Saturated Benzene

Bimolecular Rate Constants for Electron Transfer between Carotenoid Pairs in Argon Saturated Benzene... 

The absorption spectra of the silicon(IV) naphthalocyanines follows the pattern already seen with the analogous zinc(II) (Section 9.22.12.1.4) and aluminum(III) (Section 9.22.13.2) derivatives 354 the red band is shifted about 100 nm further to the red, with intensification. Bis(trihex-ylsiloxy)silicon(IV) naphthalocyanine has Amax(PhH) = 776 nm (e = 650,000 M-1 cm-1) and <1>A 0.35 (oxygen-saturated benzene).389 The solution is fluorescent (main emission at 780 nm, Tf 2.85 ns) the triplet energy (ca. 22 k cal mol-1) is a little less than the energy of the first singlet state of dioxygen, and the process (Equation (9)) is reversible (cf. compounds (40) and (41), Section 9.22.10.2). 

Pulse radiolysis is used also for preparation of excited states of dienes and polyenes. This is done by irradiation of the diene/polyene in toluene solution. The radiolysis of toluene yield high concentration of molecules in the triplet excited state of the solute. Wilbrandt and coworkers61 pulse-radiolysed 1 mM solution of al I -lrans-1,3,5-heptatriene in toluene solution and observed the absorption spectra of the triplet state of the heptatriene with a maximum at 315 nm. The same group62 produced and measured the absorption spectra of several isomeric retinals in their lowest excited triplet state by pulse irradiation of their dilute solution in Ar-saturated benzene containing 10 2 M naphthalene. Nakabayashi and coworkers63 prepared the lowest triplet states of 1,3-cyclohexadiene,... 

Monobasic solutes that have no carbinyl hydrogens may also show nonequivalence. 3-Methyl-2-butanone, 4-methyl-2-pentanone, 2-methylpropanal, methyl 2-methylbutyrate, 2,2,6,6-tetramethyl-piperidine, methyldiisopropylcarbinol, and methylethyl-n-butyl-carbinol in TFAE-saturated benzene all show nonequivalence of sufficient magnitude (0.01-0,03 ppm) to allow nonequivalence sense determination at 220 MHz. An especially striking example is that provided by pyrazolines 26. With only a severalfold excess of (S)-TFAE, 3(5),5(S)-enriched samples of these compounds show nonequivalence in their methyl resonances (downfield sense for the singlets and upfield sense for the triplets) sufficient for enantiomeric purity determination at 90 MHz (52). 

Scheme 30 Photorelease from 47 in argon-saturated benzene and methanol.

In the presence of oxygen the hydroamination products can not be obtained. Instead - especially with secondary amines or diamines - dehydrogenated di- and polyadducts are formed [79]. By reaction of morpholine or piperidine in air-saturated benzene solution the bisadduct, tetraadduct epoxide and the dimer shown in Figure 3.8 could be isolated and characterized. A defined 1,4-addition pattern is found in all these products. 

Values estimated with air-saturated solutions compare Table VII for 4>ao2 in 02-saturated benzene solutions. c Livingston and Rao.71... 

Alternate Method of Analysis. Grade A 4.4.3.3.1 Determination of RDX + Nitrocellulose. Weigh accurately a sample calculated to contain between 0.35 and 0.40g of TNT into a tared 100-ml beaker. Add 20ml of RDX saturated benzene to the beaker. The prepn of the RDX saturated benzene is described in 4.4.3.5.5. Cover beaker with a watch glass and place on a steam bath for 30 mins, swirl soln frequently. (An oscillating hot... 

More recently, photochemical reactions of 138 with cyclic and acyclic olefins have been described. When 138 is irradiated (Pyrex) with cyclo-heptatriene, [4 + 4]- and [4 + 6]-adducts (247-250, Scheme 16) are obtained in addition, photodimer 242 and o-dibenzoylbenzene (140) were isolated. The ratio of the [4 + 6]-adducts to the [4 + 4]-adducts [(249 + 250)/(247 + 248)] is increased in air-saturated benzene solutions compared with oxygen-free benzene solutions, and enhanced in heavy atom solvents (e.g., chloroform compared with cyclohexane) furthermore, this ratio is decreased in the presence of the triplet quencher azulene. These observations suggest that [4 + 6]- and [4 + 4]-adducts are formed by different mechanisms. 

