Alkyl chain, homologation

However, this class of compound is unstable to hydrolysis and has been replaced by the more stable 4-cyano-4 -alkylbiphe-nyls (2) the longer alkyl chain homologs... 

Table 1. Transition temperatures for the longer alkyl chain homologs of 4-cyano-4 -alkyl- and -4 -alkoxy-biphenyls.

A distinct dependence between LAS alkyl chain length and the chronic or long-term toxicity is also shown (see Table 22) [290,291]. As can be seen, the ecotoxicity of LAS for fishes and daphnia increase significantly with increasing alkyl chain length of the LAS homolog. 

Sodium a-sulfonated fatty acid esters of long-chain alcohols have a structural effect on the Krafft point different from that of amphiphiles with short alkyl chains [60]. In a series of homologs with the same total carbon number the Krafft points are highest when the hydrophilic alkyl chain lengths in the a-sulfonated fatty acid and the alcohol are fairly long and equal. In this case the packing of the molecules becomes close and tight. 

The effect of surfactant structures and properties on emulsion polymerization have been investigated by numerous authors [82-89]. Efforts were made to study the effects of surfactants with different molecular weights on the rate of polymerization [82], swelling and solubilization effects [83], effects of alkyl chain length of homologous series on the rate of polymerization, particle size... 

Issaq, H. J. and Jaroniec, M., Enthalpy and entropy effects for homologous solutes in HPLC with alkyl chain bonded phases, /. Liq. Chromatogr., 12, 2067,... 

Figure 3. A homologous series of three tyrosine dipeptide derivatives gave rise to three new polyiminocarbonates that differed only in the length of the alkyl chain attached to the carboxylic acid group of the dipeptide.

Influence of subphase temperature, pH, and molecular structure of the lipids on their phase behavior can easily be studied by means of this method. The effect of chain length and structure of polymerizable and natural lecithins is illustrated in Figure 5. At 30°C distearoyllecithin is still fully in the condensed state (33), whereas butadiene lecithin (4), which carries the same numEer of C-atoms per alkyl chain, is already completely in the expanded state (34). Although diacetylene lecithin (6) bears 26 C-atoms per chain, it forms both an expanded and a condensed phase at 30°C. The reason for these marked differences is the disturbance of the packing of the hydrophobic side chains by the double and triple bonds of the polymerizable lipids. At 2°C, however, all three lecithins are in the condensed state. Chapman (27) reports about the surface pressure area isotherms of two homologs of (6) containing 23 and 25 C-atoms per chain. These compounds exhibit expanded phases even at subphase temperatures as low as 7°C. 

The soil used in this study was a mineral oil (see Figure 1) manufactured by Squibb, which had a trace amount of an oil-soluble red dye added for visual acuity. The linear alkylben-zene sulfonate sodium salts (LAS) were homologously pure samples, each with a different linear alkyl carbon chain of 10, 11, 12, 13, or 14 carbon atoms. Each of the LAS samples was a mixture of isomers with phenyl attachment ranging in nearly equal amounts from 2 through 5, 6, or 7 (depending on the alkyl chain length). These LAS samples were made with an HF catalyst. 

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