Of cyclopentanol

Griffin M, PW Trudgill (1972) The metabolism of cyclopentanol by Pseudomonas NCIB 9872. Biochem J 129 595-603. 

The aim of this study is to develop model reaction for the characterization of the acidity and basicity of various transition aluminas, the experimental conditions being close to that for catalysis use. Among various model reactions, the transformation of cyclopentanol and cyclohexanone mixture was chosen for this work. Indeed, this reaction was well known for estimating simultaneously the acid-base properties of oxide catalysts [1], Two reactions take place the hydrogen transfer (HT) on basic sites and the alcohol dehydration (DEH) on acid sites. The global reaction scheme is shown in Figure 1. 

Figure 1. Reaction scheme of cyclopentanol-cyclohexanone mixture transformation.

The transformation of cyclopentanol-cyclohexanone mixture was carried out in a fixed-bed reactor at 200°C and 250°C under atmospheric pressure and in the presence of nitrogen (nitrogen/reactant molar ratio = 4). The reactant was an equimolar mixture of cyclopentanol and cyclohexanone. The reaction products were analyzed on line by GC (VARIAN 3400 chromatograph, equipped with a SGE CIDEX B 25 m x 0.22 mm column and a flame ionization detector). The deactivation profile was obtained by analyzing reaction effluent for various times-on-stream (TOS). 

The transformation of cyclopentanol-cyclohexanone mixture was carried out on aluminas, and compared with a basic (MgO) and acidic (HMOR zeolite, Si/Al = 80) catalysts. Figure 2 shows the activities, expressed as mmol.h 1.m 2, for the two reactions, for the different catalysts. 

Figure 2. Transformation of cyclopentanol-cyclohexanone mixture at 250°C. Initial activity in mmol.h. m 2. (a) basic character and (b) acid character.

The transformation of cyclopentanol/cyclohexanone mixture was also carried out at 200°C. The strength of the acid and basic sites was estimated from the activation energy (Ea) for the both reaction (Table 1). 

Alumina is an amphoteric catalyst, which can difficult to characterize via chemical and physic methods. The transformation of cyclopentanol/cyclohexanone mixture allows us to estimate at the same time the acid-base properties of aluminas. From this transformation, it was shown that aluminas can be classified into two families only basic aluminas, such as theta, which were more basic than MgO, and acido-basic aluminas, eta, gamma and delta, which possess an acidic character less pronounced than dealuminated HMOR zeolite... 

More recently, it was found that the incorporation of N-heterocychc car-bene ligands to the Cp lr moiety (Eq. 12) considerably enhances catalyst activity for alcohol oxidation reactions [50,51]. By way of example, the oxidation of secondary alcohols occurs with high turnovers, up to 3,200 for the oxidation of 1-phenylethanol and 6,640 for that of cyclopentanol (95% yield, 40 °C, 4 h) using the complex with the carbene derived from the tetram-ethyhmidazole (Eq. 12). 

Cyclopentanone is prepared by oxidation of cyclopentanol. Any one of a number of oxidizing agents would be suitable. These include PDC or PCC in CH2C12 or chromic acid (H2Cr04) generated from Na2Cr207 in aqueous sulfuric acid. 

Ru(III)-catalysed oxidation of p-hydroxyazobenzene (PHAB) by four sodium N-haloarenesulfonamidates show first-order dependences on the oxidant, PHAB and Ru(III), and less than first-order dependence on hydrogen ions. The rates follow the sequence BAB > BAT > CAB > CAT. This effect is attributed to electronic factors.118 Ru(III)-catalysed oxidation of cyclopentanol and cyclohexanol with... 

Mechanisms have been suggested for the N-bromosuccinimide (NBS) oxidation of cyclopentanol and cyclohexanol, catalysed by iridium(III) chloride,120 of ethanolamine, diethanolamine, and triethanolamine in alkaline medium,121 and for ruthenium(III)-catalysed and uncatalysed oxidation of ethylamine and benzylamine.122 A suitable mechanism has been suggested to explain the break in the Hammett plot observed in the oxidation of substituted acetophenone oximes by NBS in acidic solution.123 Oxidation of substituted benhydrols with NBS showed a C-H/C-D primary kinetic isotope effect and a linear correlation with er+ values with p = —0.69. A cyclic transition state in the absence of mineral acid and a non-cyclic transition state in the presence of the acid are proposed.124 Sulfides are selectively oxidized to sulfoxides with NBS, catalysed by ft-cyclodextrin, in water. This reaction proceeds without over-oxidation to sulfones under mild conditions.125... 

A solution of 1 g of the diacetate (III) in 100 cc of n-heptane containing 2.5 cc of cyclopentanol and 50 mg of p-toluenesulfonic acid is heated under reflux for 20 hours. After cooling, a few drops of pyridine are added and the solvent is eliminated by evaporation under vacuum. The residue is taken up with methanol to give 3-cyclopentyl enolether of 17a-ethynyl-19-nortestosterone acetate which, after recrystallization from methanol, melts at 182°C to 184°C. 

However, with cyclppentanone only a 33% yield of cyclopentanol was obtained, the remainder of the material probably having undergone the above-mentioned condensation.6 As no appreciable condensation of this type occurs if dilute solution (approximately 0.05 molar) is used,10 it seems possible that dilution may improve the yields with particularly sensitive ketones such as cyclopentanone. 

Benzyl chloride is an acceptable starting material, because the problem has specified that we must start with alkyl halides. However, we must still prepare the alkoxide anion. This is the conjugate base of cyclopentanol and can be made by the reaction of the alcohol with sodium metal ... 

Loss of water from the molecular ions of cyclopentanol occurs by two pathways as evidenced by the composite metastable peak [415, 430], the major pathway being a 1, 3 (and/or 1, 4) elimination from the a-cleaved molecular ion. Deuterium substitution at the 3 or 4 positions on the ring has been shown to result in an isotope effect of 2—2.5 for this mode of decomposition. 

Radical cyclisation-anionic sequences, in which the radical cyclisation involves the addition of a ketyl radical anion to an alkene, are also possible. For example, carbonyl-alkene cyclisation of unsaturated ketone 19 and quenching of the resultant organosamarium with electrophiles allow access to an impressive range of cyclopentanol products (Scheme 6.7).12... 

Hypohalites (RO—Hal) are similar to nitrates (see p. 155) in their photochemical behaviour. Ultraviolet irradiation gives an (n,Jt ) excited state that cleaves to form an alkoxy radical and a halogen atom. The radical may undergo alpha-cleavage before recombination with the halogen atom occurs, and this accounts for the formation of 5-iodopentanal (5.69) from the hypoiodite of cyclopentanol such hypoiodites are generated in situ from the alcohol, iodine and mercury(ll) oxide. In open-chain systems the alkoxy radical can... 

The prediction that the (7S,2/ )-( + )-norephedrine salt of acid 9a should lead to the (/ )-enantiomer of cyclopentanol 10 could not be verified directly... 

The use of resting cells of microorganisms to biotransform organic compounds by specific reactions is a well-established technique. Thus, incubation of norbornanone (12) with a washcd-cell suspension of cyclopentanol grown Pseudomonas sp. NCIB 9872 resulted in the rapid oxidation of the substrate to a mixture of lactones 13 and 14398. 

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