Addendum
to
Drinking
Water
Criteria
Document
for
Monochloroacetic
Acid
and
Trichloroacetic
Acid
EPA/
OW/
OST/
HECD
II­
1
Draft,
do
not
cite
or
quote
Chapter
II.
Physical
and
Chemical
Properties
Available
data
on
the
physical
and
chemical
properties
of
monochloroacetic
acid
(
MCA)

and
trichloroacetic
acid
(
TCA)
are
summarized
in
Table
II­
1,
and
the
structural
formulas
are
provided
in
Figure
II­
1.
The
data
contained
in
Table
II­
1
apply
to
the
pure
form
of
the
selected
chemicals.
These
chemicals
usually
exist
in
the
environment
in
an
aqueously
dissolved
form.

Table
II­
1.
Physical
and
Chemical
Properties
of
Chlorinated
Acetic
Acids1.

Property
Monochloroacetic
acid
(
MCA)
Trichloroacetic
acid
(
TCA)

CAS
Registry
No.
79­
11­
8
76­
03­
9
Formula
ClCH
2
COOH
Cl
3
CCOOH
Molecular
weight
94.50
163.39
Appearance/
color/
form
White
hygroscopic
monoclinic
crystals
White
hygroscopic
rhombohedral
crystals
Odor
penetrating,
pungent,

(
similar
to
vinegar)
sharp,
pungent
Density
(
g/
mL)
1.40­
1.60
1.60­
1.63
Melting
point
(

C)
52.5
58.0
Boiling
point
(

C)
187.8
197.5
Octanol­
water
partition
coefficient
(
log
P)
0.22
1.33­
1.7
Vapor
Pressure
(
mmHg)
at
25

C
0.065
0.16
(
1.0
at
51

C)

(
pK
a)
at
25

C
2.866
0.512­
0.70
Henry's
Law
constant
(
atm­
m3/
mole)

at
25

C
nd2
1.35
x
10­
8
Solubility:

Water
Alcohol
Ether
very
soluble
soluble
soluble
miscible
miscible
miscible
Addendum
to
Drinking
Water
Criteria
Document
for
Monochloroacetic
Acid
and
Trichloroacetic
Acid
EPA/
OW/
OST/
HECD
II­
2
Draft,
do
not
cite
or
quote
Figure
II­
1.
Chemical
Structures
of
Monochloroacetic
Acid
and
Trichloroacetic
Acid
TCA
Cl
C
OH
O
Cl
Cl
C
MCA
Cl
H
H
C
C
OH
O
1.
Adapted
from
U.
S.
EPA
(
1994),
and
HSDB
(
2001)
2.
nd
­
no
experimental
data
available
