1,4-Dioxane Chemistry, Uses, and Occurrence - Environmental Investigation and Remediation - page 76

O

O

O

O

O

O

FIGURE 2.2 1,4-Dioxane in the chair conformation (black = oxygen, gray = carbon, white = hydrogen). The
three conformations of 1,4-dioxane are shown below the ball and stick molecule. (After Mazurkiewicz, J. and
Tomasik, P., 2006, Journal of Molecular Liquids 126: 111-116.)

1,4-Dioxane is a Lewis base because its oxygen molecules have electrons available for sharing
(a base is a proton acceptor; a Lewis base is an electron-pair donor). The molecular structure of
1,4-dioxane is shown in Figure 2.1 . Its two oxygen atoms (in black) make it hydrophilic and ini -
nitely soluble in water. Conventional rankings of solvency for different solvents predict that pure
1,4-dioxane should have a medium degree of solvency; however, its anomalously high dipole moment
in aqueous solutions allows it to act as an efi cient water-structure breaker, which gives 1,4-dioxane
a higher solvency than expected. 1,4-Dioxane is most stable in the “chair conformation,” shown in
Figure 2.2 (Mazurkiewicz and Tomasik, 2006), but can shift between two boat and two chair con-
formations, occupying a different energy state in each conformation (Caulkins et al., 2006).
Table 2.3 summarizes structural properties of the 1,4-dioxane molecule, and Table 2.4 provides
a list of chemical and physical properties compiled from a variety of sources. The key property
controlling the fate and transport of 1,4-dioxane is its solubility. A tabulation of environmental fate
and transport properties is presented in Chapter 3.

TABLE 2.3
Structural Properties of the 1,4-Dioxane Molecule

Bond Length Bond Angle Bond Angle

Bond (Å) Components (°) Structure

C-H 1.112

C-C-O 109.2

C-O 1.423 Chair

C-O-C 112.45

C-C 1.523

Source: Lide, D.R., 2007, In: D.R. Lide, (ed.), CRC Handbook of Chemistry and Physics , Internet Version 2007, 8th Edition,
Boco Raton, FL: Taylor & Francis.
Note: Determined on vapor phase 1,4-dioxane.