Acetylenic compound

Cl8 Acetylenic Fatty Acids Allylic Oxidation and Rearrangement Compounds Derived by Modification of Cig Acetylenic Fatty Acids 

Reduction of Chain Length by One Carbon Atom Oxidative Cleavage of the Chain Cyclization of Acetylenic Compounds Sulfur Derivatives of Acetylenes Distribution of Acetylenic Compounds in Plants and Fungi 

Physiological and Pharmacological Properties Biologically Active Acetylenic Compounds Acetylenes as Phytoalexins Plant-Insect and Plant-Nematode Relationships Phototoxic Effects of Acetylenic Compounds Allenic Fatty Acids References 

There are three main types of acetylenic compounds in plants. Acetylenic acids, usually derived from oleic acid, 

The facts that radioactively labeled acetate and malonate label acetylenes in the same manner as fatty acids and that few branched-chain acetylenic compounds are known strongly suggest that naturally occurring acetylenes are derived from fatty acids. Additionally, many acetylenic compounds with a Z double bond have the double bond in the same position as the double bond of oleic acid. In a similar manner to fatty acids, introduction of double bonds into acetylenic compounds requires molecular oxygen. Although the triple bond is usually introduced into a position where a double bond would be expected, in some instances no prior double-bond formation is observed. The enzymes responsible for the introduction of triple bonds have been little studied. 

TABLE 2. Bond lengths, given as diet or o-/), in parent acetylenes —C=C—(R R = 

The X-ray C=C distance in crystalline acetylene of 1.178(2) is consistent with values 

Detectable asphericity shifts are not, however, restricted to H and can be significant for elements of the first row of the periodic table. Recently a systematic pairwise analysis of X and N bond lengths showed X—N differences across a wide range of bonding situations - 0.0096(9) for C=C (ethylenic), - 0.0052(9) for C=C (aromatic), - 0.0078(16) for C=N, etc. The data of Table 3a show clearly that a similar effect operates for C=C as well. For Csp —C=C—Csp it is reasonable to assign a Csp —Csp separation of 2 X 1.461 +1.209 = 4.131 A in the gas phase. This separation is 2 x 1.474+1.184 = 4.132 A across 44 X-ray crystal structures. The principal geometrical difference between these two cases lies in an inward movement of the two Csp atoms by - 0.0125 A each. This X—G value is entirely consistent with the X—N differences described earlier  

One individual structure, that of 3,3-bistrimethylsilylethynyl-5-trimethylsilylpenta-1,4-diyne, appeared just as this review was being completed and is worthy of mention. The structure is the first to contain a tetraethynylmethyl group in which the mean C=C distance is foreshortened to 1.152 A (range 1.142 to 1.161 A) and the mean Csp —Csp distance is elongated to 1.492 A (range 1.479 to 1.502 A). 

The vast majority of diazo (generically C—N=N) compounds studied by X-ray diffraction involve extensive delocalization through unsaturated groups involving the C atom. Very few diazoalkanes or azidoalkanes have been reported and even here the canonical forms contributing to the effective resonance hybrids involve considerable electron delocalization. For these reasons, the geometries of diazo and azido compounds for all types of substitution are covered in Section III.B.4. 

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CH = C = CH— are called allenes after the simplest member of the series. They are said to have cumulated double bonds. They react in most cases normally, that is, each double bond is unaffected by the proximity of the other they are converted by heating into the isomeric acetylenes. Compounds of the type... 

Force fields like MM3, MM4, CFF, or MMFF therefore use cubic and/or quartic or even higher contributions, up to the sixth power. Special attention has to be paid in the case of reference angles approaching 180°, e.g., for molecules with linear firag-ments such as acetylene compounds. In this circumstance, replacing Eq. (23) by a... 

VI,16. REACTIONS IN LIQUID AMMONIA. SOME ACETYLENIC COMPOUNDS ... 

CONDENSATIONS WITH SODAMIDE IN LIQUID AMMONIA Acetylenic compounds are conveniently prepared with the aid of Uquid ammcx as a solvent. The preparation of a simple acetylenic hydrocarbon ( -butylacetylene or 1-hexyne) and also of phenylacetylene is described. Experimental details are also given for two acetylenic carbinols, viz., 1-ethynyl-eyciohoxanul and 4-pentyn-l-ol. It will be noted that the scale is somewhat laige smaller quantities can readily be prepared by obvious modifications of the directions. 

Compounds containing a double or triple bond, usually activated by additional unsaturation (carbonyl, cyano, nitro, phenyl, etc.) In the ap position, add to the I 4-positions of a conjugated (buta-1 3-diene) system with the formation of a ax-membered ring. The ethylenic or acetylenic compound is known as the dieTwphile and the second reactant as the diene the product is the adduct. The addition is generally termed the Diels-Alder reaction or the diene synthesis. The product in the case of an ethylenic dienophile is a cyctohexene and in that of an acetylenic dienophile is a cyctohexa-1 4-diene. The active unsaturated portion of the dienophile, or that of the diene, or those in both, may be involved in rings the adduct is then polycyclic. 

