Nonalkyl groups

As an example of how this may be used, we return to the group contribution model for the octanol-water partition coefficient discussed above. As already shown, this model was quite good for monofunctional (i.e., only one nonalkyl group) solutes when applied to multiple functional solutes, the large deviations shown in Fig. 4a were found. The failure of the GCSKOW model is the result of strong proximity effects in multifunctional compounds. 

The values of the van der Waals radii are taken from Charton. By using this equation, steric constants were also calculated for ortho-substituted and nonalkyl groups. 

An isopropyl group also can be represented by (CH3)2CH—. As shown in Table 1.5, four butyl groups can be derived from butane, two from the straight-chain, or normal, butane, and two from the branched-chain isobutane. A number of nonalkyl groups are also commonly used in naming organic compounds (see > Table 1.6). 

Group contribution methods, such as the one discussed above, have been reasonably successful for estimating many physical and thermodynamic properties of pure substances and mixtures, especially when each molecule contains no more than one nonalkyl functional group. These methods dissect a molecule into functional groups that are assumed to be independent of each other. Tliat is, a functional group is assumed to behave the same in its interactions with other functional groups independent of the molecule of which it is... 

The number of isomers increase rapidly with alkyl substitution for example, substitution of one methyl group onto each of the 248 tricyclodecanes gives 2,889 tricyclic Ci I s in addition to the 434 nonalkylated tricyclodecanes (Tables 4 and 5). For the larger systems, prior experience and application of basic rules of thermodynamic stability (vide infra) must be relied on to generate a manageable list of likely structures. 

Under the influence of suitable ligands such as carbon monoxide, the allyl groups of X couple to form 1,5-hexadiene. Probably the bis(ff-allyl) species (XI) is involved as a reactive intermediate (Walter and Wilke, 1966). Reaction of bis(K-crotyl)nickel(0) with an atmospheric pressure of carbon monoxide at — 40° gives tran5, /raw5-2,6-octadiene (98%), where the coupling is taking place selectively at the nonalkylated termini (Wilke et ai, 1966). 

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