S 10. The kinetics and mechanism of the sandmeyer reaction

We have examined the kinetics and mechanism of the dediazoniation reaction of p-methylbenzenediazonium tetrafluoroborate in the presence and absence of CuCl 2 using a methodology developed by us that allows, simultaneously, and within the same experiment to identify, to quantify, and to obtain the rate constants for the formation of all dediazoniation products, and, indirectly, the rate constant for the diazonium salt decomposition. The methodology developed combines the use of coupling reactions, to form a stable azo dye, followed by analysis by HPLC.

show abstract

“…complexes in the medium constant [17,18,20]. The k obs values are not affected by changing Cu(II) concentration from and they are…”

Section: Influence Of Cucl 2 On K Obsmentioning

confidence: 95%

A new method for monitoring dediazoniation reactions: Simultaneous monitoring of concentration and rates of product formation and loss of starting material for the dediazoniation ofp-methylbenzenediazonium tetrafluoroborate

Garcia-Meijide

Bravo‐Díaz

Romsted

1998

Int. J. Chem. Kinet.

View full text Add to dashboard Cite

show abstract

“…A rN 2, CuCl2, so th a t no free electrons and probably but few free aryl radicals escaped from the sur rounding cage of solvent molecules. This view has been accepted by some subse quent workers (Pfeil & Velten 1949;Pfeil 1953) though others regard the Sandmeyer reaction asawholly intramolecular process (Cowdrey & Davies 1949). Arguments for believing th a t the reaction is essentially heterolytic but occurring within a cage of solvent molecules (Hodgson and colleagues, 1941-44) are not supported by kinetic studies (Cowdrey & Davies).…”

Section: Cyclic One-electron-transfer Mechanism a R--n£mentioning

confidence: 99%

“…Its value ranges from 7 to 35 % and is highest with the p-chlorobenzenediazonium salt with which the homolysis (B) through isomerization to the diazo-hydroxide and the electron transfer reaction with cuprous ion ( C)would be f attracting chlorine substituent. Though some heterolytic decomposition (A) of the diazonium cations may have occurred during the long period (16 h) allowed for completing these reactions, published evidence (De Tar & Ballentine 1956;Cowdrey & Davies 1949) indicates th a t this is a slow process compared with the first stage (C, (i)) of the Sandmeyer reaction. Consequently table 3 can be taken to indicate th a t to a major extent the Sandmeyer reaction involves vicinal cations and radicals colliding within a surrounding cage of solvent molecules and only produces a relatively small fraction of 'free' radicals.…”

Section: E Stimation Of the Extent Of Free Aryl Radical Formationmentioning

confidence: 99%

“…The effect of added chloride is less pronounced. W ith the p-methoxybenzenediazonium cation it increases the molecular weight of the polymer; this could be ascribed to the shift of the equilibrium CuCl^ + 2 C F^ (CuCl4)3so as to reduce the electron-transferring ability of the cuprous salt (compare Cowdrey & Davies 1949) and consequently the rate of initiation of polymerization. However, benzenediazonium cation and p-chlorobenzenediazonium cation, which are both much more easily reduced, do not appear to show this effect.…”

Section: S Reactiomentioning

confidence: 99%

See 1 more Smart Citation

A study of the mechanism of the Sandmeyer reaction

Nonhebel

Waters

1957

Proc. R. Soc. Lond. A

View full text Add to dashboard Cite

The one-electron-transfer mechanism for the Sandmeyer reaction, proposed by W. A. Waters in 1942 has now been confirmed by diagnostic experiments. Its initial stage, Ar ·N + 2 + Cu + → Ar · + N 2 + Cu 2+ , has been shown to produce free aryl radicals capable of initiating vinyl polymerization; this observation is also true for related reactions of diazonium salts for which analogous one-electron-transfer mechanisms have been suggested. The cupric ions thus produced are oxidizers that, like ferric ions, can effect chain-ending of vinyl polymerization. They bring about the final step in the Sandmeyer reaction by a similar process that apparently involves chlorine atom transfer; Ar · + Cl—Cu—Cl → Ar —Cl + Cu—Cl. Product studies show that cupric ions are needed to enable the Sandmeyer reaction to give aryl chlorides in high yield; in their absence other reactions of aryl radicals can occur extensively. Molecular weight measurements with acrylonitrile polymers indicate that in dilute solution up to 35% of the initial aryldiazonium cations can produce free aryl radicals by interaction with cuprous ions in chloride solutions, but that in more concentrated solutions the secondary reaction with the cupric chloride generated occurs so extensively that the full cycle of the Sandmeyer reaction becomes predominantly an intramolecular process.

show abstract

“…The amount of trapping could be determined by measuring the amount of RX and M 11 "" 1 X n--1 formed. In the present work gasliquid chromatography was used to measure the amount of RX formed.…”

Section: Introductionmentioning

confidence: 99%

Effects of metal ions in free radical reactions

Kriens

View full text Add to dashboard Cite

show abstract

S 10. The kinetics and mechanism of the sandmeyer reaction

Cited by 13 publications

References 0 publications

A new method for monitoring dediazoniation reactions: Simultaneous monitoring of concentration and rates of product formation and loss of starting material for the dediazoniation ofp-methylbenzenediazonium tetrafluoroborate

A new method for monitoring dediazoniation reactions: Simultaneous monitoring of concentration and rates of product formation and loss of starting material for the dediazoniation ofp-methylbenzenediazonium tetrafluoroborate

A study of the mechanism of the Sandmeyer reaction

Effects of metal ions in free radical reactions

Contact Info

Product

Resources

About