Environmental Fate and Transport of Solvent-Stabilizer Compounds - Environmental Investigation and Remediation - page 129

TABLE 3.6
Ranges of Measured and Calculated Aqueous Photo-Oxidation Half-Lives for
Solvent-Stabilizer Compounds

Aqueous Photo-Oxidation, t 1/2

Compound High Low References

1,4-Dioxane 9.1 years 67 days Anbar and Neta (1967),

Dorfman and Adams (1973)

sec -Butyl alcohol 23 years 129 days Anbar and Neta (1967),

Dorfman and Adams (1973)

1,2-Butylene oxide 55 years 1.4 years Howard et al. (1991)

tert -Butyl alcohol 64,500 years 2.1 years Anbar and Neta (1967),

Dorfman and Adams (1973)

Ethyl acetate 110 years 2.75 years Dorfman and Adams (1973),

Howard et al. (1991)

Pyridine 24.4 years 14.7 years Dorfman and Adams (1973),

Howard et al. (1991)

Acetonitrile 12,560 years 314 years Dorfman and Adams (1973),

Howard et al. (1991)

Methyl ethyl ketone 81.4 years 48.8 years Anbar and Neta (1967),

Howard et al. (1991)

Cyclohexane 7,800,000 years 160,000 years Howard et al. (1991)

summary is given in Hemond and Fechner (1994), and a detailed, analytical treatment is given in
Thibodeaux (1996). The potential for photolysis and photo-oxidation of stabilizer compounds and their
relative potential rates of volatilization from surface-water bodies is discussed in the previous sections
of this chapter. This section focuses on the physical and chemical fate of stabilizer compounds in sur-
face-water bodies. Most of these processes are common to the groundwater fate and transport of stabi-
lizer compounds; adsorption and biological processes are discussed in Section 3.3 .

3.2.1 H YDROLYSIS
Hydrolysis is a form of nucleophilic substitution reaction in which water is the nucleophile (Hemond
and Fechner, 1994; Harris, 1990b). More specii cally, hydrolysis is a chemical reaction in which an
organic molecule, RX, * reacts with hydroxide from the ionization of a water molecule, forming a
new carbon-oxygen bond and cleaving a carbon-X bond in the organic molecule, producing H + X − .
Both the organic compound and the water molecule are split in a hydrolysis reaction, which is essen-
tially a displacement of X by a hydroxyl group (-OH):

RX + H 2 O → ROH + X − + H + . (3.18)

Hydrolysis acts on organic molecules that possess electrophiles, that is, electron-seeking atoms
such as carbon and phosphorous. The nucleophile (water or hydroxide) attacks the electrophile (e.g.,
H + ) and displaces the functional group that leaves the molecule, often chloride or phenoxide. Some
groups of chemicals are resistant to hydrolysis, including many of the solvent-stabilizer compounds,

* In the RX notation, R usually represents a hydrocarbon, such as an alkyl group, and X represents an organic functional
group, such as an ester, amine, or aldehyde.