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Menshutkin reaction

January 08, 2023

In organic chemistry, the Menshutkin reaction converts a tertiary amine into a quaternary ammonium salt by reaction with an alkyl halide. Similar reactions occur when tertiary phosphines are treated with alkyl halides.

Menshutkin reaction
Named after Nikolai Menshutkin
Reaction type Coupling reaction
Identifiers
RSC ontology ID RXNO:0000223

The reaction is the method of choice for the preparation quaternary ammonium salts.[1] Some phase transfer catalysts (PTC) can be prepared according to the Menshutkin reaction, for instance the synthesis of triethyl benzyl ammonium chloride (TEBA) from triethylamine and benzyl chloride:

Scope

Reactions are typically conducted in polar solvents such as alcohols.[1] Alkyl iodides are superior alkylating agents relative to the bromides, which in turn are superior to chlorides. As is typical for an SN2 process, benzylic, allylic, and α-carbonylated alkyl halides are excellent reactants. Even though alkyl chlorides are poor alkylating agents (gem-dichlorides especially so), amines should not be handled in chlorinated solvents such as dichloromethane and dichloroethane, especially at high temperatures, due to the possibility of a Menshutkin reaction. (Sometimes, kinetically facile reactions like acylations are sometimes conducted in chlorinated solvents nonetheless.) Highly nucleophilic tertiary amines like DABCO will react with dichloromethane at room temperature overnight and at reflux (39-40 °C) over several hours to give the quaternized product (see the article on Selectfluor). Due to steric hindrance and unfavorable electronic properties, chloroform reacts very slowly with tertiary amines over a period of several weeks to months.[2] Even pyridines, which are considerably less nucleophilic than typical tertiary amines, react with dichloromethane at room temperature over a period of several days to weeks to give bis(pyridinium)methane salts.[3]

In addition to solvent and alkylating agent, other factors strongly influence the reaction. In one particular macrocycle system the reaction rate is not only accelerated (150000 fold compared to quinuclidine) but the halide order is also changed

 

History

The reaction is named after its discoverer, Nikolai Menshutkin, who described the procedure in 1890.[5][6][7][8] Depending on the source, his name (and the reaction named after him) is spelled as Menšutkin, Menshutkin, or Menschutkin.

References

  1. ^ a b W. R. Brasen, C. R. Hauser (1954). "o-Methylethylbenzyl Alcohol". Org. Synth. 34: 58. doi:10.15227/orgsyn.034.0058.{{cite journal}}: CS1 maint: uses authors parameter (link)
  2. ^ Hansen, Steen Honoré; Nordholm, Lars (16 January 1981). "N-alkylation of tertiary aliphatic amines by chloroform, dichloromethane and 1,2-dichloroethane". Journal of Chromatography A. 204: 97–101. doi:10.1016/S0021-9673(00)81643-X.
  3. ^ Reaction of Dichlormethane with Pyridine Derivatives under Ambient Conditions Alexander B. Rudine, Michael G. Walter, and Carl C. Wamser J. Org. Chem. 2010, 75, 4292–95 doi:10.1021/jo100276m
  4. ^ Dramatic Acceleration of the Menschutkin Reaction and Distortion of Halide Leaving-Group Order Keith J. Stanger, Jung-Jae Lee, and Bradley D. Smith J. Org. Chem. 2007, 72, 9663–68 doi:10.1021/jo702090p
  5. ^ N. Menschutkin. Beiträgen zur Kenntnis der Affinitätskoeffizienten der Alkylhaloide und der organischen Amine Z. Physik. Chem. 5 (1890) 589.
  6. ^ N Menschutkin. Über die Affinitätskoeffizienten der Alkylhaloide und der Amine Z. Physik. Chem. 6 (1890) 41.
  7. ^ M B Smith, J March. March's Advanced Organic Chemistry (Wiley, 2001) (ISBN 0-471-58589-0)
  8. ^ Lexikon bedeutender Chemiker (VEB Bibliographisches Institut Leipzig, 1989) (ISBN 3817110553

