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CHAPTER 2
CHLORINATED SOLVENT CHEMISTRY: STRUCTURES,
NOMENCLATURE AND PROPERTIES
David M
...
Scherer2
1

University of California at Riverside, Riverside, CA 92521; 2The University of Iowa, Iowa
City, IA 52242

2
...


2
...
For the current discussion, chlorinated solvents will be further divided into
three categories based upon common structural characteristics: chlorinated methanes, chlorinated ethanes and chlorinated ethenes
...
1
...
1
...
From the perspective of groundwater contamination, perhaps the
most well known chlorinated methane is carbon tetrachloride (CT)
...
By IUPAC conventions, the modifier of
“tetra” serves as an indicator of the number of chlorine atoms bound to the carbon center
...
Named in a
similar fashion by IUPAC, the chlorinated methanes with a lower degree of halogenation are
trichloromethane (commonly referred to as chloroform [CF]), dichloromethane (DCM, more
commonly called methylene chloride [MC]) and chloromethane (CM, also referred to as
methyl chloride)
...

Common groundwater pollutants from this class include 1,1,1-trichloroethane (1,1,1-TCA) and
1,2-dichloroethane
...
Common acronyms for this class follow the pattern in which the first letter (or series
of letters) refers to the number of total halogen substituents (e
...
, “T” for trichloro- or “Te” for
H
...
Stroo and C
...
Ward (eds
...
1007/978-1-4419-1401-9_2, # Springer Science+Business Media, LLC 2010

29

30

D
...
Cwiertny and M
...
Scherer
Cl

Cl

C

C
H

H

H

Cl

Cl

H

Cl

dichloromethane
(DCM)

carbon tetrachloride
(CT)

Cl

Cl

H
C

Cl

H

Cl
C

C
Cl
H

Cl

Cl

H

H
C

1,1,1 - trichloroethane
(1,1,1-TCA)

C

C

Cl
Cl

1,1,2,2 - tetrachloroethane
(1,1,2,2-TeCA)

H

vinyl chloride
(VC)
H

Cl
C

Cl

Cl

Cl
C

C
Cl

trichloroethene
(TCE)

Cl

C
Cl

perchloroethene
(PCE)

Figure 2
...
Chemical structures of some common chlorinated solvents
...
g
...

In addition, the numbers preceding the name or abbreviation indicate the location of the
chlorine substituents on the two possible carbon centers
...
In certain instances, there can
be more than one way in which the same number of chlorine atoms distribute themselves on the
carbon centers, as is the case for 1,1,2-TCA and 1,1,1-TCA
...

Chlorinated ethenes (sometimes referred to as chlorinated ethylenes) also possess two
carbon centers, but unlike chlorinated ethanes, these carbon atoms are joined by a carboncarbon double bond known as a p-bond (pi-bond) system
...
The double-bonded carbon centers in chlorinated
ethenes can accommodate at most two halogen (or hydrogen) substituents, whereas the singlebonded ethanes can accommodate three halogen (or hydrogen) substituents
...

Another chlorinated ethene of note is the monochlorinated species that is most commonly
referred to as vinyl chloride (VC)
...
g
...
The same is true for the acronyms
commonly applied to this solvent class, only this time the last letter in all cases is “E”, which
represents “ethenes”
...


Table 2
...
Nomenclature for Selected Chlorinated Solvents
IUPAC Name

Common Name

Abbreviation/Acronym

Molecular Formula

carbon tetrachloride

CT

CCl4

trichloromethane

chloroform

CF

CHCl3

dichloromethane

methylene chloride

DCM

CH2Cl2

methyl chloride

CM

CH3Cl

hexachloroethane

perchloroethane

HCA

C2Cl6

pentachloroethane

----

PCA

C2HCl5

1,1,1,2-tetrachloroethane

----

1,1,1,2-TeCA

C2H2Cl4

1,1,2,2-tetrachloroethane

----

1,1,2,2-TeCA

C2H2Cl4

1,1,2-trichloroethane

----

1,1,2-TCA

C2H3Cl3

1,1,1-trichloroethane

methyl chloroform

1,1,1-TCA

C2H3Cl3

1,2-dichloroethane

----

1,2-DCA

C2H4Cl2

1,1-dichloroethane

----

1,1-DCA

C2H4Cl2

chloroethane

----

CA

C2H5Cl

perchloroethene

PCE

C2Cl4

----

TCE

C2HCl3

Chlorinated Methanes
tetrachloromethane

chloromethane
Chlorinated Ethanes

Chlorinated Ethenes
tetrachloroethene
trichloroethene
cis-1,2-dichloroethene
trans-1,2-dichloroethene
1,1-dichloroethene
chloroethene

