Ethylene bonds, saturation

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

OM-DM reaction of ewdo-tricyclo[5.2.2.02,6]undeca-3,8-diene (194) was found166 to proceed with high regio- and stereoselectivity, giving mainly 4-ew-hydroxy-encfo-tricyclo [5.2.2.02,6]undec-8-ene (195) together with 196 (equation 164). Saturation of the 8,9-ethylenic bond in 194 resulted in a large reduction in reactivity as well as in stereoselectivity. 

Q , 8-Ethylenic sulfones exhibit a behavior that could be considered as specific and totally different from that of Q , 8-ethylenic ketones or nitriles. Thus, with the present series, there is practically no case of dimerization or double-bond saturation. This seems to be because of the fact that reduction of compounds of this series cannot be completed neither in acidic nor in aqueous solutions because a fast cleavage occurs at the level of the anion radical. 

One of the celebrated successes of orbital hybridization is the elucidation of multiple bonding, which stems from the Lewis formulation of a chemical bond as a shared electron pair. In a compound such as ethylene the saturation of the carbon valence shells can only be achieved by the sharing of two electron pairs between the two carbon atoms. 

Reductions of a)S-unsaturated oxo-compounds with sodium borohydride may be complicated by saturation of the ethylenic bond, and by base-catalysed conjugate addition of alkoxide to give a 1,3-diol monoether. The factors controlling these reactions have been studied for a variety of aliphatic compounds, and the findings may prove useful in steroid chemistry. ... 

Other complex metal hydrides can only rarely be applied to reduction of C=C bonds. Sodium borohydride, which can be used in aqueous-alcoholic solution, seems not normally to attack ethylenic bonds. A few cases only of partial reduction of cyclic iminum salts96 and of selective reduction of unusually activated ethylenic bonds97 have been reported. However, some polynitro aromatic compounds, e.g., 1,3,5-trinitrobenzene, can be converted in high yield with saturation of the aromatic system into nitrocyclohexanes or nitro-cyclohexenes.98 Sodium hydridotrimethoxyborate has proved valuable as a mild reducing agent for preparation of a series of nitroparaffins from nitro-alkenes."... 

Similarly electrocatalytic hydrogenation of acetylenic compounds on Pt, Pd, Ni, and Co cathodes does not, in general, halt at the ethylenic stage and a mixture of the ethylenic and saturated compounds results.However acetylenic and ethylenic bonds are hydrogenated at different rates and potentials and selective reduction may be achieved. Selective reduction of acetylenic compounds to ethylenic compounds has been achieved on cathodes of Cu, Ag, and alloys of Cu-Ag ° with low current densities (0.01-0.02 A cm ) in order to maintain a potential of around — 1.2 to — 1,4 V. 

It is probable that our ancestors of several million years ago developed the characteristics leading to our modem biochemistry by eating animal fats (Crawford and Marsh, 1989 Sinclair and O Dea, 1990 O Dea, 1991). At first glance this should simplify discussion of animal fats, as shown by the basic fatty acids of Table 10.1. A popular shorthand notation is used to indicate the stmctures of common fatty acids. In the format x yn-z, x is the chain length or number of carbons in the chain, y is the number of methylene-interrupted cis ethylenic bonds and z is the inclusive number of carbon atoms from the terminal methyl group to the center of the nearest bond. As few as six fatty acids appear to adequately describe animal depot fats. Those fats listed are dominated by two fatty acids, 16 0 (palmitic) and 18 1 (oleic) add. Although tropical seed oils may be rich in C12-C18 saturated fatty adds (Elson, 1992), temperate oilseeds are rich in oleic acid and tend to include quantities of two fatty acids more unsaturated than oleic, especially 18 2n-6 (linoleic), and sometimes 18 3n-3 (linolenic). Even the original rapeseed (Brassica sp.) oil, with up to 50% of 22 ln-9 (emdc) acid usually had approximately 20% 18 2/1-6 and 10% 18 3/i-3 adds (Ackman 1983, 1990). 

These radicals add, in turn, to the double bond of an ethylene molecule to produce a carbon-centered monomer radical. The double bond becomes a single bond (saturated) and a new radical species is formed. 

Chlorine reacts with saturated hydrocarbons either by substitution or by addition to form chlorinated hydrocarbons and HCl. Thus methanol or methane is chlorinated to produce CH Cl, which can be further chlorinated to form methylene chloride, chloroform, and carbon tetrachloride. Reaction of CI2 with unsaturated hydrocarbons results in the destmction of the double or triple bond. This is a very important reaction during the production of ethylene dichloride, which is an intermediate in the manufacture of vinyl chloride ... 

The ethylene addition product is saturated, that of benzene, on the other hand, is more unsaturated than is benzene itself, since the symmetrical cancelling of residual valency (Thiele) is upset and the aromatic character is destroyed. In order to re-establish this character it is only necessary for hydrogen bromide to be eliminated, which takes place with liberation of energy. The elimination occurs with extraordinary speed, even before the other double bonds, which have become reactive, have time to take up bromine. 

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