97788-15-3Relevant academic research and scientific papers
Dynamic Covalent Chemistry of Nucleophilic Substitution Component Exchange of Quaternary Ammonium Salts
Kulchat, Sirinan,Lehn, Jean-Marie
, p. 2484 - 2496 (2015/11/02)
Dynamic covalent libraries (DCLs) of quaternary ammonium cations were set up by reversible nucleophilic substitution (SN2′ and SN2) exchange reactions of ammonium salts and tertiary amines. The reactions were conducted at 60 °C to generate thermodynamically and kinetically controlled mixtures of quaternary ammonium compounds and tertiary amines, and were accelerated by using iodide as a nucleophilic catalyst. Microwave irradiation was used to assist the exchange reaction between the pyridinium salts and pyridine derivatives. Finally, experiments towards the generation of dynamic ionic liquids were performed. The results of this study pave the way for the extension of dynamic combinatorial chemistry to nucleophilic substitution reactions.
NUCLEOPHILIC SUBSTITUTION REACTION OF BENZYL BROMIDE WITH N,N-DIMETHYLANILINE: SIGNIFICANCE OF EQUILIBRIUM CROSS-INTERACTION CONSTANT
Lee, Ikchoon,Park, Yong Kyun,Huh, Chul,Lee, Hai Whang
, p. 555 - 560 (2007/10/02)
Kinetic studies on the reversible reactions of benzyl bromides with N,N-dimethylanilines were carried out for both the forward (kf) and reverse (kr) directions.The equilibrium constants, K were calculated using the ratio kf//kr and the equilibrium cross-interaction constant, ρeXY was determined.The ρeXY value was shown to represent a maximum intensity of interactions between substituents X and Y through covalent bonds within a molecule.The normalized values of ρX (ρnuc) and ρXY indicate that in the transition state the fractional development or loss of polar and resonance interactions in the benzyl system are imbalanced or non-perfectly synchronized.In the forward reaction the fractional loss of resonance interaction becomes enhanced, whereas in the reverse reaction the fractional development of resonance interaction lags behind the corresponding changes of polar interaction by ca 45percent.
Rate-Equilibrium Relationships for Reactions of Families of Carbanion Nucleophiles with N-Benzyl-N,N-dimethylanilinium Cations and with Alkyl Chlorides, Bromides, and Iodides
Bordwell, Frederick G.,Hughes, David L.
, p. 7300 - 7309 (2007/10/02)
Rates of reaction of a family of 9-methylfluorenide anions, 9-MeFl-, with 15 substituted N-benzyl-N,N-dimethylanilinium cations, GC6H4CH2N(Me)2C6H4Y+, were measured in a 0.8 M KNO3 solution of Me2SO at 25 deg C.Substitution in the benzyl moiety produced a U-shaped Hammett plot, with m-CN reacting 9- to 15-fold faster than H and p-MeO reacting 1.5- to 3-fold faster than H, depending on the basicity of the 9-RFl- ion.Broensted ΒNu values obtained by varying nucleophile basicity in the 9-MeFl- ion family were 0.28 for N-(p-methoxybenzyl)-N,N-dimethylanilinium ion, 0.33 for N-benzyl-N,N-dimethylanilinium ion, and 0.39 for N-(m-cyanobenzyl)-N,N-dimethylanilinium ion.These βNu values were unaffected by substitution in the aniline portion of the substrate.Hammett pLg values were obtained by substitution of m-Cl, p-Br, H, p-Me and p-MeO groups (Y) in the dimethylaniline leaving group; pLg values were all near 2.0 and were insensitive to the basicity of the attacking nucleophile and the substituent G in the benzyl group of the substrate. βNu values for families of 9-RFl- ions reacting with ArCH2X, n-BuX, and CNCH2X also remained constant as the leaving group, X, was changed (Cl, Br, and I) for a given substrate and when the donor atom was changed along the series C-, N-, O-, and S-.These results indicate that there is no direct relationship between the size of βNu and the extent of bond making or bond breaking in the transition state for SN2 reactions, as has been generally assumed in theoretical attempts to rationalize the effects of structural variations on rate.It is suggested that SN2 reactions occur in two stages.The size of βNu is determined in the first stage where an ion-dipole complex is formed.The rate is determined largely in the second stage where bonds are formed and cleaved and where molecular and solvent reorganization occurs.
