Acyclic alkanes isomerization

Two new reactive, very powerful organic peroxides, dimethyldioxirane and methyl(trifluoromethyl)dioxirane (4), have been introduced.81-83 The latter is more reactive and can be used more conveniently.84 85 Acyclic alkanes give a mixture of isomeric ketones on oxidation with methyl(trifluoromethyl)dioxirane,84,85 while cyclohexanone is the sole product in the oxidation of cyclohexane (99% selectivity at 98% conversion).85 With the exception of norbomane, which undergoes oxidation at the secondary C-2 position, highly selective tertiary hydroxylations can be carried out with regioselectivities in the same order of magnitude as in oxidations by peracids.85-87 A similar mild and selective tertiary hydroxylation by perfluorodialkyloxaziridines was also reported.88 Oxidation with dioxiranes is highly stereoselective 85... 

The determinant of the -> distance matrix D. In an isomeric series, this index takes the same values for all compounds, alternating from negative values for isomers with an even number of non-hydrogen atoms to positive values for compounds with an odd number of non-hydrogen atoms [Schultz et al., 1990 Schultz et ai, 1993]. In fact, for acyclic alkanes with the same number A of atoms, the following relation holds [Knop et ai, 1991] ... 

The inability of most transition metals to promote the isomerization of acyclic alkanes, especially by the cyclic type mechanism, may be understood if one considers in some detail the mechanisms of hydrocracking. In Tables VIII and IX (39,102,125-128) are reported the distributions of the products... 

On platinum, the a, -dicarbene mechanism which accounts for the hydrogenolysis of cycloalkanes (Scheme 34) is no longer predominant in the hydrocracking of acyclic alkanes. It has already been emphasized that the internal fission of isopentane and n-pentane is related to the metallocyclobutane bond shift mechanism of isomerization (see Section III, Scheme 29), and that in more complex molecules, the favored rupture of the C-C bonds in a p position to a tertiary carbon atom is best explained by the rupture of an a,a,y-triadsorbed species (see Section III, Scheme 30). The latter scheme can account for the mechanism of hydrocracking of methylpentanes on platinum. Finally, the easy rupture of quaternary-quaternary C-C bonds in... 

K. Altenburg, Brennst.-Chem., 47, 100, 331 (1966). Dependence of the Boiling Point of Isomeric Hydrocarbons on the Form of the Molecules. I. Theoretical Basis and Applications to Isomeric Acyclic Alkanes. 

Investigations which concern the mechanisms of skeletal rearrangements of saturated hydrocarbons induced by heterogeneous transition metal catalysis are of great interest for industrial applications, e.g. for petroleum reforming processes The developments in this field were reviewed recently by Hejtmanek, and by Maire and Garin , who focussed on the probable reaction mechanisms which include bond-shift and cyclic mechanisms for the skeletal isomerization of acyclic alkanes. Scheme 1 summarizes the... 

Sidedne and Handedness. You have the broad outlines of structure under control now—acyclic alkanes, alkenes, and alkynes have appeared, as have rings. Now we come to the details, to stereochemistry. Sidedness"—cis/trans isomerism—is augmented by questions of chirality— handedness. "Learning to see one level deeper into three-dimensionality is the next critical skiU. 

The brief glinpse into the world of polycyclic hydrocarbons in Section 4-6 provides further examples of the divCTsity of the carbon frame in organic chemistry (see Table 2-4 for the number of possible isomeric acyclic alkanes). Wheneva- possible, such molecules adopt stractures in which cyclohexane rings exist in the chair configuration, for example, traws-decaUn. We constructed this molecule by fusing one cyclohexane ring to... 

It is easy to list the various chemical and biological events influenced by flexibility, but unfortunately efforts to quantitate this structural attribute have been few. Mann analyzed the conformation of alkanes by modifying the number of gauche arrangements with Pitzer s steric partition function. Luisiranked alkanes on a. scale of conformational rigidity based on three-states rotational isomerism. Unfortunately, these schemes are designed for acyclic hydrocarbons and have no inherent capability to be adapted to heteroatomic molecules. 

Reactions of acyclic hydrocarbons of various skeletal structures with CO in superacid media were recently studied by Yoneda and coworkers " as discussed in the previous section. Products obtained were only isomeric carboxylic acids with lower number of carbon atoms than the starting alkanes. Formation of the carboxylic acids were accounted by the reactions of parent, isomerized and fragmented alkyl cations with CO to form the oxocarbenium ion intermediates (Koch-Haaf reaction) followed by their quenching with water. No formylated products in these reactions have been identified. 

Randid et al. (2013a) illustrated on smaller alkanes that CVM is sensitive to branching, and that the ordered row sums of CVM may facilitate solving a graph isomerism problem for acyclic graphs. Randid and his coworkers (Randid et al., 2013b) used the common vertex matrix for novel characterization of the central vertex or vertices in acyclic and cyclic graphs. 

---