Heavy ketones reactivity

Although the high reactivity of metal-chalcogen double bonds of isolated heavy ketones is somewhat suppressed by the steric protecting groups, Tbt-substituted heavy ketones allow the examination of their intermolecular reactions with relatively small substrates. The most important feature in the reactivity of a carbonyl functionality is reversibility in reactions across its carbon-oxygen double bond (addition-elimination mechanism via a tetracoordinate intermediate) as is observed, for example, in reactions with water and alcohols. The energetic basis... 

Remarkable progress in the chemistry of main group elements enabled us to synthesize and isolate heavy ketones which are capable of existence as stable species if their highly reactive M=X bond is adequately protected toward dimerization... 

Double-bond compounds between heavier group 14 and 16 elements (heavy ketones) undergo ready addition reactions with various reagents to give the corresponding single-bond compounds. The details of the reactivities are described in the next section (Schemes 20 and 21). 

On the other hand, an electronically stabilized heavy ketone by the coordination of the nitrogen atom shows extremely low reactivity. It does not react with phosphanes, phosphates, ketones, epoxides, Mel, HC1, etc., although it undergoes methanolysis and hydrolysis (Scheme 21).168... 

Carbonyl compounds such as ketones and aldehydes are another important class of doubly bonded systems in organic chemistry. However, their heavier element congeners, heavy ketones , are much less explored because of the extremely high reactivities. 

The extremely high reactivity of heavy ketones, RR M=Ch (M = Si, Ge, Sn, Pb, Ch = O, S, Se, Te), obviously results from the fact that their M-Ch r-bond energies are much smaller than the corresponding M-Ch a-bond energies, as one can see from Table Therefore, heavy ketones... 

Aramendia et al. (22) investigated three separate organic test reactions such as, 1-phenyl ethanol, 2-propanol, and 2-methyl-3-butyn-2-ol (MBOH) on acid-base oxide catalysts. They reached the same conclusions about the acid-base characteristics of the samples with each of the three reactions. However, they concluded that notwithstanding the greater complexity in the reactivity of MBOH, the fact that the different products could be unequivocally related to a given type of active site makes MBOH a preferred test reactant. Unfortunately, an important drawback of the decomposition of this alcohol is that these reactions suffer from a strong deactivation caused by the formation of heavy products by aldolization of the ketone (22) and polymerization of acetylene (95). The occurrence of this reaction can certainly complicate the comparison of basic catalysts that have different intrinsic rates of the test reaction and the reaction causing catalyst decay. 

From Table 29.1, it is obvious that chemicals with many different functional groups are cardiovascular toxins. These include hydrocarbons, chlorinated hydrocarbons, ketones, pesticides, heavy metals, and others. A unifying mechanism for the action of these far different chemicals has been proposed. This mechanism is based on a consideration of oxidative stress (OS) and postulates that chemicals or their metabolites that give rise to reactive oxygen species (ROS) that are formed by electron transfer (ET) may be cardiovascular toxins. The ET-OS-ROS mechanistic perspective has been used to account for the cardiotoxicity of the chemicals listed in Table 29.3. ... 

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