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Paclobutrazol

Paclobutrazol NOMENCLATURE
Common name paclobutrazol (BSI, draft E-ISO, (m) draft F-ISO, ANSI)
IUPAC name (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)pentan-3-ol
Chemical Abstracts name (R*,R*)-(?--[(4-chlorophenyl)methyl]--(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol
CAS RN [76738-62-0] stated stereoisomers Development codes PP333 (ICI)

Paclobutrazol PHYSICAL CHEMISTRY
Composition Tech. material is 90% pure. Mol. wt. 293.8 M.f. C15H20ClN3O Form White, crystalline solid. M.p. 165-166 ºC V.p. 0.001 mPa (20 ºC) KOW logP = 3.2 Henry 1.13  10-5 Pa m3 mol-1 (calc.) S.g./density 1.22 g/ml Solubility In water 26 mg/l (20 ºC). In acetone 110, cyclohexanone 180, dichloromethane 100, hexane 10, xylene 60, methanol 150, propylene glycol 50 (all in g/l, 20 ºC). Stability Stable for more than 2 years at 20 ºC, and more than 6 months at 50 ºC. Stable to hydrolysis (pH 4-9), and not degraded by u.v. light (pH 7, 10 days).

Paclobutrazol COMMERCIALISATION
History Plant growth regulator reported by B. G. Lever et al. (Proc. Br. Crop Prot. Conf. - Weeds, 1982, 1, 3), introduced by ICI Agrochemicals (now Syngenta AG) and first marketed in 1986. Patents GB 1595696; US 1595697 Manufacturers Sharda; Sundat; Syngenta

Paclobutrazol APPLICATIONS
Biochemistry Inhibits gibberellin and sterol biosynthesis, and hence the rate of cell division. Mode of action Plant growth regulator taken up into the xylem through the leaves, stems, or roots, and translocated to growing sub-apical meristems. Produces more compact plants and enhances flowering and fruiting. Uses Used on fruit trees to inhibit vegetative growth and to improve fruit set; on pot-grown ornamentals and flower crops (e.g. chrysanthemums, begonias, freesias, poinsettias and bulbs) to inhibit growth; on rice to increase tillering, reduce lodging, and increase yield; on turf to retard growth; and on grass seed crops to reduce height and prevent lodging. To be applied as a foliar spray, as a soil drench, or by trunk injection. Has some fungicidal activity against mildew and rusts. Phytotoxicity Non-phytotoxic, though it intensifies greening. Some spotting has been noted on periwinkle foliage at higher temperatures. Formulation types GR; SC; WP. Selected products: 'Bonzai' (ornamentals) (Syngenta); 'Cultar' (fruit trees) (Syngenta); 'Smarect' (Syngenta); 'Multeffect' (Sanonda); 'Paclo' (Vipesco); mixtures: 'Parlay C' (+ chlormequat chloride) (Syngenta)

Paclobutrazol OTHER PRODUCTS
'Clipper' (Syngenta); 'Profile' (Dow AgroSciences) Discontinued products: 'Bounty' * (Syngenta); 'Club' * (Zeneca); 'Drize' * (Zeneca); 'Inevitan' * (Zeneca); 'Molass' * (Zeneca); 'Oryze' * (Zeneca); 'Parlay' * (grass seeds) (Zeneca); 'Predict' * (Zeneca); 'Trimmid' * (Zeneca) mixtures: 'Holdfast D' * (+ dicamba) (Zeneca)