74431-47-3Relevant articles and documents
Electron Transfer Induced Isomerization of cis-4,4'-Diphenylstilbene into Its Trans Form
Chien, C. K.,Wang, H. C.,Szwarc, M.,Bard, A. J.,Itaya, K.
, p. 3100 - 3104 (1980)
The 4,4'-diphenylstilbenes, denoted by C and T for the cis and trand isomers, as well as T-. and T2-, were characterized spectroscopically and electrochemically.The disproportionation 2T-.,Na+ T + T2-,2Na+ has equilibrium constant in THF 0.04, ΔH = 18.2 kcal/mol, and ΔS = 54 cal/moldeg, and its rate constant is 9.0 108 M-1 s-1.The cis-trans isomerization was studied in THF at ambient temperature in three systems: T + T-.,Na+ + C, T2-,2Na+ + C, and B-.,Na+ + C, B denoting biphenyl.In the first two systems the reaction is governed by the three interrelated equilibria, namely, C + T-.,Na+ T + C-.,Na+ (K1), C + T2-,2Na+ C-.,Na+ + T-.,Na+, (K2 = K1/Kdispr), and 2T-.,Na+ T + T2-,2Na+ (Kdispr), the rate-determining step being C-.,Na+ -> T-.,Na+ (ki).The results give kiK1 or kiK2.In the last system the rapid electron transfer B-.,Na+ + C -> B + C-.,Na+ produces momentarily high concentration of C-.,Na+ and, since its disproportionation is favored, a relatively large amount of C2-,2Na+.The latter rapidly isomerizes into T2-,2Na+.Thus, in early stages of the reaction, the concentration of T2-,2Na+ exceeds that expected for the disproportionation equilibrium had the reaction with B-.,Na+ formed only C-.,Na+ and then T-.,Na+.This observation provides the evidence for the existence of C2-,2Na+.
