Документ взят из кэша поисковой машины. Адрес оригинального документа : http://electr003.chem.msu.ru/rus/lectures/dubna.pdf Дата изменения: Wed Jan 6 10:54:56 2010 Дата индексирования: Mon Oct 1 21:07:14 2012 Кодировка:

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( )


A

ln (-dcA/dt) = ln kr + n ln c
:


A



1 dc A 1 dc B m - =- = k r cA c a dt b dt
aA + bB

n B


=
: E + S ES « » ES E + S

ES P + E

(!) : - - - - ...............


heteronuclear

Cr(H2O)

6

3+

+ Fe(H2O)

6

2+

Fe(H2O)

6

3+

+ Cr(H2O)

6

2+

homonuclear

Fe( H2O)62+ + *Fe( H2O)6

3+

Fe( H2O)63+ + *Fe( H2O)6

2+

Simultaneous transfer of two electrons is extremely rare

S2 O

8

2-

+ 2 Fe( H2O)6

2+

2SO
S2O
3­·

4

2-

+ 2 Fe( H2O)6
2­

3+

8

SO

4

+ SO

4

­·



















D

=




kne t =

k k

diff k r



diff

+k
-1

r
10-9
-1

k diff = 4 N(DA + D B)a
10
10

M-1s

-1

6·1023

10-9 2

!


spectroscopic techniques

electron transfer fs nuclear motion ps

«jumps» (temperature, pressure, electric field) «flow» techniques «usual chemistry»

ns

ms
-6 -4 -2 0

s
2

-18 -16 -14 -12 -10

-8

log(half life time, s)


heteronuclear

homonuclear

Arrhenius empirical expression kr = Ar exp(-Ea / RT) transition state theory; activated complex

Values of

10­7 ­ 108 M-1s-1
are known for various systems


Rudolph Arthur Marcus
1992: Nobel Prize in Chemistry
«For his contributions to the theory of electron transfer reactions in chemical systems»

There's a difference between «it can't be» and «ithasn'tbeen»
The Spectrum, 16(2003)5


out

2 N Ae0 = 4 0

1 1 - r d 11 = -



op



s

outersphere innersphere Pecar factor


25 ° C.


H2O MeOH EtOH 1-PrOH 2-PrOH N, N' N-

s

1 , 10

-12





1

2 , 10

-12





2

3 , 10

-12







77.97 32.50 24.32 20.43 19.40 37.24 183.3 108.8 38.43

8.32 51. 5 163 329 359 10. 4 128 37.3 16

6.18 5.91 4.49 3.74 3.47 4.38 6.16 7. 08 4.10

1.02 7.09 8.97 15.1 14.5 0.76 7.93 1. 16 1.33

4.90 3.82 3.20 3.04

1.12 1.81 2.40 1.96

4.49 2.79 2.69 2. 44 2. 42 2.94 3.20 4. 48 3.04

4.60

0.78

(, )






E/4 (/) -

, ,

MSA = mean spherical approximation


activation energy vs. reaction free energy: Marcus predicts non-linear dependence Bronsted formula Ea = ·F (or =·F for electrochemical reactions): works only accidentally
j = [c]Fk exp(- Ea / RT ) Ea = F ( - zi ) ' - F - Frumkin slow discharge theory, 1932 + (- F + W f - Wi ) - Marcus, 1956 - ..... Ea = Wi + 4 = const decreases with overvoltage
2

and becomes negative?


: 25


,







LDK=Levich, Dogonadze, Kuznetsov Frumkin LDK
- «»

Marcus








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