Description
Piperonyl butoxide (PBO, 51-03-6) is a water insoluble colorless to pale
yellow liquid that was developed in the 1940s to increase the
effectiveness of various pesticides. It is currently registered as an
active ingredient in more than 1500 products used for indoor
or outdoor pesticides, including agricultural maintenance of
some food crops.
Chemical Properties
Piperonyl butoxide (PB) is a Light Yellow Liquid. It has no smell or a faint smell and a slightly bitter taste. It does not dissolve in water but can be dissolved in mineral oil and most organic solvents. It is stable to light, resistant to hydrolysis, and is not corrosive. In terms of toxicity, the LD50 (lethal dose for 50% of a test population) is 7500mg/kg in rats when administered orally.
Uses
Piperonyl butoxide is used as a synergist for pyrethrins and their synthetic analogues. It is typically added to carbamate, pyrethrin, pyrethroid, and rotenone pesticides to greatly enhance their potency. PBO alone does not have pesticidal properties.
Definition
ChEBI: Piperonyl butoxide is a member of benzodioxoles. It has a role as a pesticide synergist.
Preparation
First, safrole is obtained from allyl chloride and methylenedioxybenzene. Then, piperonyl butoxide is produced by catalytic hydrogenation, chloromethylation, and etherification reactions.
General Description
Pale yellow to light brown liquid with a mild odor and a faint bitter taste.
Air & Water Reactions
Insoluble in water.
Reactivity Profile
Piperonyl butoxide can react with oxidizing materials.
Fire Hazard
Piperonyl butoxide is combustible.
Agricultural Uses
Insecticide synergist: A U.S. EPA restricted Use Pesticide (RUP). Not listed for use in EU countries. Piperonyl butoxide is a synergist, i.e., not a pesticide itself, but enhances the properties of other chemicals. It is used with other pesticides such as pyrethrins, pyrethroids, rotenone and carbamates in food and non-food agricultural products, home and garden products, termite and mosquito products, and veterinary pesticide products. It inhibits the insect’s ability to break down an insecticide before it takes effect, thereby prolonging the action, and reduces the necessity for using a stronger formulation.
Trade name
Trade names have included Butoxide, Butacide, Butocide, and Pyrenone (mixture with allethrin).
Environmental Fate
PBO is rapidly degraded (half-life 8 h) in the environment by
photolysis and is metabolized by soil microorganisms. Its
estimated atmospheric half-life is approximately 3 h.
Metabolic pathway
Piperonyl butoxide is used primarily in admixture with pyrethrins and
some of the pyrethroids to enhance and prolong their insecticidal action.
Much of this use is in domestic and industrial situations. Metabolism
studies were conducted soon after its discovery and first use in the 1950s
and 1960s. The main impetus initially was to understand the mode of
action as a synergist. When this was shown to be due to the inhibition of
oxidative metabolism, further studies were conducted to address possible
toxic interactions with other pesticides and drugs in man.
Piperonyl butoxide undergoes rapid photodegradation and microbial
degradation in soil. It is also rapidly metabolised in insects and mammals
by oxidative attack at the methylenedioxy carbon atom and in the side
chain. A comprehensive review by Casida (1970) describes the chemistry,
mode of action and metabolism of piperonyl butoxide and several related
methylenedioxyphenyl compounds. Though published nearly 30 years
ago, the review remains a very useful compilation of a large amount of
information, supported by more than 300 references.
Degradation
Piperonyl butoxide is stable to hydrolysis at pH 5,7 and 9 in sterile buffers
in the dark at 25 °C. It is rapidly degraded in aqueous solution at pH 7 in
sunlight with a DT50 of 8.4 hours (PM). The compound was found to be
relatively stable under a variety of irradiation conditions as a thin film on
glass or in organic solvent (methanol, benzene and cyclohexane). Loss of
the butoxyethoxy side chain was observed to give 5-methyl-6-propyl-l,3-
benzodioxole (2), butoxyethanol (3) and ethanediol (4) (Fishbein and
Gaibel, 1970). These studies did not utilise radiolabelled compound. The
partial pathways are shown in Scheme 1.
Toxicity evaluation
Piperonyl butoxide has low to very low toxicity in birds.Researchers consider piperonyl butoxide moderately toxic to fish，although it is unlikely to accumulate.Some aquatic invertebrates may be highly sensitive to this compound.
As a synergist, PBO inhibits mixed-function oxidases, including cytochrome P450, and resistance-associated esterases that allow insects to degrade an insecticide, allowing enhanced insecticide efficacy. It does not effectively act as a synergist in mammals.
