NITROPHENOLS 71
CHAPTER 4. CHEMICAL AND PHYSICAL INFORMATION
4.1 CHEMICAL IDENTITY
Nitrophenols (also referred to as mononitrophenols) exist in three isomeric forms: 2-nitrophenol (or
ortho- or o-), 3-nitrophenol (or meta- or m-), and 4-nitrophenol (or para- or p-). All three of these
nitrophenols are manmade. Table 4-1 lists common synonyms, trade names, and other pertinent
identification information for 2-nitrophenol, Table 4-2 lists this information for 3-nitrophenol, and
Table 4
-3 lists this information for 4-nitrophenol.
Table 4-1. Chemical Identity of 2-Nitrophenol
Characteristic
Information
Chemical Name
2-Nitrophenol
Synonym(s) and Registered trade
name(s)
O-Hydroxynitrobenzene; 2-Hydroxynitrobenzene; o-Nitrophenol;
Phenol, o-nitro-; Phenol, 2-nitro
Chemical formula
C
6
H
5
NO
3
Chemical structure
CAS registry number
88-75-5
CAS = Chemical Abstracts Service
Source: NLM 2022a
NITROPHENOLS 72
4. CHEMICAL AND PHYSICAL INFORMATION
Table 4-2. Chemical Identity of 3-Nitrophenol
Characteristic
Information
Chemical Name
3-Nitrophenol
Synonym(s) and Registered trade
name(s)
M-Hydroxynitrobenzene; 3-Hydroxynitrobenzene; m-Nitrophenol;
Phenol, m-nitro-; Phenol, 3-nitro-;
Chemical formula
C
6
H
5
NO
3
Chemical structure
CAS registry number
554-84-7
CAS = Chemical Abstracts Service
Source: NLM 2022b
Table 4-3. Chemical Identity of 4-Nitrophenol
Characteristic
Information
Chemical Name
4-Nitrophenol
Synonym(s) and Registered trade
name(s)
P-Hydroxynitrobenzene; 4-Hydroxynitrobenzene; Niphen;
P-Nitrophenol; Paranitrophenol; Phenol, p-nitro-; Phenol, 4-nitro-;
PNP
Chemical formula
C
6
H
5
NO
3
Chemical structure
CAS registry number
100-02-7
CAS = Chemical Abstracts Service
Source: NLM 2022c
NITROPHENOLS 73
4. CHEMICAL AND PHYSICAL INFORMATION
4.2 PHYSICAL AND CHEMICAL PROPERTIES
2-Nitrophenol is a light yellow, aromatic solid; 3- and 4-nitrophenol are colorless to pale yellow solids.
The nitrophenols are expected to be highly soluble in water. They also have low vapor pressures, and
therefore, low potential for long range atmospheric transport (Harrison et al. 2005). Tables 4-4, 4-5, and
4-6
. List important physical and chemical properties of 2-, 3-, and 4-nitrophenol, respectively.
