Homologs, higher

The second most important reaction scheme is the next higher homolog to that shown in Figure 3-13, involving the breaking and making of three bonds. Figure 3-15 shows this reaction scheme and some reaction types that follow it. 

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 three thiazoleacetic acids and higher homologs such as the derivatives of propionic acid have been synthesized (5), They are usually prepared by the Hantzsch s method, either as the free acid or as the ester from which the free acid is obtained by hydrolysis (49, 73). 

With higher homologs e.g., propynyl, butynyl), 3j5-hydroxyandrost-5-en-17-one does not react well with the alkyne and potassium r-butoxide, or with the lithium alkyne in tetrahydrofuran. However, satisfactory results are obtained by use of the alkynylmagnesium bromide in tetrahydrofuran, ... 

A reaction related to the Michael addition reactions of enamines to unsaturated esters, which leads to S-ketoesters, is the reaction with 1-carb-ethoxy-l-cyanocyclopropane (318). This gives access to ketones substituted with the next higher homologous acid chain. 

A useful reaction sequence has been developed for conversion of an aromatic aldehyde into the next higher homologous acid. The nitro analog of 45, prepared from m-nitrobenzaldehyde, is converted into the azide 51 by hydrazinolysis and treatment with nitrous acid. The... 

The Arndt-Eistert synthesis allows for the conversion of carboxylic acids 1 into the next higher homolog 4. This reaction sequence is considered to be the best method for the extension of a carbon chain by one carbon atom in cases where a carboxylic acid is available. 

Instead of a-halo esters, related reactants can be used e.g. the a-halo derivatives of ketones, nitriles, sulfones and A,A-disubstituted amides. The Darzens condensation is also of some importance as a synthetic method because a glycidic acid can be converted into the next higher homolog of the original aldehyde, or into a branched aldehyde (e.g. 5) if the original carbonyl substrate was a ketone ... 

Since the -elimination mechanism requires formation of a six-membered cyclic transition state, this reaction is not possible for five- or six-membered lactones, but may be applied to higher homologs. 

In addition to its application for structural analysis, the Hofmann elimination also is of synthetic importance. For instance the method has been used to prepare fi-cyclooctene 16, as well as higher homologs ... 

Solvent Naphtha (160° benzol). A mixt of small percentages of benzene and toluene with xylene and higher homologs from coal tar. In crude form, a dark straw-colored liq, bp about 160° (80%), d 0.862—0.892g/cc, flash p about 78°F. When refined, a w-white liq, bp about 160° (90%), d 0.862-0.872g/cc, flash p about 78°F. May be obtained from coal tar by fractional distillation. When nitrated, used in Dynamites (Ref 5)... 

Higher homologs tend to hydrolyze to original aldehyde redn to carbonyl and hydroxy compds ferrous salts catalyze decompn to free radicals thermal decompn involves homolytic and hetero-... 

C. Among sodium salts, hexadecyl sulfate gave a maximum foam volume, above 700 cm3, at 75 °C while at 50°C the maximum corresponds to tetradecyl sulfate but, as expected, with a lower volume (around 550 cm3). The fact that solubility in water decreases as the chain length increases can explain the progressive displacement of the maximum to higher homologs as the temperature increases. 

Various cyclic phosphonate esters 36 and 37 have been described previously as products from the HHT reaction of 25 with the appropriate cyclic phosphite. A complementary method has also been developed from the V-protected phosphonyl chloride 84, which was readily prepared from the corresponding phosphonic acid 83. Subsequent reaction of 84 with the appropriate diol produced the cyclic phosphonate esters 85 (63). Higher homologs of 85 have also been prepared from the analogous propane or butane diols. 

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. 

Butadiene and isoprene give rise to mixtures of what are usually called telom-ers, namely 1 1 telomers between the amine and the 1,3-diene (trae hydroamination products), 1 2 telomers and even higher homologs together with oligomers of the diene as exemplified in Eq. (4.41). 

If the alkyl substituent in a dialkyl substituted polysilane is either too short or is branched, it cannot pack properly to allow side chain crystallization, and hence, one would expect very different, properties from PDHS and its higher homologs. In order to study this possibility, we synthesized and characterized the di-n-butyl (PDBS), di-n-pentyl (PDPS) and di-5-methylhexyl polymers (PDMHS). 

A film of the branched chain 5-methylhexyl polymer absorbed at 315 nm and the position of this maximum was relatively insensitive to temperature. Likewise, no thermal transition was observed in the region where the side chain melting transition was seen for PDHS and its higher homologs. 

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). 

Diesters and even triesters have been converted to bis- and tris(cyclopropanol)s, respectively. Dimethyl succinate gave the bis (cyclopropanol) derivative 17 in 80% yield, while triethyl trans-cyclopropanetricarboxylate (18) yields the tris (cyclopropanol) 19 (90%) (Scheme 11.4 selected examples in Table 11.2) [77,78], Higher homologous dicarboxylic acid diesters are likewise smoothly converted with ethylmagnesium bromide in the presence of Ti(OiPr)4 to provide the corresponding bis (cyclopropanol) s [71,78]. 

The next higher homologs of 28-30 have all been prepared without difficulty as shown in Scheme 5.37. Single and double addition of dibromocarbene to 1,5-hexa-diene (biallyl) (240) leads to the adducts 241 and 242, respectively, which on methyl-lithium treatment are debrominated/rearranged to 32 and 34 in the usual way [43, 96, 97]. 

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