Solvents pentane

The effect of monomer concentration was studied using n-pentane solvent and maintaining the total volume of isobutylene plus n-pentane constant. Methyl halide concentration was kept constant so as to maintain constant medium polarity. Attempts were made to keep conversions below 20%. At -30 °C, due to almost explosive polymerizations, conversions could only be maintained below 40%. 

Isobutylene Polymerization Using H20 /EtAlCl2 Initiator and n-Pentane Solvent... 

Figure 2. IR spectrum of poly(5-methyl-l,4-hexadiene) prepared with a EttAlCl/ h-TiCl3 catalyst at 0°C in pentane solvent. Reproduced, with permission from Ref. 13. Copyright 1979, American Institute of Physics.

Samples filtered then extracted with pentane. Solvent dried then partitioned with sodium hydroxide. Organic fraction cleaned up with alumina and silica. 

To avoid the possible loss of the volatile product, the pentane solvent should be removed by distillation through a 20-30-cm. Vigreux column rather than by distillation under reduced pressure in a rotary evaporator. 

Product studies (Table 5) demonstrate that 2-cyanophenylnitrene (8c) prefers to cyclize towards the cyano group in pentane solvent. Thus, the spin localization effect and steric effect essentially cancel and there is no... 

Propynyl Vinyl Sulfide (or Propargyl vinyl sulfide). HC = C.CH2.S.CH CH2 mw 98.17 colorl liq bp 28° at 10mm RI 1.5183. Sol in pentane. Prepn is by reacting Na ethyl vinyl sulfide with propynyl bromide in pentane at 0° and then dstlg off the pentane solvent under vac at 20—25°. The residual is then redistld to remove the sulfide at 28°/10mm. The yield is 88—93%. Expl decompn occurs above 80° Refs 1) Beil, not found 2) L. Brandsma, Preparative Acetylenic Chemistry , Elsevier, NY (1971), 7 181... 

Molecular dynamics simulations have been used to predict solvent and temperature effects in the nucleophilic addition of a-chiral carbonyl compounds.253 Prediction of diastereoselectivity break temperatures (i.e. inversion points) has been achieved with fair accuracy by comparison with experimental data on n-BuLi addition. Dramatic differences are seen for additions to 2-phenylpropanol in pentane solvent, compared with octane. 

Secondly, the AlMe3-terf-BuCl catalyst system does not initiate the polymerization of isobutylene in n-pentane solvent, whereas AlEtCl2 is an efficient catalyst in this solvent. 

The general procedure is similar to that described by Gronowitz5 in the preparation of 3-thiophenethiol, the principal differences being the use of tetrahydrofuran-pentane solvent and the omission of a 10% potassium hydroxide extraction before acidification with sulfuric ac id. This omission leads to higher yields of thiol. 

A fourth and final example, shown in Fig. 7d, illustrates a lipophilic compound with a single polar, ionizable functional group. After appropriate pH adjustment to protonate the acid group (below pH 4), the compound will extract well into most nonpolar organic solvents, including pentane or a mixture of alcohol and pentane. Solvent choice can be made on the basis of volatility or selectivity requirements and excellent analyte recovery can be obtained. 

Enantiodifferentiating anti-Markovnikov polar photoadditions of alcohols to 1,1-diphenyl-l-alkenes 107 and 108 sensitized by optically active naphthalene(di)car-boxylates 41-43, 71, 72, and 91 were investigated in detail (Scheme 19) [70], Since this photoaddition involves the attack of alcohol to a radical cationic species of the substrate alkene [71], the use of polar solvents is desirable for obtaining the adduct in a high yield. However, in polar solvents, the radical ionic sensitizer-substrate pair produced upon photoexcitation is immediately dissociated by solvation, and no chirality transfer is expected to occur. Thus the optical and chemical yields are often conflicting issues, and therefore the critical control of solvent polarity is essential for obtaining the optically active product with an appreciable ee in reasonable chemical yield. In fact, the initial attempts on 107, employing naphthalenecarboxylate sensitizers with chiral terpenoid auxiliaries (a-c and f) and a pentane solvent afforded a best ee of 27% for adduct 110 (R = Me), but in < 2% yield [70a]. 

Separation. A residue from Paraho shale oil was obtained by vacuum distillation at 40 torr to an end point of 300°C (equivalent to 420°C at one atmosphere pressure). The residue was then separated on activated silicagel into a saturate fraction, an aromatic fraction, and a polar fraction. The saturate fraction was removed from the silica with n-pentane solvent, then the... 

Product studies demonstrated that or /io-cyanophenylni-trene (62b) prefers slightly to cyclize toward the carbon bearing the cyano-group (63 37) in pentane solvent. Thus, the spin localization effect and the steric effect of cyano, relative to hydrogen, essentially cancel, and there is no net influence of the substitutent on the reaction barrier. The barrier to cyclization of 2,6-dicyanophenylnitrene 62c increases, but the increase is smaller than that found for 2,6-dimethylphenylni-trene (69b). 

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