Hydrolysis alkyl hydrogen sulfates

Alkyl hydrogen sulfates can be converted to alcohols by heating them with water This IS called hydrolysis, because a bond is cleaved by reaction with water It is the oxygen-sulfur bond that is broken when an alkyl hydrogen sulfate undergoes hydrolysis... 

Unlike the addition of concentrated sulfuric acid to form alkyl hydrogen sulfates this reaction is carried out m a dilute acid medium A 50% water/sulfuric acid solution is often used yielding the alcohol directly without the necessity of a separate hydrolysis step Markovmkov s rule is followed... 

When alkenes react with concentrated sulfuric acid, the corresponding sulfate esters (alkyl hydrogen sulfate, dialkyl sulfate) are formed. Depending on the alkene structure and the acid concentration, ester formation is accompanied by polymer formation (see Section 13.1.1). Hydrolysis of the sulfate esters allows the synthesis of alcohols. The reaction, called indirect hydration, is applied in the manufacture of ethanol and 2-propanol (see Section 6.1.3). 

Two basic methods of production are in commercial use 11) jhsnrption of propylene in sulfuric acid to form alkyl hydrogen sulfate, followed by the hydrolysis of the estei and (2) by direct hydration with water, using a catalyst. An inherent disadvantage in the lirst process is the need lo handle sulfuric acid. Further, the first process yields liuic more ihan 7() f isopropanol as compared with the second process, in which liquid propylene is used as the charge stock. All direct-hydration processes can he represented by CiH + HO) — CiFLOH + heat. 

Recall that alkyl substituents on the double bond increase the reactivity of alkenes toward electrophilic addition. Propene therefore reacts faster than ethylene with sulfuric acid, and the mixture of alkyl hydrogen sulfates is mainly isopropyl hydrogen sulfate, and the alcohol obtained on hydrolysis is isopropyl alcohol. 

Concentrated sulfuric acid (95-98%) adds to alkenes to give alkyl hydrogen sulfates. Markovnikov s rule is followed. The reaction is useful in an industrial synthesis of isopropyl alcohol because the resulting alkyl hydrogen sulfate gives isopropyl alcohol by O—S bond cleavage on hydrolysis. 

Alkyl hydrogen sulfates can be easily hydrolyzed to alcohols by heating them with water. The overall result of the addition of sulfuric acid to an alkene followed by hydrolysis is the... 

Alcohols react with nascent hydroiodic acid to form alkyl iodides. When the starting material is an alcohol ether sulfate, the resulting alcohol ethoxylate obtained by acid hydrolysis of the sulfate gives the corresponding alkyl iodides. The number of moles of diiodoethane equals the number of moles of ethylene oxide present in the alcohol ethoxylate. Diiodoethane decomposes or reacts with more hydrogen iodide to give iodine quantitatively in both cases. However,... 

Sodium alkyl sulfates are esters. Thus sodium dodecyl sulfate is sensitive towards hydrolysis, especially in acid solutions. In this case, the starting fatty alcohol and sodium hydrogen sulfate is formed. Hydrolysis, once started, will run autocatalytically because the sodium hydrogen sulfate formed in this reaction is an acid in itself. Alkyl sulfates are stable in storage when in their highly pure states. 

The alkyl chain distribution of the base alcohol in alcohol sulfates is easily determined by gas chromatography. However, alcohol sulfates and alcohol ether sulfates are not volatile and require a previous hydrolysis to yield the free alcohol. The extracted free alcohol can be injected directly [306] or converted to its trimethylsilyl derivative before injection [307]. Alternatively, the alcohol sulfate can be decomposed by hydroiodic acid to yield the alkyl iodides of the starting alcohols [308]. A preferred method forms the alkyl iodides after hydrolysis of the alcohol sulfate which are analyzed after further extraction of the free alcohol, thus avoiding the formation of hydrogen sulfide. This latter method is commonly used to determine the alkyl chain distribution of alcohol ether sulfates. 

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