Zur Papierchromatographie der kondensierten Phosphate

The disproportionation of Cu(I)X mediated by ligand and solvent into Cu(0) and Cu(II)X2 and its implications for SET‐LRP

“…The most definitive result of these electrochemical experiments is that Cu(I)X is least stable to disproportionation in water ( K disp = 10 6 to 10 7 M –1 ) (Table 1) and most stable to disproportionation in nitriles such MeCN ( K disp = 6.3 × 10 –21 M –1 ) (Table 1). However, the exact magnitude of K disp , in water and organic solvents is a matter of some debate in the literature 2–4, 43–47. Additionally, it is not certain whether these half‐reactions occurring at electrodes are relevant analogs of the homogenous electron transfer process.…”

“…Essential to SET‐LRP is the establishment of an appropriate balance of Cu(0) and Cu(II) species by the disproportionation of the Cu(I)X generated in situ via activation and deactivation. Disproportionation is not rapid or extensive under most conditions, but rather requires a combination of an appropriate solvent,33–36 typically DMSO ( K disp = 1.5–4.4 M –1 ) (Table 1),40, 41 alcohols (MeOH ( K disp = 4–6.3 × 10 3 M –1 ) (Table 1)42, 47 and EtOH ( K disp = 3.6 M –1 ) (Table 1),42 or water ( K disp = 10 6 to 10 7 M –1 ) (Table 1)2–4, 43–47 and an appropriate N‐ligand such as Me 6 ‐TREN, TREN, PMDETA, and PEI 48. Cu(0)/Me 6 ‐TREN‐catalyzed SET polymerization of methyl acrylate (MA) in solvents that do not mediate disproportionation such as acetone14 ( K disp = 0.03 M –1 ) (Table 1),37, 38 MeCN36 ( K disp = 6.3 × 10 –21 M –1 ) (Table 1),49 and toluene33, 34 results in nonfirst order kinetics and a nonliving polymerization.…”

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“…In the previous study,6 the addition of water to various organic solvents was investigated. Regardless of the organic solvent employed, water exhibits a higher disproportionation constant ( K disp = 10 6 –10 7 M −1 )32–39 (Table 1) and higher polarity ( E = 1.00) (Table 2). Therefore, even in the case of DMSO which has a higher disproportionation constant ( K disp = 1.5–4.4 M −1 )43, 44 (Table 1) and polarity ( E = 0.444) (Table 2) than most organic solvents, the addition of 5–10% water resulted in a linear increase in the k .…”

“…In fact, most organic solvents do not mediate sufficient disproportionation of Cu(I)X even in the presence of Me 6 ‐TREN for SET‐LRP. On the other hand, H 2 O has the highest intrinsic disproportionation constant for Cu(I)X, K disp = 10 6 –10 7 M −1 ( K disp = [Cu(II)X 2 ]/[Cu(I)X)] 2 ) (Table 1), when measured in the absence of a ligand 32–39. Therefore, the addition of H 2 O to organic solvents will enhance disproportionation allowing for the self‐regulation of Cu(0) and Cu(II)X 2 levels.…”

Reply to Is There an Optimal Comorbidity Index for Prostate Cancer?

“…Among all solvents, H 2 O has the highest intrinsic disproportionation constant for Cu(I)X, K disp = 10 6 –10 7 M −1 ( K disp = [Cu(II)X 2 ]/[Cu(I)X)] 2 ),when measured in the absence of a ligand (Table 1). 33–40 Here, we report the investigation of the kinetics of SET‐LRP of MA initiated with methyl 2‐bromopropionoate (MBP) in mixtures of organic solvents with H 2 O that mediate different degrees of disproportionation (Table 1) and exhibit different polarities. Both a higher equilibrium constant of disproportionation and polarity of the reaction medium are expected to favor the SET‐LRP process.…”