Paraquat (trivial name; /ˈpærəkwɒt/), or N,N′-dimethyl-4,4′-bipyridinium dichloride (systematic name), also known as methyl viologen, is a toxic organic compound with the chemical formula [(C₆H₇N)₂]Cl₂. It is classified as a viologen, a family of redox-active heterocycles of similar structure. It is one of the most widely used herbicides worldwide. It is quick-acting and non-selective, killing green plant tissue on contact.

Paraquat

Names
Preferred IUPAC name 1,1′-Dimethyl[4,4′-bipyridine]-1,1′-diium dichloride
Other names Paraquat dichloride; Methyl viologen dichloride; MVCl2; Crisquat; Dexuron; Esgram; Gramuron; Ortho Paraquat CL; Para-col; Pillarxone; Tota-col; Toxer Total; PP148; Cyclone; Gramixel; Gramoxone; Pathclear; AH 501; Bai Cao Ku.
Identifiers
CAS Number	1910-42-5 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:28786 Y
ChEMBL	ChEMBL458019 Y
ChemSpider	15146 Y
ECHA InfoCard	100.016.015
IUPHAR/BPS	4552
PubChem CID	15938
UNII	2KZ83GSS73 Y
CompTox Dashboard (EPA)	DTXSID7024243
InChI InChI=1S/C12H14N2.2ClH/c1-13-7-3-11(4-8-13)12-5-9-14(2)10-6-12;;/h3-10H,1-2H3;2*1H/q+2;;/p-2 Y Key: FIKAKWIAUPDISJ-UHFFFAOYSA-L Y InChI=1/C12H14N2.2ClH/c1-13-7-3-11(4-8-13)12-5-9-14(2)10-6-12;;/h3-10H,1-2H3;2*1H/q+2;;/p-2/fC12H14N2.2Cl/h;2*1h/qm;2*-1 InChI=1/C12H14N2.2ClH/c1-13-7-3-11(4-8-13)12-5-9-14(2)10-6-12;;/h3-10H,1-2H3;2*1H/q+2;;/p-2 Key: FIKAKWIAUPDISJ-NUQVWONBAF
SMILES C[n+]1ccc(cc1)c2cc[n+](cc2)C.[Cl-].[Cl-]
Properties
Chemical formula	C12H14Cl2N2
Molar mass	257.16 g·mol−1
Appearance	Yellow solid
Odor	faint, ammonia-like
Density	1.25 g/cm3
Melting point	175 to 180 °C (347 to 356 °F; 448 to 453 K)
Boiling point	> 300 °C (572 °F; 573 K)
Solubility in water	High
Vapor pressure	<0.0000001 mmHg (20 °C)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Toxic, environmental hazard
GHS labelling:
Pictograms
Hazard statements	H301, H311, H315, H319, H330, H335, H372, H410
Precautionary statements	P260, P273, P280, P284, P301+P310, P305+P351+P338
Lethal dose or concentration (LD, LC):
LD50 (median dose)	57 mg/kg (rat, oral) 120 mg/kg (mouse, oral) 25 mg/kg (dog, oral) 22 mg/kg (guinea pig, oral)
LC50 (median concentration)	3 mg/m3 (mouse, 30 min respirable dust) 3 mg/m3 (guinea pig, 30 min respirable dust)
LCLo (lowest published)	1 mg/m3 (rat, respirable dust, 6 h) 6400 mg/m3 (rat, nonrespirable dust, 4 h)
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 0.5 mg/m3 (resp) [skin]
REL (Recommended)	TWA 0.1 mg/m3 (resp) [skin]
IDLH (Immediate danger)	1 mg/m3
Safety data sheet (SDS)	Aldrich MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Paraquat is highly toxic to humans and other animals. The toxicity and lethality depends on the dose and how the herbicide is absorbed by the body. In humans, paraquat damages the mouth, stomach, and intestines if it is ingested orally. Once absorbed in the body, paraquat causes particular damage to the lungs, kidneys, and liver. Paraquat's lethality is attributed to its enhancing production of superoxide anions and human lung cells can accumulate paraquat. Paraquat exposure has been strongly linked to the development of Parkinson's disease.

Paraquat may be in the form of salt with chloride or other anions; quantities of the substance are sometimes expressed by cation mass alone (paraquat cation, paraquat ion). The name is derived from the para positions of the quaternary nitrogens.