Enantioselective enzymatic esterifications of trimethylsilyl-substituted alcohols with racemic 2-(4-chlorophenoxy)propanoic acid in water-saturated benzene, catalyzed by the Candida cylindracea lipase OF 360 CCL OF 360 E.C. 3.1.1.3) have been used to prepare (—)-2-(4-chlorophenoxy)propanoic acid76,77. As shown in Scheme 23, the (trimethylsilyl)alkanols 95, 97 and 99 were converted enantioselectively into the corresponding (trimethylsilyl)alkyl (+)-2-(4-chlorophenoxy)propanoates 96, 98 and 100. The enantiomeric purity of the remaining (—)-2-(4-chlorophenoxy)propanoic acid was 95.8% ee (95), 76.1% ee (97) and 77.5% ee (99). 

Analogous results were obtained for the enantioselective enzymatic esterifications of the related t-butyl-substituted alcohols 101 and 103 (carbon analogues of the silanes 95 and 97, respectively). Reaction with racemic 2-(4-chlorophenoxy)propanoic acid in water-saturated benzene yielded the corresponding t-butylalkyl (+)-2-(4-chlorophenoxy)propanoates 102 and 104, respectively76,77. The enantiomeric purity of the remaining (—)-2-(4-chlorophenoxy)propanoic acid was somewhat lower than that observed for the esterification of the analogous silicon compounds [91.1% ee (101), 71.6% ee (103)]. No esterification was observed for the Si/C analogues trimethylsilanol (MesSiOH) and t-butanol (MesCOH). 

Holah et al.50,51 have reported that the products of the reaction of CoCl2, NaBH4, and tertiary phosphines in ethanol are markedly dependent upon the phosphines and the conditions. With triphenylphosphine, Co(PPh3)3Cl and then Co(BH4XPPh3)3 (/Jcff = 2.71 BM) are formed both are tetrahedral d8 systems. Recrystallization of Co(BH4)(PPh3)3 from nitrogen-saturated benzene produced Co(N2)(BH4)(PPh3)3. 

Xenon Adsorption Isotherms and 129Xe NMR Measurements. Figure 1 displays the room temperature (22 °C) xenon adsorption isotherms of the coadsorbed xenon for the three different zeolite samples loaded with various amounts of benzene. A consistent decrease of adsorption with increasing 6 was found for each benzene/zeolite system. By comparing the slope at low xenon pressures, i.e. in the Henry s Law region, we obtained for the adsorption strength NaX(1.23) > NaY(2.49) > NaY(2.70). Moreover, the saturation benzene concentration in faujasite-type zeolites with different Si/Al ratios follows the relation NaX(1.23) < NaY(2.49) < NaY(2.70). 

Direct rearrangement to cyclobutanones can be achieved under four sets of conditions a) with 48% aqueous fluoroboric acid in ether, at room temperature b) with anhydrous stannic chloride in methylene chloride, normally at room temperature c) with p-toluenesulfonic acid in benzene saturated with water, at reflux and d) with trimethyloxonium tetrafluoroborate in methylene chloride (Meerwein s reagent). For instance, the cyclopropylcarbinol 233 was rearranged to 2-/-butyl-2-methylcyclo-butanone 235, upon treatment with one equivalent of pTsOH in water-saturated benzene at reflux for 1.5 hr, Eq. (72) 139). In a slightly different approach, the alcohol... 

The reactions which proceed very rapidly and often exothermally in liquid SO2 can be controlled by the use of an organic solvent. Although advantage has been frequently taken of this procedure in synthesis (e.g., 57, 131), little information is available on the relative reactivities of the metal alkyls toward SO2 in various solvents. This is because of the slow and sluggish reactions of the more stable complexes with SO2 in dilute solution. The use of concentrated solutions, possible since SO2 is highly soluble in organic solvents [e.g., 127.5 gm of SO2 in 1 liter of its saturated benzene solution at 30°C (113)], can markedly alter the medium polarity and dielectric. Therefore, it no longer casts information on the solvent itself. 

In Fig. 4 the after-pulse growth of the PR-TRMC transients due to positive ion scavenging by different Tt-bond conjugated polymers in oxygen saturated benzene is illustrated. From kinetic fits to the transients, using the known free-ion yield in benzene, the intrachain hole mobility could be determined and the values were found to vary from a low of 0.02 cm /Vs for the polythiophene to a high of 0.74 cm /Vs for the polyfluorene derivative. Mobility values in the... 

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