Bands with primarily v (C=O) and v (C=O) character in the spectra of 4‐hydroxycoumarin and its anion were identified by isotopic substitution with either 13C or deuterium. Two bands of each type were found for spectra of 4‐hydroxycoumarin in solution in chloroform, dioxane, or dimethylsulfoxide, with v (C=O) at 1704–1733 cm−1 and ∼ 1567 cm−1. Two bands, at 1618 and 1559 cm−1, are associated with v (C=C) in the spectrum of crystalline 4‐hydroxycoumarin monohydrate, but only a single v (C=O) band at ∼ 1655 cm−1 was observed. Anhydrous 4‐hydroxycoumarin has v (C=O) bands at ∼ 1700 cm−1 and a shoulder at ∼ 1670 cm−1. The strong band at 1660 cm−1 in the spectrum of 4‐hydroxycommarin anion in dimethylsulfoxide solution is due to a delocalized v (O = C = O) vibration, whereas the band at 1555 cm−1 has partial v (C=C) character and involves C(3) but not C(2), supporting a fully delocalized char structure for the anion. No evidence for the existence of the 2‐hydroxychromone tautomer was found, except in the case of anhydrous 4‐hydroxycoumarin in the solid state.

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The anticoagulant activities of 6-, 7-, 8-, 4'-hydroxy, 6-chloro- and 6-bromowarfarin were determined in rabbits after intraperitoneal administration of 16.2 mumol kg-1 over 96 h. Substitution on the 4-hydroxycoumarin moiety resulted in reduction of the anticoagulant activity. 6-Chlorowarfarin was more potent than 6-bromowarfarin suggesting that the molecular size of 4-hydroxycoumarin moiety may be crucial for biological activity.

Some derivatives of salicylic acid containing substituents meta to the carboxyl group were used to prepare analogs of the anticoagulant drug warfarin, 3‐(1‐phenyl‐3‐oxobutyl)‐4‐hydroxycoumarin, containing substituents in either the 6‐or 8‐position of the courmarin ring. When the substituent was the hydroxyl group, the resulting products are previously identified metabolites of warfarin. The substituted salicylic acid is first acetylated with acetic anhydride, then either converted to the acid chloride and condensed with diethyl malonate in the presence of sodium hydroxide or converted to the mixed anhydride with formic acid and condensed with ethoxymagnesium diethyl malonate to yield, in either case, the corresponding 3‐carbethoxy‐4‐hydroxycoumarin substituted in the 6‐ or 8‐position of the coumarin ring. These compounds readily condense with benzalacetone to form the corresponding substituted warfarin in the presence of 5 mole % tertiary amine catalyst. This method offers an improved route for the synthesis of 8‐hydroxywarfarin.

tonitrile extract. One advantage of the HPLC method is that it allows the simultaneous determination of TCB and PCB. The quantity of adsorbant required for a transformer fluid cleanup is dependent upon the total concentration of chlorine-containing contaminants (TCB and PCB). The HPLC method is capable of measuring PCB levels well below the limits specified by state and federal regulations for the transformer fluid application.The gas chromatographic procedure for PCB levels >5 ppm is quite simple and straightforward. A solvent dilution of the sample is the only preparation required. Samples with PCB levels >500 ppm require successive dilutions to keep sample and standard concentrations comparable. For samples containing 25 ppb to 5 ppm PCB, the charcoal column extraction procedure separates the P C B from the siloxane fluid and produces a siloxane-free concentrate which can be analyzed by electron capture. As with HPLC, the lower detection limit is dependent upon the presence of extraneous contaminants which can interfere with the measurements. LITERATURE CITED(1) Hobbs, E. J.; Keplinger, M. L. Eflviron.The overall rate of the N-rnethylimidazole-catalyzed reaction of acetic anhydride with isopropyl alcohol is rather insensitive to the solvent polarity. Of the nine solvents studied, N,Ndirnethylformamide is the best for practical analytical use. A series of N-alkyl substituted imidazoles was investigated as catalysts in this reaction. The most effective catalyst was N-n-pentylimidazole, which is about 60 YO more reactive than N-rnethylirnidazole.N-Methylimidazole (NMIM) was recently introduced as a catalyst for analytical acetylations of hydroxy compounds ( 1 , 2 ) . Among the advantages of NMIM for this purpose are its moderate basicity, liquid state a t room temperature, solvent power, and high catalytic efficiency, which is about 4 X 10' greater than that of pyridine in the reaction of acetic anhydride with isopropyl alcohol. As a reasonable extension of this work, the effect of modification of the N-substituent on catalytic power has been investigated. For practical analytical purposes and mechanistic reasons, the effect of the reaction solvent on the rate has also been studied. EXPERIMENTALMaterials. Solvents and reagents were the best commercially available grades and were used directly.The synthesis of N-ethylimidazole is typical of the preparation of N-alkylimidazoles ( 3 ) . Sixty-eight grams of imidazole (2methylimidazole was the starting material in the synthesis of 2-methyl-N-ethylimidazole) was dissolved in 100 mL of methanol, 120 mL of 10 M NaOH was added, followed by the dropwise addition, with stirring, of 107 mL of iodoethane. The temperature, which was 20 "C initially, was maintained between 30 and 40 "C during this process, which took about 3.5 h. The solution was allowed to stand for 2 h, the solvent was removed under reduced pressure, and the residue was mixed with 150 mL of chloroform.The chloroform solution was dried with sodium sulfate, the chloroform was removed by distillation, and the r...