2- -3-alken-1 - alkanal Transformation

Cytochrome P-450 is a heme-containing monooxygenase that catalyzes a number of important substrate oxidations, including hydroxylation of alkanes and epoxidation of alkenes. These transformations are an important part of the metabolic processes involved in the formation of biologically active compounds from lipids and aromatics, and for the excretion of exogenous compounds in detoxification processes. The stoichiometric reaction of cytochrome P-450 is given in equation 1. 

Oxoreductases include enzymes such as dehydrogenases, oxidases and peroxidases which catalyse transformations such as oxidation of alcohols to carbonyls and dehydrogenation of functionalized alkanes to alkenes. 

Considerable effort has been devoted to the anaerobic transformation of polychlorinated Cj alkanes and C2 alkenes in view of their extensive use as industrial solvents and their identification as widely distributed groundwater contaminants. Early experiments, which showed that tetrachloroethene was transformed into chloroethene (Vogel and McCarty 1985) (Figure 7.67), aroused concern though it has now been shown that complete dechlorination can be accomplished by some organisms. 

This catalyst can catalyze a new reaction, called alkane metathesis. By this reaction, alkanes are transformed into higher and lower alkanes.265 Silica-supported zirconium catalysts were also used for the mild oxidation of alkenes by H202 266... 

Finally, whilst rhenium hydride complexes have not been reported to hydrogenate alkenes, there are several reports of the dehydrogenation of alkanes in the presence of tBuCH=CH2 as an hydrogen acceptor (Scheme 6.14) [136-142]. For example, cycloalkanes are transformed catalytically into the corresponding cyclic alkene, which shows that, in principle, a Re-based catalyst could be designed. 

The direct protonation of isobutane, via a pentacoordinated carbonium ion, is not likely under typical alkylation conditions. This reaction would give either a tertiary butyl cation (trimethylcarbenium ion) and hydrogen, or a secondary propyl cation (dimethylcarbenium ion) and methane (37-39). With zeolites, this reaction starts to be significant only at temperatures higher than 473 K. At lower temperatures, the reaction has to be initiated by an alkene (40). In general, all hydrocarbon transformations at low temperatures start with the adsorption of the much more reactive alkenes, and alkanes enter the reaction cycles exclusively through hydride transfer (see Section II.D). 

FIGURE 6.2 Representation of multivariate data by icons, faces, and music for human cluster analysis and classification in a demo example with mass spectra. Mass spectra have first been transformed by modulo-14 summation (see Section 7.4.4) and from the resulting 14 variables, 8 variables with maximum variance have been selected and scaled to integer values between 1 and 5. A, typical pattern for aromatic hydrocarbons B, typical pattern for alkanes C, typical pattern for alkenes 1 and 2, unknowns (2-methyl-heptane and meta-xylene). The 5x8 data matrix has been used to draw faces (by function faces in the R-library Tea-chingDemos ), segment icons (by R-function stars ), and to create small melodies (Varmuza 1986). Both unknowns can be easily assigned to the correct class by all three representations. 

Comparison of Anodic Conversions of Alkanes, Alkenes, and Aromatic Compounds with their Chemical Transformations... 

In organic chemistry, reduction is defined as a reaction in which a carbon atom forms fewer bonds to oxygen, O, or more bonds to hydrogen, H. Often, a C=0 bond or C=C bond is reduced to a single bond by reduction. A reduction that transforms double C=C or C=0 bonds to single bonds may also be classified as an addition reaction. Aldehydes, ketones, and carboxylic acids can be reduced to become alcohols. Alkenes and alkynes can be reduced by the addition of H2 to become alkanes. 

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