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On the abbreviated notation of electrode reactions
J Electroanal. Chem., 97 (1979) 103--105 © Elsevier Sequoia S A., Lausanne -- Printed in The Netherlands
103
Short communication ON THE ABBREVIATED NOTATION OF E L E C T R O D E REACTIONS
V.G. MAIRANOVSKY
All-Union Institute for Vitamin Research, 11 7246, Moscow (U.S.S.R.) (Reeeived 16th May, 1978)
Testa and Reinmuth [1 ] suggested a convenient abbreviated notation of electrode reactions. The process appears as a sequence of electrochemical ( " e " ) and chemical ("c") steps. Symbol " e " refers here to the heterogeneous (surface) electron transfer (ET); " c " does not indicate the localization of a chemical stage, as a rule it indicates a homogeneous (volume) chemical reaction. The conceptions on mechanisms of electrode processes have been greatly broadened since the publication of ref. 1; surface chemical reactions have been revealed [2], the nuances caused b y volume ET reactions have been found [3], the processes with reverse ET [4], catalytic processes with two-step regeneration of catalyst [5] and others have been considered. To improve ref. 1 for the sake of rational representation of mechanisms of complicated electrode reactions we suggest the following notation which has partially been used in refs. 6--8. (1) The scheme is drawn up applying to the "initial depolarizer" which is present in the solution or formed chemically from the components of the system. The transformations refer to a definite range of potentials of electrochemical activity of the initial depolarizer. (2) The "usual" electrochemical stage (surface ET) is designated as " e " and volume ET as "ev"; " c " denotes the chemical stage; the symbol " c s " is used if the stage is established to be surface *. "Reverse" ET is denoted b y the minus sign ("--e") **, the one-stage two-electron ET [6] is designated as " 2 e " . (3) Consecutive stages are written from left to right as they follow, parallel reactions are given in brackets. Regeneration of a substance is designated b y the arrow above. (4) Bimolecular reactions may be detailed if necessary. The origin of a reagent is indicated by the lines at the b o t t o m (the arrow always directed from left to right may be omitted, see example 2 in Table 1). When two products are formed the transformation of one of them is separated from the main notation by the sign ";", the same sign separates independent stages of ET when several "initial depolarizers" are present in the system (see example 8 in Table 1). Examples illustrating the abbreviated notation suggested are given below.
* The chemical stage may be detailed, for example one may use symbols " p " (protonation), " - - p " (deprotonation), " r " rupture instead of the general symbol " c " . ** It was suggested to designate this by oppositely directed arrows, e.g. -6c~- [4 ].
TABLE 1 Abbreviated notation of some electrode reactions No. 1
Electrode process
Notation
Comment
A+e~B B~C C+e~-D
ece
"Classic" ece-mechanism (aromatic hydrocarbon reduction, see ref. 9)
A+e~B
~e c 1e v
"Regenerating" mechanism (aromatic hydrocarbon reduction, see ref. 10)
t
LJ
B~C
.J
4
B +C~ D + A
I
(~_c_. ev)
A+e~-B
T
2B~D+ D-->E
8
A--]
~je v c
A+e~B 2B->C C-->D
ecc
A+e~-B B-+C 2C--> D
ecc
U
Electrohydrodimerization (carbonyl compounds, see ref. 13)
A-->B B+e~-C
c~c,
Electrohydrodimerizatio n (acid medium, see ref. 2)
2C--> D
Cs ~jCs
A+e~B B--> C C + D-->E
eec$,
U
e Cs Cs
A+e~-~(1)
(1) (2)(3)
A + D - > C + B(3) 9
A+e~-B B+C~D+A D~E E+e-+F
10
N
--j
eevc e
A+e~B
A +e~ B
t
7 ev c [ev
(1)
B+C~D+A~ (2) D-->E (3) B + E--> F + A--J (4) B + E->G(5) 12
evc( [c) [ev (1)(2)(3)(5)(4)
A+e~B
t
B+C~D+A--~ D+E-+F | B + F - + G + A--~ B+E~H | B + H-> I + A - - J
Electrohydr odimerization (activated olefines, see ref. 12)
Reaction with electrode material (reduction of ethyl iodide on mercury, see ref. 14) Catalytic process with regeneration of two substances (reduction of Fe 3+ + Cr 3+, see ref. 15) Catalytic process with twostep regeneration of catalyst (A = aromatic hydrocarbon, C = arylhalide, see ref. 5b) The same with two volume steps of ET (see refs. 5 and
t
B+C~D+.~-~ D~E B+E-+F+A 11
"Disproportionation" mechanism (conjugated hydrocarbon reduction, see refs. 10 and 11)
i(evc lev)clev
16)
The same with deactivation (alkylation of A) (A = aromatic hydrocarbon, C = alkylhalide, see ref. 17)
