Alkenes, Cycloalkenes

Alkenes moderate intensity Monocycloalkenes medium intensity Loeal maxima for alkenes Loeal maxima for monocyclic alkenes Usually, double bonds cannot be localized n-Alkenes unspecific except for  

Isolated double bonds for highly substituted double bonds often absorption tail 

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The mixtures are particularly dangerous with alkenes, cycloalkenes and dienes. Accidents have been reported with propene, butenes, isobutylenes, 1-hexene, butadiene and cyclopentadiene. However, the reaction below is not thought to be dangerous if one operates at a temperature of 30°C and under two bar. 

Finally, if you have not studied the material already, you may wish to return to the last part of Chapter 3 and become acquainted with the nomenclature of cycloalkanes, alkenes, cycloalkenes, and alkynes (Sections 3-2 to 3-4). 

Many complexes of alkenes, cycloalkenes, alkynes, and cycloalkynes with transition metals are now known. Some examples are ... 

Houben-Weyl, Methoden der Organischen Chemie, 4th ed, Vol V/lb (alkenes, cycloalkenes, aryl alkenes), G. Thieme, Stuttgart (1972)... 

Rh(cod)(PCy3)2r Alkenes, cycloalkenes, ketones, cyclic ketones 111... 

Examples of nitrofluorination reactions of alkenes, cycloalkenes, halogenated and other substituted alkenes are shown in Tables 28 and 29. It should be mentioned that the yield of the fluoro nitro product is higher if the starting alkene is substituted by electron-withdrawing substituents. 

More examples of epoxidations of alkenes, cycloalkenes, and aromatic compounds having double bonds in their side chains are shown in equations 59-63 [129, 210, 217, 251, 300, 315, 330, 338, 679, 689, 746, 751]. 

Alkenes, cycloalkenes, dienes, conjugated dienes, activated alkenes 94... 

Gasoline hydrocarbons volatilized to the atmosphere quickly undergo photochemical oxidation. The hydrocarbons are oxidized by reaction with molecular oxygen (which attacks the ring structure of aromatics), ozone (which reacts rapidly with alkenes but slowly with aromatics), and hydroxyl and nitrate radicals (which initiate side-chain oxidation reactions) (Stephens 1973). Alkanes, isoalkanes, and cycloalkanes have half-lives on the order of 1-10 days, whereas alkenes, cycloalkenes, and substituted benzenes have half- lives of less than 1 day (EPA 1979a). Photochemical oxidation products include aldehydes, hydroxy compounds, nitro compounds, and peroxyacyl nitrates (Cupitt 1980 EPA 1979a Stephens 1973). 

The catalytic activity of low-valent ruthenium species in carbene-transfer reactions is only beginning to emerge. The ruthenium(O) cluster RujCCO), catalyzed formation of ethyl 2-butyloxycyclopropane-l-carboxylate from ethyl diazoacetate and butyl vinyl ether (65 °C, excess of alkene, 0.5 mol% of catalyst yield 65%), but seems not to have been further utilized. The ruthenacarborane clusters 6 and 7 as well as the polymeric diacetatotetracarbonyl-diruthenium (8) have catalytic activity comparable to that of rhodium(II) carboxylates for the cyclopropanation of simple alkenes, cycloalkenes, 1,3-dienes, enol ethers, and styrene with diazoacetic esters. Catalyst 8 also proved exceptionally suitable for the cyclopropanation using a-diazo-a-trialkylsilylacetic esters. ... 

Bis(camphorquinone-a-dioximato)cobalt(II) (10) has been developed as a catalyst for enan-tioselective cyclopropanation reactions. It allows selective carbene transfer from diazoacetic esters to terminal C-C double bonds which are in conjugation with vinyl, aryl, alkoxycarbonyl or cyano groups, but not to alkyl-substituted alkenes, cycloalkenes, 1,3-dienes and al-lenes. The unusual chemoselectivity and some other experimental observations make the two mechanistic pathways proposed vide supra) questionable for these special carbene-transfer reactions. In contrast, the cobalt(II) complex 11 allows not only the cyclopropanation of styrene but also of oct-l-ene, a nonactivated alkene (ethyl diazoacetate, 35 °C, 3mol% of catalyst yield 50-60%). ... 

Copper-, rhodium-, palladium-, and ruthenium-catalyzed cyclopropanation with diazoacetic esters is possible for a wide range of electron-rich alkenes, including alkylated acyclic alkenes, cycloalkenes, styrenes, 1,3-dienes, enol ethers, enol acetates, and ketene acetals (examples are given in this section, in Houben-Weyl Vol.E19b, ppl099-1155 and in refs 2, 152, 155 and 184). Furthermore, the construction of cyclopropanes with additional strain is possible, for example ... 

Photochemical decomposition of diazo(trimethylsilyl)methane (1) in the presence of alkenes has not been thoroughly investigated (see Houben-Weyl Vol. E19b, p 1415). The available experimental data [trimethylsilylcyclopropane (17% yield) and la,2a,3j8-2,3-dimethyl-l-trimethylsilylcyclopropane (23% yield)] indicate that cyclopropanation occurs only in low yield with ethene and ( )-but-2-ene. In both cases the formal carbene dimer is the main product. In reactions with other alkenes, such as 2,3-dimethylbut-2-ene, tetrafluoroethene or hexafluoro-propene, no cyclopropanes could be detected.The transition-metal-catalyzed decomposition of diazo(trimethylsilyl)methane (1) has been applied to the synthesis of many different silicon-substituted cyclopropanes (see Table 3 and Houben-Weyl Vol.E19b, p 1415) 3.20a,b,2i.25 ( iQp. per(I) chloride has been most commonly used for carbene transfer to ethyl-substituted alkenes, cycloalkenes, styrene, and related arylalkenes. For the cyclopropanation of acyl-substituted alkenes, palladium(II) chloride is the catalyst of choice, while palladium(II) acetate was less efficient, and copper(I) chloride, copper(II) sulfate and rhodium(II) acetate dimer were totally unproductive. The cyclopropanation of ( )-but-2-ene represents a unique... 

Hundreds of VOCs are found in a typical nonindustrial indoor environment. Many of these compounds are aromatic hydrocarbons, alkenes, alcohols, aliphatic hydrocarbons, aldehydes, ketones, esters, glycols, glycolethers, halocarbons, cycloalkanes and terpenes [2] but amines hke nicotine, pyridine, 2-pi-coline, 3-ethenylpyridine and myosmine are also widespread, especially in smoking microenvironments [3]. Moreover, low molecular weight carboxylic acids, siloxanes, alkenes, cycloalkenes and Freon 11 are frequently encountered in typical nonindustrial indoor air [1]. 

Similar to the benzynezirconocene, cyclohexyne, cyclopen-tyne, alkyne, alkene, cycloalkene zirconocenes, and related species insert various substrates such as alkynes, alkenes, aldehydes, ketones, nitriles or phosphaalkynes. They lead in general five-membered zirconacycles, which can be converted by transmetalation or exchange reactions into fused-ring aromatic or heterocyclic compounds. The extension of this chemistry to heterobenzyne complexes can be realized, for instance, in phosphinine compounds.Consequently, under mild conditions, -phosphabenzyne-zirconocene complexes are formed and can be isolated either as PMeg adducts or as dimers when the elimination reaction is carried out without added phosphane (Scheme 28). 

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