Menschutkin reactions

The kinetic aspects of the Sn2 quaternization (the Menschutkin reaction) have been covered by Zoltewicz and Deady (78AHC(22)72), the latter author having done most of the experimental work related to pyrazoles and indazoles. In C-unsubstituted methyl deriva-... 

Fig. 5.P23. The substituent effect in the Menschutkin reaction of 1-arylethyl bromides with pyridine in acetonitrile at 35°C. Circles represent kj for the bimolecular process and squares (for the uni-molecular process.

Table 8-S. Kinetic Data on the Menschutkin Reaction of Triethylamine and Ethyl Iodide at 25°C...

Table 8-5 gives data for the Menschutkin reaction of triethylamine and ethyl... 

Figure 8-3. Plot of free energy of activation for the Menschutkin reaction EtjN + EtI Et4N + 1 against the Kirkwood dielectric constant function. Data are from Table 8-5, where the solvents are identified.

Table 8-10 gives pertinent data for the Menschutkin reaction of triethylamine with ethyl iodide. These reactant molecules are volatile, so their transfer free energies were determined by a gas chromatographic variation of the vapor pressure method. For this reaction Eq. (8-57) is written... 

Figure 8-6. Ploi according to Fig. 8-5 of transfer free energies of the transition state (ordinate) and reactant state (abscissa) for the Menschutkin reaction of triethylamine and ethyl iodide. The reference solvent is N, Af-dimethylformamide (No. 27). Data are from Table 8-10, where the solvents are identified by number. Closed circles are polychlorinated solvents.

Nucleic acids are anionic under the neutral conditions. Thus, the syntheses of model compounds of the opposite charge are interesting for the discussion of electrostatic contributions in specific interactions of nucleic acids. We have tried to synthesize cationic models by the Menschutkin reaction of poly-4-vinylpyridine with 9-(2-chlo-roethyl)adenine, l-(2-chloroethyl)thymine, and 7-(2-chloroethyl)theophylline15,16 The obtained polymers are poly l-[2-(adenin-9-yl)ethyl]-4-pyridinioethylene chloride 7(APVP), poly l-[2-(thymin-l-yl)ethyl]-4-pyridinioethylene chloride 8 (TPVP), and poly l-[2-(theophyllin-7-yl)ethyl]-4-pyridiniothylene chloride 9 (THPVP), respectively. 

A 12), 0-(thymin-l-yl)ethyldodecyldimethylamrnonium chloride), 25 (T12), j3-(theophyllin-7-yl)ethyldodecylammonium chloride, 26 (TH12), j3-(adenin-9-yl)-ethyloctadecyldimethylammonium chloride (A 18), and /3-(thymin-l-yl)ethylocta-decyldimethylammonium chloride (T18)47. These model compounds were prepared by the Menschutkin reaction of dodecyldimethyl amine or octadecyldimethylamine with chloroethylated bases. 

Reactions that take place through dipolar transition states Menschutkin reaction (10-44), electrophilic aromatic substitution. 

Aminodehalogenation - Menschutkin Reaction (Formation of Quaternary Amines)... 

Drivers for Performing the Menschutkin Reaction in Micro Reactors... 

The Menschutkin reaction was carried out as a test reaction to show the feasibility of such novel micro flow concepts that allow to process fouling-sensitive reactions (see also Section 4.2.6 here another test reaction is decribed for the same purpose) [78]. The reaction of alkyl bromide with ternary bases such as pyridine or triethylamine gives quaternary salts insoluble in most solvents. Often, fairly rapid precipitation of this salt occurs, hence ideally serving as a test reaction for fouling sensitivity of micro-channel devices. The reaction of 4,4 -bipyridyl and ethyl bromoacetate [78] belongs to the category of fast-predpitating Menschutkin reactions, as the halide function is activated by the carbonyl fimction. 

Beneficial Micro Reactor Properties for the Menschutkin Reaction... 

To pursue the development of environmentally benign synthesis routes for ionic liquids, the alkylation step (Menschutkin reaction) was investigated by the authors in detail. The preparation of the ionic liquid 1-hexyl-3-methyhmidazohum chloride ([CeMlMJCl) was taken as a representative experiment (Scheme 7.2). The process parameters temperature (T = 70-100°C), solvent (ethanol, xylene, cyclohexane, n-heptane, solvent free), concentration of the N-base (c = 1.6-6.7 M), molar ratio n n = 1 0.5-1 4) and reaction time (f = 10-144 h) were investigated. In addition, the N-base was altered in order to proof the transferability of the reaction parameters. 

In this contribution, we describe and illustrate the latest generalizations and developments[1]-[3] of a theory of recent formulation[4]-[6] for the study of chemical reactions in solution. This theory combines the powerful interpretive framework of Valence Bond (VB) theory [7] — so well known to chemists — with a dielectric continuum description of the solvent. The latter includes the quantization of the solvent electronic polarization[5, 6] and also accounts for nonequilibrium solvation effects. Compared to earlier, related efforts[4]-[6], [8]-[10], the theory [l]-[3] includes the boundary conditions on the solute cavity in a fashion related to that of Tomasi[ll] for equilibrium problems, and can be applied to reaction systems which require more than two VB states for their description, namely bimolecular Sjy2 reactions ],[8](b),[12],[13] X + RY XR + Y, acid ionizations[8](a),[14] HA +B —> A + HB+, and Menschutkin reactions[7](b), among other reactions. Compared to the various reaction field theories in use[ll],[15]-[21] (some of which are discussed in the present volume), the theory is distinguished by its quantization of the solvent electronic polarization (which in general leads to deviations from a Self-consistent limiting behavior), the inclusion of nonequilibrium solvation — so important for chemical reactions, and the VB perspective. Further historical perspective and discussion of connections to other work may be found in Ref.[l],... 

Meniscus surgery, 3 723 Menispermaceae, alkaloids in, 2 75 Menke s disease, 7 709 Menschutkin reaction, 20 490 26 846 Men s colognes/fragrances, 18 356, 359-361 Menstruum process carburization, 4 675 solid solutions of industrial carbides, 4 688-689... 

As early as 1967, after their success in isolating atropisomers of haloacetamide derivatives (12), Chupp and Olin (49) examined the separate reactivities of these atropisomers in Menschutkin reactions with pyridine (Scheme 7). They found... 

Figure 11.6 Menschutkin reaction of ammonia and chloromelhane. In the gas phase nucleophilic displacement fails to take place, while in water solvation of the anions allows the reaction to proceed...

Heterocyclic amines have also been used as phase transfer catalysts. However, because these amines quaternize easily, the question is whether the operative catalyst is the tertiary amine or the quaternary ammonium salt formed in situ Furukawa et al.286 have shown that a methyl 2-pyridyl sulfoxide may be used as a phase transfer catalyst and promote substitution reactions between lithium chloride or sodium cyanide and benzyl bromide. According to the authors, the catalyst behaves as a cation complexer and not as a quaternary ammonium salt formed in situ by a Menschutkin reaction. 

The Menschutkin reaction has been used to prepare poly(viologens) (115) directly (Scheme 31). These polymers were found to be quite useful as polyelectrolyte redox-polymers and for the preparation of conductive polymers when complexed with the 7,7, 8,8 -tetracyanoquinodimethane (TCNQ) radical anion (71MI11100). 

---