Experimental procedures 3- -cyclohexanone

Transition state models 8 and 9 have been proposed for the formation of the major and minor products, respectively 5. For an experimental procedure for the reduction of a ketone with a dialkylborane, see Section 2.3.3.1.2.2.1 on alkyl-substituted cyclohexanones. 

N,N-Dibutylcyclohexvlamine by reductive alkylation of dibutvlamine with cyclohexanone. The results are shown in Table 1. A detailed description of one experiment illustrates the procedure. In all other experiments we list the starting materials, the autoclave and the experimental conditions. 

Any explanation of facial selectivity must account for the diastereoselection observed in reactions of acyclic aldehydes and ketones and high stereochemical preference for axial attack in the reduction of sterically unhindered cyclohexanones along with observed substituent effects. A consideration of each will follow. Many theories have been proposed [8, 9] to account for experimental observations, but only a few have survived detailed scrutiny. In recent years the application of computational methods has increased our understanding of selectivity and can often allow reasonable predictions to be made even in complex systems. Experimental studies of anionic nucleophilic addition to carbonyl groups in the gas phase [10], however, show that this proceeds without an activation barrier. In fact Dewar [11] suggested that all reactions of anions with neutral species will proceed without activation in the gas phase. The transition states for reactions such as hydride addition to carbonyl compounds cannot therefore be modelled by gas phase procedures. In solution, desolvation of the anion is considered to account for the experimentally observed barrier to reaction. 

The curing kinetics of system EPS-l/DDM was studied by a method of reverse gas chromatography (RGC) [29]. The basic parameter received from processing of the experimental data, was the constant of reaction rate k determined for an interval of conversion degrees a = 0.1-0.7 of the kinetical curve degree of conversion-time (a-t). For the determination of k the standard procedure was used the dependences, a, on the reaction time t, as lg[a/(l-a)]=/ (t) which have appeared linear were made. Then the value k (see Equation (10.4)) was determined from a slope of these linear diagrams. Ketones (metyl ethyl ketone, 1,4-dioxane, cyclohexanone) were chosen as the standard substances for the determination of retention time with argon as the gas-carrier. 

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