Paclobutrazole

Structural formula
Mixture of four stereoisomers - structural formula without stereochemistry
General
Surname	Paclobutrazole
other names	(2 RS , 3 RS ) -1- (4-chlorophenyl) -4,4-dimethyl-2- (1,2,4-triazol-1-yl) pentan-3-ol α- tert -Butyl-β- (4-chlorobenzyl) -1 H -1,2,4-triazole-1-ethanol Paclobutracol PBZ
Molecular formula	C 15 H 20 ClN 3 O
Brief description	white, crystalline solid
External identifiers / databases
CAS number 76738-62-0 EC number 616-379-6 ECHA InfoCard 100.121.374 PubChem 73671 Wikidata Q3270569
properties
Molar mass	293.79 g mol −1
Physical state	firmly
density	1.23 g cm −3
Melting point	164 ° C
boiling point	384 ° C
Vapor pressure	0.0019 mPa (25 ° C)
solubility	practically insoluble in water (22.9 mg l −1 at 20 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 228-302-361 P: 210-280-301 + 312 + 330-370 + 378
Toxicological data	1336 mg kg −1 ( LD 50 ,  rat ,  oral ) > 20000 mg kg −1 ( LD 50 ,  rat ,  transdermal )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Paclobutrazole is a mixture of four isomeric chemical compounds from the triazole family that is used as a growth regulator with side effects as a fungicide . Paclobutrazol inhibits the formation of gibberellin and acts as a shortening of the internodes, which improves the stability and winter hardiness of grain and rape. In the past, paclobutrazole was used in concentrations of 500 to 1000 ppm to inhibit growth and promote flower formation in apple cultivation.

In subtropical growing countries such as South Africa it is used for litchi , avocado and mango . The potent growth inhibitor paclobutrazole is hardly broken down in the soil and maintains its effect for years.

Stereoisomers of paclobutrazole
(2 R , 3 R ) stereoisomer
(2 S , 3 S ) stereoisomer
(2 R , 3 S ) stereoisomer
(2 S , 3 R ) stereoisomer

Extraction and presentation

Paclobutrazole can be obtained by reacting 1,2,4-triazole with p -chlorobenzyl chloride , bromopinacolone and sodium borohydride .

Admission

In a number of EU countries, including Germany, Austria and Switzerland, plant protection products with this active ingredient are approved.

Trade names

PP 333 , Bonzi , Cultar , Clipper , Toprex

Individual evidence

1. ↑ ^{a b c d e f g h} Entry on paclobutrazole in the Pesticide Properties DataBase (PPDB) of the University of Hertfordshire , accessed on March 21, 2014.
2. ↑ ^{a b} Paclobutrazol data sheet from Sigma-Aldrich , accessed on May 21, 2017 ( PDF ).
3. ^ W. Aufhammer and K.-G. Federolf: Seed treatment with active ingredients to improve the cold tolerance of durum wheat ( T. durum ) 1991.
4. ↑ Lucas' Instructions for Fruit Growing, 31st edition 1992, p. 207.
5. ↑ David Jackson, Norman Earl Looney, Michael Morley-Bunker: Temperate and Subtropical Fruit Production . CAB International , 2011, p. 99 ( limited preview in Google Book search).
6. ↑ Thomas A. Unger: Pesticide Synthesis Handbook . William Andrew, 1996, ISBN 0-8155-1853-6 , pp. 690 ( limited preview in Google Book search).
7. ↑ General Directorate Health and Food Safety of the European Commission: Entry on paclobutrazole in the EU pesticide database; Entry in the national registers of plant protection products in Switzerland , Austria and Germany ; accessed on February 17, 2016.
8. ↑ Implementing Directive 2011/55 / ​​EU of the Commission of April 26, 2011 (PDF) amending Council Directive 91/414 / EEC to include the active substance paclobutrazole and amending Commission Decision 2008/934 / EC Text of significance for the EEA.