Picloram

Structural formula
General
Surname	Picloram
other names	4-amino-3,5,6-trichloropyridine-2-carboxylic acid 4-amino-3,5,6-trichloropicolinic acid Tordon
Molecular formula	C 6 H 3 Cl 3 N 2 O 2
Brief description	colorless powder with a chlorine-like odor
External identifiers / databases
CAS number 1918-02-1 EC number 217-636-1 ECHA InfoCard 100.016.034 PubChem 15965 ChemSpider 15170 Wikidata Q424662
properties
Molar mass	241.46 g · mol -1
Physical state	firmly
Melting point	190 ° C (16 mbar, sublimation)
Sublimation point	190 ° C (16 h Pa )
solubility	very heavy in water (430 mg l −1 at 25 ° C)
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 319 P: 305 + 351 + 338
MAK	Switzerland: 10 mg m −3 (measured as inhalable dust )
Toxicological data	8200 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Picloram is a chlorinated derivative of picolinic acid , an isomer of nicotinic acid . The heterocyclic compound from the group of azines is derived from pyridine . The active ingredient is known as a herbicide under the trade name Tordon .

history

Picloram was originally developed around 1964 by the Dow Chemical Cooperation for military purposes (as a defoliant , i.e. as a chemical warfare agent for the destruction of vegetation ). It was part of the warfare agent Agent White - a mixture of 2,4-dichlorophenoxyacetic acid (2,4-D) and picloram - the United States Army , who in the Vietnam War was used to defoliate (→ Operation Ranch Hand ).

properties

The colorless, flammable powder dissolves little in water (430 mg / l at 25 ° C). From 218.5 ° C the substance begins to decompose into hydrogen chloride , nitrogen oxides , carbon monoxide and carbon dioxide .

use

Estimated US application volume in 2012

Picloram is a selective herbicide with systemic properties that is quickly absorbed through roots and leaves. The effects are similar to those of auxins (such as indole-3-acetic acid ). By influencing the RNA and protein biosynthesis , the hormonal balance of the plants is disrupted and cell division and stretching are disrupted . Curvatures, adhesions, stem and leaf deformations and adventitious root formation are typical symptoms .

Depending on the dose used, Picloram has a wide range of effects, for example against hardwood and knotweed . In South and North America, Picloram is the most important active ingredient for weed control on grassland .

The active ingredient Picloram is approved in the European Union. In Germany, Austria and Switzerland it is used in the product Effigo together with clopyralid for weed control in winter rape .

Picloram is persistent for a relatively long time with higher amounts of active ingredient . For this reason, there can be problems with reproducing legumes and nightshade plants .

It is also often used in the form of its esters or salts. So are picloram-2-ethylhexyl ester (CAS number: 36374-99-9), picloram isooctyl ester (26952-20-5), picloram methyl ester (14143-55-6), picloram-2-aminoethanol salt (55871-00 -6), Picloram potassium salt (2545-60-0), Picloram triethylammonium salt (35832-11-2), Picloram tris (2-hydroxypropylammonium salt (6753-47-5) and other derivatives are known, with only two of the derivatives have a license as a pesticide.

Individual evidence

1. ↑ ^{a b c d e f g h} Entry on 4-amino-3,5,6-trichloropyridine-2-carboxylic acid in the GESTIS substance database of the IFA , accessed on February 9, 2017(JavaScript required) .
2. ↑ Schweizerische Unfallversicherungsanstalt (Suva): Limit values ​​- current MAK and BAT values (search for 1918-02-1 or Picloram ), accessed on November 2, 2015.
3. ^ Extension Toxicology Network: Picloram Pesticide Information Profile , Pesticide Management Education Program, Cornell University .
4. ↑ EPA : Consumer Factsheet on: PICLORAM .
5. ↑ Entry on Picloram. In: Römpp Online . Georg Thieme Verlag, accessed on December 29, 2014.
6. ↑ General Directorate Health and Food Safety of the European Commission: Entry on Picloram in the EU pesticide database; Entry in the national registers of plant protection products in Switzerland , Austria and Germany ; Retrieved February 19, 2016.
7. ↑ pesticide.org: Pesticide Factsheet Picloram ( Memento of May 13, 2015 in the Internet Archive ), spring 1998.