CHAPTER 11 • Hydrolysis Processes of Organotin(lV) Compounds in Sea Water
215
11.2.1
Trialkyltin Compounds
Among trialkyltin compounds, tributyl derivatives are the most widely distributed in
the aquatic environment, owing to their industrial applications (see Table 11.1).A number of articles on their toxicological effects exist in literature. Useful updated information on this subject can be found in the very recent book by Champ and Seligman
(1996).
The acidity of some low water soluble trialkyltin(IV) ions was first studied by
Janssen and Luijten (1963), in mixed ethanol-water solvent. Differences in the hydrolysis
constants of various trialkyltin(IV) cations were discussed by the authors in terms
of steric and inductive effects. Surprisingly, the values obtained for tributyltin cation
and other systems in the mixed solvent are very close to those found by Tobias et al.
(1966) for (CH 3 hSn+ and (C2H s hSn+ in 3 mol dm- 3 aqueous NaCI0 4 solution. Apart
from the difficulty of interpretation of acidity measurements in mixed water organic
solvents, it must be said that the good agreement with hydrolysis constant values of
analogous water soluble systems, such as (CH 3hSn +, allows us to extrapolate the same
considerations for low water soluble systems too. Acid-base properties of (CH3hSn+
and (C 2 H s hSn+ cations in aqueous solutions were also studied by Asso and Carpeni
(1968), by means of potentiometry, at 25°C and different ionic strengths. Hynes and
O'Dowd (1987) reported the hydrolysis constant value of (CH3hSn(OH) in a study
of the interactions of trimethyltin cation with carboxylic acids and aminoacids. Further investigations into the hydrolysis process of (CH3hSn(H20)t were conducted
by Hynes et al. (1991) by means of 119Sn-NMR spectroscopy. Investigations into the
hydrolysis processes of trimethyltin(IV) cation, with the aim of defining the chemi
cal speciation of that cation in natural fluids, have been very recently reported by
Takahashi et al. (1997) (NaCI04 ionic medium, 1= 0.1 mol dm-3, T = 25°C) and by
Cannizzaro et al. (1998) (NaN03, NaCI and Na2S04 aqueous media, 0.1 ~I~ 1.0 mol dm- 3
and 5 ~ T (OC) ~ 45). Hydrolysis constants are expressed as log f3pq according to the reaction:
(11.2)
Table 11.1. literature data for the hydrolysis constants of the (CH3hSn + at T = 25 DC
Ionic medium
l(moldm- 3 )
-log fJ 11
-log fJ 12
Reference
NaCI0 4
3
6.59
Tobias et al. (1966)
KCI
2
6.40
Asso and Carpeni (1968)
NaClO 4
0.3
6.26
Hynes and O'Dowd (1987)
KN0 3
0.5
6.35
Hynes et al. (1991)
KCI
0.5
6.38
Hynes et al. (1991)
NaN0 3
0.5
6.21
18.95
Cannizzaro et al. (1998)
NaCI
0.5
6.25
18.99
Cannizzaro et al. (1998)
215
11.2.1
Trialkyltin Compounds
Among trialkyltin compounds, tributyl derivatives are the most widely distributed in
the aquatic environment, owing to their industrial applications (see Table 11.1).A number of articles on their toxicological effects exist in literature. Useful updated information on this subject can be found in the very recent book by Champ and Seligman
(1996).
The acidity of some low water soluble trialkyltin(IV) ions was first studied by
Janssen and Luijten (1963), in mixed ethanol-water solvent. Differences in the hydrolysis
constants of various trialkyltin(IV) cations were discussed by the authors in terms
of steric and inductive effects. Surprisingly, the values obtained for tributyltin cation
and other systems in the mixed solvent are very close to those found by Tobias et al.
(1966) for (CH 3 hSn+ and (C2H s hSn+ in 3 mol dm- 3 aqueous NaCI0 4 solution. Apart
from the difficulty of interpretation of acidity measurements in mixed water organic
solvents, it must be said that the good agreement with hydrolysis constant values of
analogous water soluble systems, such as (CH 3hSn +, allows us to extrapolate the same
considerations for low water soluble systems too. Acid-base properties of (CH3hSn+
and (C 2 H s hSn+ cations in aqueous solutions were also studied by Asso and Carpeni
(1968), by means of potentiometry, at 25°C and different ionic strengths. Hynes and
O'Dowd (1987) reported the hydrolysis constant value of (CH3hSn(OH) in a study
of the interactions of trimethyltin cation with carboxylic acids and aminoacids. Further investigations into the hydrolysis process of (CH3hSn(H20)t were conducted
by Hynes et al. (1991) by means of 119Sn-NMR spectroscopy. Investigations into the
hydrolysis processes of trimethyltin(IV) cation, with the aim of defining the chemi
cal speciation of that cation in natural fluids, have been very recently reported by
Takahashi et al. (1997) (NaCI04 ionic medium, 1= 0.1 mol dm-3, T = 25°C) and by
Cannizzaro et al. (1998) (NaN03, NaCI and Na2S04 aqueous media, 0.1 ~I~ 1.0 mol dm- 3
and 5 ~ T (OC) ~ 45). Hydrolysis constants are expressed as log f3pq according to the reaction:
(11.2)
Table 11.1. literature data for the hydrolysis constants of the (CH3hSn + at T = 25 DC
Ionic medium
l(moldm- 3 )
-log fJ 11
-log fJ 12
Reference
NaCI0 4
3
6.59
Tobias et al. (1966)
KCI
2
6.40
Asso and Carpeni (1968)
NaClO 4
0.3
6.26
Hynes and O'Dowd (1987)
KN0 3
0.5
6.35
Hynes et al. (1991)
KCI
0.5
6.38
Hynes et al. (1991)
NaN0 3
0.5
6.21
18.95
Cannizzaro et al. (1998)
NaCI
0.5
6.25
18.99
Cannizzaro et al. (1998)