Sulfated primary alcohols

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. 

Organic Reactions. Primary alcohols react with sulfamic acid to form alkyl ammonium sulfate salts (21—23) ... 

The resulting 4-methylhexanone-2 oxime separates and is dried by any suitable means, such as with a dehydrating agent, for example, sodium sulfate or magnesium sulfate. After drying, 4-methylhexanone-2 oxime is reduced with hydrogen by means of a catalyst, such as Raney nickel, or by reaction of sodium and a primary alcohol, such as ethanol. The resulting 2-amino-4-methylhexane may be purified by distillation, as described in U.S. Patent 2,350,318. 

Higher molecular primary unbranched or low-branched alcohols are used not only for the synthesis of nonionic but also of anionic surfactants, like fatty alcohol sulfates or ether sulfates. These alcohols are produced by catalytic high-pressure hydrogenation of the methyl esters of fatty acids, obtained by a transesterification reaction of fats or fatty oils with methanol or by different procedures, like hydroformylation or the Alfol process, starting from petroleum chemical raw materials. 

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]. 

However, they behave similarly to alcohol sulfates since linear alcohol ether sulfates are more easily biodegradable than branched alcohol ether sulfates. Also linear secondary alcohol ether sulfates are poorer than linear primary alcohol ether sulfates [425]. 

Steinle et al. [426] studied the primary biodegradation of different surfactants containing ethylene oxide, such as sulfates of linear primary alcohols, primary oxoalcohols, secondary alcohols, and primary and secondary alkyl-phenols, as well as sulfates of all these alcohols and alkylphenols with different degrees of ethoxylation. Their results confirm that primary linear alcohol sulfates are slightly more readily biodegradable than primary oxoalcohol sulfates and that secondary alcohol sulfates are also somewhat worse than the corresponding linear primary. 

Alkyl sulfates and alcohol ether sulfates have been established for use in emulsion polymerization. AOS, although it has been used for many detergent applications during the past four decades, does not find any large-scale use as a primary surfactant system in emulsion polymerization. A study by Kreis [92] has shown that AOS surfactants are very well able to produce a small size latex and have excellent foaming characteristics (i.e., foam height and stability) in latex. They should therefore be able to compete with alkyl sulfates and alcohol ether sulfates. 

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 neutralization process consists of an exothermic reaction between a neutralizing agent and either sulfonic acid (e.g., LAB, a-olefins, FAME) or acid sulfate (e.g., primary alcohols, ethoxylated alcohols). Neutralization can be carried out after prolonged storage if the acid stability permits (LAS, FAMES). 

The final example in this section is the synthesis of a tristetrahydrofuran 2-606 described by the group of Rychnovsky [313]. Here, the tris(sulfate) 2-605 was converted into 2-606 by simply heating it in a mixture of MeCN and H20 (Scheme 2.138). The domino reaction is most likely initiated by deprotection of the primary alcohol, which then attacks the adjacent sulfonate unit in a SN2-type manner to afford the first furan moiety. Under the reaction conditions the formed acyclic sulfate is hydrolyzed affording a free secondary alcohol which then attacks the next adjacent cyclic sulfate unit. Overall, the SN2/hydrolyzation sequence proceeds three times to finally provide the poly(tetrahydrofuran) 2-606 as a single isomer in 93 % yield. 

This enzyme [EC 2.S.2.2], also referred to as hydroxyste-roid sulfotransferase, catalyzes the reaction of 3 -phos-phoadenylylsulfate with an alcohol to produce adenosine 3, 5 -bisphosphate and an alkyl sulfate. The alcohols that can act as substrates include ahphatic alcohols, ascorbate, chloramphenicol, ephedrine, hydroxysteroids, and other primary and secondary alcohols. However, phenolic steroids will not serve as substrates (such alcohols can be acted upon by steroid sulfotransferases). 

Alcohol sulfates (AS) are usually manufactured by the reaction of a primary alcohol with sulfur trioxide or chlorosulfonic acid followed by neutralization with a base. These are high foam surfactants but they are sensitive to water hardness and higher levels of phosphates are required. This latter requirement has harmed the market for this type of detergent, but they are 2% of production for the major household surfactant market. Sodium lauryl sulfate (R = Cn) is a constituent of shampoos to take advantage of its high-foaming properties. 

More recently, the Noyori group described an organic solvent- and haUde-free oxidation of alcohols with aqueous H202 . The catalyst system typically consists of Na2W04 and methyltrioctylammonium hydrogen sulfate, with a substrate-to-catalyst ratio of 50-500. Secondary alcohols are converted to ketones, whereas primary alcohols, in particular substituted benzyUc ones, are oxidized to aldehydes or carboxylic acid by selecting appropriate reaction conditions This system also catalyzed the chemoselective oxidation of unsaturated alcohols, the transformation exemplified in equation 65, with a marked prevalence for the hydroxy function. 

Ternary and secondary alcohols are less acidic than primary alcohols. Methylation of HOCCfCH OH with Me2S04 and alkali hydroxide in aqueous medium, analogous to die procedure for HG=CCH20CH3 (exp. 2.1), is therefore expected to give a poor result. In the aprotic DMSO, however, the concentration of the alkoxide HC=CC(CH3>20K will be sufficient, while the alkylation will proceed smoothly in this strongly polar solvent. Undoubtedly, pan of the dimethyl sulfate will react with KOH to give methanol (which may further react to dimethyl ether). Therefore, an excess of Me2S04 and KOH is used. 

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. 

Conversion of the oxonium hydrogen sulfate to the ester probably proceeds by an SN2 mechanism with primary alcohols and an SN1 mechanism with tertiary alcohols ... 

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