Nucleophiles and displacement

Then a bromide ion acts as a nucleophile and displaces HOPBr2. 

Oxime reactivators (R-CH N0H) are weak acids that partly Ionize at biologic pH. This property allows them to function as nucleophiles and displace organophosphate moieties from inhibited acetylcholinesterase. It also makes them vulnerable to decomposition by other mechanisms in the body. 

The reaction proceeds to form the alkyl p-toluenesulfonate as expected, but the chloride anion formed in this step subsequently acts as a nucleophile and displaces p-toluenesulfonate from RCH2OTs. 

Step 5 is a nucleophilic substitution of the SN2 type. Acetate ion is the nucleophile and displaces bromide from the primary carbon. 

Water acts as a nucleophile and displaces the OR leaving group from silicon the most common case is the synthesis of silica by hydrolytic polycondensation of tetraalkoxysi-lanes as shown in equations 1, 2 and 3. The condensation leading to Si—O—Si bonds apparently occurs by hydrolysis, hetero-condensation and homo-condensation3 4. Interest in silicon is also based on the fact that very useful and common materials like silicates... 

Cyanide ion is a good small nucleophile and displaces tosylate from primary carbon atoms and adds one carbon atom Lo the chain. As the cyanide (nitrile) group can be converted directly to a carboxylic acid or ester (Chapter 14) this sequence is a useful chain extension. 

Table 1. Anionic Metal Complexes" That Serve as Nucleophiles and Displace Halide Ion from Alkyl or Acyl Halides ...

The reaction with dimethyl sulfoxide provides a useful method of oxidizing an alkyl halide to a ketone. Thiols are powerful nucleophiles and displace alkyl halides. 

Now for the organometallk bit. As described in the chapter (p. 1318) the ferrate anion is ver nucleophilic and displaces the tosylate from the primary carbon. Carbonyl insertion gives an ire acyl complex and the neutral iron atom forms a it-complex with the alkene. The carbonyl transferred to the far end of the alkene as six-membered rings are preferred to five-membered ore and protonation of the C-Fe bond completes the reaction. 

For simple triorganotin halides it has been established that the rate of the inversion process is accelerated if external nucleophiles, e.g., pyridine, are present (123). Based on the fact that the inversion process is second order in nucleophile, two possible mechanisms have been proposed (i) addition of a nucleophile to the metal center, followed by addition of a second nucleophile and displacement of the halogen atom giving the achiral transition state (A) (see Fig. 23) or (ii) addition of two nucleophiles without loss of the halogen atom to give the achiral transition state (B), Fig. 23 (123). 

Proton transfer (acid-base) reactions are much faster than almost any other reaction. Methoxide will act as a base and remove a proton from the oxygen much faster than methoxide will act as a nucleophile and displace water.. ... 

Alkylation involves treating ammonia or an amine with an alkyl halide. The amine, as a Lewis base with a non-bonding electron pair, is a good nucleophile and displaces the halide ion from the alkyl halide the reaction is nucleophilic substitution with a neutral nucleophile. SN2 reactions are common. Since alkylation tends to continue until four groups are bonded to the nitrogen, it has limited synthetic utility. 

The chemical properties of isopentenyl pyrophosphate and dimethylallyl pyrophosphate are complementary in a way that permits them to react with each other to form a carbon-carbon bond that unites two isoprene units. Using the tt electrons of its double bond, isopentenyl pyrophosphate acts as a nucleophile and displaces pyrophosphate from dimethylallyl pyrophosphate. 

First hydroxide ion removes the proton from the hydroxy group. Then the negative oxygen acts as a nucleophile and displaces the Cl. Because this step is an intramolecular 8, 2 reaction, the oxygen nucleophile must approach from the side opposite the leaving Cl. This can occur readily in the case of the trans-isomer but is impossible in the case of the cis-isomer. 

Introduction of the oxygen atom presumably occurred through reaction with dimethyl sulfoxide acting as a nucleophile and displacing a chlorine in 16. A mechanistic rationale involving such an attack was proposed and is outlined in Scheme 7 <2000J(P1)1081>. 

The alkynide anion acts as a nucleophile and displaces the halide ion from the primary alkyl halide. We now recognize this as an 5 2 reaction (Section 6.5). 

The steps in a Merrifield synthesis are summarized for a dipeptide in Figure 17.7. In step 1, the polymer is first treated with an N-protected amino acid. The carboxylate ion acts as an oxygen nucleophile and displaces the chloride ion from the polymer, thus forming an ester link. The first amino acid attached to the polymer will eventually become the C-terminal amino acid of the synthetic peptide. 

Substitution reactions, analogous to an S].j2 substitution in solution, occur more frequently in the gas phase because of poor solvation and low activation energy. Many aromatics give a peak at (M -I-15) , which can be attributed to substitution of H by an 0 radical. Substitution reactions are also known for fluorides and chlorides. Fluoride is the stronger nucleophile and displaces chloride from alkyl halides. 

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