NITROPHENOLS 74
4. CHEMICAL AND PHYSICAL INFORMATION
Table 4-4. Physical and Chemical Properties of 2-Nitrophenol
Property
Information
Reference
Molecular weight
139.109
NLM 2022a
Color
Light yellow
O'Neil 2006
Physical state
Crystalline solid
NLM 2022a
Melting point
44–45°C
O'Neil 2006
Boiling point
216°C
Haynes et al. 2015
Density:
1.29 g/cm
3
at 40°C
Haynes et al. 2015
Odor
Aromatic
O'Neil 2006
Odor threshold:
Water
Air
10 mg/L
8x10
-11
moles/m
3
Verschueren1983
Fazzalari 1978
Taste threshold
0.001 mg/L
Verschueren1983
Solubility:
Water
2,100 mg/L at 20°C
2,500 mg/L at 25°C
10,800 mg/L at 100°C
Verschueren 1983
Yalkowsky et al. 2010
Verschueren 1983
Organic solvent(s)
Very soluble in ethanol, ether, acetone,
benzene, pyridine, chlorine; freely soluble
in carbon sulfide, alkali hydroxides
Budavari 1996; Haynes
et al. 2015
Partition coefficients:
Log K
ow
Log K
oc
1.79
1.76–2.04
Hansch et al. 1995
Gawlik et al. 1998; Tülp
et al. 2009
Vapor pressure
At 20°C
0.113 mm Hg at 25°C NLM 2022a
Henry’s law constant
1.3x10
-5
at 20°C
1.63x10
-5
at 25°C
Tremp et al. 1993
Harrison et al. 2002
Disassociation constant (pKa)
7.23
NLM 2022a
Autoignition temperature
550°C
NLM 2022a
Flashpoint
108°C
NLM 2022a
Flammability limits
No data
NLM 2022a
Conversion factors
ppm (v/v) to mg/m
3
in air at 20°C
mg/m
3
to ppm (v/v) in air at 20°C
1 ppm=5.783 mg/m
3
1 mg/m
3
=0.173 ppm
NLM 2022a
Explosive limits
No data
NLM 2022a
NITROPHENOLS 75
4. CHEMICAL AND PHYSICAL INFORMATION
Table 4-5. Physical and Chemical Properties of 3-Nitrophenol
Property
Information
Molecular weight
139.11 g/mol
Color
Colorless to pale yellow
Physical state
Crystalline solid
Melting point
96.8°C
Boiling point
194°C
Density:
At 20°C/4°C
1.485
Odor
Aromatic to sweetish
Odor threshold:
Water
Air
0.6 m/L
3.0 mg/m
3
Verschueren 1983
Taste threshold
No data
Solubility:
Water
Organic solvent(s)
13,550 mg/L at 25°C
133,000 mg/L at 90°C
Very soluble in acetone, ether, ethanol,
benzene
Yalkowsky et al. 2010
Verschueren 1983
Haynes et al. 2015
Partition coefficients:
Log K
ow
Log K
oc
2.00
1.68
Hansch et al. 1995
Vapor pressure
5.85x10
-5
mm Hg at 25°C
Henry’s law constant
2.00x10
-9
atm-m
3
/mole at 25°C
Dissociation constant
8.36
Autoignition temperature
400°C
Flashpoint
>100°C
Flammability limits
No data
Conversion factors
ppm (v/v) to mg/m
3
in air at 20°C
mg/m
3
to ppm (v/v) in air at 20°C
1 mg/m
3
=0.18 ppm
1 ppm=5.69 mg/m
3
NLM 2022b
Explosive limits
No data
NITROPHENOLS 76
4. CHEMICAL AND PHYSICAL INFORMATION
Table 4-6. Physical and Chemical Properties of 4-Nitrophenol
Property
Information
Molecular weight
139.11
Color
Colorless to slightly yellow
Physical state
Solid
Melting point
113–114°C
Boiling point
279°C
Density: At 20°C
1.479 g/cm
3
Odor
Odorless
Odor threshold:
Water
Air
2.5 mg/L
2.3 mg/m
3
Verschueren1983
Taste threshold
43.4 mg/L
Solubility:
Water
Organic solvent(s)
10,000 mg/L at 15°C
15,600 mg/L at 25°C
Very soluble in ethanol, ether, and
acetone; freely soluble in alcohol,
chloroform; soluble in solution of fixed
alkali hydroxides and carbonates
Verschueren1983
Yalkowsky et al. 2010
Haynes et al. 2015; O'Neil
2006
Partition coefficients:
Log K
ow
Log K
oc
1.91
2.37
Hansch et al. 1995
Vapor pressure
1.2x10
-5
mm Hg at 25°C Bannan et al. 2017
Henry’s law constant
1.28x10
-8
atm-m
3
/mol at 20°C
Dissociation constant
7.15
Autoignition temperature
490°C
Flashpoint
169°C
Flammability limits
No data
Conversion factors
ppm (v/v) to mg/m
3
in air at 20°C
mg/m
3
to ppm (v/v) in air at 20°C
1 mg/m
3
=0.173 ppm
1 ppm=5.783 mg/m
3
NLM 2022c
Explosive limits
No data