Electrophilic agents

Among the most common and synthetically-usef electrophiles are nitronium and acyl cations, NO2+ at CH3CO+, respectively. The former is the active agent electrophilic nitration while the latter is the active reage in Friedel-Crafts acylation. 

Fluorinated olefins, 77 866 Fluorinated organics, production of, 77 847 Fluorinated polyimides, 20 278 Fluorinated thermoplastics, 10 8 Fluorinated titanocycle, 25 118 Fluorinating agents, electrophilic, 77 847 Fluorination, 9 281, 678-679 aromatic ring, 77 866 chlorocarbons, 6 235 direct, 77 864, 882 electrochemical, 77 864—865, 882 of germanium, 72 552 halogen exchange, 77 861-864 selective, 77 831... 

Thiourea is known to behave as a C nucleophile at its sulfur atom toward an alkylating cigent to yield thiuronium salt. From the similarity in the resonance structures between thiourea and diaminocyclopropenethione (79). as shown in Fig. 5, it might be expected that diaminocyclopropenethione when allowed to react with an alkylating agent (electrophile) wiU afford the diaminoalkylthiocyclopropenium ion (37). 

HVHjO Nucleophiles, bases, reducing agents Electrophiles, oxidising agents... 

In the course of my studies I also introduced silver tetrafluoroborate, AgBp4, as a metathetic cation forming agent suitable for forming varied ionic (electrophilic) reagents. 

The fact that nitration with acetyl nitrate is sometimes accompanied by acetoxylation has been mentioned ( 5.3.3). In proposing the ion pair ACONO2H+ NOg- as the nitrating agent, Fischer, Read and Vaughan also suggested that it was responsible for the acetoxylation, which was regarded as an electrophilic substitution. 

Quaternarj salts are obtained by alkylation of selenazole bases, the heterocyclic nitrogen atom playing the role of nucleophile with regard to the electrophilic carbon of the alkylating, agent. 

Reduction of arenes by catalytic hydrogenation was described m Section 114 A dif ferent method using Group I metals as reducing agents which gives 1 4 cyclohexadiene derivatives will be presented m Section 1111 Electrophilic aromatic substitution is the most important reaction type exhibited by benzene and its derivatives and constitutes the entire subject matter of Chapter 12... 

Alkyl halides by themselves are insufficiently electrophilic to react with benzene Aluminum chloride serves as a Lewis acid catalyst to enhance the electrophihcity of the alkylating agent With tertiary and secondary alkyl halides the addition of aluminum chlonde leads to the formation of carbocations which then attack the aromatic ring... 

Complex Formation. AH four Cg aromatic isomers have a strong tendency to form several different types of complexes. Complexes with electrophilic agents ate utilized in xylene separation. The formation of the HE-BF —MX complex is the basis of the Mitsubishi Gas—Chemical Company (MGCC) commercial process for MX recovery, discussed herein. Equimolar complexes of MX and HBr (mp — 77°C) and EB and HBr (mp — 103°C) have been reported (32,33). Similatly, HCl complexes undergo rapid formation and decomposition at —80°C (34). 

Whereas the above reactions are appHcable to activated aromatics, deactivated aromatics can be formylated by reaction with hexamethylenetetramine in strong acids such as 75% polyphosphoric acid, methanesulfonic acid, or trifluoroacetic acid to give saUcylaldehyde derivatives (117). Formyl fluoride (HCOF) has also been used as formyl a ting agent in the Friedel-Crafts reaction of aromatics (118). Formyl fluoride [1493-02-3] in the presence of BF was found to be an efficient electrophilic formyl a ting agent, giving 53% para-, 43% ortho- and 3.5% meta-tolualdehydes upon formylation of toluene (110). 

Several electrophiles, such as acetic anhydride, nitric acid or alternative nitrating agents, such as ammonium nitrate in trifluoroacetic anhydride (41), or sodium hypochlorite, react at N-1, which is followed by reaction at N-3 under suitable conditions. In the case of acetic anhydride, the reaction can take place exclusively at N-3 if N-1 is hindered this fact has served as a criterion for studying the stereochemistry of 5-spirohydantoin derivatives (42,43). 

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