Fert-Butyl alcohol dehydration

You have learned that 2-methyl-2-propanol (fert-butyl alcohol) dehydrates in the presence of acid (Section 9-2). Suggest a synthesis of 1,1-dimethylethyl acetate (tert-butyl acetate, shown in the margin) from acetic acid. Avoid conditions that might dehydrate the alcohol. 

Other methods that have been less regularly used are the dehydration of alcohols with dimethyl sulfoxide to form symmetrical ethers, the photochemical transformation of benzylic chlorides with fert-butyl alcohol, or radical reactions of hcxafluoroacetone with alkanes, Mercury acetate promoted couplings of alcohols with vinyl acetate or vinyl ethyl ether to form vinyl... 

These common features suggest that carbocations are key intermediates in alcohol dehydrations, just as they are in the reaction of alcohols with hydrogen halides. Mechanism 5.1 portrays a three-step process for the acid-catalyzed dehydration of fert-butyl alcohol. Steps... 

Compare and contrast the major products of dehydrohalogena-tion of 2-chloro-4-methylpentane with (a) sodium ethoxide in ethanol and (b) potassium ferf-butoxide in 2-methyl-2-propanol (fert-butyl alcohol). Write the mechanism of each process. Next consider the reaction of 4-methyl-2-pentanol with concentrated H2SO4 at 130°C, and compare its product(s) and the mechanism of its (their) formation with those from the dehydrohalogenations in (a) and (b). (Hint The dehydration gives as its major product a molecule that is not observed in the dehydrohalogenations.)... 

Dehydration of either alcohol yields 4-fert-butyl-l-phenylcyclohexene. 

In the first process, isobutane is oxidized by air at 120-150°C and about 3 MPa (30 atmospheres) to give fert-butyl hydroperoxide. This is then treated with propylene in the liquid phase at 120-140°C and about 3.5 MPa (35 atmospheres) in the presence of a molybdenum catalyst to give propylene oxide. tert-Butyl alcohol is obtained as a by-product. In the second process, ethylbenzene is utilized under similar conditions and 1-phenylethanol (which can be dehydrated to styrene) is the by-product. 

Esterification of linalool requires special reaction conditions since it tends to undergo dehydration and cyclization because it is an unsaturated tertiary alcohol. These reactions can be avoided as follows esterification with ketene in the presence of an acidic esterification catalyst below 30 °C results in formation of linalyl acetate without any byproducts [71]. Esterification can be achieved in good yield, with boiling acetic anhydride, whereby the acetic acid is distilled off as it is formed a large excess of acetic anhydride must be maintained by continuous addition of anhydride to the still vessel [34]. Highly pure linalyl acetate can be obtained by transesterification of tert-butyl acetate with linalool in the presence of sodium methylate and by continuous removal of the fert-butanol formed in the process [72]. 

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