The same with deactivation (protonation of B) (A = and C = conjugated hydrocarbons, E = proton donor, see ref. 16)
105 REFERENCES 1 2 3 4 5
6 7 8 9 10 11 12 13 14 15 16 17
A. Testa and W. R e i n m u t h , Anal. Chem., 33 (1961) 1320. S.G. Ma~ranovsky, Catalyttc and Kinetic Waves m Polarography, Plenum Press, New York, 1968. M. Hawley and S. Feldberg, J. Phys. Chem., 70 (1966) 3459. S. Feldberg and L. Jefttc, J. Phys. Chem., 76 (1972) 2439. (a) V.G. Mairanovsky, Electrosintez i Bioelektrokhimija, Plenary Lectures on the VIII-th All-Union Conference on Organic Electrochemistry ("ECHOS-73"), Riga, 1973, Nauka, Moscow, 1975, p. 141; (b) H. Lund, H. Michel and J. Simonet, Acta Chem. Scand., B28, (1974) 900; (c) J. Sease and C. Reed, Tetrahedro n Lett., (1975) 393. V.G. Mairanovsky, A.A. Ev~ovatov, N.T. Ioffe and G.L Samokhvalov, J. Electroanal. Chem., 66 (1975) 123. V.G. Maixanovsky, Zh. Vses. Khlm. Obshchestva Mendeleeva, 22 (1977) 334. Yu.V. Bendersky and V.G. Mairanovsky, J. Electroanal. Chem., 79 (1977) 401. G. Hoijtink, J. Van Schooten, E. de Boer and W. Aalbersberg, Rec. Tray. Chim., 73 (1954) 355. M. Fujihira, H. Suzuki and S. Hayano, J. Electroanal. Chem., 33 (1971) 393. T. Troll and M. Baizer, Electrochim. Acta, 19 (1974) 951. M. Baizer, J. Electrochem. Soc,, 111 (1964) 215. L. Nadjo and J. Saveant, J. Electroanal. Chem., 33 (1971) 419. O. Brown and K. Taylor, J. ElectroanaL Chem., 50 (1974) 211. R. Schwall, L Ruzic and D. Smith, J. Eleetroanal. Chem., 60 (1975) 117. V.G. Mairanovsky, N.F. Loginova and LA. Titova, DokL Akad. N a uk SSSR, 223 (1975) 643; Yu.V. Bendersky and V.G. Mairanovsky, J. ElectroanaL Chem., 97 (1979) 1 (this issue). J. Simonet, M. Michel and H. Lund, Acta Chem. Scand., B29 (1975) 489.
103
Short communication ON THE ABBREVIATED NOTATION OF E L E C T R O D E REACTIONS
V.G. MAIRANOVSKY
All-Union Institute for Vitamin Research, 11 7246, Moscow (U.S.S.R.) (Reeeived 16th May, 1978)
Testa and Reinmuth [1 ] suggested a convenient abbreviated notation of electrode reactions. The process appears as a sequence of electrochemical ( " e " ) and chemical ("c") steps. Symbol " e " refers here to the heterogeneous (surface) electron transfer (ET); " c " does not indicate the localization of a chemical stage, as a rule it indicates a homogeneous (volume) chemical reaction. The conceptions on mechanisms of electrode processes have been greatly broadened since the publication of ref. 1; surface chemical reactions have been revealed [2], the nuances caused b y volume ET reactions have been found [3], the processes with reverse ET [4], catalytic processes with two-step regeneration of catalyst [5] and others have been considered. To improve ref. 1 for the sake of rational representation of mechanisms of complicated electrode reactions we suggest the following notation which has partially been used in refs. 6--8. (1) The scheme is drawn up applying to the "initial depolarizer" which is present in the solution or formed chemically from the components of the system. The transformations refer to a definite range of potentials of electrochemical activity of the initial depolarizer. (2) The "usual" electrochemical stage (surface ET) is designated as " e " and volume ET as "ev"; " c " denotes the chemical stage; the symbol " c s " is used if the stage is established to be surface *. "Reverse" ET is denoted b y the minus sign ("--e") **, the one-stage two-electron ET [6] is designated as " 2 e " . (3) Consecutive stages are written from left to right as they follow, parallel reactions are given in brackets. Regeneration of a substance is designated b y the arrow above. (4) Bimolecular reactions may be detailed if necessary. The origin of a reagent is indicated by the lines at the b o t t o m (the arrow always directed from left to right may be omitted, see example 2 in Table 1). When two products are formed the transformation of one of them is separated from the main notation by the sign ";", the same sign separates independent stages of ET when several "initial depolarizers" are present in the system (see example 8 in Table 1). Examples illustrating the abbreviated notation suggested are given below.
* The chemical stage may be detailed, for example one may use symbols " p " (protonation), " - - p " (deprotonation), " r " rupture instead of the general symbol " c " . ** It was suggested to designate this by oppositely directed arrows, e.g. -6c~- [4 ].
