1- Hexanol oxidation

Gallot, J.E., M.P. Kapoor and S. Kaliaguine, "Kinetics of 2-hexanoI and 3-Hexanol Oxidation Reaction over TS-I Catalysts", AIChE Journal, 44 (6), 1438-1454(1998). 

According to the proposed mechanism, the introduction of substituents at the 2 and 9 positions in the PhenS ligand would, as a result of steric hindrance (see Figure 5.15), promote dissociation of the dimer and enhance the reactivity of the catalyst. This proved to be the case introduction of methyl groups at the 2 and 9 positions (the ligand is commercially available and is known as bathocuproin) tripled the activity in 2-hexanol oxidation [82]. 

Oxidation of tim5-4-(2,2,2-tnfluoro-l-hydroxy 1 tnfluoromethylethyl)cyclo-hexanol with pyridinium chlorochromate results m the correspondmg cyclic ketone whereas oxidation with nitnc acid m the presence of a catalyst causes ring cleavage [50] (equation 46)... 

The dehydration of 1-hexanol to hexene was conducted over heterogeneous sulfated zirconium oxide catalyst [19, 138]. The zirconia was treated with sulfuric acid and is known as super acid catalyst, having well documented performance for many reactions [19]. The reaction conditions are notably milder as for other acid catalysts, such as silica-alumina. 

OS 80] [R 7] [P 60] The acid-catalyzed dehydration of of 1-hexanol to hexene was conducted in a micro reactor made of PDMS, which also contained a heahng fimc-hon [19, 138], Sulfated zirconium oxide was coated as catalyst on the top plate of the micro reactor. A yield of 85-95% was obtained by-products could not be detected. This performance exceeds those of conventional reactors (30%). 

Gallot et al. (1998) studied the catalytic oxidation of 3-hexanol with hydrogen peroxide. The data on the effect of the solvent (CH3OH) on the partial conversion, y, of hydrogen peroxide are given in Table 4.1. The proposed model is ... 

Table 16.1 Catalytic Oxidation of 3-Hexanol Estimated Parameter Values and Standard Deviations...

Table 16.2 Catalytic Oxidation of 3-Hexanol Experimental Data and Model Calcidations...

Table 16.3 Catalytic Oxidation of 3-Hexanol Reduction of the LS Objective Function (Data for 0.75 g CH OH)...

When methanol was used to rinse a pestle and mortar which had been used to grind coarse chromium trioxide, immediate ignition occurred due to vigorous oxidation of the solvent. The same occurred with ethanol, 2-propanol, butanol and cyclo-hexanol. Water is a suitable cleaning agent for the trioxide [1]. For oxidation of sec-alcohols in DMF, the oxide must be finely divided, as lumps cause violent local reaction on addition to the solution [2]. Use of methanol to reduce the Cr(VI) oxide to a Cr(III) derivative led to an explosion and fire [3], The ignitability of the butanols decreases from n -through sec- to iert-butanol [4],... 

The question about the competition between the homolytic and heterolytic catalytic decompositions of ROOH is strongly associated with the products of this decomposition. This can be exemplified by cyclohexyl hydroperoxide, whose decomposition affords cyclo-hexanol and cyclohexanone [5,6]. When decomposition is catalyzed by cobalt salts, cyclohex-anol prevails among the products ([alcohol] [ketone] > 1) because only homolysis of ROOH occurs under the action of the cobalt ions to form RO and R02 the first of them are mainly transformed into alcohol (in the reactions with RH and Co2+), and the second radicals are transformed into alcohol and ketone (ratio 1 1) due to the disproportionation (see Chapter 2). Heterolytic decomposition predominates in catalysis by chromium stearate (see above), and ketone prevails among the decomposition products (ratio [ketone] [alcohol] = 6 in the catalytic oxidation of cyclohexane at 393 K [81]). These ions, which can exist in more than two different oxidation states (chromium, vanadium, molybdenum), are prone to the heterolytic decomposition of ROOH, and this seems to be mutually related. 

In reactions carried out for 24 h at room temperature, a 95% yield of cyclo-hexanol from cyclohexanone was obtained. Other ketones and aldehydes were also hydrogenated under identical conditions, but with slower rates (38% conversion for hydrogenation of 2-hexanone, 25% conversion of acetophenone, 45% for 3-methyl-2-butanone). Insertion of the C=0 bond of the ketone or aldehyde into the Cr-H bond was proposed as the first step, producing a chromium alk-oxide complex that reacts with acid to generate the alcohol product. The anionic chromium hydride [(COJsCrH]- is regenerated from the formate complex by... 

