Primary alcohol sulfates

Primary alcohol sulfates are half esters of sulfuric acid. These substances are relatively simple organic molecules and have been known for a long time. The first alcohol sulfate was prepared by Dumas in 1836 [1] but long-chain alcohol sulfates were not used as surfactants until the 1930s [2]. 

Alcohol and alcohol ether sulfates are commonly considered as extremely rapid in primary biodegradation. The ester linkage in the molecule of these substances, prone to chemical hydrolysis in acid media, was considered the main reason for the rapid degradation. The hydrolysis of linear primary alcohol sulfates by bacterial enzymes is very easy and has been demonstrated in vitro. Since the direct consequence of this hydrolysis is the loss of surfactant properties, the primary biodegradation, determined by the methylene blue active substance analysis (MBAS), appears to be very rapid. However, the biodegradation of alcohol sulfates cannot be explained by this theory alone as it was proven by Hammerton in 1955 that other alcohol sulfates were highly resistant [386,387]. 

The first step in the complete biodegradation of primary alcohol sulfates seems to be the hydrolysis to yield alcohol. Sulfatases are able to hydrolyze primary alcohol sulfates. Different authors have isolated and used several sulfia-tase enzymes belonging to Pseudomonas species. The alcohol obtained as a result of the hydrolysis, provided that dehydrogenases have been removed to avoid the oxidation of the alcohol, was identified by chromatography and other methods [388-394]. The absence of oxygen uptake in the splitting of different primary alcohol sulfates also confirms the hydrolysis instead of oxidation [395, 396]. The hydrolysis may acidify the medium and stop the bacterial growth in the absence of pH control [397-399]. 

Linear primary alcohol sulfates can also be biodegraded under anaerobic conditions but the process seems to be limited to the hydrolysis of the sulfate [407]. 

Some enzymes isolated in studies of primary alcohol sulfate biodegradation are specific for these sulfates [390,396]. However, other enzymes are more versatile. A strain isolated by Payne et al. [408] was capable of hydrolyzing secondary alcohol sulfates and also primary alcohol sulfates. Similar results were found by Vaicum and Eminovici [409]. 

Linear primary alcohol sulfates often need only one day for 95 % primary biodegradation and degrade faster than other anionic surfactants, which usually need several days. This difference has been confirmed by Ruschenberg [412, 413]. 

Alcohol ether sulfates also biodegrade rapidly but not as rapidly as alcohol sulfates. Primary biodegradation of alcohol (2 EO) ether sulfates determined in the same conditions as primary alcohol sulfates in Table 30 is shown in Table 33 as reported by Borsari [414]. 

Theoretically, the mechanism for ethoxylated alcohol sulfation is similar to primary alcohol sulfation, involving the rapid formation of a metastable product. The stoichiometry of this almost instantaneous and highly exothermic initial reaction corresponds again to more than one molecule of S03 per molecule of feedstock (Table 4). The desired ethoxylate acid sulfate product formed is... 

The shift to oleochemicals has been supported by increasing environmental concerns and a preference by some consumers, especially in Europe, for materials based on natural or renewable resources. Although linear alkylbenzenesulfonates (LASs) are petrochemically based, alcohol ethoxylates, alcohol ethoxysulfates, and primary alcohol sulfates are derived from long-chain alcohols that can be either petrochemically or oleochemically sourced. There has been debate over the relative advantages of natural (oleochemical) vs synthetic (petrochemical) based surfactants. However, detailed analyses have shown there is litde objective benefit for one over the other. 

Sulfated Primary Alcohols (AS), ROSO, M Primary alcohol sulfates are one of the workhorse surfactants and are formed by the direct sulfation of an alcohol. 

The mechanism and kinetics of the sulfation of the lower alcohols with sulfuric acid have been studied. The reaction proceeds by a bimolecular displacement mechanism like that of the acid-catalyzed esterification of alcohols with carboxylic acids no oxygen-alkyl fission occurs. Neopentyl alcohol sulfates at a rate comparable to other secondary alcohols these results indicate that within the groups of primary and secondary alcohols steric effects are minor. However, primary alcohols sulfate at a rate ten times that of secondary alcohols. The experimentally determined rate law... 

Alkyl sulfates or primary alcohol sulfates (PAS), which were the first synthetic surfactants used in personal care in the United States, are mainly used in toothpaste formulations. As for the AES, the alkyl moiety is typically a mixture of Ci2-Cjg chains. According to the application, one can find sodium, ammonium, magnesium, or triethanolamine salts of fatty alcohol sulfuric acid. They are obtained by the sulfation of a fatty (natural or synthetic) primary alcohol with a mixture of air/SOj according to the following reaction ... 

Chem. Descrip. Sodium primary alcohol sulfate Ionic Nature Anionic... 

Chem. Descrip. Primary alcohol, sulfated, sodium salt... 

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