Distribution of carbon-chain

As the name suggests, LABs consist of a benzene nucleus to which an alkyl chain is bound. The alkyl chain shows a distribution of carbon chain lengths dependent on the cut of the starting material, while point of attachment to the benzene ring (phenyl isomer distribution) is governed to a large extent by the manufacturing process. 

Table 4. Distribution of carbon chain molecules (updated from Winnewisser 1981)...

However, the present discussion pertains to dark cloud chemistry. The experimental interstellar observations clearly indicate that the distribution of carbon chain molecules is correlated, and that the column densities of the longer chain members decreases about linearly with increasing chain length. Several mechanisms have been proposed for the chain building. For cool dark clouds Churchwell et al. (1978) and in further detail Walmsley et al. (1979) have proposed a formation scheme by which the longer chain molecules are formed via the acetylene backbone reaction ... 

Figure 15.1 highlights the differences between thermal and catalytic cracking in terms of the breath and distribution of carbon chain lengths of the products. 

Commercial soya bean lecithin is a complex mixture of phosphatides and triglycerides with minor amounts of fatty acids, sterols and other organic compounds, and with a total phospholipid content of 65-70%. (Crude soya bean lecithin contains 50% phospholipids.) The most common phosphatide components are phosphatidyl choline (-12%), phosphatidyl ethanolamine (-10%) and phosphatidyl inositol (-9%) (10.46). There is a distribution of carbon chain lengths with palmitic... 

TABLE 11.5.1 Distribution of Carbon Chain Lengths for Jojoba Oil Esters ... 

DiisononylPhthalate andDiisodeeylPhthalate. These primary plasticizers are produced by esterification of 0x0 alcohols of carbon chain length nine and ten. The 0x0 alcohols are produced through the carbonylation of alkenes (olefins). The carbonylation process (eq. 3) adds a carbon unit to an alkene chain by reaction with carbon monoxide and hydrogen with heat, pressure, and catalyst. In this way a Cg alkene is carbonylated to yield a alcohol a alkene is carbonylated to produce a C q alcohol. Due to the distribution of the C=C double bond ia the alkene and the varyiag effectiveness of certain catalysts, the position of the added carbon atom can vary and an isomer distribution is generally created ia such a reaction the nature of this distribution depends on the reaction conditions. Consequendy these alcohols are termed iso-alcohols and the subsequent phthalates iso-phthalates, an unfortunate designation ia view of possible confusion with esters of isophthaUc acid. 

The effect of carbon chain length and high vs. low 2-phenyl isomer distribution on viscosity and solubility (cloud/clear point) of a liquid hand dishwashing formulation is shown in Table 5. Two sets of pure LAS homolog samples ranging from Cl0 to Cl3 were prepared. All samples were prepared with pure olefins, but one set was produced with an HF alkylation catalyst (low 2-phenyl) and the other set was alkylated with A1C13 (high 2-phenyl). Each LAB... 

The Ziegler process produces linear alcohols with an even number of carbon atoms and is based on the polymerization of ethylene under catalytic conditions, generally with triethylaluminum as in the Alfol and the Ethyl processes. The distribution of alkyl chains depends on the version of the process employed but the alcohols obtained after fractionation can be equivalent to those obtained from fats and oils or have purpose-made distributions depending on the fractionation conditions. 

The successive reactions of the olefins over these three catalysts may cause the different dependences of the product distribution on the conversion of carbon monoxide. Two reaction paths of olefins, which influence differently the conversion dependence of the distribution, may be of importance, that is, the hydrogenation and the chain growth. If the hydrogenation predominantly occurs, the distribution of carbon number is not affected by conversion. On the other hand, the chain growth may cause the conversion dependence of the distribution and the deviation from the S-F distribution pattern. 

The low correlation coefficient observed when combining the data for alcohol ethoxylates from two different manufacturers is probably due to chemical structure variables not incorporated in equation 1. These include different degrees of hydrophobe linearity, different distributions of carbon numbers and ethylene oxide chain lengths around the average values used in the correlation equation, and the presence of differing amounts of other components such as unreacted alcohols in the surfactants. 

Phenol was successfully extracted from water using pure supercritical carbon dioxide at pressures up to 31 MPa for two isotherms 298 and 323 K. The distribution coefficient increased with increasing pressure, but decreased with increasing temperature. This is expected since increasing the temperature severely drops the carbon dioxide density and hence the solubility of the phenol in it. Increased volatility at the higher temperature is not sufficient to off-set the density effect, since phenol has a low vapor pressure. Benzene was foimd to be a suitable entrainer since its solubility in water is very small and it enhances the distribution of phenol into the supercritical phase. The presence of methanol was found to have no effect. Since methanol is polar and completely soluble in water, it favors the aqueous phase and therefore does not change the characteristics of the supercritical phase. Others have found that the distribution of short chain alcohols between water and supercritical carbon dioxide highly favors the aqueous phase (ifl). 

These results indicate that the complexity of the fluorescence decay of meso l e and meso IqC, where the pyrene is non symmetrically substituted, is not due to a conformational distribution of the chain but to rotational isomerism around the carbon carbon bond linking the chromophore to the chain backbone providing the possibility to form more than one excimer in these systems. 

Although the ratio of 180 160 in carbonate tests of marine invertebrates can be used to examine sea surface temperatures, the extent of continental glaciation, the balance between precipitation and evaporation, the carbonate compensation depth and the diagenetic alteration of carbonate all influence whether an estimation can be made and its accuracy (Boxes 5.6, 5.7 Marshall 1992). There is also a reliable organic geochemical palaeothermometer based on the distributions of long-chain (C37-C39) unsaturated ketones (Brassell et al. 

Successively, this result was confirmed using Monte Carlo simulation techniques on model oligomers of PET in a confined geometry [261]. In these simulations, a model chain was placed inside a cylinder with hard walls (simulated by a continuous distribution of carbon atoms) in order to mimic the chain environment in the mesomorphic state. These calculations indicated that highly extended chain conformations of PET with transverse radius < 6 A are compatible with narrow deviations from the trans state for all dihedral angles, with the exception of the backbone dihedral angles... 

Alcohol ethoxylates are relatively inexpensive and readily available, and are considered to be one of the key work-horse surfactants. The primary advantage of alcohol ethoxylates, however, lies in the flexibility of their structure. The hydrophobe can vary in terms of carbon chain length (from Ca to C20+), carbon chain distribution (single homologues or various blends), feedstock source (petrochemically based or oleochemically based), and the degree of minor (methyl) branching. 

The second reflection, A2, is observed to be strong, and calculated as weak. An additional side-chain carbon atom in phase for this reflection (near the line x + z = 1) would bring the value of Icaic. to 103. (We have not attempted to find a distribution of side-chain atoms that would give... 

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