Hydration cyclohexene

Because of projected nylon-6,6 growth of 4—10% (167) per year in the Far East, several companies have announced plans for that area. A Rhc ne-Poulenc/Oriental Chemical Industry joint venture (Kofran) announced a 1991 startup for a 50,000-t/yr plant in Onsan, South Korea (168,169). Asahi announced plans for a 15,000-t/yr expansion of adipic acid capacity at their Nobeoka complex in late 1989, accompanied by a 60,000-t/yr cyclohexanol plant at Mizushima based on their new cyclohexene hydration technology (170). In early 1990 the Du Pont Company announced plans for a major nylon-6,6 complex for Singapore, including a 90,000-t/yr adipic acid plant due to start up in 1993 (167). Plans or negotiations for other adipic acid capacity in the area include Formosa Plastics (Taiwan) (171) and BASF-Hyundai Petrochemical (South Korea) (167). Adipic acid is a truly worldwide... 

Silicalite-1 (MFI) xylene isomerization cyclohexene hydration Beckmann rearrangement... 

The Asahi process involves initial partial hydrogenation of benzene to cyclohexene using heterogeneous ruthenium catalyst. The cyclohexene hydration proceeds with >99% selectivity at 10-15% conversion (Figure 11.11) [44]. 

Cyclohexane, produced from the partial hydrogenation of benzene [71-43-2] also can be used as the feedstock for A manufacture. Such a process involves selective hydrogenation of benzene to cyclohexene, separation of the cyclohexene from unreacted benzene and cyclohexane (produced from over-hydrogenation of the benzene), and hydration of the cyclohexane to A. Asahi has obtained numerous patents on such a process and is in the process of commercialization (85,86). Indicated reaction conditions for the partial hydrogenation are 100—200°C and 1—10 kPa (0.1—1.5 psi) with a Ru or zinc-promoted Ru catalyst (87—90). The hydration reaction uses zeotites as catalyst in a two-phase system. Cyclohexene diffuses into an aqueous phase containing the zeotites and there is hydrated to A. The A then is extracted back into the organic phase. Reaction temperature is 90—150°C and reactor residence time is 30 min (91—94). 

Cyclohexene can also be oxidized in cyclohexene-2-one which is hydrated into cyclohexan-l-ol-3-one. Dehydrogenation of this compound gives resorcinol selectively (57). 

The liquid-phase hydration of cyclohexene is carried out by a Japanese company with a slurry of zeolite ZSM-5 as the catalyst. Here, the product separates into two layers and cyclohexano leaves in the organic cyclohexene phase and the catalyst stays in the aqueous phase, which is recycled. The two-phase strategy, therefore, has special significance in this case. A recent publication by Ogawa et al. (1998a) gives some details of this system. 

The use of zeolites like ZSM-5 for hydration of cyclohexene has seen successful in industry. Van der Waal et al. (1996) have hydrated a-pinene to a-terpeniol with p-zeolite bycyclic terpenes are obtained as by-products. 

Conversion of benzene to cyclohexene by partial catalytic hydrogenation is a very important industrial process, since it provides a new route to cyclohexanol, a precursor of nylon, when combined with hydration of cyclohexene. For example, Asahi Chemical Company of Japan developed a selective bilayer catalytic system including a Ru catalyst, Zr02 and ZnS04 under 50 atm of H2 pressure, a process affording the olefin with up to 60% selectivity after 90% conversion of benzene.72... 

Hydrogen donors that function poorly with homogenous catalysts include hydrazine hydrate, alkenes (e.g., cyclohexene), and ascorbic acid. This is somewhat surprising as they can be very effective in heterogeneous transfer hydrogenation. 

Cyclohexene oxide (1,2-epoxycyclohexane, 10.5, Fig. 10.29) has received particular attention as a substrate for EH (see Table 10.1). The compound has a meso-cis geometry like d.v-stilbcnc oxide (10.7), and, like the latter, is hydrated preferentially to the chiral (/ ,/ )-/ran.y-cyclohexane-1,2-diol (10.124) [185], There was a difference, however, between the activities of the rabbit liver microsomal and cytosolic EHs. The former was ca. 20-fold more active than the latter toward this substrate also, it formed the (R,R)-diol with 94% enantiomeric excess (ee) compared to only 22% ee for the cytosolic EH. 

Limonene (10.128) is an analogue of 4-vinylcyclohexene, and, like the latter, it undergoes epoxidation of both the C(1)=C(2) and C(8)=C(9) bonds. Like in the dioxide 10.127, the two epoxide groups are hydrated at different rates by EH. Indeed, incubations in rat liver microsomes showed that hydrolysis of limonene 1,2-epoxide was 70 times slower than that of the 8,9-epoxide, a much larger difference than that observed for the dioxide 10.127 [192], Comparison of EH-catalyzed hydration of the four epoxy groups in 4-vinyl-cyclohexene and limonene confirmed that the relative rates decreased with increasing steric hindrance at these groups. 

Unfortunately, these reactions tend to afford mixtures. Similar mixtures are observed when using 2-cy-clohexen-l-ol,315 3-cyclohexen-l-ol,31s,32s or the corresponding ethers or esters.326-327 The regio- and stereo-selectivity of the hydration of bicyclic alkenes has also been carefully examined (equation 2 1 3).328-330... 

Chemical Name 5-Hydroxy-a,a,4-trimethyl-3-cyclohexene-l-methanol Common Name Pinol hydrate Structural Formula ... 

Michael BD, Hart EJ. The rate constants of hydrated electron, hydrogen atom, and hydroxyl radical reactions with benzene, 1,3-cyclohexadiene, 1,4-cyclo-hexadiene, and cyclohexene. J Phys Chem 1970 74 2878-2884. 

Because the C=C double bond of the cyclohexene used in Figure 3.22 is labeled with deuterium, it is possible to follow the stereochemistry of the whole reaction sequence. First there is a c -selective hydroboration. Two diastereomeric, racemic trialkylboranes are produced. Without isolation, these are oxidized/hydrolyzed with sodium hydroxide solution/ H202. The reaction product is the sterically homogeneous but, of course, racemic di-deuteriocyclohexanol. The stereochemistry of the product proves the cw-selectivity of this hydration. 

Indeed, starting from the densely hydroxylated compound 122, formation of stannane 123 and [2,3]-sigmatropic rearrangement under Still s condition easily gave cyclohexene 124, whose hydroboration-oxidation led to protected carbapyranose 125. On the other hand, silylation of the hydroxymethyl moiety and hydration of double bond in... 

The main industrial routes for cyclohexanone manufacture have as starting points cyclohexane and phenol, by oxidation and hydrogenation, respectively. Another interesting method is based on the hydration of cyclohexene obtained by selective hydrogenation of benzene. The intermediate cyclohexanol is further dehydrogenated or separated if desired. 

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