Dialkyltetralins

Diphenylalkene, cyclohexylbenzene, and dialkyltetralin- and indane derivatives can be formed from the dienes (12-14) [100]. 

Dialkyltetralins (DATs) and dialkylindanes are formed as byproducts during the alkylation process and these byproducts co-distill with LAB [9]. Examples of the unsulfonated and sulfonated dialkyltetralin are shown in Fig. 4. The level of DAT in LAB will vary depending on the type of alkylation process [10,11]. Table 3 lists the composition of several types of LABs and their DAT content as determined by gas chromatography-mass spectrometry (GCMS). It is important to note that a high level of DAT is not the result of alkylation with A1C13 catalyst. As seen in Table 3, AlCl3-catalyzed LAB can have a very low DAT content. 

TABLE 3 Dialkyltetralin Levels in Commercial Linear Alkylbenzenes... 

The DATs present in LAB will readily sulfonate to form dialkyltetralin-sulfonate or DATS. The foam and detergency performance properties of individual C DATS homologs are very similar to that of the corresponding C j LAS homologs [21]. Thus, even at a level of 10% DATS in the LAB, no decrease in foam or detergency performance is observed. In some liquid formulations, the presence of DATS can provide a beneficial hydrotropic effect to LAS [22]. Figure 8 illustrates that DATS are indeed surfactants, as evidenced by their surface tension vs. concentration plot. 

Trehey et al. [9] determined alkyl benzene sulphonates and dialkyltetralin sulphonates in sediments by this technique with a detection limit of 0.5g kg 1. 

The simultaneous determination of LAS and their co-products (dialkyltetralin sulfonates (DATSs) and alkylbenzene sulfonates with... 

Commercial LAS blends usually contain some sulfonated impurities, mainly dialkyltetralin sulfonates (DATS) with a similar distribution of aliphatic carbons than that of LAS (C10-C13). The (- )-ESI-MS spectra of DATS display a series of equally spaced signals with A m/z 14, shown for Cn-DATS in Fig. 2.10.3, arising from the cleavage of the alkyl... 

The detection of short-chain sulfophenylcarboxylic acids (SPCs) [2,9, 13,17,18] is clear proof of the primary biodegradation of LAS in the natural medium. In general the concentrations detected are small, one order of magnitude less than those found for LAS [2,9,13], with the exception of the river Osellino [18] where the total concentration of SPC found exceeded that of LAS. The highest concentrations are also observed near zones into which wastewater effluents are discharged [9, 18]. Both SPC and dialkyltetralines (DATSs) have also been detected in some samples of fluvial sediments [9],... 

The fourth LAB quality measure is the distribution of phenyl substitution on the alkyl chain, which can influence solubility and viscosity. A higher concentration of the 2-phenyl isomer generally improves the solubility of the resultant LAS surfactant. Much like the concentration of dialkyltetralin present in the LAB, the concentration of the 2-phenyl isomer in the LAB is largely determined by the particular LAB production process. Table 2.1 compares these three additional LAB quality measures as they typically result from the different alkylation processes. 

Particularly, 2-phenyl isomers and dialkyltetralins (DAT) are the components that can be considered as more representative of the adopted alkylation process, as shown in Table 5.2. 

Biodegradation of commercial surfactant mixtures is also affected by the presence of co-products with differing structures. For example, there was concern that methyl branched LAS (i.e., iso-LAS) and dialkyltetralin sulfonates (DATS) in all commercial LAS would be recalcitrant. However, studies have shown that these co-products mineralize in receiving environmental compartments such as waters and soils [47, 48]. 

LAS and dialkyltetralin sulphonates are converted to their sulphonyl chlorides by reaction with phosphorus pentachloride and then to their trifluoroethyl derivatives by reaction with trifluoroethanol. These derivatives are separated on a 15 m x 0.25 mm i.d. (0.25 micron film) of DB-5 temperature programmed from 125°C (1 min) to 230°C at 5°C per min with a final hold of 5 min. Helium is the carrier gas and detection is by negative-ion chemical ionisation mass spectrometry [3]. 

Contaminants. Examples of contaminants in surfactants and surfactant products determined by HPLC are 1,4-dioxane, sultones and dialkyltetralins in LAB. 

In Cl the main ions are due to (M + H)" and (M + H —HCl)". LAS and dialkyltetralin sulphonates (DATS) may be quantified at the /xg/l level in environmental water samples by first converting them to their trifluoroethanol derivatives [16]. The derivatives can then be analysed by negative-ion CL... 

Linear alkylbenzene produced from chloroparaffms contains 6-8% dialkyltetralin and dialky lindane. Alkylbenzene produced from olefins contains about 1% of these compounds. Thus, LAS may contain about 1%, or about 7% of the sulfonated indanes and tetralins, with the indanes being at very low concentration compared to the tetralins. These byproducts are surfactants, and their presence is beneficial in liquid formulations since they act as hydrotropes and viscosity improvers. They can be determined by GC or GC/MS by the same methods as are used for determining the alkyl chain distribution. The compounds are made volatile by desulfonation or by derivatization as discussed in Chapter 8 (58,59). 

Ci(rCi4 dialkyltetralin- and di-alkylindanesulfonates and their carboxylated intermediates, C3-C10 sulfophenylcarboxylates C 2-dialkyltetralinsulfonate and its carboxylated intermediates, C3-C10 sulfophenylcarboxylates... 

MBAS value (72). The so-called interference-limited methylene blue test is also likely to return high values when used for unpolluted samples. The MBAS method is discussed in Chapter 12. For routine wastewater analysis, the determination is frequently automated by use of flow injection analysis. The LAS degradation product sulfophenylcarboxylic acid will contribute to the MBAS response if the alkyl chain length is greater than 6 carbons. Dialkyltetralin-and dialkylindanesulfonates are also presumed to be MBAS-active (35). There are many variations of the methylene blue method used by various regulatory agencies. These differ mainly in the amount of effort expended to eliminate interferences (73). 

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