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Vol.
25 No. 3
May - June 2003
Critical
Evaluation of Stability Constants and Thermodynamic Functions
of Metal Complexes of Crown Ethers (IUPAC Technical Report)
by
F. Arnaud-Neu, R. Delgado, and S. Chaves
Pure
and Applied Chemistry,
Vol. 75, No. 1, pp. 71102 (2003)
Stability
constants and thermodynamic functions of metal complexes of
crown ethers in various solvents published between 1971 and
the beginning of 2000 have been critically evaluated. The
most studied crown ethers have been selected: 1,4,7,10 tetraoxacyclododecane
(12C4); 1,4,7,10,13 pentaoxacyclopentadecane (15C5); and 1,4,7,10,13,16
hexaoxacyclooctadecane (18C6). The metal ions chosen are alkali
and alkaline earth metal ions, Ag+, Tl+,
Cd2+, and Pb2+. The solvents considered
are water, methanol, ethanol, and their mixtures, as well
as acetonitrile, N,N-dimethylformamide, dimethylsulfoxide,
and propylene carbonate. The published data have been examined
and grouped into two categories, "accepted" and "rejected."
The "accepted" values were considered as (i) recommended (R),
when the standard deviations (s.d.) on the constant K or on
DrH were inferior to 0.05 lg unit
or inferior to 1 kJ mol-1, respectively; (ii) provisional
(P), when s.d. is superior to 0.05 and inferior to
0.2 for lg K or s.d. is superior to 1 and inferior to 2 kJ
mol-1 for DrH; (iii)
recommended 1 (R1), if the values were obtained by
a single research group, but were considered reliable in comparison
with related systems, and considering that the research team
usually presents R-level values for other similar systems.
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