Acetylenes and Allenes

Ph3SnCl and propargylmagnesium bromide give a 90 10 mixture of the acetylenic and allenic tin derivatives, while in the case of Me3SnCl this ratio is 30 70 . 

Trimethylsilylation with trimethylchlorosilane affords the corresponding allene derivative, hydroxyalkylation with aldehydes and ketones gives mixtures of comparable amounts of acetylenic and allenic carbinols. 

T.F. Rutledge, "Acetylenes and Allenes", Reinhold Book Corporation, New York, Amsterdam, London, (1969). 

The facile thermal decomposition of the dimethyl and diethyl derivatives of (II) to nitrogen and carbene intermediates is emphasized by the readily discernible correlations between the reactant and product orbitals. On the other hand, the greater delocalization of the molecular orbitals of (I) may be a factor in its preference to rearrange, without decomposition, to methyl acetylene and allene. 

Summary of Electrophilic Additions to Acetylenes and Allenes Involving Vinyl Cations... 

Acetylene and Allene Complexes Their Implication in Homogeneous Catalysis, 14, 245... 

Reductive Cyclization of Acetylenic and Allenic Carbonyl Compounds 524... 

Particular organic ligands such as acetylenes and allenes can induce opening of the tetrahedron to give a folded rhombus, which is usually classified as a butterfly structure (Fig. 17). This butterfly structure is also rather surprisingly found for the anion [Fe4(CO)13H] 178, as shown in Fig. 18. 

Many valuable reviews of the chemistry of these species are given in the new book Dicoordinated Carbocations An introduction by Grob " is followed by reviews of various theoretical studies of vinyl cations, their gas-phase chemistry, their generation by nuclear decay, and their NMR spectroscopic characterization. Vinyl cation production by addition to acetylenes and allenes, by solvolysis, and photolytically are covered, together with the chemistry of the species generated in these various ways. The next chapter deals with the synthetic applications of vinyl cations,and alkynyl and aryl cations are covered in the last chapter. A review of the NMR spectroscopic and quantum-chemical investigation of vinyl cations in superacid media (also of dienyl and 1-cyclopropylvinyl cations) is published separately,as is a review of alkynylcar-... 

Steroid Systems Labeling of steroid systems, 46, 447 irreversible inhibitors of A -3-ketosteroid isomerase acetylenic and allenic 3-0X0-5,10-secosteroids, 46, 461 labeling of AC3-ketosteroid isomerase by photoexcited steroid ketones, 46, 469. 

As one can notice, the monoUthiated allenic isomer seems to be preferred in almost aU cases in hexane. However, West and Gomowicz reported that the IR spectrum of monolithio-I,3-bis(trimethylsilyl)-3-phenylpropyne exhibits two bands at 2000 and 1850 cm and attributed them to the acetylenic and allenic forms ". In light of the new interpretation, Priester and coworkers ascribed the band at 2000 cm to the propargyl anion, where both phenyl and silicon stabilized the charge at carbon atom 3 . 

T.F. Rudledge, "Acetylenic Compounds", Reinhold Publ. Comp., 1968 and "Acetylenes and Allenes", 1969. 

Different catalysts bring about different types of isomerization of hydrocarbons. Acids are the best known and most important catalysts bringing about isomerization through a carbocationic process. Brpnsted and Lewis acids, acidic solids, and superacids are used in different applications. Base-catalyzed isomerizations of hydrocarbons are less frequent, with mainly alkenes undergoing such transformations. Acetylenes and allenes are also interconverted in base-catalyzed reactions. Metals with dehydrogenating-hydrogenating activity usually supported on oxides are also used to bring about isomerizations. Zeolites with shape-selective characteristics... 

Orientation in the HD Addition to Methyl Acetylene and Allene, and Isotope, Effects in the Addition of //2 and D2 at Room Temperature on MoS2... 

Carbocations with trivalent carbon may have carbon with coordination number 2. Acyl ions have already been mentioned the vinyl cations, or car-bynium ions (26), have been detected as intermediates in addition of electrophiles to acetylenes and allenes and in solvolysis reactions with the highly reactive trifluoromethanesulfonate (triflate) leaving group.84 Vinyl cations are expected... 

T. F. Rutledge, Acetylenes and Allenes, Addition, Cyclization and Polymerization. Reinhold, New York, 1969. 

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