Cyclohexane solutions

For adsorption on Spheron 6 from benzene-cyclohexane solutions, the plot of N N2/noAN2 versus N2 (cyclohexane being component 2) has a slope of 2.3 and an intercept of 0.4. (a) Calculate K. (b) Taking the area per molecule to be 40 A, calculate the specific surface area of the spheron 6. (c) Plot the isotherm of composition change. Note Assume that is in millimoles per gram. 

Cyclohexane. An excellent sohent for many determinations, particularly as, owing to the high value of K, a large fall in the freezing-point is obtained, and the accuracy of the determination is therefore correspondingly increased. Care should be taken to avoid super-cooling, however, as it has a marked effect on the true freezing-point of cyclohexane solutions. 

The conclusion of all these thermodynamic studies is the existence of thiazole-solvent and thiazole-thiazole associations. The most probable mode of association is of the n-rr type from the lone pair of the nitrogen of one molecule to the various other atoms of the other. These associations are confirmed by the results of viscosimetnc studies on thiazole and binary mixtures of thiazole and CCU or QHij. In the case of CCU, there is association of two thiazole molecules with one solvent molecule, whereas cyclohexane seems to destroy some thiazole self-associations (aggregates) existing in the pure liquid (312-314). The same conclusions are drawn from the study of the self-diffusion of thiazole (labeled with C) in thiazole-cyclohexane solutions (114). 

For example, a thiazole-cyclohexane solution at 25 C is less viscous than the ideal system, and the deviation from ideality can be explained assuming that in solution there is a breakage between the existing association of the thiazole molecules in pure state (157). 

Complex tautomerism for azoles with heteroatoms in the 1,2-positions occurs for pyrazoles which are not substituted on nitrogen. Scheme 10 shows the four important tautomeric structures (148)-(151) for 3-methylpyrazolin-5-one, and (152) and (153) as examples of other possible structures. A detailed investigation of this system disclosed that in aqueous solution (polar medium) the importance of the tautomers is (149) > (151) (150) or (148), whereas in cyclohexane solution (non-polar medium) (151) > (148) (149) or (150). 

Estrone, estradiol, estnol Dip silica gel foil 2 cm in saturated Fast Black Salt K. solution and dry in a stream of warm air. Apply sample solution, dip again in reagent solution and dry. Dip the TCL plate 2 cm in 4% pyridine-cyclohexane solution, dry at 100 to 200°C and develop the azo-dyestuffs that are formed. [294]... 

It has been reported recently that 17/ -acetoxy-5a,14a-androstan epimerizes at C-14 when photolyzed in cyclohexane solution in the presence of mercuric bromide. When the reaction is carried out in perdeuterated cyclohexane, the product consists of 55 % d - and 12% d2-labeled species. This reaction may develop into an interesting deuteration technique if the incorporated deuterium can be securely assigned to the epimerized position. 

Benzylenol ethers rearrange in an apparently similar fashion via photolytic fission of the benzyl-oxygen bond and subsequent recombination steps. Irradiation in quartz of a cyclohexane solution of 3-benzyloxycholesta-3,5-diene (250) leads to 23% (251), 13% (252) [presumably formed from (251) during workup] and 10% (253). ... 

P. Terech, P. Maldivi, C. Dammer. Living polymers in organic solvents Stress relaxation in bicopper tetracarboxylate/tert-butyl cyclohexane solutions. J Phys II (France) 4 1799-1811, 1994. 

The association of the excited state derived from four 2-substituted imidazo [4,5-/]quinolines with 2-propanol in cyclohexane has been studied. The unusual bathochromic shift and the bandwidth of the fluorescence spectra of these heterocyclic compounds in 2-propanol-cyclohexane solutions, compared with those... 

A solution of 76 g (S)-( + )-mandelic acid in 400 ml methanol and 5 ml acetic acid was reduced over 5% rhodium-on-alumina under 100 psig for 10 h. The catalyst was removed by filtration through Celite, and the methanol was removed in a rotary evaporator. The white, solid residue was dissolved in I 1 of hot diethyl ether and filtered while hot. After reduction of the volume to 400 ml, 250 ml cyclohexane was added. The remainder of the ether was removed, and the cyclohexane solution was stored for several hours in a refrigerator. The white crystals were filtered and dried in vacuo at 40 C the yield of (S)-( + )-hexahydromandelic acid was 71%. 

