Substitution and addition reactions

From Soper and Smith (1926). Reprinted by permission of the Royal Society of Chemistry (U.K.). 

Other 4-substituted phenols also reacted with HOCl to give ipso cyclohex-adienones, either as stable compounds or as intermediates in the displacement of side chains by chlorine (Dence and Sarkanen, 1960 Larson and Rockwell, 1979). For example, /7-hydroxybenzoic acid reacted rapidly with HOCl at environmentally realistic concentrations to give a mixture of substitution and decarboxylation products (Larson and Rockwell, 1979). It is plausible that such decarboxylation and side-chain cleavage products are at least partially responsible for the occurrence of chlorinated phenol derivatives in drinking water and in paper pulp bleaching effluents. 

Dimeric products have been observed in some studies of the chlorination of phenol. On the basis of chromatographic and spectroscopic considerations, these compounds have been tentatively identified as diphenyl ethers with 2 to 5 chlorine 

As in atmospheric chemistry. Cl- and CIO- could be important chain-carrying or -initiating radicals. 

Another possibility for the formation of free radical species from hypochlorite is through its reactions with transition metal ions. Thus, Guilmet and Meunier (1980) reported a manganese-promoted epoxidation of olefins such as styrene (Equation 5.13) and cyclohexene in a two-phase dichloromethane-water solvent mixture. The epoxide oxygen was derived from HOCl, not from air, but no mechanistic details were speculated upon. Further evidence needs to be obtained on the possibility of free-radical reactions in water and wastewater chlorination. 

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Other reactions taking place throughout the hardening period are substitution and addition reactions (29). Ferrite and sulfoferrite analogues of calcium monosulfoaluminate and ettringite form soHd solutions in which iron oxide substitutes continuously for the alumina. Reactions with the calcium sihcate hydrate result in the formation of additional substituted C—S—H gel at the expense of the crystalline aluminate, sulfate, and ferrite hydrate phases. 

Elimination, Substitution, and Addition Reactions Resulting in Carbon-Carbon Bond Formation... 

Thus, in spite of its lack of reactivity, iodine reacts chemically with unsaturated compounds, whereby the silica gel of the TLC layer can sometimes be assigned a catalytic role [11, 12]. Irreversible oxidations and electrophilic substitution and addition reactions have been observed on the interaction of iodine with tertiary nitrogen compounds such reactions possibly depend on particular steric relationships or are favored by particular functional groups [13, 14]. 

The gain in stabilisation in going from (2) — (4) helps to provide the energy required to break the strong C—H bond that expulsion of H necessitates in the reaction of, for example, HC1 with alkenes (p. 184) there is no such factor promoting substitution and addition reactions are therefore the rule. 

Thus the carbanion owe their importance in the synthesis of great variety of bond-forming reactions. Unlike carbocations most carbanions do not undergo rearrangements but in many cases react in substitution and addition reactions in high yields. Changing the cation and solvent can greatly affect the reaction. 

Free halogens are generally inconvenient to use, owing to their toxic and corrosive nature, but can be replaced by quaternary ammonium polyhalides. Quaternary ammonium tribromides are well established [e.g. 1] as solid, readily handled and relatively non-toxic alternatives for electrophilic bromine. More recently, other quaternary ammonium polyhalides have been produced, which together with the tribromides, have wide application as catalysts or in stoichiometric quantities in electrophilic substitution and addition reactions, oxidations, etc. 

Electrogenerated radical ions nicely supplement the methodology of chemical synthesis, whose reactions are less suited to generate and use radical ions, but rather apply polar substitution and addition reactions. 

Oxazoline-directed aromatic substitution and addition reactions provide synthetic chemists with powerful tools for the construction of complex aromatic compounds. Since the last authoritative review by Meyers, these technologies have matured and found widespread applications in organic synthesis. While there has been somewhat limited methodological research in this area in the intervening years, one particularly exciting new development is the diastereoselective ortho-metalations directed by chiral oxazolines. Sections 8.3.9.1-8.3.9.3 will discuss these new developments as well as new synthetic applications of these reactions. 

The carbon-carbon double bond is the distinguishing feature of the butylenes and, as such, controls their chemistry The carbon-carbon bond, acting as a substitute, affects the reactivity of the carbon atoms at the alpha positions through the formation of the allylic resonance structure. This structure can stabilize both positive and negative charges. Thus allylic carbons are more reactive to substitution and addition reactions than alkane carbons. Therefore, reactions of butylenes can be divided into two broad categories (J) those that take place at the double bond itself, destroying the double bond and ( 2 > those that take place at alpha carbons. 

Although naphthalene, phenanthrene, and anthracene resemble benzene in many respects, they are more reactive than benzene in both substitution and addition reactions. This increased reactivity is expected on theoretical grounds because quantum-mechanical calculations show that the net loss in stabilization energy for the first step in electrophilic substitution or addition decreases progressively from benzene to anthracene therefore the reactivity in substitution and addition reactions should increase from benzene to anthracene. 

Heterocyclization of two-carbon one-heteroatom synthon with two-carbon two-heteroatom synthon is the most common approach to the synthesis of monocyclic and fused seven-membered heterocycles with 1,3,5-heteroatoms. These reactions can be further subdivided to substitution and addition reactions. 

Miller, W. T. Fried, J. H. Goldwhite, H. Substitution and addition reactions of the fluoroo-lefins. IV. Reactions of fluoride ion with fluor-oolefins./. Am. Chem. Soc. 1960, 82, 3091-3099. 

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