Cyclohexanone primary process

Bamford and Norrish observed that the free radical formation is the sole primary process in the photolysis of cyclohexanone, while step II is the major reaction occurring in the photolysis of 1-menthone. These results are rather difficult to interpret if reaction II occurs through a four-centred ring complex however, if a six-centred complex is involved, the consideration of the steric factors leads to a conclusion which is reconcilable with the results of Bamford andNorrish. The significance of steric factors (stereoelectronic requirements) appears from the fact that type II elimination is the major intramolecular path in the photolysis of ciy-2- -propyl-4-t-butyl cyclohexanone, while the photolysis of the tram compound yields the cis isomer as the major product The difference has been explained... 

Reductive amination of cyclohexanone using primary and secondary aHphatic amines provides A/-alkylated cyclohexylamines. Dehydration to imine for the primary amines, to endocycHc enamine for the secondary amines is usually performed in situ prior to hydrogenation in batch processing. Alternatively, reduction of the /V-a1ky1ani1ines may be performed, as for /V,/V-dimethy1 cyclohexyl amine from /V, /V- di m e th y1 a n i1 i n e [121 -69-7] (12,13). One-step routes from phenol and the alkylamine (14) have also been practiced. 

Kinetic data exist for all these oxidants and some are given in Table 12. The important features are (i) Ce(IV) perchlorate forms 1 1 complexes with ketones with spectroscopically determined formation constants in good agreement with kinetic values (ii) only Co(III) fails to give an appreciable primary kinetic isotope effect (Ir(IV) has yet to be examined in this respect) (/ ) the acidity dependence for Co(III) oxidation is characteristic of the oxidant and iv) in some cases [Co(III) Ce(IV) perchlorate , Mn(III) sulphate ] the rate of disappearance of ketone considerably exceeds the corresponding rate of enolisation however, with Mn(ril) pyrophosphate and Ir(IV) the rates of the two processes are identical and with Ce(IV) sulphate and V(V) the rate of enolisation of ketone exceeds its rate of oxidation. (The opposite has been stated for Ce(IV) sulphate , but this was based on an erroneous value for k(enolisation) for cyclohexanone The oxidation of acetophenone by Mn(III) acetate in acetic acid is a crucial step in the Mn(II)-catalysed autoxidation of this substrate. The rate of autoxidation equals that of enolisation, determined by isotopic exchange , under these conditions, and evidently Mn(III) attacks the enolic form. 

A new series of some spiro-1,4-dihydropyridines 2 has been synthesized by Hatamjafari [42] in good yields using a four-component, solvent-free process by the condensation of isatin, a primary amine, ethyl cyanoacetate and cyclohexanone absorbed on different solid supports under microwave irradiation applying a domestic oven. The report reveals that the application of montmorillonite KIO led to higher yields as compared to other solid supports (Scheme 2). 

Example 9.3. Oxidation of cyclohexane [63-65]. Air oxidation of cyclohexane to a mixture of cyclohexanol and cyclohexanone is an important step in a process for production of adipic acid and caprolactam. The reaction is carried out in the presence of a small amount of a cobalt salt (typically naphthanate or 2-ethylhexanoate) at 140 to 165° C and moderate pressure (e.g., 10 atm). The primary reaction product is cyclohexyl hydroperoxide ... 

Besides, successful attempts based on the oxidation of cyclohexanone/ cyclohexanol mixture by HNO3 were obtained for controlling N2O as primary side product from adipic acid plant (Eqs. (27.1) and (27.2)). Indeed, the abatement of huge amount of N2O from the exothermic decomposition of N2O (AH — -81.5 kj/mol) can be valorized through the production of steam that can be reused for others chemical processes [6]. In this specific case, two different technologies have been envisioned thermal destruction and catalytic decomposition. 

Srinivas and Mukhopadhyay (246) have investigated the selective thermal oxidation of cyclohexane in SCCO2 to produce cyclohexanone and cyclohexanol as the primary reaction products. Kinetic experiments were conducted at three temperatures (137°C, 150°C, and 160°C) and two pressures (170 and 205 bar), and the presence of a homogeneous SCF was verified experimentally for the initial reactor composition under these conditions (10 mol % cyclohexane, 10% O2, and 80% CO2). Kinetic results were interpreted assuming a free-radical reaction mechanism comparable to that observed in the conventional liquid-phase process, and the reaction was observed to be autocatalytic. Reported conversions are low relative to those in the liquid-phase process, which the authors attribute to... 

This retro aldol protocol enabled an ideal catalytic kinetic resolution of racemic aldol adducts that are usually difficult to be obtained through forward processes as illustrated by the resolutions of cyclohexanone aldol adducts. An intriguing feature of this process is that one chiral primary amine (e.g. 29) could catalyze stereoselectively the resolution of both anti- and yn-configured aldol adducts, whereas the forward reactions with the same catalyst yield selectively anti-configured aldol products. In addition, the catalytic power of 29-TfOH on both aldol and retro aldol reactions has also made possible an unprecedented asymmetric transfer aldol reaction that can generate two enantioenriched aldol adducts with opposite chiral induction from a single chiral catalyst (e.g. aldol products 48 and 49 in Scheme 5.14) [27],... 

---