Alkynes olefins

Hydrocarbons, compounds of carbon and hydrogen, are stmcturally classified as aromatic and aliphatic the latter includes alkanes (paraffins), alkenes (olefins), alkynes (acetylenes), and cycloparaffins. An example of a low molecular weight paraffin is methane [74-82-8], of an olefin, ethylene [74-85-1], of a cycloparaffin, cyclopentane [287-92-3], and of an aromatic, benzene [71-43-2]. Cmde petroleum oils [8002-05-9], which span a range of molecular weights of these compounds, excluding the very reactive olefins, have been classified according to their content as paraffinic, cycloparaffinic (naphthenic), or aromatic. The hydrocarbon class of terpenes is not discussed here. Terpenes, such as turpentine [8006-64-2] are found widely distributed in plants, and consist of repeating isoprene [78-79-5] units (see Isoprene Terpenoids). 

General Reaction Chemistry of Sulfonic Acids. Sulfonic acids may be used to produce sulfonic acid esters, which are derived from epoxides, olefins, alkynes, aHenes, and ketenes, as shown in Figure 1 (10). Sulfonic acids may be converted to sulfonamides via reaction with an amine in the presence of phosphoms oxychloride [10025-87-3] POCl (H)- Because sulfonic acids are generally not converted directiy to sulfonamides, the reaction most likely involves a sulfonyl chloride intermediate. Phosphoms pentachlotide [10026-13-8] and phosphoms pentabromide [7789-69-7] can be used to convert sulfonic acids to the corresponding sulfonyl haUdes (12,13). The conversion may also be accompHshed by continuous electrolysis of thiols or disulfides in the presence of aqueous HCl [7647-01-0] (14) or by direct sulfonation with chlorosulfuric acid. Sulfonyl fluorides are typically prepared by direct sulfonation with fluorosulfutic acid [7789-21-17, or by reaction of the sulfonic acid or sulfonate with fluorosulfutic acid. Halogenation of sulfonic acids, which avoids production of a sulfonyl haUde, can be achieved under oxidative halogenation conditions (15). 

The analytical data obtained, particularly by the PUMA mass spectrometer on board Vega 1 during the flyby, indicate the presence of a large number of linear and cyclic carbon compounds, such as olefins, alkynes, imines, nitriles, aldehydes and carboxylic acids, but also heterocyclic compounds (pyridines, pyrroles, purines and pyrimidines) and some benzene derivatives no amino acids, alcohols or saturated hydrocarbons are, however, present (Kissel and Krueger, 1987 Krueger and Kissel, 1987). 

Hydration of olefins, alkynes and nitriles calls explicitely for the use of aqueous solvents. Indeed, one of the earliest investigations originates from 1969, when hydration of fluoroalkenes were studied with Ru(II)-chloride catalysts (Scheme 9.6). The reaction has no synthetic value but the studies helped to clarify the mechanism of the interaction of olefins with Ru(II)... 

Figure 4.22 Entropies of hydrocarbons at 25 °C paraffins, olefins, alkynes, cyclo-paraffins, and aromatics...

Photochemical irradiation of (i-Pr3Si)3SiH (14) with light of 254 nm in either 2,2,4-trimethylpentane or pentane leads to the elimination of f-Pr3SiH and the generation of bis(triisopropylsilyl)silylene (/-Pr3Si)2Si (15). Silylene 15 can also be generated by the thermolysis of the same precursor 14 at 225 °C in 2,2,4-trimethyl-pentane (Scheme 14.11). Reactions of 15 include the precedented insertion into an Si H bond, and additions to the ti bonds of olefins, alkynes, and dienes. 

Rhodium(II) acetate catalyzes C—H insertion, olefin addition, heteroatom-H insertion, and ylide formation of a-diazocarbonyls via a rhodium carbenoid species (144—147). Intramolecular cyclopentane formation via C—H insertion occurs with retention of stereochemistry (143). Chiral rhodium (TT) carboxamides catalyze enantioselective cyclopropanation and intramolecular C—N insertions of CC-diazoketones (148). Other reactions catalyzed by rhodium complexes include double-bond migration (140), hydrogenation of aromatic aldehydes and ketones to hydrocarbons (150), homologation of esters (151), carbonylation of formaldehyde (152) and amines (140), reductive carbonylation of dimethyl ether or methyl acetate to 1,1-diacetoxy ethane (153), decarbonylation of aldehydes (140), water gas shift reaction (69,154), C—C skeletal rearrangements (132,140), oxidation of olefins to ketones (155) and aldehydes (156), and oxidation of substituted anthracenes to anthraquinones (157). Rhodium-catalyzed hydrosilation of olefins, alkynes, carbonyls, alcohols, and imines is facile and may also be accomplished enantioselectively (140). Rhodium complexes are moderately active alkene and alkyne polymerization catalysts (140). In some cases polymer-supported versions of homogeneous rhodium catalysts have improved activity, compared to their homogenous counterparts. This is the case for the conversion of alkenes direcdy to alcohols under oxo conditions by rhodium—amine polymer catalysts... 

