Nitrogen dioxide

Nitrogen dioxide

Nitrogen dioxide at −196 °C, 0 °C, 23 °C, 35 °C, and 50 °C. (NO 2) converts to the colorless dinitrogen tetroxide (N 2O 4) at low temperatures, and reverts to NO 2 at higher temperatures.
Names
IUPAC name Nitrogen dioxide
Other names Nitrogen(IV) oxide, Deutoxide of nitrogen
Identifiers
CAS Number	10102-44-0 Y
3D model (Jmol)	Interactive image Interactive image
ChEBI	CHEBI:33101 Y
ChemSpider	2297499 Y
ECHA InfoCard	100.030.234
EC Number	233-272-6
Gmelin Reference	976
PubChem	3032552
RTECS number	QW9800000
UNII	S7G510RUBH N
UN number	1067
InChI InChI=1S/NO2/c2-1-3 Y Key: JCXJVPUVTGWSNB-UHFFFAOYSA-N Y InChI=1/NO2/c2-1-3 Key: JCXJVPUVTGWSNB-UHFFFAOYAA
SMILES N(=O)[O] [N+](=O)[O-]
Properties
Chemical formula	NO• 2
Molar mass	46.0055 g mol−1
Appearance	Vivid orange gas
Odor	Chlorine like
Density	1.88 g dm−3
Melting point	−11.2 °C (11.8 °F; 261.9 K)
Boiling point	21.2 °C (70.2 °F; 294.3 K)
Solubility in water	Hydrolyses
Solubility	soluble in CCl 4, nitric acid,chloroform
Vapor pressure	98.80 kPa (at 20 °C)
Magnetic susceptibility (χ)	+150.0·10−6 cm3/mol
Refractive index (nD)	1.449 (at 20 °C)
Structure
Point group	C2v
Molecular shape	Bent
Thermochemistry
Specific heat capacity (C)	37.5 J/mol K
Std molar entropy (So298)	240 J mol−1 K−1
Std enthalpy of formation (ΔfHo298)	+34 kJ mol−1
Hazards
Main hazards	Poison, oxidizer
Safety data sheet	ICSC 0930
GHS pictograms
GHS signal word	Danger
GHS hazard statements	H270, H314, H330
GHS precautionary statements	P220, P260, P280, P284, P305+351+338, P310
EU classification (DSD)	O T+
R-phrases	R26, R34, R8
S-phrases	(S1/2), S9, S26, S28, S36/37/39, S45
NFPA 704	0 3 2 OX
Lethal dose or concentration (LD, LC):
LC50 (median concentration)	30 ppm (guinea pig, 1 hr) 315 ppm (rabbit, 15 min) 68 ppm (rat, 4 hr) 138 ppm (rat, 30 min) 1000 ppm (mouse, 10 min)
LCLo (lowest published)	64 ppm (dog, 8 hr) 64 ppm (monkey, 8 hr)
US health exposure limits (NIOSH):
PEL (Permissible)	C 5 ppm (9 mg/m3)
REL (Recommended)	ST 1 ppm (1.8 mg/m3)
IDLH (Immediate danger)	20 ppm
Related compounds
Related Nitrogen oxides	Dinitrogen pentoxide Dinitrogen tetroxide Dinitrogen trioxide Nitric oxide Nitrous oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Dinitrogen tetroxide
Dinitrogen trioxide
Nitric oxide
Nitrous oxide

Nitrogen dioxide is the chemical compound with the formula NO
2. It is one of several nitrogen oxides. NO
2 is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. At higher temperatures it is a reddish-brown gas that has a characteristic sharp, biting odor and is a prominent air pollutant. Nitrogen dioxide is a paramagnetic, bent molecule with C_2vpoint group symmetry.

Nitrogen dioxide is a reddish-brown gas above 70 °F (21 °C; 294 K) with a pungent, acrid odor, becomes a yellowish-brown liquid below 70 °F (21 °C; 294 K), and converts to the colorless dinitrogen tetroxide (N
2O
4) below 15 °F (−9 °C; 264 K).

The bond length between the nitrogen atom and the oxygen atom is 119.7 pm. This bond length is consistent with a bond order between one and two.

Unlike ozone, O₃, the ground electronic state of nitrogen dioxide is a doublet state, since nitrogen has one unpaired electron, which decreases the alpha effect compared with nitrite and creates a weak bonding interaction with the oxygen lone pairs. The lone electron in NO
2 also means that this compound is a free radical, so the formula for nitrogen dioxide is often written as ^•NO
2.