Phenyl-isomer distribution

Carbon chain homolog distribution is nearly always the most important factor in determining performance and formulation characteristics of LAS [19]. Phenyl isomer distribution and dialkyltetralinsulfonate content have their greatest impact on the formulation characteristics of LAS in liquid detergents. 

In formulating liquid detergent products with LAS, the carbon chain distribution, phenyl isomer distribution, and DATS level can all contribute to the solubility and viscosity characteristics. Hydrotrope requirements for isotropic liquid detergents can vary widely for different types of commercial LAS. 

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... 

Dishwashing foam stability performance of an LAS-based light-duty liquid (LDL) is strongly affected by the carbon chain distribution, by water hardness, and, under some conditions, by phenyl isomer distribution. Foaming characteristics of C)2 phenyl isomer blends have been reported previously for conditions where LAS is the single anionic surfactant in the formulation (phosphate-built laundry powder) and the level of residual water hardness is low [30,31]. Under these conditions the internal phenyl isomers of C,2 LAS gave better foam performance than the 2-phenyl isomer. 

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. 

Uchiyama, T., A. Kawauchi, Acid pyrolysis for alkyl homolog and phenyl isomer distribution of LAS, J. Surfactants Deterg., 1999,2, 331-335. 

The nitration of phenylpyridines and related compounds has attracted attention for a long time, and measurements of isomer proportions have been made for several compounds of this type. Nitration occurs in the phenyl ring. For 2-phenylpyridine and 2-phenylpyridine i-oxide measurements of the dependence of rate of nitration upon acidity in 75-81 % sulphuric acid at 25 °C show that both compounds are nitrated as their cations (table 8.1). The isomer distribution did not depend significantly upon the acidity, and by comparison with the kinetic data for quinolinium ( 10.4.2) the partial rate factors illustrated below were obtained.They should be compared with those for the nitration of 2-nitrobiphenyl ( 10.1). The protonated heterocyclic groups are much... 

The solubility of LAS is dependent on various factors. For homologs with different molecular weights, it is normally the case that the higher the molecular mass, the lower the solubility. If the homologs have the same molecular weights, those with symmetrical isomer distribution will be easily dissolved branched homologs lead to a deterioration of solubility. The Na salts of the 2-and 3-phenylalkanes are less soluble then those of the internal phenyl isomers (for calcium salts the opposite is true) [187,188]. 

An interesting feature of the cyclization of y, -unsaturated alcohols is the marked effect on product isomer distribution by the nature of substituents remote from the double bond (cf. 42 and Scheme 59).98 Complete stereospecificity is observed for the phenyl derivative 42a in contrast to 42b and c, and the isomer ratio is reversed for 42d. The suggested mechanism98 is shown in Scheme 60 the trisubstituted alkene (45) is mainly converted into a pyran (46) rather than a tetrahydrofuran derivative (Scheme 61). 

Linear alkylbenzene (LAB) is produced by alkylating benzene with either alkylhalides or mono-olefins, the second option being the most widely used in commercial processes. The characteristics of final LAB, namely the isomer distribution, depend on the alkylation catalyst used HF catalyst produces a LAB known a Low 2-phenyl with a 2-phenyl isomer content around 17%, while fixed bed and A1C13 processes produce a High 2-phenyl LAB, which consists of approximately 30% of this isomer. Commercial LAB is a mixture of Ci0, Cu, C12 and Ci3 homologues with all positional isomers except the terminal one... 

A further indicator giving hints on the progression of biodegradation of LAS and thereby the build-up of SPC was the peak pattern of phenyl isomers of individual SPC homologues. Since the degradation rate of a particular isomer depended on the position of the attachment of the phenyl ring on the oxidised alkyl chain [19], the peak distribution observed in the Macacu samples could be used as a marker and be compared to the one recorded from a surface water sample where a steady state in SPC breakdown was reached [17]. 

In the absence of distribution data (and knowledge of preferred conformation — at least in the axial phenyl examples), the significance of potency differences amongst the isomeric esters (LXXXIll-LXXXV) cannot, however, be judged. Of the more rigid reduced acridine congeners (LXXXVI), only the e-phenyl isomer has been obtained and this lacks hot-plate activity in mice [286]. 

In order to explain some of the peculiarities of the decomposition reaction and isomer distribution of the products 99, 105), a reaction mechanism has been postulated that involves complex formation between At and the diazonium ion, followed by electron transfer, leading to the release of nitrogen, while the phenyl radical recombines with astatine according to Eq. (12). 

The relative rates of phenylation (benzene = 1) for thiophene and benzo[6 ]thiophene are 2.6 and 7.3 respectively <73IJS295). The isomer distribution in benzo[6]thiophene and dibenzothiophene is shown in Table 7. 

Table 7 Isomer Distribution in Homolytic Phenylation (73iis29s)...

Table 2 Isomer Distribution in the Cyclization of m-Substituted Phenyl Propargyl Ethers...

To determine whether this isomer distribution was the result of epi-merization, hydroformylation of (Z)-2-phenyl-2-butene was studied. 

LAB is often described as high or low 2-phenyl. As already seen, the level of 2-phenyl isomer is determined by the catalyst choice, with low 2-phenyl product made by HF catalyst being dominant. Isomer distribution has a very significant effect on solubility. Figure 4.6 shows how the cloud point (the temperature below which the formulation becomes turbid) varies with LAS type and concentration. 

Isomer Distribution Obtained on Nitration in the Phenyl Ring of Phenylthiazoles and Phenylisothiazoles"... 

The reaction of ate complexes (24), formed from trialkylboranes and trimethyl-silylpropargyl phenyl ether, with a mixture of acetic acid and hexamethylphosphoric triamide (HMPT) gives trimethylsilylacetylenes (25) selectively (Eq. 54) whereas the corresponding trimethylsilylallenes (26) are selectively prepared by the reaction with sodium methoxide instead of acetic acid and HMPT (Eq. 54) In the latter, when primary alkylboranes are used, the corresponding allene derivatives are obtain in high purity, but secondary alkylboranes give reverse ratios of the isomer distribution. 

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