Cyclohexane functionalization

Figure C2.1.5. Reduced osmotic pressure FT / (RTc as a function of the weight concentration c of polystyrene (M = 130 000 g mor ) in cyclohexane at different temperatures. At 7"= 35 °C and ambient pressure, tire solution is at tire 0 conditions. (Figure from 1741, reprinted by pennission of EDP Sciences.)...

Structural keys describe the chemical composition and structural motifs of molecules represented as a Boolean array. If a certain structural feature is present in a molecule or a substructure, a particular bit is set to 1 (true), otherwise to 0 (false). A bit in this array may encode a particular functional group (such as a carboxylic acid or an amidelinkage), a structural element (e.g., a substituted cyclohexane), or at least n occurrences of a particular element (e.g., a carbon atom). Alternatively, the structural key can be defined as an array of integers where the elements of this array contain the frequency of a specific feature in the molecule. 

Figure 8-6. Comparison of the radial distribution function of the ctiair, boat, and twist conformations of cyclohexane (hydrogen atoms are not considered).

Perhaps the greatest utility of (36-39) (and many of their precursors, such as 41, 42 and 48) is as starting points for the synthesis of highly functionalized cyclohexanes. For example, (38) has been converted in five steps (overall yield 70-75%) to streptamine (57) the key step is selective ring-opening with hydrazine to give intermediate (56) (75AG(E)630). 

For substituted cyclohexanes, the slow-exchange condition is met at temperatures below about —50 C. Table 3.5 presents data for the half-life for conformational equilibration of cyclohexyl chloride as a function of temperature. From these data, it can be seen that conformationally pure solutions of equatorial cyclohexyl chloride could be maintained at low temperature. This has been accomplished experimentally. Crystallization of cyclohexyl chloride at low temperature affords crystals containing only the... 

Small chiral molecules. These CSPs were introduced by Pirkle about two decades ago [31, 32]. The original brush -phases included selectors that contained a chiral amino acid moiety carrying aromatic 7t-electron acceptor or tt-electron donor functionality attached to porous silica beads. In addition to the amino acids, a large variety of other chiral scaffolds such as 1,2-disubstituted cyclohexanes [33] and cinchona alkaloids [34] have also been used for the preparation of various brush CSPs. 

Figure 9-64. Pressure drop at the flood point as a function of ioad-ing. Values are calculated using the Stichimair et al. model and distillation conditions using cyclohexane/n-heptane and Gempak 2A packing. Note ordinate (N/m /m)/3.3853 = in. Hg/m. Reproduced by permission of the American Institute of Chemical Engineers, Fair, J. R. and Bravo, J. L., Chemical Engineering Progress, V. 86, No. 1 (1990) p. 19 ail rights reserved.

Figure 5.3 shows V and V2 for the (benzene + cyclohexane) system as a function of mole fraction, obtained in this manner.3 Shown on the graph are Fm, i and F, 2, the partial molar volumes (which are the molar volumes) of the pure benzene and pure cyclohexane. The opposite ends of the curves gives Vf and Vf, the partial molar volumes in an infinitely dilute solution. We note that... 

It is possible to perform the conversion CH2 C=0 on an alkane, with no functional groups at all, though the most success has been achieved with substrates in which all CH2 groups are equivalent, such as unsubstituted cycloalkanes. One method uses H2O2 and bis(picolinato)iron(II). With this method, cyclohexane was converted with 72% efficiency to give 95% cyelohexanone and 5% cyclohexanol. ... 

Wiberg and Koch 167) also disagreed with Littler s results, and found that the major product (75%) obtained on treatment of cyclohexanone with aqueous thallium(III) perchlorate was cyclopentanecarboxylic acid (XL). 2-Hydroxycyclohexanone was isolated in only 3 % yield unchanged starting material accounted for the remainder of the product. Wiberg and Koch were unable to detect any cyclohexane-1,2-dione in the product mixture, but did prove that 2-hydroxycyclohexanone did not function as the precursor to the ring-contracted acid. From the results obtained from a study of the oxidation of 2,2,6,6-[Pg.196]

FIGURE 2 Glass transition temperature of a polymer prepared from 3,9- bis ( ethylidene- 2,4,8,10-tetraoxaspiro [ 5,5 ] undecane ) and mixtures of trans-cyclohexane dimethanol and 1,6-hexanediol as a function of mol% 1,6-hexanediol. (From Ref. 13.)... 

Reciprocals of the critical temperatures, i.e., the maxima in curves such as those in Fig. 121, are plotted in Fig. 122 against the function l/x +l/2x, which is very nearly 1/x when x is large. The upper line represents polystyrene in cyclohexane and the lower one polyisobutylene in diisobutyl ketone. Both are accurately linear within experimental error. This is typical of polymer-solvent systems exhibiting limited miscibility. The intercepts represent 0. Values obtained in this manner agree within experimental error (<1°) with those derived from osmotic measurements, taking 0 to be the temperature at which A2 is zero (see Chap. XII). Precipitation measurements carried out on a series of fractions offer a relatively simple method for accurate determination of this critical temperature, which occupies an important role in the treatment of various polymer solution properties. 

Fig. 122.—A plot of the reciprocal of the critical temperature against the molecular size function occurring in Eq. (7) for polystyrene fractions in cyclohexane (O) and for polyisobutylene fractions in diisobutyl ketone (0). (Shultz and Flory. )...

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