Unsaturated substances

Clemmensen reduction of aldehydes and ketones. Upon reducing aldehydes or ketones with amalgamated zinc and concentrated hydrochloric acid, the main products are the hydrocarbons (>C=0 —> >CHj), but variable quantities of the secondary alcohols (in the case of ketones) and unsaturated substances are also formed. Examples are ... 

Other Derivatives and Applications. Copolymerization of DCPD with other unsaturated substances has received wide attention, and several useful appHcations have been developed. With drying oils (qv) thermal copolymerization leads to the production of resinous products, the so-called bodied oils, that give improved drying and result in paint and varnish coatings of greater resistance to weathering. 

The treatment of unsaturated substances with halogen leads to addition to these molecules. This is true not only of bromine and chlorine vapor but also of the less reactive iodine. Substitution also occurs in the presence of light. Examples of such halogenations are listed in Table 12. Figure 32 illustrates the characterization of fluorescein in a bubble bath preparation. Bromination of the fluorescein in the start zone yields eosin. 

Hydrobrotnic acid converts dihydrocarvone into a hydrobromide, CioHjyOBr, which, when treated with cold alcoholic potash, readily loses hydrogen bromide. Instead, however, of the unsaturated substance, -dihydrocarvone, being regenerated as the result of this decomposition, a remarkable formation of a c /cZopropane ring takes place and carone is produced—... 

There have been numerous theoretical and experimental efforts to explain the mechanism by which ozone reacts with double bonds of unsaturated substances (11,12,35). Perhaps the more widely accepted reaction is the Criegee mechanism which produces the two groups A and B (as shown below) ( 36-42) ... 

Chlorinated butyl rubber. Chlorination or bromination of butyl rubber overcomes the difficulty of vulcanising butyl rubber in mixtures with more highly unsaturated substances due to the preferential absorption of the sulphur by the more highly unsaturated component. Chlorohydrin Rubbers... 

The third hypothesis (C) is that reaction takes place through an aldol condensation between the ethyl acetoacetate and the carbonyl form of the sugar. There is some precedent indicating that it is possible for /3-ketonic esters to undergo aldol condensation. These compounds react mole to mole with the aliphatic aldehydes and afford unsaturated substances, which could be formed via an aldol condensation with subsequent dehydration. 

The unstable per-acid, which like all per-acids is much weaker than the corresponding carboxylic acid, is taken up in chloroform after acidification of the solution of the sodium salt. The chloroform solution serves in the reaction with unsaturated substances which has already been formulated on p. 111. Ethylene itself does not give this reaction. 

This condensation is completely analogous to that of ethyl diazoacetate, mentioned on p. 281, and, in general, azides and aliphatic diazo-compounds are strikingly similar in the manner in which they react with unsaturated substances like acetylenes, olefine derivatives, and hydrogen cyanide to yield heterocyclic compounds. 

George P. Sakellaropoulos Solvent and Structure Effects in Hydrogenation of Unsaturated Substances on Solid Catalysts... 

The first rapid and practical system for the homogenous reduction of alkenes, alkynes and other unsaturated substances at 25° C and 1 atm pressure used the complex RhCl(PPh3)3 known as Wilkinson... 

A wide variety of unsaturated substance can be hydroformylated by cobalt or rhodium catalysts but conjugated alkenes (e.g., butadiene) may give a number of products including hydrogenated monoaldehydes. The mechanism is different, since addition of M H to dienes leads to alicyclic species which may be present as a-bonded intermediate or as h3allyls. 

Hydrido species such as HCo[P(OPh)3]3(MeCN) catalyze the homogeneous hydrogenation of unsaturated substances. In the crystal HCo(CO)2(PPh3)2 can adopt both sp and tbp structures.35 The ion [Co(bipy)3]+ reduces water to H2 and C02 to CO the complex can be generated photochemically from [Co(bipy)3]"+ precursors.36... 

The reaction of alkenes and other unsaturated substances with transition metal hydrido or alkyl complexes is of prime importance in catalytic reactions such as hydrogenation, hydroformylation, and polymerization (see Chapter 22). It is one of the major methods for synthesizing metal-to-carbon bonds. The reverse reaction, the /3-hydride or /3-alkyl transfer-alkene elimination reaction has already been discussed (Section 21-3). 

