Addition to carbon

Carbon forms a number of oxides in addition to carbon monoxide and dioxide but they are beyond the scope of this book. 

In addition to carbon and glass fibers ia composites, aramid and polyimide fibers are also used ia conjunction with epoxy resias. Safety requirements by the U.S. Federal Aeronautics Administration (FAA) have led to the development of flame- and heat-resistant seals and stmctural components ia civiUan aircraft cabias. Wool blend fabrics containing aramids, poly(phenylene sulfide), EDF, and other inherently flame-resistant fibers and fabrics containing only these highly heat- and flame-resistant fibers are the types most frequently used ia these appHcations. 

Radicals are employed widely in the polymer industry, where their chain-propagating behavior transforms vinyl monomers into polymers and copolymers. The mechanism of addition polymeri2ation involves all three types of reactions discussed above, ie, initiation, propagation by addition to carbon—carbon double bonds, and termination ... 

Residual Elements. In addition to carbon, manganese, phosphoms, sulfur, and silicon which are always present, carbon steels may contain small amounts of hydrogen, oxygen, or nitrogen, introduced during the steelmaking process nickel, copper, molybdenum, chromium, and tin, which may be present in the scrap and aluminum, titanium, vanadium, or zirconium, which may have been introduced during deoxidation. 

Fixed carbon, the residue left after the volatile matter is driven off, is calculated by subtrac ting from 100 the percentages of moisture, volatile matter, and ash of the proximate analysis. In addition to carbon, it may contain several tenths of a percent of hydrogen and oxygen, 0.4 to 1.0 percent nitrogen, and about half of the sulfur that was in the coal. 

The time necessary for completion of the reaction may vary from 0.5 to 4 hours, depending on the actual activity of the alumina. The progress of conversion should be monitored by infrared analysis of a concentrated sample of the solution. Stirring should be continued for 15 minutes after the nitroso band at 1540 cm. has disappeared. A strong diazo band at about 2100 cm. will then be present. The carbonyl band at 1750 cm. initially due to nitrosocarbamate, will usually not disappear completely during the reaction, because some diethyl carbonate is formed in addition to carbon dioxide and ethanol. Diethyl carbonate is removed during the work-up procedure. 

In addition to carbon monoxide (CO) and unbumed hydrocarbons (UHC), the most significant products of combustion are the oxides of nitrogen (NOx). At high temperatures, free oxygen not consumed during combustion reacts with nitrogen to form NO and NO2 (about 90% and lO /i of total NOx, respectively). 

Tnfluoromethyldiazomethane behaves as atypical diazoalkane in its additions to carbon-carbon multiple bonds [9] For example, its reactions with ethylene and... 

In addition to carbon, all coals contains many noncombustible mineral impurities. The residue from these minerals after coal has been burned is called ash. Average ash content of the entire thickness of a coal seam typically ranges from 2 to 3 percent, even for very pure bituminous coals, and 10 percent or... 

Unlike carbocyclic (or homocyclic) hydrocarbons which have been discussed previously, heterocyclic compounds contain in their rings other atoms, such as nitrogen, oxygen, or sulfur, in addition to carbon. Some examples are shown below ... 

In addition to carbonates and/or phosphates, a variety of substances have also been used to act as sludge conditioners —e.g. starches, lignins, polyacrylates etc. Other substances, such as nitrites and sulphates are claimed to have some value in the suppression of caustic cracking (see Section 5.1). 

Figure 7.9 Pathway for the biosynthesis of prostaglandins from arachidonic acid. Steps 2 and 5 are radical addition reactions to 02 steps 3 and 4 are radical additions to carbon-carbon double bonds.

Ester enolates which contain the chiral information in the acid moiety have been widely used in alkylations (see Section D.1.1.1,3.) as well as in additions to carbon-nitrogen double bonds (sec Section D.1.4.2.). Below are examples of the reaction of this type of enolate with aldehydes720. The (Z)-enolate generated from benzyl cinnamate (benzyl 3-phenylpropcnoate) and lithium (dimethylphenylsilyl)cuprate affords the /h/-carboxylic acid on addition to acetaldehyde and subsequent hydrogenolysis, The diastereoselectivity is 90 10. 

A clear demonstration of the relative importance of steric and resonance factors in radical additions to carbon-carbon double bonds can be found by considering the effect of (non-polar) substituents on the rate of attack of (nonpolar) radicals. Substituents on the double bond strongly retard addition at the substituted carbon while leaving the rate of addition to the other end essentially unaffected (for example, Table 1.3). This is in keeping with expectation if steric factors determine the regiospeeificity of addition, but contrary to expectation if resonance factors are dominant. 

A stereoelectronic requirement in radical addition to carbon-carbon double bonds first became apparent from studies on radical cyelization and the reverse (Fragmentation) reactions.54 56 It provides a rationalization for the preferential formation of the less thermodynamically stable exo-product (i.e. head addition) from the cyelization of to-alkcny] radicals (16 - Scheme 1.5). s 57 G4... 

Additions to carbon-carbon double bonds have already been mentioned. Carbenes also add to aromatic systems, but the immediate products rearrange. 

In Part 2 of this book, we shall be directly concerned with organic reactions and their mechanisms. The reactions have been classified into 10 chapters, based primarily on reaction type substitutions, additions to multiple bonds, eliminations, rearrangements, and oxidation-reduction reactions. Five chapters are devoted to substitutions these are classified on the basis of mechanism as well as substrate. Chapters 10 and 13 include nucleophilic substitutions at aliphatic and aromatic substrates, respectively, Chapters 12 and 11 deal with electrophilic substitutions at aliphatic and aromatic substrates, respectively. All free-radical substitutions are discussed in Chapter 14. Additions to multiple bonds are classified not according to mechanism, but according to the type of multiple bond. Additions to carbon-carbon multiple bonds are dealt with in Chapter 15 additions to other multiple bonds in Chapter 16. One chapter is devoted to each of the three remaining reaction types Chapter 17, eliminations Chapter 18, rearrangements Chapter 19, oxidation-reduction reactions. This last chapter covers only those oxidation-reduction reactions that could not be conveniently treated in any of the other categories (except for oxidative eliminations). 

Protonation of the enolate ion is chiefly at the oxygen, which is more negative than the carbon, but this produces the enol, which tautomerizes. So, although the net result of the reaction is addition to a carbon-carbon double bond, the mechanism is 1,4 nucleophilic addition to the C=C—C=0 (or similar) system and is thus very similar to the mechanism of addition to carbon-oxygen double and similar bonds (see Chapter 16). When Z is CN or a C=0 group, it is also possible for Y to attack at this carbon, and this reaction sometimes competes. When it happens, it is called 1,2 addition. 1,4 Addition to these substrates is also known as conjugate addition. The Y ion almost never attacks at the 3 position, since the resulting carbanion would have no resonance stabilization " ... 

ADDITION TO CARBON-CARBON MULTIPLE BONDS unstabilized by resonance ... 

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