General Reaction Chemistry of Sulfonic Acids. Sulfonic acids may he used to produce sulfonic acid esters, which are derived from epoxides, olefins, alkynes, allenes, and kelenes, as shown in Figure 1. Phosphorus pentachloride and phosphorus pentabromide can be used to convert sulfonic acids to the corresponding sulfonyl halides. 

A primary alcohol and amines can be used as an aldehyde precursor, because it can be oxidized by transfer hydrogenation. For example, the reaction of benzyl alcohol with excess olefin afforded the corresponding ketone in good yield in the presence of Rh complex and 2-amino-4-picoline [18]. Similarly, primary amines, which were transformed into imines by dehydrogenation, were also employed as a substrate instead of aldehydes [19]. Although various terminal olefins, alkynes [20], and even dienes [21] have been commonly used as a reaction partner in hydroiminoacylation reactions, internal olefins were ineffective. Recently, methyl sulfide-substituted aldehydes were successfully applied to the intermolecu-lar hydroacylation reaction [22], Also in the intramolecular hydroacylation, extension of substrates such as cyclopropane-substituted 4-enal [23], 4-alkynal [24], and 4,6-dienal [25] has been developed (Table 1). 

Singlet phenyl cations are unselective electrophiles, and reaction via such intermediacy mostly results in solvolysis, giving new C—O or C—N bonds. Triplet phenyl cations react selectively with n nucleophiles such as electron-rich olefins, alkynes and aromatics, forming new Ar—C bonds. 

Octahedral olefin-alkyne d4 complexes are characterized by a one-to-one match of each of the three metal dir orbitals with a ligand tt function as mentioned above. Three constructive two-center-two-electron metal-ligand tt bonds result. Extended Huckel calculations on W(H2C=CH2)-(HC=CH)(S2CNH2)2 produce the dv level ordering shown in Fig. 16... 

No reaction was observed with internal alkynes, and carbonyl alkyne analogs undergo rapid alkyne substitution at much lower temperatures as mentioned above. Only these olefin alkyne derivatives are known to pro-... 

It has been known for many years that molecular structure of a fuel has a direct bearing on the tendency of that fuel to smoke, i.e., to form carbon or soot in a flame. For example, in 1954 Schalla (41), reporting on a study of diffusion flames, indicated that the rate at which hydrocarbons could be burned smoke free varied in the order n-paraffins — mono-olefins — alkynes — aromatics. This same phenomena has been reconfirmed by many authors in a variety of systems and always in the same general order (j6, J3, J 5, 1 7, J 9, 26, 43, 45). Paraffins have the least tendency to smoke, whereas the naphthalene series have the greatest tendency to smoke. 

Pyridinium (trifluoroacetyl)methylide forms [3-1-2] cycloadducts with a wide variety of perfluorinated and partially fluorinated olefins, alkynes, and nitriles [86JFC(34)275]. Photolysis of a mixture of hexafluoro-3-diazobutan-2-one and perfluoro-2-butyne in the gas phase results in the formation of tetrakis(trifluoromethyl)furan a ketocarbene is the key intermediate of this reaction sequence (87JOC2680) (Scheme 79). 

The indenyl complexes are also efficient precatalysts for the hydrosUylation see Hydrosilation) of olefins, alkynes, and ketones. This reaction is believed to involve a hydrido intermediate, which can be generated initially via different routes (Scheme 9). 

Alkylrheniumoxides are known to be versatile, highly active and efficient catalysts for the oxidation of various organic substrates such as olefins, alkynes, amines, ketones, sulfides, or metal carbonyls (a) Hoechst AG (W. A. Herrmann, D. W. Marz, J. G. Kuch-ler, G. Weichselbaumer, R. W. Fischer) DE 3.902.357 (1989) (b) W. A. Herrmann,... 

There are common steps in the homogeneously catalyzed reaction of olefins, alkynes, and heteroolefinic substrates with hydrogen cyanide, which facilitate comprehension of the reaction principle. 

Diimide, HN=NH. The reagent, generated in situ by cupric ion-catalyzed oxidation of hydrazine with oxygen (air), hydrogen peroxide, potassium ferricyanide, or mercuric oxide, reduces olefins, alkynes, and azo compounds. Reduction of the... 

Catalytic reactions of carbon dioxide need not necessarily involve coordination complexes of C02, this seems to be required only for reactions with C-O bond breaking. In other processes (e.g., C-C coupling), the role of the catalyst metal complex may be the activation of the reaction partner (e.g., olefins, alkynes), which then can react with C02 directly.33... 

Figure 55. Reactivity of olefins, alkynes, and organic halides toward electrochemically generated [Rh (TPP)] (or its dimethylamine adduct ).

Alkynes enter into a remarkable variety of metal-promoted coupling reactions with olefins, alkynes, and other unsaturated species leading to a diversity of cyclization, oligomerization, and polymerization products of synthetic value. In many instances alkyne complexes are presumed intermediates in these reactions but often this has not been proven. The reader is referred to other reviews [95-97] for more complete coverage of this topic. We briefly summarize here the most useful of these processes, highlighting those systems in which metal-alkyne complexes have been demonstrated as intermediates. 

---