Single-Substitution Reactions

When a free element reacts with a compound of different elements, the free element will replace one of the elements in the compound if the free element is more reactive than the elanent it replaces. A new compound and a new free element are produced during the algorithm, a compound and an element are selected and a decomposition reaction is applied to the compound two elanents are generated from this operation. Then, one of the new generated elements is combined with the non-decomposed selected element (C -I- AB AC + B). The pseudocode for the single-substitution reaction procedure is as follows  

a = selected elementsi, selected elementS2, , selected elementsi 

6 = selected elementsi+i, selected elementSi+2, , selected elementSa2 

Apply Synthesis Procedure (b + Decoi) Get Synthesisjvector Output SingleSubstitution jvector (Synthesisjvector, Deco2) 

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Can a single substitution reaction occur between an element and a compound of that same element ... 

Explain how to recognize that O2 and MgO will not react wifo each other In a single substitution reaction. 

Which table in this chapter should be used when working with single substitution reaction, and which ones with double substitution reactions ... 

To predict which single substitution reactions will occur, we need to know a little about the relative reactivities of some of the important metals and nonmetals. Some metals and a few nonmetals are listed in Table 8.2 in order of decreasing reactivity. A more complete list is given in Section 17.2. Hydrogen is included in the list of metals because it can be displaced from aqueous acids by reactive metals (Figure 8.5) and can displace less active metals from their compounds ... 

There is another common way to classify chemical reactions acid-base reactions, oxidation-reduction reactions, and reactions of more complicated types (beyond the scope of this book). Acid-base reactions are considered to involve the reactions of hydrogen ions with hydroxide ions. The reactions of acids and bases will be taken up in this section, and a more sophisticated view of these reactions is presented in Chapter 19. Oxidation-reduction reactions involve the transfer of electrons from one substance to another. Many combination reactions, many decomposition reactions, all single substitution reactions, and all combustion reactions are of this type, but more complex examples are presented in Chapters 16 and 17. 

In order for the 2-(trimethylsilyl)ethylthio unit to lose its protecting group upon treatment with the fluoride, the sulfur must be attached to an unsaturated carbon. Hence the fluoride mediated sulfur deprotection is feasible for 2-(trimethyl-silyl)ethylthio substituted (het)arenes, alkenes, alkynes, and acid derivatives such as carboxylic and selenothiophosphinic acid salts. In thiolate form, the substrates have value for the formation of self-assembled monolayers or as metal complexing agents. Simple addition of acid to the thiolate to give a stable thiol characterizes 2-(trimethylsilyl)ethanethiol as a simple M" (HS) equivalent that is only capable of a single substitution reaction. ... 

The product is a diacyl derivative of an amine. Thus, the lone pair electrons of nitrogen are so effectively delocalized that they cannot displace a halide even from a compound as reactive as allyl chloride. Thus, only a single substitution reaction occurs. 

C-Methylation products, o-nitrotoluene and p-nitrotoluene, were obtained when nitrobenzene was treated with dimethylsulfoxonium methylide (I)." The ratio for the ortho and para-methylation products was about 10-15 1 for the aromatic nucleophilic substitution reaction. The reaction appeared to proceed via the single-electron transfer (SET) mechanism according to ESR studies. 

Hie use of chiral catalysts as an approach to enantiomer icaliy enriched products by means of coppet-mediated substitution reactions is covered in this chapter. Reactions in which a chiral auxiliary resides in the leaving group of the substrate w ill also he dealt with, since these reactions provide direct and efBcient routes to single enantiomers of the desired products. Most studies so far have been concerned with allylic substrates, with a new chiral center being produced in the course of a selec-... 

Acidic ether cleavages are typical nucleophilic substitution reactions, either SN1 or Sn2 depending on the structure of the substrate. Ethers with only primary and secondary alkyl groups react by an S 2 mechanism, in which or Br attacks the protonated ether at the less hindered site. This usually results in a selective cleavage into a single alcohol and a single alkyl halide. For example, ethyl isopropyl ether yields exclusively isopropyl alcohol and iodoethane on cleavage by HI because nucleophilic attack by iodide ion occurs at the less hindered primary site rather than at the more hindered secondary site. 

The chemistry of all acid derivatives is similar and is dominated by a single reaction—the nucleophilic acyl substitution reaction that we saw briefly in A Preview ofC ubonyl Compowuls. 

It is regrettable that the evidence afforded by reaction kinetics is rarely, if ever, uniquely consistent with a single mechanism or a single explanation. The results for nucleophilic aromatic substitution reactions are no exception. Legitimate questions can be raised with respect to the extent to which observations made on a particular system permit generalization to other systems. Even for the specific systems studied points of detail arise, and choices have to be made where alternatives are possible. Every such choice introduces an element of uncertainty and imposes a limitation on the extent to which the reaction mechanism is, in fact, known. 

Substitution reactions where the nucleophilic group was a single free hydroxyl group of a saccharide, the other ones being protected, were also studied. The expected ether-amides or glycoside-amides were obtained from... 

When 35 was heated in acetic acid containing hydrogen bromide, the tribromide 46 was obtained as a single product in 74% yield. Debromina-tion of 46 with zinc dust in acetic acid furnished the cyclohexene derivative 47, which was converted into compound 48 by osmium tetraoxide hydroxyl-ation and acetylation. The substitution reaction of 48 with acetate ions provided carba-a-DL-glucopyranose pentaacetate (49), which gave the carba-sugar 50 on hydrolysis. ... 

Reaction of the same neutral borabenzene-ligand adduct, C5H5B-PMe3, with a transition, rather than an alkali, metal alkyl or amide can furnish r 6-boratabenzene complexes in a single step (Scheme 8).17 This efficient transformation presumably proceeds through initial ir-coordination of CsHsB-PMes to the transition metal, followedby an intramolecular substitution reaction. In contrast to other approaches to the synthesis of T 6-boratabenzene complexes, this synthetic route does not have a parallel in if-cyclopentadienyl chemistry. 

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