2-Phenyl-1-propanol dehydration

Friedel-Crafts alkylation can occur intramolecularly to form a fused ring. Intramolecular Friedel-Crafts reactions provide an important method for constructing polycyclic hydrocarbon frameworks. It is somewhat easier to form six-membered than five-membered rings in such reactions. Thus, whereas 4-phenyl-1-butanol gives a 50% yield of a cyclized product in phosphoric acid, 3-phenyl-1-propanol is mainly dehydrated to alkenes.43... 

Melhyl-l-propanol Isobutyl Alcohol) and 2-Phenyl-1-propanol Herling and Pines (SO) studied the dehydration of 2-methyl-l-propanol and 2-phenyl-1-propanol. The two alcohols were passed over alumina under nonacidic conditions at temperatures of 350° and 270°, respectively (Tables III and IV). The 2-methyl-l-propanol underwent, in part, skeletal isomerization forming butenes, whereby the ratio of cisjtrans 2-butene produced was four to six times greater than the equilibrium ratio. The extent of skeletal isomerization depended to some extent on the method of preparation of the alumina. 

Dehydration of 2-Phenyl-1-propanol over Alumina Catalysts at 270°... 

Problem 13.42 Why does dehydration of l-phenyl-2-propanol in acid form l-phenyl-l-propene rather than l-phenyl-2-propene ... 

Dehydrohalogenation of l-phenyI-2-chloropropane, or dehydration of l-phenyl-2-propanol, could yield two products l-phenylpropene or 3-phenyl-propene. Actually, only the first of these products is obtained. We saw earlier (Secs. 5.14 and 5.23) that where isomeric alkenes can be formed by elimination, the... 

Cumyl hydroperoxide is eventually cleaved in the presence of an acid catalyst, to yield phenol and acetone, together with minor amounts of by-products such as a-methylstyrene, arising from dehydration of 2-phenyl-2-propanol, and dicumyl peroxide. a-Methylstyrene can be recovered to cumene in a hydrogenation stage. 

The importance of the acid-catalyzed side reactions are illustrated in Table 3 by the product distribution obtained using either TBHP or cumene hydroperoxide (CHP) as oxidant. The epoxidation with TBHP is faster and considerably more selective. When using CHP, about 20 mol% of the coproduct 2-phenyl-2-propanol was dehydrated to a-methylstyrene. It is likely that the simultaneously formed water increases the (Brpnsted) acidity of the aerogel and thus accelerates the ring opening and - to a smaller extent - the isomerization reactions. No oxidation products were formed in the absence of peroxide, as expected. Slow isomerization from p- to a-isophorone catalyzed by titania-silica was the only reaction observed. The data in Table 3 indicate that the simultaneous presence of peroxide and catalyst in the reaction mixture markedly accelerates the acid-catalyzed isomerization reaction. 

Treatment of the reduced adduct with pronase and subsequent reduction with Raney nickel led to the release and isolation of trans-/3-methylstrene 39. Raney nickel is known to cleave carbon-sulfur bonds specifically (777). Furthermore, the expected product from cleavage of the carbon-sulfur bond of the reduced adduct is 1-phenyl-1-propanol however, under the conditions of the Raney nickel reduction, 1-phenyl-1-propanol is dehydrated to trans-/3-methylstyrene (770). This result suggests that the amino acid residue is cysteine. The finding that the total number of cysteine residues detected with 5,5 -dithiobis(2-nitro-benzoic acid) decreases by one in the denatured, 1-phenylcyclopropylamine-... 

Acidic clays are widely applied in the dehydration of alcohols [38]. Although similar to zeolites in their capacity to induce the formation of both alkenes and ethers, selective alkene synthesis is possible. Various layered materials (clays, ion-exchanged montmorillonite, pillared layered clays) are very active and, in general, selective in transforming primary, secondary, and tertiary aliphatic alcohols to 1-alkenes [39-43]. Al -exchanged montmorillonite, however, induces ether formation from primary alcohols and 2-propanol [41]. Substituted 1-phenyl-1-ethanols yield the corresponding styrene derivatives at high temperature (653-673 K) [44]. 

A more detailed study of the dehydration of 2-phenyl-1-propanol was reported and a radio tracer technique using C was used to delineate the mechanism. Of the reaction products, the allyl benzene formed was labelled only on the benzylic carbon and was thus produced by y hydrogen abstraction and concerted phenyl migration. In the a-methylstyrene, the label was equally distributed between the I and 3 carbon atoms and this product arose either through a symmetrical cyclopropane intermediate or a tertiary carbonium ion. viz-... 

Table 3.6 and Scheme 3.31, in the model reaction of lauric acid with 3-phenyl-1-propanol, commercially available DOWEX 500W-X2 (H+-form, 9) did not promote esterification. The result indicates that a highly hydrophobic nature of the polymer-supported catalysts is important for activity in the dehydration reaction in water. It was found that resin 9 swelled significantly in water due to its high sulfonic acid content. On the other hand, both 11 and 12 scarcely swelled in water but worked as efficient catalysts. Resin 11 was easily recovered by simple filtration after the esterification was complete, and the catalyst could be continuously reused at least four times without loss of catalytic activity (Scheme 3.32). 

With the exception of implications regarding solubility, a feature not yet apparent is any recognized trend in the emissions from sulphur cures with variations in the base polymer. This is not the case with peroxide cures, where the reactivity of the polymer can influence both the quantity and type of emissions. A well-studied example is that of NR which carries an abundance of abstractable allylic hydrogens to favour alcohol formations (eqn (29)). Thus when DTOP (R = Me) is the peroxide, fert-butanol (BP 82°C) is obtained, whilst cumyl alcohol (2-phenyl-2-propanol BP 202°C) is obtained from Dicup (R = Ph). Ketone formation (eqn (30)) competes with hydrogen abstraction and can predominate in the presence of a different polymer emissions from formulations based on EPDM, silicone and a fluoroelastomer have been characterized. Other by-products include alkenes from alcohol dehydration, although numerous other reactions can occur. 

Write the expected product of the acid-cataly2ed dehydration of l-phenyl-2-propanol. The reaction is more rapid than the... 

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