cis-dichloroethene

cis-DCE

C2H2Cl2

trans-dichloroethene

trans-DCE

C2H2Cl2

vinylidene chloride

1,1-DCE

C2H2Cl2

vinyl chloride

VC

C2H3Cl

Additional nomenclature is necessary in order to distinguish the possible isomers of
dichloroethene
...
In addition, the p-bond system in chlorinated
ethenes differs from the single carbon-carbon bond in chlorinated ethanes because it does not
allow the halogen substituents to rotate freely in the plane perpendicular to the direction of the
p-bond
...
2)
...

Alternatively, the chlorine atoms can be located on the opposite side of the p-bond system in a
configuration known as trans
...


32

D
...
Cwiertny and M
...
Scherer
Cl

Cl
C

C

H

H
C

H
cis-DCE

Cl
C

H
Cl
trans-DCE

Figure 2
...
Conformational isomers of 1,2-dichloroethene
...
For instance, chlorinated
propanes, which possess three carbon atoms joined by single bonds, can represent important
groundwater pollutants
...
S
...
Another example is 1,2,3-trichloropropane, which has been detected at more than 20
National Priorities List sites identified by the USEPA (ATSDR, 1992)
...

Although this chapter is devoted to treatment strategies for chlorinated solvents, solvents
with other halogen substituents (such as bromine or fluorine) are also frequently encountered in
contaminated groundwater
...

Methanes, ethanes and ethenes with mixed halogen substituents can represent important
environmental pollutants as well, as is the case for common disinfection byproducts bromodichloromethane (CHBrCl2) and dibromochloromethane (CHBr2Cl)
...


2
...
The properties considered most relevant to chlorinated
solvent fate and transport in the subsurface are summarized in Table 2
...
In order to maintain
some consistency among the values presented, the majority of the values were obtained from
Mackay et al
...
In general, there is reasonable agreement between these values
and several other summary tables available (e
...
, Pankow and Cherry, 1996; Fetter, 1999;
Schwarzenbach et al
...
Table 2
...
For a review of the primary literature,
Pankow and Cherry (1996) is recommended because it provides a detailed review of the
chlorinated solvent properties discussed herein as well as an excellent discussion of the history
of production and industrial uses of chlorinated solvents
...
An overview linking these partitioning processes to the relevant chlorinated solvent
properties is provided in Figure 2
...
The discussion concludes with an introduction to transformation reactions, which are discussed in greater detail in Chapters 3 and 4
...
2
...
Unless otherwise noted, all values have been taken from Mackay et al
...


Species

Formula Carbon
Weight Oxidation
Statea
(g/mol)

Henry’s
Law
Vapor
Constant
Density Solubility (S) Pressure (KH) ( 10-3
(po) (torr) atm·m3/mol)
(r) (g/mL)
(mg/L)

Log
(Kow)

Log
(Koc)b

MCLc
(mg/L)

Chlorinated Methanes
CT

153
...
59

800

153
...
9

2
...
9

0
...
4

+III

1
...
8

3
...
97

1
...
10d

DCM

84
...
33

13,200

415

1
...
25

----

0
...
5

+I

0
...
6

0
...
38f

----

3
...
7

+III

2
...
3

+II

1
...
7

2
...
89

----

NR

1122-TeCA

167
...
60

2,962

5
...
44

2
...
9

NR

1112-TeCA

167
...
54

1,100

11
...
4

----

----

NR

111-TCA

133
...
35

1,495

123
...
5

2
...
25

0
...
4

0

1
...
2

0
...
38

----

0
...
0

-I

1
...
0

1
...
48

1
...
005

11-DCA

99
...
17

4,676

227

6
...
79

----

NR

CA

64
...
90

5,700

120

1
...
43

----

NR

Chlorinated Ethenes
PCE

165
...
63

150

18
...
3

2
...
29

0
...
4

+I

1
...
2

11
...
53

1
...
005

cis-DCE

96
...
28

3,500

203

7
...
86

----

0
...
9

0

1
...
8

1
...
1

11-DCE

96
...
22

3,344

604

23
...
13

----

0
...
5

-I

0
...
2

1
...
002

Average value calculated using oxidation states for H ¼ þI and Cl ¼ I
...
(2005)
...