The metabolism of 77-hexane takes place in the liver. The initial reaction is oxidation by cytochrome P-450 isozymes to hexanols, predominantly 2-hexanol. Further reactions convert 2-hexanol to 2-hexanone, 2,5-hexanediol, 5-hydroxy-2-hexanone, 4,5-dihydroxy-2-hexanone and the neurotoxicant 2,5-hexanedione. Hydroxylation at the 1- and 3- positions can be considered detoxification pathways hydroxylation at the 2- position is a bioactivation pathway. A diagram of the proposed pathway for mammalian metabolism of -hexane is presented in Figure 2-3. 

No information is available as to whether metabolism of -hexane in children differs from that of adults. No studies were located comparing metabolism in young and adult animals. The toxicity of -hexane results from biotransformations yielding the active metabolite, 2,5-hexanedione. The initial step is an oxidation to 2-hexanol catalyzed by a cytochrome P-450 enzyme. Some P-450 enzymes are develop-mentally regulated (Leeder and Keams 1997). As the above discussion indicates, it is not completely clear which P-450 enzymes are involved in -hexane metabolism. 

Because many other chemicals can affect the enzymes responsible for n-hexane metabolism (see Section 2.3.3, Metabolism), the possibility of interactions is a significant concern. The initial step in n-hexane metabolism is oxidation to a hexanol by a cytochrome P-450 isozyme other chemicals can induce these enzymes, possibly increasing the rate of metabolism to the neurotoxic 2,5-hexanedione, or competing with M-hexanc and its metabolites at enzyme active sites, reducing the rate of metabolism. Interactive effects can be concentration and/or duration dependent. 

Reaction of 299 with benzaldehyde was found to give an equimolar mixture of diastereomeric j3-hydroxysulfoxides (314). Addition of 299 to a-tetralone 300 was more satisfactory, since the corresponding diastereomeric/3-hydroxysulfoxides 301 were formed in a 1.8 1 ratio. Their subsequent desulfuration with Raney nickel yielded levorota-tory 1-hydroxy-1-methyl-1,2,3,4-tetrahydronaphthalene 302 of unknown absolute configuration and optical purity. Similarly, addition of 299 to cyclohexene oxide leads to the formation of diastereomeric /3-hydroxysulfoxides 303 in a 2 1 ratio which, after separation, may be desulfurized to give (R,R)- and (S,S)- trans-2-methylcyclo-hexanols 304, respectively. Analysis of NMR spectra of the... 

Name and draw the product of the oxidation of 3-ethyl-4-methyl-l-hexanol. If this product is oxidized further, what second product will be formed ... 

The use of zeolites can overcome many of these limitations and provide new controlled entries into these oxidized hydrocarbons and new materials. For example, some of the most valuable industrial intermediates are terminally oxidized hydrocarbons, snch as n-hexanol or adipic acid, that are not readily available in free-radical chain processes. The ability of zeolites to function as shape-selective catalysts can, in principle, be used to restrict access, by reactant or transition state selectivity, to sites not normally attacked by oxidants [3]. 

Oxidation of -hexane with Co AlPO-18 with 10% rather than 4% of the framework AP ions replaced with Co resulted in a dramatic enhancement in the formation of adipic acid [65]. It was argued that in these catalysts two Co ions are ideally separated by 7-8 A on the inner wall of the zeolite, allowing both methyl groups unfettered access to catalytically active sites. Furthermore, it was demonstrated that 1,6-hexanediol and 1,6-hexanedial served as precursors to the adipic acid. On the other hand, 1-hexanol, hexanoic acid, and hexanal, which were also formed in the reaction, did not serve as precursors for the adipic acid. It is tempting to suggest that the mono-oxidized hexane products were produced in regions of the zeolite where simultaneous access to two catalytically active sites was not possible. 

Early electrochemical processes for the oxidation of alcohols to ketones or carboxylic acids used platinum or lead dioxide anodes, usually with dilute sulphuric acid as electrolyte. A divided cell is only necessary in the oxidation of primary alcohols to carboxylic acids if (he substrate possesses an unsaturated function, which could be reduced at the cathode [1,2]. Lead dioxide is the better anode material and satisfactory yields of the carboxylic acid have been obtained from oxidation of primary alcohols up to hexanol [3]. Aldehydes are intermediates in these reactions. Volatile aldehydes can be removed from the electrochemical cell in a... 

One of the best known explosion disasters took place in Flixborough, England, in 1974. Nypro Limited manufactured 70,000 tons/year of caprolactam as intermediate for the manufacturing of nylon. This is done by air oxidation of cyclohexane to cyclo-hexanol, with the help of a number of catalysts in the reactors. At that time, cracks developed in the reactor combined with pipe rupture, which released 30 tons of cyclohexane in a cloud. It was ignited by an unknown source and exploded, which resulted in 28 deaths and 36 injured, and the fire burned for 10 days. This disaster was also devastating to the future of the company. 

---