Dimethyl 2,7-dimethyI-4//-azepine-3,6-dicarboxylate (7) with platinum and hydrogen in cyclohexane solution at atmospheric pressure undergoes rapid partial reduction to the 4,5-dihydro-l//-azepine 8.29... 

Reagents. Perylene was obtained from Sigma Chemical Company (St. Louis, Missouri). All other PAHs were supplied by Aldrich Chemical Company (Milwaukee, Wisconsin) and were reported to contain less that 3% impurities. All PAHs were used without further purification. Isopropyl ether (99%) for extraction work was also purchased from Aldrich. Hydroquinone, a fluorescent stabilizer present in the ether, was removed prior to solution preparation by rotary evaporation. Fluorometric-grade 1-butanol was supplied by Fisher Scientific Company (Fair Lawn, New Jersey). All solutions for extractions of PAHs were prepared by evaporating portions of a stock cyclohexane solution and diluting to the appropriate volume with isopropyl ether. Fluorescence measurements were performed on 1 10 dilutions of the stock and final organic phase solutions. The effect of dissolved CDx on the fluorescence intensity of the organic phase PAH was minimized by dilution with isopropyl ether. 

It seems that deep-seated cleavage of the dioxin nucleus must accompany dechlorination in methanol. When pure dibenzo-p-dioxin (II) was irradiated in cyclohexane solution in a quartz cuvette, it darkened in color, and a precipitate of intractable dark brown material was collected and was insoluble in the common solvents except for methanol. 

In order to prepare ZSM-5 zeolite nanocrystals, an A1 source of aluminium isopropoxide was added into solution A, and hydrothermal synthesis of the solution A containing Si and A1 sources was carried out in an 0-15/cyclohexane solution at 120 degree C for 50 h. Figures 4 show ac-NHj-TPD spectra and a SEM photograph of the ZSM-5 zeolite nanocrystals. Nanocrystals with a diameter of approximately 150 nm were observed, and the NH3-TPD spectrum showed desorption of NHj above 600 K, indicating that the nanocrystals possessed strong acid sites. 

The pseudo-first order decay kinetics of this absorption are consistent with the decay of Cr(CO)5. Thus, in cyclohexane solution under 1 atm pressure CO, the half-life of decay is 25 /xseconds k = 2.8 x 10-4 second-1) 30). 

As discussed above, the solution environment provides for a set of time scales different from the gas phase environment. In solution, there are typically 1013 collisions second"1 of a solute molecule with solvent molecules. Thus, if a photolytically generated species is expected to have a large cross section for reaction with solvent and it is desired to monitor that reaction, both generation and monitoring must be done on a picosecond (psecond) or even sub-psecond timescale. That monitoring this rapid is necessary has been confirmed in an experiment on Cr(CO)6 in cyclohexane solution where psecond photolysis and monitoring was not rapid enough to detect the naked Cr(CO)5 that existed before coordination with cyclohexane (55). 

It had already been established by uv-vis flash photolysis (35) that Cr(CO)5 (solvent) was the first observable intermediate in the photolysis of Cr(CO)6. Figure 9 shows the IR spectrum (96) of the photoproduct Cr(CO)5(C6Hi2) in cyclohexane solution. The spectra were obtained using Cr(CO)5(13CO) (96). The extra spectroscopic information provided by the 13CO group was sufficient to show that the spectrum was consistent... 

Fig. 12. Transient IR difference spectra showing changes in absorbance (a) 5 / seconds, (b) 25 seconds, and (c) 1.25 mseconds after the UV flash photolysis of [CpFe(CO)2]2 in cyclohexane solution under 1 atm pressure of CO. Bands pointing upward represent an increase in absorbance (i.e., formation of a compound) and those pointing downward a decrease [i.e., depletion of starting material, (A)]. The bands are assigned as follows A, [CpFe(CO)2]2 B, CpFe(CO)2 and C, CpFe(p.-CO)3Fe(Cp). Points marked were recorded with a 12CO laser and those marked + with a 13CO laser. [Reproduced with permission from Moore et al. (61).]...