d
MCL for total trihalomethanes, which is defined as the summed concentration of chloroform, bromoform (CHBr3),
bromodichloromethane (CHBrCl2), and dibromochloromethane (CHBr2Cl)
...

f
Reported vapor pressure for solid-phase hexachloroethane
...

a
b

Water
KH @

p°

S, KOW, KOC

S

Air

Soil
p°

Figure 2
...
The three major phases present in the subsurface and the properties of chlorinated
solvents that govern the partitioning between these phases
...
3
...


34

D
...
Cwiertny and M
...
Scherer

Chlorinated solvents are typically discharged into the environment as pure organic liquids or as
mixtures of several organic liquids
...

For a chlorinated solvent, the extent of dissolution is controlled by the solvent’s aqueous
solubility (S), defined as the maximum amount of a chlorinated solvent that will partition
into water at a given temperature (Lyman, 1982)
...
, 2003), aqueous solubilities are typically reported with units of
moles of chlorinated solvent per liter of water (molarity or M) or milligrams of chlorinated
solvent per liter of water (mg/L, which is equivalent to parts per million [ppm])
...
2)
...
Another consequence of their limited solubility is their tendency to occur in the subsurface as a separate
liquid phase at the base of an aquifer commonly referred to as dense nonaqueous phase
liquid (DNAPL)
...
2 reveals the general solubility trend among chlorinated solvents- as the number
of chlorine atoms on a compound increases, the aqueous solubility of that species decreases
...
, 1999]) exerts on the miscibility of a chlorinated solvent in water
...
One such variable is
temperature, although changes in the solubility of most chlorinated solvents are relatively
minor over environmentally relevant temperature ranges (Horvath, 1982)
...
The presence of other organic
chemicals (referred to as co-solutes) also can increase the saturation concentration of
chlorinated solvents in water, behavior that is utilized for the treatment of chlorinated
solvents during surfactant-enhanced aquifer remediation (SEAR) (e
...
, Pennell et al
...
, 1996)
...
3
...
As a class, chlorinated solvents can be considered moderately hydrophobic;
although they partition (or sorb) onto aquifer solids, their affinity for such processes is not
as great as that for other organic pollutants such as polycyclic aromatic hydrocarbons (PAHs)
or polychlorinated biphenyls (PCBs)
...
For a two-phase system containing octanol and water, values of Kow are
defined as the equilibrium concentration of the chlorinated solvent in octanol relative to its
equilibrium concentration in water (Equation 2
...



Coctanol
Kow ¼
(Eq
...
1)
Cwater
For laboratory investigations of hydrophobicity, octanol is chosen as a convenient reference
solvent because it is immiscible with water
...


Chlorinated Solvent Chemistry: Structures, Nomenclature and Properties

35

More pertinent for describing processes in the subsurface are values of Koc, which
represent a measure of a chemical’s equilibrium partitioning between water and the organic
carbon fraction of aquifer solids (Equation 2
...



Corganic carbon
Koc ¼
(Eq
...
2)
Cwater
Accordingly, a key factor controlling the extent of chlorinated solvent sorption is the
organic carbon content of the subsurface material and the dissolved organic matter
...

In Table 2
...
These larger values of solid-water partitioning coefficients will result in slower rates of subsurface transport
...
2; chemicals with limited
aqueous solubilities generally prefer to partition into a phase such as octanol or soil organic
matter rather than associate with water
...
3
...
Accordingly, air-water partitioning
is expected to take place when contaminated groundwater comes into contact with air, as is the
case in unsaturated subsurface zones (e
...
, the vadose zone)
...
The Henry’s Law constant, KH, relates the
equilibrium concentration of the chlorinated solvent in air to its equilibrium concentration in
water (Equation 2
...



