Acetylenic series

Acetylenic groups are used for their electronic effects, as equivalents of aromatic rings and to impose structural constraints. 

The acetylenic CH can act as an hydrogen bond donor (like for the antiparkinsonian rasagiline), and thus allow an additional interaction with the receptor.  

Because of the potential biologic activity of ethynyl group, it should not be systematically avoided during SAR exploration, even if mono-substituted ethynyl derivatives can sometimes be highly cytotoxic.  

Thanks to their tt electron clouds and to their small volume, ethynyl groups can sometimes function as bioisos-teres of aromatic rings and give similar donor-acceptor interactions. 

FIGURE 20.25 Acetylenic groups as aromatic ring equivalents. 

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Alkyne ( Acetylene Series). A group of unsaturated aliphatic hydrocarbons of the general formula C, contg triple bonds. 

ACETYLENE SERIES. A senes of unsalurated hydrocarbons having the general formula and containing a triple bond between two... 

The Acetylene Series. Acetylene, which has the structural formula H—C=C—H, is the first member of a homologous series of hydrocarbons containing triple bonds. Aside from acetylene, these sub stances have not found wide use, except for the manufacture of other chemicals. 

A third series of unsaturated hydrocarbons of considerable importance is the acetylene series. These compounds have a triple bond. The first member of this series has the structure shown here, and is... 

What are the general fonnulaa for following hydrocarbon series (a) parafim series, (b) olefin eeries, (c) diolefin series, (d) acetylene series, (e) naphthene series, (f) eyolopamfSn series, g) aromatic series. 

The reaction with acetylene is probably general for the acetylene series. The main reaction appears to be the sulfur atom-initiated polymerization of the substrate. 

Alkyn s( Acetylene Series). A group of unsaturated aliphatic hydrocarbons of the general formula C Jljn.2, contg triple bonds. These compds were also called Alkines ALL (Propel I ant) is described in conf "Propellant Manual," SPIA/M2, Johns Hopkins Univ, Silver Spring, M aryl an d( 1959), Unit No 406... 

Interaction of Hydrocarbons of tJie Acetylene Series with Arsenic... 

Isoprene.—Isomeric with the acetylene series of hydrocarbons are those which contain not one but Hwo sets of doubly linked carbon atoms. As each additional bond between carbons means the loss of two hydrogen atoms, then two double bonds and one triple bond will be equivalent and will represent a loss of four hydrogen atoms from the saturated hydrocarbon. Therefore the general formula is C H2n-2. Hydrocarbons containing two pairs of doubly linked carbons or ethylene groups are termed di-ethylenes or di-enes. The only compound to be mentioned contains five carbons, and is known as isoprene, CsHs. Its constitution has been established as a four carbon chain with a substituting methyl linked to carbon 2 and with double bonds at carbons I and 3, as follows ... 

Propargyl Alcohol.—Only one alcohol of this series will be considered. The simplest primary alcohol possible derived from hydrocarbons of the acetylene series is the one derived from allylene, CH = C—CH3, methyl acetylene. 

It is best to speak at this time of hydrocarbons derived from benzene by the substitution in the ring of unsaiurated open chain radicals. Just as the homologues of benzene are prepared by substitution of a saturated paraffin radical, methyl, ethyl, propyl, etc., in the benzene ring, so other series of hydrocarbons have been obtained by substituting radicals of the unsaturated open chain hydrocarbons of the ethylene and acetylene series. These new compounds will be poorer in hydrogen than the benzene series by two and four atoms respectively. 

C. Acetylenic series VI. EFFECTS OF THIOLS A. To increase lipophilicity... 

With regard to their classification, we will distinguish four series of unsaturated derivatives the vinyl series, the allyl series, the acetylenic series, and the ring-unsaturated derivatives that are bioisosteric to aromatic rings. 

To gain insight into the specific interactions between double bonds and water, compare the results from the acetylenic series, where triple bond—water interactions are more likely (5), with the results from the ethylenic series. The view that water—triple bond interactions are sig-... 

These radicals are unknown in the separate state, unless they are identical with the dyad radicals of the acetylene series... 

A number of hydrocarbons are known which are isomeric with members of the acetylene series, but do not contain a triple bond. They contain four less hydrogen atoms than the saturated hydrocarbon with the same number of carbon atoms. A study of the reactions of these hydrocarbons has shown that the property of unsaturation which they possess is produced as the result of the presence of two double bonds. Allene, which is isomeric with allylene, has the structure represented by the formula H2C = C = CH2. The hydrocarbons of this series are called diolefines on account of the fact that they contain two double bonds. Allene is sometimes called propadiene. The first two syllables indicate that the compound contains three carbon atoms (from propane CaHs) the termination diene indicates the presence of two double bonds in the compound. Other compounds are named in a similar way. The methods of preparation and reactions of the members of this series are analogous to those of the hydrocarbons of the ethylene series. 

Propargyl Alcohol, HC = C.CH20H, is an illustration of an alcohol derived from a hydrocarbon of the acetylene series. The compound is a colorless liquid of peculiar odor, which dissolves in water. It boils at 115°. It can be prepared by methods which involve the principles made use of in the preparation of alcohols and of triple-bonded compounds. One method is illustrated by the following formulas —... 

The halogen substitution-products of the hydrocarbons of the acetylene series resemble those derived from hydrocarbons which contain a double bond. The derivatives of acetylene are very unstable. Chloroacetylene is a gas which decomposes instantaneously, with explosion. The substitution-products which contain the =CH group form precipitates with ammoni-acal solutions of silver and cuprous salts. 

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