Raphael, Acetylenic Compounds in Organic Synthesis, 1955 (Butterworths). 

Acetylenic Grignard compounds or the corresponding organoalkali metal derivatives are important intermediates in many syntheses of acetylenic compounds. The various methods for their formation in organic solvents and in liquid ammonia have been discussed extensively and we here give only a brief summary. 

R.A. Raphael, "Acetylenic Compounds in Organic Synthesis", Butterworths Scientific Publications, London, (1955). 

In 1971 we published "Preparative Acetylenic Chemistry", a collection of procedures for various acetylenic compounds. An important aim of this book was to make acetylenes more accessible, so that barriers for starting research in this field could be lowered. 

We have exemplified the principal methods for allenes, cumulenes and also some new methods for acetylenic compounds by procedures for relatively simple structures. For each of the compounds the most suitable and economic method was selected. 

Mercury Acetylenic compounds, chlorine, fulminic acid, ammonia, ethylene oxide, metals, methyl azide, oxidants, tetracarbonylnickel... 

Acylation of acetylenic compounds provides /ra/ j -P-chlorovinyl ketones (181). Vinyl cations were proposed to be the intermediates in these reactions. 

Acetylenic compounds have often been used as precursors to certain pyrroles. Thus, 2-butyne-l,4-diol reacts with aniline ia the presence of alumina to produce A/-phenylpyrrole [635-90-5] (27). 

Solutions of RC triple-bond C—Ti(0-/-C2H2)2 can be prepared by treating acetylenic compounds, such as phenylacetylene, with butyl lithium and then Cl—Ti(0-/-C2H2)2. These materials can react with aldehydes and epoxides to give the expected addition products (215). 

The presence of other functional groups ia an acetylenic molecule frequendy does not affect partial hydrogenation because many groups such as olefins are less strongly adsorbed on the catalytic site. Supported palladium catalysts deactivated with lead (such as the Liadlar catalyst), sulfur, or quinoline have been used for hydrogenation of acetylenic compound to (predominantiy) cis-olefins. 

Addition of HOCl to vinyl chloride yields chloroacetaldehyde (106) addition to acetylenic compounds produces dichloroketones (107) (see... 

Acetylenic compounds Alkyl hydroperoxides, peroxyacids Aminachromiiim peroxocomplexes Ammonium perchlorates Arenediazoates... 

Acetylenic Compounds Metal Acetyl ides Haloacetylene derivatives Diazirines... 

An unusual and different use of an aryldifluorovinyllithium compound is the synthesis of acetylenic compounds containing no fluorine [65] (equation 32)... 

The six-membered nng in polyfluoropyndazmes is much more stable, and pyrolysis at 680-725 °C is needed to eliminate mirogen, resulting m various fluonnated acetylene compounds in 80-90% yield [77](equation 46)... 

The use of the Hammett equation has also been extended to several new types of applications. Since these are not germane to the subject matter of the present chapter, we wiU simply mention work on applications to ethylenic and acetylenic compounds the various applications to physical properties, such as infrared frequencies and intensities, ultraviolet spectra, polarographic half-wave potentials, dipole moments,NMR and NQR spectra,and solubility data and applications to preparative data and biological activity. 

Acetylenic compounds have been described for inhibition in acid solutionsTypical inhibitors include 2-butyne-l,4-diol, l-hexyne-3-ol and 4-ethyl-l-octyne-3-ol. 

Compounds with triple bonds, i.e. acetylenic compounds, continue to receive attention. Patents have been filed for mixtures of propargyl alcohol with, for example, cellosolve + a phenol formaldehyde resin + tar bases heterocyclic nitrogen compounds + acetylenic + dialkylthiourea or a quaternary + antimony oxide . 

Reaction of adsorbed inhibitors In some cases, the adsorbed corrosion inhibitor may react, usually by electro-chemical reduction, to form a product which may also be inhibitive. Inhibition due to the added substance has been termed primary inhibition and that due to the reaction product secondary inhibition " . In such cases, the inhibitive efficiency may increase or decrease with time according to whether the secondary inhibition is more or less effective than the primary inhibition. Some examples of inhibitors which react to give secondary inhibition are the following. Sulphoxides can be reduced to sulphides, which are more efficient inhibitorsQuaternary phosphonium and arsonium compounds can be reduced to the corresponding phosphine or arsine compounds, with little change in inhibitive efficiency . Acetylene compounds can undergo reduction followed by polymerisation to form a multimolecular protective film . Thioureas can be reduced to produce HS ions, which may act as stimulators of... 

Cycloaddition of diazoindazole 376 with acetylenic compounds afforded (77S556 78CB2258) triazinoindazoles 377. The synthesis of the diaza analogue of 377 was also successful (Scheme 83). 

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