Cair
KH ¼
(Eq
...
3)
Cwater
By definition, large KH values indicate a chemical’s preference to partition from water into
air, although additional chemical properties and several environmental factors will also influence the volatility of a species (Thomas, 1982a)
...
2, KH values are reported with units of atm·m3/mol, but KH values also are
commonly reported with alternative units that depend upon the conventions used to report the
chlorinated solvent’s concentrations in air and water
...
2 do not reveal any significant trends within or across the
different classes of chlorinated solvents
...
3
...
As with volatilization between air and
water, several chemical and environmental factors are at play in solid-air partitioning processes
(Thomas, 1982b), but our mechanistic understanding of this process is rather limited
...
, 2003)
...
M
...
M
...
Values of p
tend to decrease with increasing chlorination, although
exceptions to this generalization are frequently observed (e
...
, compare the p
values for
chloroethane and 1,1,2-trichloroethane in Table 2
...


2
...
5 Transformation Reactions
Not included in Figure 2
...
Rates and products of transformation
reactions will depend upon many of the chemical and physical properties discussed above, as
well as the average oxidation state of carbon in the chlorinated solvent (Table 2
...
The carbon
oxidation state is a measure of the number of electrons associated with the carbon atoms
in a chlorinated solvent; this value ranges from I to +IV for the chlorinated solvents listed in
Table 2
...
The more negative the oxidation state, the more electrons associated with the carbon
atom
...
g
...
On the other hand,
chlorinated solvents with more reduced carbon centers, such as vinyl chloride (C oxidation state
of I), are more susceptible to being oxidized (losing electrons)
...
Biotic reactions are typically those that involve microbial processes associated with
bacterial metabolism, whereas abiotic reactions are defined as those processes that involve
another chemical species
...

The classification does, however, provide a convenient organizational structure for discussing the principles of chlorinated solvent remediation, and it has been adopted for use by the
authors in Chapter 4
...
Chapter 4 describes the important abiotic processes for chlorinated solvents, including sorption, volatilization and transformation reactions such as substitution, elimination, oxidation and reduction
...


REFERENCES
ATSDR (Agency for Toxic Substances and Disease Registry)
...
Toxicological profile
for 1,2,3-trichloropropane
...
S
...
http://www
...
cdc
...
pdf
...

Baird C, Cann M
...
Environmental Chemistry, 3rd ed
...
H
...
652 p
...
1999
...
Prentice-Hall, Inc
...
500 p
...
1996
...
Ground Water 34:910–916
...
1982
...
Marcel
Dekker, New York, NY, USA
...


Chlorinated Solvent Chemistry: Structures, Nomenclature and Properties

37

Horvath AL, Getzen FW, Maczynska Z
...
IUPAC-NIST solubility data series 67
...
J Phys Chem Ref Data 28:395–628
...
1982
...
In Lyman WJ, Reehl WF, Rosenblatt DH, eds, Handbook
of Chemical Property Estimation Methods: Environmental Behavior of Organic
Compounds
...

Mackay D, Shiu WY, Ma KC
...
Illustrated Handbook of Physical-Chemical Properties and
Environmental Fate for Organic Chemicals
...

Nguyen TH, Goss K, Ball WP
...
Polyparameter linear free energy relationships for
estimating the equilibrium partition of organic compounds between water and the natural
organic matter in soils and sediments
...

Pankow JF, Cherry JA
...
Dense Chlorinated Solvents and Other DNAPLs in Groundwater:
History, Behavior, and Remediation
...
525 p
...
1994
...
J Contam Hydrol 16:35–53
...
2003
...

John Wiley & Sons, Inc
...
1313 p
...
1982a
...
In Lyman WJ, Reehl WF, Rosenblatt DH, eds,
Handbook of Chemical Property Estimation Methods: Environmental Behavior of Organic
Compounds
...
1–15
...

Thomas RG
...
Volatilization from Soil
...
1–16
...

USEPA (U
...
Environmental Protection Agency)
...
Ground Water and Drinking Water
...
EPA-816-F-03-016
...

Vollhardt KPC, Schore NE
...
Organic Chemistry
...
H
...
1156 p
...
springer

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