The Higher Homologs

Thus good yields of cyclized products will only be obtained with 3 if a poor transfer agent is employed in low concentration. This conclusion could be put on a more quantitative basis, by using the value k Cy= 1 X 10 sec at 25-40°C obtained by Ingold in the Cy5/Cy6 case, which will be discussed in Section XII.2.  

With these higher homologs of the 5-hexenyl radical a new complication sets in, namely, 1,5-intramolecular hydrogen atom transfer this is particularly important when n = 4, the 5-hydrogen atom being allylic in this case.  

The results shown in Table 3 are in accord with those obtained in the 5-hexenyl case formation of methylcycloalkanes is again favored with the higher homologs. From the enthalpy and entropy values, it can be seen that the former makes the more important contribution to this selectivity. Nevertheless, the 

TABLE 3. Relative Kinetic Parameters Obtained in the Cyclization of CH2=CH(CH2) CH2 Radicals 

Cy5/Cy6 selectivity, which is about 50, is only 6 in the Cy6/Cy7 case. These data may be rationalized on the same basis as was used in Section IIL1.B (Table 1). The values obtained for the general Cy6/Cy7 case (n = 4), using the same hypothesis, are given in Table 4 for CH2=CH(CH2)4X radicals.  

---

Natural gas, depending on its source, contains—besides methane as the main hydrocarbon compound (present usually at >80-90%) — some of the higher homologous alkanes (ethane, propane, butane). In wet gases the amount of C2-C5 alkanes is higher (gas liquids). 

The more reactive bromacetone gives not only 2-mercapto-4-methylthiazole but also its substitution products. The higher homologs, as far as C15. are obtained in reasonably good yield in absolute ethanol (150, 156. 234. 316, 530). The best result (85%) was obtained by working in aqueous solution with the 3-bromobutan-2-one (597). 

The metabolism of cinnamate and w-phenylalkane carboxylates has been studied in Rhodopseudomonaspalustris (Elder et al. 1992), and for growth with the higher homologs additional CO2 was necessary. The key degradative reaction was ()-oxidation, for compounds with chain lengths of three, five, and seven carbon atoms, benzoate was formed and further metabolized, but for the even-numbered compounds with four, six, and eight carbon atoms phenylacetate was a terminal metabolite. 

To the Buchta heterocycles the higher homologs must also be added. The cyclopentane-1,1,2,2-substituted tetrol 54 was cyclized, in this case heated rapidly with H2S04 at 160-170°, to give the dioxa[3.3.3]propellane 55 in 74 % yield, no dispiran by-product being mentioned here either13). 

Paraffin (alkane) one of a series of saturated aliphatic hydrocarbons, the lowest numbers of which are methane, ethane, and propane. The higher homologs are solid waxes. 

For the higher homologs (i.e., 12 to 14 LAS), the values of Gguif more nearly, but not completely, constant. They vary first due to hardness. This reflects on the fact that Gg j f values of Yw 50 ppm are higher than at 150 and 300 ppm. At the higher hardnesses, the sulfonate group repulsion for the adsorbed LAS molecules is at a minimum in the presence of excess divalent cation (i.e., hardness). This results in better LAS packing in the interface, lower surface tensions, and lower CED values which finally culminates in a lower Gg xf should be... 

The preceding differences and similarities indicate a considerable difference in the stabilities of cis and trans cyclopentane-fused heterocycles as compared with those of the higher homologs. Such differences are especially striking when the formation of the heterocycles proceeds through an equilibrium reaction. 

Malonyl fluoride forms the diacyl cation (24), which is in equilibrium with the donor-acceptor complex (23). The higher homologs of the dications are quite stable. ... 

The additivity mles described in Ref. 129 can be appfied with confidence to constmct the ZPE + (7/j- — Hq) energies of polycycfic aromatic hydrocarbons. For example, using the result ZPE + (//t-—//q) = 94.90 kcal/mol for naphthalene, deduced from its vibrational spectmm [194], we add to it the difference 28.68 kcal/mol between naphthalene and benzene, thus obtaining 123.6 kcal/mol for anthracene. The same procedure is used for the higher homologs. Finally, using the fundamental frequencies of pyrene [195], it is found that ZPE + (7/j- Hq) =... 

Approach 1 by forcing the dissociation of the higher homolog under the high pressure of CO... 

Approach 2 by discouraging the formation of the higher homolog in the presence of a bulky ligand... 

Chung provided one of the simple solutions based on this line of concept. Under the high pressure of carbon monoxide, the higher homolog of cobalt carbonyls including Co4(CO)i2 is depressed, and the considerable amount of Co2(CO)8 becomes available. This is now used for the catalytic reaction at high temperature of 150 °C. 

This general procedure is effective for the preparation of many types of phenylhydrazones. For example, a substituted diazo compound can be employed.2 Alkylated acetoacetic esters 8 and ethyl benzoylacetate 4 may be used. For the higher homologs, the a-formyl derivatives of ketones may be used in place of ethyl acetoacetate.6 6 Ethyl pyridylacetates may also be substituted for ethyl acetoacetate.7 The products in these cases are the phenylhydrazones of 2-acylpyridines. 

In their first paper54a), they reported their failure in photoisomerization of the (Z)[8.8] precursor 64b which was prepared from cyclodecyne (62b) via the similar-synthetic sequence as described for the higher homolog 61a. Irradiation 54b) with a low pressure Hg lamp, however, saved the situation, yielding a 9 1 mixture of (Z)[8.8] and ( )[8.8] isomers after 4 h irradiation in cyclohexane. 

An extension to the synthesis of dihydropyrans was reported by Gockel and Krause [34]. The use of the higher homologs P-hydroxyallenes afforded efficient access to the six-membered rings with axis-to-center chirality transfer, which can be explained using the mechanistic model shown in Scheme 8.2, and which once again... 

The experimental evidence as a whole suggests that both isothiocyanate oxides and sulfides, in the form of their salts, possess the dithiazolidine structures 153 and 155, respectively the lower alkyl isothiocyanate oxides when liberated rearrange to the 1,2,4-thiadiazolidines (152), but the higher homologs do not. In the isothiocyanate sulfides,... 

Tables IV-XVI show that the tetraalkylammonium salts have a large effect on both solvents in the binary solvent mixture, especially the larger tetraalkylammonium bromides, i.e., (n-C3H7)4NBr and (n-C4Hg)4NBr. This can be seen from consideration of the boiling temperature alone. This observation is also borne out by the surface tensions and solubilities at 25°C of the individual salts studied, the results of which are tabulated in Table XVII in water, in ethanol, and in an ethanol-water mixture at x = 0.206. For the higher homologs of the R4NBr series, these salts exert a large effect on the surface tensions of the solvent systems studied and show a marked increase in their solubility in ethanol.

Other alkyl diazo compounds can be prepared readily by the same general method with some alterations because of the lower volatility of the higher homologs.2... 

The sodium bisulfite purification step may be omitted, and the alkylidene ester purified directly by distillation. Care must be taken to separate the product from ethyl cyanoacetate by fractionation through a moderately efficient column. Purification through the bisulfite addition compound is recommended for alkylidene cyanoacetic esters derived from ketones containing four and five carbon atoms, but not for the higher homologs. 

The described procedure is a modification of the method of Carmody and Zletz2 and of Burg and Slota.3 The higher homologs were reported by Stuebe and Lankelma.4... 

---