pAT in the range of 52-62. Electrochemical measurements in DMF have given the results shown in Table 7.3. These measurements put the pK of methane at about 48, with benzylic and allylic stabilization leading to values of 39 and 38 for toluene and propene, respectively. The electrochemical values overlap with the pATdmso scale for compounds such as diphenyl-methane and triphenylmethane. 

Fluorobenzene is readily alkylated with alkenes in the presence of protic acids, however, the isomenc purity of the product is poor, and polysubstitution can result Thus, propene and sulfuric acid alkylate fluorobenzene at 20 C to yield a 45 55 ortho/para ratio of the inonoalkyl product m addition to di- and triiso propylfluorobenzene [i5] The reaction of benzene and trifluoropropene at 25 °C in HF-BF3 gives a mixture of mono-, bis-, and tns(3,3,3-trifluoropropyl)ben zene [72, 75] (equation 12)... 

Based on the results for propene, we might guess that the transition structure i. halfway between the two minima the structure with a C-C-O-H dihedral angle ul 90°. We would need to verify this with optimization and frequency calculations. 

We ll go through this process in some detail for ethylene and propene and then summarize the results for the remaining systems. 

Is the stable cation that formed as a result of protonation of the more electron-rich end of the alkene Examine electrostatic potential maps for propene, 2-methylpropene and 2-methyl-2-butene. For each, can you tell whether one end of the 7t bond is more electron rich than the other end If so, does protonation on the more electron-rich end lead to the more stable carbocation ... 

Obtain the energies of propene, dimethylborane, and 1-propyldimethyl borane, and calculate AH n for dimethylborane addition. Is this reaction exothermic or endothermic Use this result and the Hammond Postulate to predict whether the transition state will be more reactant like or more product like . Compare the geometry of the transition state to that of the reactants and products. Does the Hammond Postulate correctly anticipate the structure of the transition state Explain. 

Examine spin density surfaces for l-bromo-2-propyl radical and 2-bromo-l-propyl radical (resulting from bromine atom addition to propene). Eor which is the unpaired electron more delocalized Compare energies for the two radicals. Is the more delocalized radical also the lower-energy radical Could this result have been anticipated using resonance arguments ... 

In general, 2-substituted allylic alcohols are epoxidized in good enantioselectivity. Like glycidol, however, the product epoxides are susceptible to ring opening via nucleophilic attack at the C-3 position. Results of the AE reaction on 2-methyl-2-propene-l-ol followed by derivatization of the resulting epoxy alcohol are shown in Table 1.6.1. Other examples are shown below. 

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