Alkanes, methyl substituted

Furthermore, it has been demonstrated in acetals of phenyl alkyl ketones that the presence of the aromatic moiety at the anomeric carbon induces a further stabilization resulting in very strong anomeric stabilization.29 This phenomenon is reminiscent of the stronger methyl substitution effects discussed above for 1,3-dioxolane and 1,3-dioxane (see also Table 1) than for alkyl ethers and alkanes. 

Figures 3 to 5 show some effects of hydrocarbon structure on maximum burning velocity (30, 32, Jfi, 72). Figure 3 deals with straight-chain alkanes, alkenes, alkynes, alkadienes, and allenes Figure 4 shows the effects of methyl substitution in four-carbon-atom alkane, alkene, alkyne, and alkadiene molecules. In general, the burning velocity decreases with increased chain length or methyl substitution, except for the alkanes,...

Cleavage of l-(trimethylsilyloxy)bicyclo[n.l.O]alkanes (8, 269-270). Lead tetraacetate fragmentation of the exo- and endo-methyl substituted silyl cyclopropyl ethers (1) is essentially stereospecific.2 Thus exo-1 is fragmented to the (E)-alke-noate 2 exclusively and endo-1 is converted into (Z)-2 exclusively. 

Zarei, K. and Atabati, M. (2005). Predictions of GC retention indexes for insect-produced methyl-substituted alkanes using an artificial neural network and simple structural descriptors. J. Anal. Chem., 60, 732-737. 

Alkanes and arenes can also be activated to other reactions by platinum complexes in aqueous solution (57,58). For arenes in the presence of H2PtCl5, reduction from Pt(IV) to Pt(II) occurs and the arene undergoes chlorination. The reaction is catalyzed by platinum(II) (59). Similarly, if a platinum(IV) catalyst such as HjPtClg is used, chloroalkanes are formed from alkanes. As an example, chloromethane is formed from methane (Eq. 23) (60-62). Linear alkanes preferentially substitute at the methyl... 

Light naphtha is a mixture produced by distillation of crude oil. Light naphtha primarily contains alkane compounds (paraffins), and it can be blended into gasoline. The octane value of methyl-substituted alkanes (iso-paraffins) is higher than that of straight-chain compounds (normal paraffins), so it is often advantageous to isomerize the light naphtha to increase the proportion of branched compounds. 

Bergman has also found an iridium allyl hydride complex that reacts with arenes and alkanes, the allyl group being converted to an n-propyl group in the process. Butane and isobutane give methyl-substituted allyl derivatives under exchange with the coordinated allyl group (Eq. 23) [93]. 

The reaction of cis- and fra j-methyl-substituted l-(trimethylsiloxy)bicyclo[n.l.O]alkanes (n = 3,4,5) is stereospecific. When treated with lead(IV) acetate, followed by diazomethane, these substrates give the methyl ( )- and (Z)-alkenoates, respectively. The reaction is interpreted by assuming electrophilic attack of lead(IV) acetate on the cyclopropane carbon to cleave the ring, followed by a Grob-type fragmentation with lead(II) acetate as the leaving group. 

It is quite difficult to find accurate and detailed analyses of single isomers for branched alkanes with more than 10 C-atoms in the literature. Nevertheless, GC analysis of heavy naphtha, kerosene and light gasoils indicates the prevailing presence of isoprenoid structures characterized by an average probability of methyl substitution of about 0.20 (Altgelt and Boduszynski, 1994). 

Fig. 5. Pyrolysis of lumped component of branched alkanes C15H32. Selectivity of methyl radical and small alkenes as a function of the probability of methyl substitution.

Saturated straight chains and 2-methyl-substituted alkanes... 

FIGURE 10.23 Dependence of the melting points of isomeric methyl substituted alkanes on the position on the chain of the methyl group. 

Fio. 1. Polymorization of cydo-alkanes. Plot of free energies against ring size, (a) unsubstituted (b) methyl substituted (c) 1,1-dimethyl substituted (taken from Dainton and Ivin, ref. 119). 

Could acidic minerals catalyze the isomerization of methylhexanes to dimethylpentanes The answer is yes under certain conditions. As extensive thermal cracking generates mixtures of lighter n-alkanes and a-olefms, conversion of a-olefms into mixtures of methyl-substituted alkanes is typical for olefin transformation in the presence of acidic catalysts. The acid-catalyzed transformation of hydrocarbon such as isomerization, alkylation, and cracking play an important role in the industrial processes of petroleum industry (Brouwer and Hogeveen 1972 Poutsma 1976 Corma and Wojciechowski 1985 Boronat et al. 1996). 

A number of systems have been developed for the functionalization of C-H bonds by their conversion into carbon-boron or carbon-silicon bonds. The substrates can be alkenes (Scheme 3.35), arenes (Schemes 3.36-3.38), heteroarenes (Schemes 3.39-3.41)" ° and even alkanes (Scheme 3.42)." With arenes, the electronic properties of the aromatic ring do not always seem to control the regioselectivity, as mixtures of isomers are often formed. Methyl-substituted aromatics may be borylated on the side chain depending on the choice of catalyst." ... 

A series of unsubstituted and 3-methyl-substituted bicyclo[x,y,0]alkanes (x = 9,10 y = 3,4) have been prepared from readily available precursors (e,g. cyclodo-decanone). Bicyclic analogues of exaltone and muscone were obtained in this work. 

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