Synthesis and Testing of the Insecticide Carbaryl A Laboratory Experiment Peter F. T h a d e o l and Dwight F. Mowery Southeastern Massachusetts University, North Dartmouth, MA 02747
Carbaryl, l-naphthyl-N-methylcarhamate,is t h e biodegradable (soft) insecticide most commonly marketed by the Union Carbide Corporation under the trade name of Sevine. It has been used effectively against many lawn and garden pests such as chinch bugs, Japanese beetles, gypsy moths, and t e n t caterpillars, b u t unfortunately it has been found t o h e harmful t o birds, mammals, earthworms, and honey bees. It can be synthesized easily and tested in a two-hour laboratory period. T h e following equations show its synthesis from methyl isocyanate and n-naphthol.
#-naphthol (weak nucleophile)
triethylamine
tri&thylarnmrni~~-~-~~~hth~te (strong nucloophiie)
From these eauations it is evident that triethvlamine converts a-naphthol from a weak to a strong nucleophile for more rapid attack on t h e methyl isocyanate. Since the amine is regenerated hy proton transfer from the triethylammonium i o h the l-naphthyl-N-methylcarhamate anion, only catalytic amounts are required. Procedure Preparation of Carbaryl Two grams (0.0139 mole) of ol-naphthol (Aldrich N 199-2) is dissolved in 4 ml of dry2ethyl ether in a 25-ml ground-joint flask. Five drops of triethylamine, a boiling stone and 4 ml of an acetone solution containing 0.87 g (0.0153 mole) of methyl isocyanate3 (Eastman Kodak #6699) are added. The flask, equipped with a reflux condenser, is gently boiled on a steam bath for 15 min. Instead of this equipment, a &in. test tube cooled with a ruhher reflux condense+ may he used. Toward the end of the reflux period crystalline 1naphthyl-N-methylearbarnateseparates from the solution. The flask (or tube) is then cooled in a slush-ice bath for 10 min to complete the crystallization. The product is filtered off on a Buehner funnel and the filter cake is washed twice with 4-ml portions of ether, allowing each to stand in the filter for 5 s before sucking it through the filter. The vield is about 1.8 e of 1-naohthvl-N-methvlcarbamate meltine . , nr 112-145'. I~rrry~rnllimrion i r c m fin/5(l-,wer~me ether yieldc a product of melting rnnye 115-14"' hut r h ~ rerry~tnllrzati~m i is not necessary for the tests which follow.
742
Journal of Chemical Education
Testing of Carbaryl One milliliter of a 2% sucrose solution and 0.10 g of the crude Carbaryl are thoroughly ground together in a small mortar. The mixture is spread onto a 2 X 9 - m piece of filter paper and this is pressed lengthwise to the inside wall of a 25 X 100-mm test tuhe usinga microspatula. A similar tube is prepared using 2%sucrose solution only. One or two houseflies5are olaced in each tube and the tubes are sealed w~rh2-in. q w m s r,f Pnrilfilm*, whichare then peribratcd with alew
