Alkene aromatic hydrogenation

Beneficial Micro Reactor Properties for Alkene Aromatic Hydrogenation... 

A breakthrough in iron-catalyzed asymmetric epoxidation of aromatic alkenes using hydrogen peroxide has been reported by our group in 2008. Good to excellent isolated yields of aromatic epoxides are obtained with ee-values up to 97% for stilbene derivatives using diphenylethylenediamines 9 as ligands (Scheme 5) [45, 46]. 

At 375°C with the ZSM-5, the main products formed are n-alkanes. Other products are observed ramified alkanes and alkenes, 1-alkenes, aromatics and cyclic saturated hydrocarbons. The majority of hydrocarbons formed have a carbon number between 3 to 6. In the case of the zeolite Y, the n-alkanes and similar secondary products are formed but their repartition is different i.e. the normal and ramified alkanes are the main products and no cyclic compound can be observed. All these products are in higher quantity with the ZSM-5 than with the zeolite Y. This is in agreement with the calculated n-dodecane conversions. With the increase of the temperature, the same products are formed but their quantities increase. The analysis of the gaseous phase shows the presence of hydrogen, light normal and ramified alkanes and 1-alkenes. 

Selective hydrogenation of diolefins and alkenylaromatics in steam-cracked gasoline is of industrial importance. Specific refining by selective hydrogenation of these polymerizable hydrocarbons without hydrogenating other unsaturated compounds (alkenes, aromatics) is required to increase the stability of gasoline (see Section 11.6.1). 

Pd(OAc)2 also activates aromatic hydrogen atoms for non-oxidative addition to alkenes and alkynes [103, 104]. 

F. G. Gelalcha, B. Bitterlich, A. Anilkumar, M. K. Tse, M. Beller, Iron-catalyzed asymmetric epoxidation of aromatic alkenes using hydrogen peroxide, Angew. Chem. Int. Ed. 46 (2007) 7293. 

Hydrocarbons — Organic chemical compounds composed only of the elements carbon and hydrogen. Hydrocarbons are the principal constituents of crude oils, natural gas, and refined petroleum products and include four major classes of compounds (alkanes, alkenes, naphthenes, and aromatics) each with characteristic structural arrangements of hydrogen and carbon atoms, as well as different physical and chemical properties. (See also Alkanes, Alkenes, Aromatics, Naphthenes, Olefins, Paraffin, Saturate group.)... 

In several instances, Mannich-type cyclizations can be carried out expeditiously under photochemical conditions. The photochemistry of iminium ions is dominated by pathways in which the excited state im-inium ion serves as a one-electron acceptor. The photophysical and photochemical ramifications of such single-electron transfer (SET) processes as applied to excited state iminium ions have been expertly reviewed. In short, one-electron transfer to excited state iminium ions occurs rapidly from one of several electron donors electron rich alkenes, aromatic hydrocarbons, alcohols and ethers. Alternatively, an excited state donor, usually aromatic, can transfer an electron to a ground state iminium ion to afford the same reactive intermediates. Scheme 46 adumbrates the two pathways that have found most application in intramolecular cyclizations. Simple alkenes and aromatic hydrocarbons will typically suffer addition processes (pathway A). However, alkenic and aromatic systems with allylic or benzylic groups more electrofugal than hydrogen e.g. silicon, tin) commonly undergo elimination reactions (pathway B) to generate the reactive radical pair. 

Often the equilibrium position of a reversible process is such that the conversion to product is low at reasonable holding times (i.e., flow rates and reactor volumes). For example, the dehydrogenation of saturated alkanes and alkyl aromatics to produce alkenes and aryl-alkenes and hydrogen is a very important case in point ... 

Hydrogen fluoride (HF) is often used as a catalyst for alkenes, since there is less tar (fewer decomposition and polymeric by-products) and the volatile catalyst is easily removed. Both ferric chloride (FeCl3) and BF3 are common catalysts for alkene-aromatic coupling. Typical alkyne catalysts are aluminum chloride, gallium trichloride (GaCl3), BF3, and sulfuric acid. Reaction of a mixture of xylenes with a trace amount of BF3 in liquid HF gave the thermodynamic mixture 18% ortho, 60% meta, and 22% para but treatment with excess BF3 gave virtually 100% m-xylene. 07b,117... 

Compound A contains chlorine m/z 138/140, 3 1) and that fits CsHtCL It still has the 1,4-disubstituted benzene ring (four aromatic Hs) and it is an alkene (IR 1640) with three hydrogens on it with characteristic coupling. We can write the structure immediately as there is no choice. The four aromatic hydrogens evidently have the same chemical shift. 

As already indicated, carbonyl compounds such as ketones, aldehydes, enones, and quinones possess the property to act as effective electron acceptors in the excited state for generating radical anions in the presence of electron-donating partners such as alkenes, aromatics, ruthenium complexes, amines, and alcohols. We will not consider the reactivity of enones and quinones, but we will focus our attention on the behavior of the radical anions formed from ketones and aldehydes. Four different processes can occur from these radical anions including coupling of two radical anions and/or coupling of the radical anion with the radical cation formed from the donor, abstraction of hydrogen from the reaction media to produce alcohols, cyclization, in the case of ce-unsaturated radical anions, and fragmentation when a C -X bond (X=0, C) is present (Scheme 18). 

Hydrogenation of alkenes, aromatics, and other compounds with double bonds... 

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