Chemistry Reference
In-Depth Information
octMC6-(CH
2
)
octMC6-2(CH
2
)
octMC6-(crown)-(C
7
H
15
)
octMC6-(C
8
H
17
)
octMC6-(OC
8
H
17
)
octMC6 + C
8
H
17
octMC6 + OC
8
H
17
octMC6 + NPOE
octMC6 + (NPOE-NO
2
)
octMC + (NPOE + C
8
H
17
)
Addition
Cleavage
O
O
O
octMC6(OH)-(C
7
H
15
)
octMC6(OH)-(OC
8
H
17
)
octMC6(OH)
2
-(C
8
H
17
)
O
O
octMC6(NO
2
)+C
8
H
17
O
NPOE
O
O
γ
Oxidation
HNO
3
3 M
Aromatic substitution
octMC6(OH)
octMC6(OH)
2
octMC6(=O)
octMC6(=O)(OH)
octMC6(NO
2
)(OH)
octMC6(NO
2
)(=O)
octMC6(NO
2
)
octMC6(NO
2
)
2
FIGURe 8.16
Major radiolytic degradation compounds of (octMC6) in NPOE/HNO
3
.
(Redrawn from Lamouroux, C., Aychet, N., Lelievre, A., Jankowski, C.K., Moulin, C.,
Rapid
Commun. Mass Spectrom.
, 18: 1493-1503, 2004.)
The related radiolytic yields were low: in contact with 3 mol L
−1
nitric acid,
G
(-octMC6) ≈ 0.034 and 0.082 for 5 × 10
−2
mol L
−1
solution in NPOE and 10
−2
mol L
−1
in dodecane, respectively (
72
). But the low concentration of ligand partly
explained the values.
Moreover, in the solid form, the monocrown MC-6 was slightly less stable than
the biscrown BC-6 analog (after a 3 MGy dose, 60 and 50% of the molecules were
degraded, respectively), but the opposite effect was noted for a solution 10
−2
mol
L
−1
in NPOE (the amounts of unchanged extractant were 52% and 68%, respec-
tively) (
69
).
The stability under irradiation of the calix[4]arene-bis(
tert
-octylbenzo-crown-6)
(BOBCalixC6)-based solvent system (mixture composed of calix[4]arene, an aro-
matic fluoro-propanol as modifier, and trioctylamine in aliphatic diluent) was
tested under chemical and radiolytic conditions representative of the alkaline-side
process (
265
). After γ-irradiation doses as high as 0.16 MGy, no significant loss of
BOBCalixC6 was measured (less than 10%).
8.3.5.2.3 Influence of the Diluent
The nature of the diluent has an important role on the degradation rate of calix-
arene (see Table 8.7). In dodecane, the loss of calixarene was very high, compared
with measurements in the aromatic NPOE diluent. As already mentioned with other
ligands (like TBP), aromatic diluents had a protective effect, explained by a lower
ionization potential. However, serious radiolytic damage (e.g., a considerable rise
in viscosity) has been observed with NPOE alone (
68
). Therefore, authors, such as
Lamouroux, have suggested the use of a mixture NPOE-dodecane (
72
).
