Nucleophilic reactant

What about solvent Do solvents have the same effect in S>g 1 reactions that they have in S j2 reactions The answer is both yes and no. Yes, solvents have a large effect on S l reactions, but no, the reasons for the effects on S jl and SN2 reactions are not the same. Solvent effects in the SN2 reaction are due largely to stabilization or destabilization of the nucleophile reactant. Solvent effects in the Sjsjl reaction, however, are due largely to stabilization or destabilization of the transition state. 

Much more important than these reactions, however, are the reactions of CDI and its analogues with carboxylic acids, leading to AAacylazoles, from which (by acyl transfer) esters, amides, peptides, hydrazides, hydroxamic acids, as well as anhydrides and various C-acylation products may be obtained. The potential of these and other reactions will be shown in the following chapters. In most of these reactions it is not necessary to isolate the intermediate AAacylazoles. Instead, in the normal procedure the appropriate nucleophile reactant (an alcohol in the ester synthesis, or an amino acid in the peptide synthesis) is added to a solution of an AAacylimidazole, formed by reaction of a carboxylic acid with CDI. Thus, CDI and its analogues offer an especially convenient vehicle for activation of... 

It might seem that the Vs,min and Vs,max on a suitable molecular surface should indicate sites susceptible to electrophilic and nucleophilic reactants, respectively. Such reasoning has had some success in the past [3,14,16,17], but it is not reliable. For example, shown in Figure 17.2 is the electrostatic potential on a surface of anisole (methoxybenzene), 1, which is well known to undergo electrophilic attack at the ortho and para positions. 

The carbon nucleophiles in amine-catalyzed reaction conditions are usually rather acidic compounds containing two electron-attracting substituents. Malonic esters, cyanoacetic esters, and cyanoacetamide are examples of compounds which undergo condensation reactions under Knoevenagel conditions.115 Nitroalkanes are also effective nucleophilic reactants. The single nitro group sufficiently activates the a hydrogens to permit deprotonation under the weakly basic conditions. Usually, the product that is isolated is... 

The inverting P-glucanases also have two catalytic acid base groups but they are 0. 9-1.0 nm apart rather than 0.6 nm for retaining enzymes. This allows space for a water molecule whose OH is the nucleophilic reactant (-OY in Eq. 12-5) and in which a carboxylate group assists in dissociating the water molecule.98 (This mechanism is illustrated for glucoamylase in Fig. 12-7). 

Most C,H-acidic compounds can be condensed with aldehydes or ketones to yield alkenes. Some of these reactions have also been realized on insoluble supports, with either the C,H-acidic (nucleophilic) reactant or the electrophilic reactant linked to the support. Some illustrative examples are listed in Table 5.6. Polystyrene-bound malonic esters or amides, cyanoacetamides, nitroacetic ester [95], and 3-oxo esters undergo Knoevenagel condensation with aromatic or aliphatic aldehydes. Catalytic amounts of piperidine and heating are generally required, although reactive substrates can react at room temperature. 

Most transition metal-catalyzed cross-coupling reactions also yield small quantities of the product of homocoupling of the nucleophilic reactant[16, 114,115]. In particular terminal alkynes [116, 117] or metalated terminal alkynes [118] readily dimerize to the corresponding 1,3-butadiynes (Scheme8.14). 

Acid-catalyzed reactions of the systems under discussion with nucleophilic reactants will be.dealt with in Section 4.33.3.3. 

Hexafluoroacetone is not known to polymerize by a free radical mechanism, however, it reacts readily with nucleophilic reactants and can form copolymers via nucleophilic intermediates (13). Many of its derivatives create surfaces with low critical surface tensions ( ). It was theorized that in a mild glow discharge reaction, the carbonyl group could be activated and the C3FgO group might... 

Pyrones can in principle add nucleophilic reactants at either C-2 (carbonyl carbon), C-4 or C-6 their reactions with cyanide anion," and ammonia/amines are examples of the latter, whereas the addition of Grignard nucleophiles occurs at carbonyl carbon. 

Where the catalyst is less nucleophilic, e.g. potassium fluoride or solid caesium fluoride, only one fluoride ion is likely to coordinate at all firmly to the silane. The nucleophilic reactant will then also be able to coordinate to the electrophilic silicon atom, itself receiving further activation in the process, and reaction ensues by intramolecular transfer about the hexacoordinate silicon atom as demonstrated in the GTP process. Less nucleophilic substrates such as alkyl halides are unreactive in these circumstances. 

Cyanuric chloride can be considered as a trimeric imide chloride, the chlorine atoms of which can easily be substituted by nucleophilic reactants, such as e.g. alcohols, phenols, mercaptans, thiophenols and amines. 

The possibility of rearrangement must be borne in mind particularly when considering reactions of allylic compounds. Substitution of SN1 type, which dominates in polar solvents, always leads to mixtures of isomeric rearrangement products bimolecular substitution occurs without rearrangement. Thus choice of strongly nucleophilic reactants and, particularly, repression of SN1 reaction by selection of an apolar solvent such as acetone permit reactions of allylic compounds to be undertaken without rearrangement.13... 

Besides the typical (normal) PTC reactions involving nucleophilic reactant anions and cationic catalyst, it is reasonable to believe that the PTC technique can be applied to reactions involving electrophilic reactant cations such as aryldiazonium and carbonium cations and anionic catalysts. In such reversed phase transfer catalysis (RPTC), a cationic reactant in the aqueous phase is continuously transferred into the organic phase in the form of a lipophilic ion pair with a lipophilic, non-nucleophilic anionic catalyst, and reacts with the second reactant in the organic phase. 

Since the rate of reductive nitrosylation was shown to be controlled by the electrophihcity of the coordinated NO, as well as the chemical nature of the nucleophilic reactant (N02, HONO or HO ), systematic temperature and pressure studies on the nitrite-catalyzed reduction of ferric nitrosyl porphyrin complexes (see Equation 11) as a function of pH, nitrite concentration, and nature of the porphyrin substituents were performed (118,119). 

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