Acetylene, bond properties

Spectral research permits us to obtain additional information about the role of the molecular structure in photoelectrical properties. The photosensitivity of the copper acetylenides is higher than in polymers with triple bonds without copper atoms. So the coordinating metal atoms and n-electrons of the acetylenic bonds play an important role in increasing the photosensitivity. 

In this and similar compounds the acetylene bond is supposed to donate only two jt-electrons to the conjugated system while the other jt-bond is located in the plane of the molecule and does not participate in the conjugation. Consequently, this compound satisfies the Hiickel rule for = 4. It indeed possesses aromatic properties. Anti-aromaticism. When a cyclic polyene system is studied it is important to know whether this system is nonaromatic, i.e.not stabilized by conjugation and sufficiently reactive due to the internal tension and other causes, or destabilized by conjugation, i.e. the cyclic delocalization increases the total energy of the system. In the latter case the molecule is called anti-aromatic. Here are typical examples of anti-aromatic systems cyclobutadiene, a cyclopropenyl anion, a cyclopentadi-enyl cation, and others. 

Recent remarkable progress in the theoretical calculations has revealed the bonding properties of heavier group 14 element analogs of acetylenes. The understanding of triply bonded systems of heavier group 14 elements can be rationalized as that conceptually similar to the case of doubly bonded systems. ... 

Proximity effects between functional groups in the same molecule frequently render the properties of the molecule unusual. A well-known example concerns proximity interactions of acetylenic bonds. Thus, internally hydrogen-bonded o-hydroxy-phenylacetylene is more voiatile (b.p. 75 °C/15 mm) than its methoxy derivative (b.p. 90°C/15mm), which is reminiscent of the effect of the hydrogen bond in o-nitrophenol. 

This substance was obtained by T. Urbanski and Taraniowicz [US]. The aim was to produce an explosive of a greatei power considering that the acetylenic bond increases exothermic properties of the substance. In lead block it gave a belter performance (385 cm ) than tetryl and ethylene glycol mononitrate. 

It is known that acetylenic bond possesses endothermic cliaracteristics (Vol. Ill, p. 227) and it is interesting to point out that a number of acetylenic compounds were found in nature as early as 1889 [5 and 1892 [6). Currently important are the works of E. R. H. Jones 7 and Bohlmann 8] who isolated and established the structure of numerous naturally occurring polyacetylenes and confirmed their structure by synthesis. Most of the polyacetylenes possess explosive properties. 

Acetylene. derivatives ol. explosive properties of 1 M.2) fVcctylene. salts of 462.49H till 227-229) Acetylenic bond, endothermic chariicicr-i sucof I (HI 227)... 

This structure fits well with the properties of acetylenic bonds in being linear with high refractivity (ease of interaction of light with electrons) and high chemical reactivity (w electrons exposed). 

The antibiotic properties of a number of synthetic compounds possessing a single acetylenic bond have been known for over sixty years. This is discussed in recent reviews (Reisch, 1965 a, b). Antibiotic activity has been reported also for a number of naturally-occurring monoacetylenic compounds, e.g. acetylene-dicarboxamide (VI) (Suzuki and Okuma, 1958) isolated from a Streptomycete (Suzuki, et al., 1958 a compound (VII) (Fawcett et al., I965) isolated from the broad bean, Vida faba L., (Wain et al., I96I a, b) and 10-undecynoic acid (VIII) isolated from the yeast, Rhodotorula glutinis (Nogueira-Prista, 1955). 

Many of the reactions in which acetylene participates, as well as many properties of acetylene, can be understood in terms of the stmcture and bonding of acetylene. Acetylene is a linear molecule in which two of the atomic orbitals on the carbon are sp hybridized and two are involved in 7T bonds. The lengths and energies of the C—H O bonds and C=C<7 + 27t bonds are as follows ... 

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