TABLE 1 Abbreviated notation of some electrode reactions No. 1
Electrode process
Notation
Comment
A+e~B B~C C+e~-D
ece
"Classic" ece-mechanism (aromatic hydrocarbon reduction, see ref. 9)
A+e~B
~e c 1e v
"Regenerating" mechanism (aromatic hydrocarbon reduction, see ref. 10)
t
LJ
B~C
.J
4
B +C~ D + A
I
(~_c_. ev)
A+e~-B
T
2B~D+ D-->E
8
A--]
~je v c
A+e~B 2B->C C-->D
ecc
A+e~-B B-+C 2C--> D
ecc
U
Electrohydrodimerization (carbonyl compounds, see ref. 13)
A-->B B+e~-C
c~c,
Electrohydrodimerizatio n (acid medium, see ref. 2)
2C--> D
Cs ~jCs
A+e~B B--> C C + D-->E
eec$,
U
e Cs Cs
A+e~-~(1)
(1) (2)(3)
A + D - > C + B(3) 9
A+e~-B B+C~D+A D~E E+e-+F
10
N
--j
eevc e
A+e~B
A +e~ B
t
7 ev c [ev
(1)
B+C~D+A~ (2) D-->E (3) B + E--> F + A--J (4) B + E->G(5) 12
evc( [c) [ev (1)(2)(3)(5)(4)
A+e~B
t
B+C~D+A--~ D+E-+F | B + F - + G + A--~ B+E~H | B + H-> I + A - - J
Electrohydr odimerization (activated olefines, see ref. 12)
Reaction with electrode material (reduction of ethyl iodide on mercury, see ref. 14) Catalytic process with regeneration of two substances (reduction of Fe 3+ + Cr 3+, see ref. 15) Catalytic process with twostep regeneration of catalyst (A = aromatic hydrocarbon, C = arylhalide, see ref. 5b) The same with two volume steps of ET (see refs. 5 and
t
B+C~D+.~-~ D~E B+E-+F+A 11
"Disproportionation" mechanism (conjugated hydrocarbon reduction, see refs. 10 and 11)
i(evc lev)clev
16)
The same with deactivation (alkylation of A) (A = aromatic hydrocarbon, C = alkylhalide, see ref. 17)
The same with deactivation (protonation of B) (A = and C = conjugated hydrocarbons, E = proton donor, see ref. 16)
105 REFERENCES 1 2 3 4 5
6 7 8 9 10 11 12 13 14 15 16 17
A. Testa and W. R e i n m u t h , Anal. Chem., 33 (1961) 1320. S.G. Ma~ranovsky, Catalyttc and Kinetic Waves m Polarography, Plenum Press, New York, 1968. M. Hawley and S. Feldberg, J. Phys. Chem., 70 (1966) 3459. S. Feldberg and L. Jefttc, J. Phys. Chem., 76 (1972) 2439. (a) V.G. Mairanovsky, Electrosintez i Bioelektrokhimija, Plenary Lectures on the VIII-th All-Union Conference on Organic Electrochemistry ("ECHOS-73"), Riga, 1973, Nauka, Moscow, 1975, p. 141; (b) H. Lund, H. Michel and J. Simonet, Acta Chem. Scand., B28, (1974) 900; (c) J. Sease and C. Reed, Tetrahedro n Lett., (1975) 393. V.G. Mairanovsky, A.A. Ev~ovatov, N.T. Ioffe and G.L Samokhvalov, J. Electroanal. Chem., 66 (1975) 123. V.G. Maixanovsky, Zh. Vses. Khlm. Obshchestva Mendeleeva, 22 (1977) 334. Yu.V. Bendersky and V.G. Mairanovsky, J. Electroanal. Chem., 79 (1977) 401. G. Hoijtink, J. Van Schooten, E. de Boer and W. Aalbersberg, Rec. Tray. Chim., 73 (1954) 355. M. Fujihira, H. Suzuki and S. Hayano, J. Electroanal. Chem., 33 (1971) 393. T. Troll and M. Baizer, Electrochim. Acta, 19 (1974) 951. M. Baizer, J. Electrochem. Soc,, 111 (1964) 215. L. Nadjo and J. Saveant, J. Electroanal. Chem., 33 (1971) 419. O. Brown and K. Taylor, J. ElectroanaL Chem., 50 (1974) 211. R. Schwall, L Ruzic and D. Smith, J. Eleetroanal. Chem., 60 (1975) 117. V.G. Mairanovsky, N.F. Loginova and LA. Titova, DokL Akad. N a uk SSSR, 223 (1975) 643; Yu.V. Bendersky and V.G. Mairanovsky, J. ElectroanaL Chem., 97 (1979) 1 (this issue). J. Simonet, M. Michel and H. Lund, Acta Chem. Scand., B29 (1975) 489.