The development of the catalytic hydrogenation system based on RhCl(PPh3)3 and methods for the resolution of optical isomers of tertiary phosphines occurred around the same time (1965), and this led to the possibility of asymmetric catalytic hydrogenation of prochiral unsaturated substances with C=C, C=0, and C=N bonds using transition metal complexes with chiral phosphine ligands. Such tertiary phosphines are of three types ... 

The catalytic oxidations of alkanes, alkenes, and other substances are of enormous technological and biological importance. In addition to classical oxidations of unsaturated substances like alkenes and arenes there is an increasing number of systems capable of catalyzing the selective oxidation of saturated hydrocarbons. 

Berthollet reasoned that such an exchange of bases did not take place because the partition of acids and bases was in effect. When the exchange did occur, it was due not to the affinities in action, but to other real causes such as crystallization and precipitation. Chemists had inadvertently ascribed the strongest affinities to the substances that precipitated easily. Other causes, such as heat and efflorescence, also contributed to the outcome of complex affinities, as was the case for natron. In short, elective affinity involved an unsaturated substance, while complex affinities worked between saturated substances. The notion of elective affinity was tightly bound to the analytic procedure in which two acids, one combined in the salt and the other free, had to compete for the common base. 

A number of unsaturated substances, such as ketone, azobenzene, imine, a-diimine, carbodi-imide, nitrile, CO2, and so on can be reduced by divalent samarium complexes. For example, reaction of bi(methylcyclopentadienyl) samarium complex with carbodiimide generates, via reducing-coupling reaction, the first structurally characterized bimetallic oxalamidino complex (Figure 8.34) [114]. 

The majority of compounds that are subject to autoxidation are unsaturated substances or highly condensed polymers, and the target of ROS is commonly the diene fimctionality—or double bonds. Autoxidation of unsaturated lipids is a good model to demonstrate this mechanism. The initial reaction between molecular oxygen and a polyunsaturated fatty acid (PUFA) occurs as RH -l- O2 —> ROOH, which involves the movement of a double bond as well as the insertion... 

A recent publication from this laboratory (5) presented evidence in favor of a mechanism of ozonization of unsaturated substances differing somewhat from that previously proposed by Criegee and Werner (1). Inasmuch as the results of abnormal ozonization reactions (3, 8, 10,11) were used in partial support of Criegee s mechanism, it was thought advisable to reinvestigate some of these ozonizations from the recent point of view. 

In accordance with Criegee s mechanism as applied to abnormal ozonizations (4), an unsaturated substance which contains electron-donating groups attached to a carbon atom adjacent to a double bond will produce zwitterions which will rearrange in such a manner as to produce abnormal products. This can be illustrated by the following sequence of reactions, in which R contains an electron-donating atom attached to a carbon adjacent to the double bond ... 

It was pointed out by Robinson [86] that thebaine [cix] could be regarded as being derived from a laudanosine-type base by dehydration and coupling of the two aromatic nuclei in a way analogous to the polymerization of unsaturated substances, but that the orientation of the substituents in the hypothetical precursor [ox] is unusual. However, the positions of the substituents in sinomenine [i] is such that it could... 

The above type of addition has been used for the simple preparation, from alkenes and other unsaturated substances, of alcohols, ethers and amines— the additions of HgX2 are carried out in water, alcohols or acetonitrile, respectively. The mercury is removed from the intermediate by reduction with... 

It was later found that certain metal halides or ions other than Pt11, notably Cu1, Ag1, Hg11 and Pd11, formed complexes when treated with a variety of olefins. Thus cuprous chloride in aqueous suspension absorbs ethylene, both components dissolving well beyond their normal solubilities and in a 1 1 mole ratio. Solid cuprous halides also absorb some gaseous olefins, but the dissociation pressures of the complexes are quite high. The reaction of silver ions especially, with a variety of unsaturated substances, has been studied by physical measurements such as distribution equilibria between an aqueous and an organic solvent phase. The results can be accounted for in terms of equilibria of the type... 

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