January 08, 2023
menshutkin, reaction, organic, chemistry, converts, tertiary, amine, into, quaternary, ammonium, salt, reaction, with, alkyl, halide, similar, reactions, occur, when, tertiary, phosphines, treated, with, alkyl, halides, named, after, nikolai, menshutkinreactio. In organic chemistry the Menshutkin reaction converts a tertiary amine into a quaternary ammonium salt by reaction with an alkyl halide Similar reactions occur when tertiary phosphines are treated with alkyl halides Menshutkin reactionNamed after Nikolai MenshutkinReaction type Coupling reactionIdentifiersRSC ontology ID RXNO 0000223 The reaction is the method of choice for the preparation quaternary ammonium salts 1 Some phase transfer catalysts PTC can be prepared according to the Menshutkin reaction for instance the synthesis of triethyl benzyl ammonium chloride TEBA from triethylamine and benzyl chloride Scope EditReactions are typically conducted in polar solvents such as alcohols 1 Alkyl iodides are superior alkylating agents relative to the bromides which in turn are superior to chlorides As is typical for an SN2 process benzylic allylic and a carbonylated alkyl halides are excellent reactants Even though alkyl chlorides are poor alkylating agents gem dichlorides especially so amines should not be handled in chlorinated solvents such as dichloromethane and dichloroethane especially at high temperatures due to the possibility of a Menshutkin reaction Sometimes kinetically facile reactions like acylations are sometimes conducted in chlorinated solvents nonetheless Highly nucleophilic tertiary amines like DABCO will react with dichloromethane at room temperature overnight and at reflux 39 40 C over several hours to give the quaternized product see the article on Selectfluor Due to steric hindrance and unfavorable electronic properties chloroform reacts very slowly with tertiary amines over a period of several weeks to months 2 Even pyridines which are considerably less nucleophilic than typical tertiary amines react with dichloromethane at room temperature over a period of several days to weeks to give bis pyridinium methane salts 3 In addition to solvent and alkylating agent other factors strongly influence the reaction In one particular macrocycle system the reaction rate is not only accelerated 150000 fold compared to quinuclidine but the halide order is also changed History EditThe reaction is named after its discoverer Nikolai Menshutkin who described the procedure in 1890 5 6 7 8 Depending on the source his name and the reaction named after him is spelled as Mensutkin Menshutkin or Menschutkin References Edit a b W R Brasen C R Hauser 1954 o Methylethylbenzyl Alcohol Org Synth 34 58 doi 10 15227 orgsyn 034 0058 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint uses authors parameter link Hansen Steen Honore Nordholm Lars 16 January 1981 N alkylation of tertiary aliphatic amines by chloroform dichloromethane and 1 2 dichloroethane Journal of Chromatography A 204 97 101 doi 10 1016 S0021 9673 00 81643 X Reaction of Dichlormethane with Pyridine Derivatives under Ambient Conditions Alexander B Rudine Michael G Walter and Carl C Wamser J Org Chem 2010 75 4292 95 doi 10 1021 jo100276m Dramatic Acceleration of the Menschutkin Reaction and Distortion of Halide Leaving Group Order Keith J Stanger Jung Jae Lee and Bradley D Smith J Org Chem 2007 72 9663 68 doi 10 1021 jo702090p N Menschutkin Beitragen zur Kenntnis der Affinitatskoeffizienten der Alkylhaloide und der organischen Amine Z Physik Chem 5 1890 589 N Menschutkin Uber die Affinitatskoeffizienten der Alkylhaloide und der Amine Z Physik Chem 6 1890 41 M B Smith J March March s Advanced Organic Chemistry Wiley 2001 ISBN 0 471 58589 0 Lexikon bedeutender Chemiker VEB Bibliographisches Institut Leipzig 1989 ISBN 3817110553 Retrieved from https en wikipedia org w index php title Menshutkin reaction amp oldid 1118573891, wikipedia, wiki, book, books, library,

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