Time-resolved IR measurements by Moore, Simpson, and co-workers (61) showed that both CpFe(CO)2 and CpFe(/x-CO)3FeCp were formed within 5 / seconds of photolysis of [CpFe(CO)2]2 in cyclohexane solution. The spectra are shown in Fig. 12. CpFe(/i-CO)3FeCp has similar IR absorption frequencies in the matrix (6,7) and in solution (67). Interestingly, CpFe(CO)2 was the first unsaturated species to be identified by time-resolved IR without previous matrix isolation data being available. CpFe(/u.-CO)3FeCp reacts with CO [Eq. (16)] much more slowly (k —4.5 x 104 dm3 mol-1 second-1) than Mn2(CO)9 reacts (77)... 

Time-resolved IR measurements appear to be a general method for studying the photochemistry of [CpM(CO) ]2 compounds in solution. Thus, photolysis of [CpMo(CO)3]2 in cyclohexane solution produced two products (110) of which one is CpMo(CO)3, with IR absorptions close to those reported for matrix-isolated CpMo(CO)3 (112). 

Figure 2. Absorbance (Amon - 480 nm) vs time trace for the longer wavelength flash photolysis (A rr > 395 nm) of a cyclohexane solution of Ru3(CO)i2 plus P(OCH3>3 (0.010 M) (from reference 5).

First Order Rate Constants for Decay of Transients Seen by Longer Wavelength (A rr > 390 nm) Flash Photolysis of Ru3(C0)]o in Cyclohexane Solutions with Various Added Ligands a... 

Photolysis of the methylidyne cluster HRu3(CO)] (/1, 71"COCH3) (A) (14) in cyclohexane solution leads to an unprecedented oxygen-to-carbon alkyl migration to form the bridging acyl complex HRu3(CO)10( i-> 2-C(O)CH3) (B) ... 

The best known bis-arene system, bis-benzenechromium, Cr(Bz)2, has been studied by a number of authors (94, 95, 96), but the results of Feltham, in cyclohexane solution, are typical a broad band with a maximum (e = 25) at 15.6 kK. is the only feature at lower energies, a stronger peak (e = 8000) being found at 31.25 kK. with a rising absorption... 

With the advent of picosecond-pulse radiolysis and laser technologies, it has been possible to study geminate-ion recombination (Jonah et al, 1979 Sauer and Jonah, 1980 Tagawa et al 1982a, b) and subsequently electron-ion recombination (Katsumura et al, 1982 Tagawa et al, 1983 Jonah, 1983) in hydrocarbon liquids. Using cyclohexane solutions of 9,10-diphenylanthracene (DPA) and p-terphenyl (PT), Jonah et al. (1979) observed light emission from the first excited state of the solutes, interpreted in terms of solute cation-anion recombination. In the early work of Sauer and Jonah (1980), the kinetics of solute excited state formation was studied in cyclohexane solutions of DPA and PT, and some inconsistency with respect to the solution of the diffusion equation was noted.1... 

Reaction of the bis-chelate complex 149 and various bis(arylalkyl)barium complexes generates heteroleptic barium complexes with one chelate and one reactive arylalkyl ligand 164. The homoleptic and heteroleptic barium complexes both induce living polymerization of styrene to atactic polystyrene in cyclohexane solution. The fact that no stereocontrol is observed during polymerization despite the presence of the chiral carbanionic ligands is... 

Note added in typing In a very recent paper (81) Vaida and co-workers have used picosecond laser photolysis to show that, in cyclohexane solution, Cr(CO)5...cyclohexane (Amax 497 nm) is formed within 25 ps of the photolysis of Cr(C0)5 This suggests that, in solution, the primary photoproduct is Cr(C0)5 and that there is essentially no activation energy for the reaction of Cr(C0)5 with the solvent. Clearly, experiments with pulsed KrF lasers on carbonyls in solution and matrix may be very revealing. 

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