2,4-Pentanedione chromatography

In the distillation residue (5.7-6.3 g.) remain other byproducts, presumably l,l-dimethallyl-2-propanone, 3-methallyl-2,4-pentanedione, and 3,3-dimethallyl-2,4-pentanedione (indicated by vapor phase chromatography). The checkers carried out v.p.c. analyses using an 8-ft. column of 5% silicone oil XE-60 on Diatoport S at 100° for analysis of the distillate and 175° for analysis of the residue. 

A small forerun of 2,4-pentanedione, b p 32-100° (19 mm.), is obtained The purity of the product may be demonstrated by gas chromatography on a 2-ft column packed with silicone gum rubber (F and M Scientific Co, Avondale, Pennsylvania) programmed linearly from 100° to 300° The chromatogram obtained is a single sharp peak The three conceivable impurities, 2,4-pentanedione, 3-butyl 2,4-pentanedione, and 6,8-tridecanedione, would have been observed under these conditions if they had been present. 

A 200 mM phosphate-buffered solution, pH 6.9 (100 mL), containing 3-allyl-2,4-pentanedione (700 mg, 50 mmol), glucose (2.16 g, 120 mmol), NADPH (45 mg), glucose dehydrogenase (50 mg) and KRED-102 (50 mg) was stirred at room temperature for 24 h, until gas chromatography (GC) analysis of the crude extracts showed complete reaction. Periodically, the pH was readjusted to 6.9 with NaOH (2 m). 

Beryllium has been determined [764] in non saline waters and in sea water at oceanic levels of 2.30pM. Two ml of 0.1M EDTA, 2ml of 1.0M sodium acetate, 1.0ml of benzene and lOOpl of l,l,l-trifluoro-2-4-pentanedione were added sequentially to 150ml samples. Following liquid-liquid extraction using detailed handling procedures, the organic phase was mixed with 1.0ml of 1.0M sodium hydroxide (de-emulsifier), washed several times with distilled water and the resultant beryllium l,l,l-trifluoro-2,4-pentanedione complex analysed by gas chromatography with electron capture detection. 

The use of ethyl [2-13C]acetoacetate instead of diethyl [2-t3CJmafonafe in the condensation reaction with 4H-pyran-4-one afforded ethyl 4-hydroxy[1 -13C]benzoate in 87% yield. In this case, 1.1 equiv of 4H-pyran-4-one and 1.1 equiv of potassium tert-butoxide were optimal. The addition of catalytic amounts of the base was not satisfactory. Ethyl [2-13C]acetoacetate was prepared from ethyl (2-13C]acetate as described for diethyl [2-13C]matonate.16 The maximum yield for this reaction on a 10-mmol scale was only 70% after distillation. 4H-Pyran-4-one reacted with nitromethane and potassium tert-butoxide (each 1.1 equiv) to afford 4-nitrophenol in 75% yield after purification by flash chromatography. This gives easy access to 4-nitro[4-13C]phenol. With 2,4-pentanedione, the condensation with 4H-pyran-4-one under the same reaction conditions gave 4-hydroxyacetophenone in 45-50% yield after purification. 

A Schlenk tube equipped with a magnetic stirring bar. 100.1 mg (1.0 mmol) of 2.4-pentanedione and 196.2 mg (1.0 mmol) of the vinylcyelopropane is capped with a rubber septum and cooled to ca. — 190 C. The septum is removed. 0.023 g (2 mol%) of [Pd(PPh3)4] is added quickly against a moderate flow of Ar, and the septum is immediately replaced. Any catalyst that is adhered to the inner walls of the Schlenk tube is washed and flushed into the bottom of the vessel when 2 mL of THF are added. The mixture is freeze/thaw degassed three times and then refluxed for 7 h. The solvent is removed in vacuo, and the residue is purified by flash chromatography (25% EtOAc in hexane, Rf 0.2) to give a yellow oil yield 263.7mg (89%). 

Volatile acids in the beverages of three varieties of coffee (Columbia, Santos and robusta) were determined by Rung et al. (1967), formic acid by NMR, the remainder by gas chromatography. Heptanoic, nonanoic and decanoic acids were identified. Parliment et al. (1973) discovered the presence of trans-2-nonenal, a compound which imparts a fresh-brewed woody character to roasted and ground coffee . Rung (1974) described the identification of 3-hydroxy-3-penten-2-one with a pleasant, buttery caramel aroma. This compound [Section 5, D.45B] is, in fact, the tautomer form of the already found 2,3-pentanedione [Section 5, D.45A],... 

Sensitive monitoring of hexosamines in high-performance liquid chromatography by fluorimetric postcolumn labelling using the 2,4-pentanedione-fomialdehyde system. 22. J. Chromatogr. 1983,281, 340. 

The authors reported the generation of polymers in the presence of a large excess of oxidant (monomer oxidant 1.6 1.0 vol/vol) without any information on the mechanism of polymerization, polymer molecular weight, or role and influence of oxidant on the enzyme or reaction kinetics. Subsequently, the laccase-catalyzed polymerization of acrylamide in water without any initiator (b-diketone) at temperatures ranging from 50 to 80 °C was reported however, the reactions were efficiently carried out at room temperature with the use of laccase/b-diketone (2,4-pentanedione) initiator to produce polyacrylamide in 97% yield (Mn = 2.3 x 10 ) [24,25]. The molecular weight of the polymer in these studies was determined by size exclusion chromatography. At 50, 65, and 80 °C when the polymerization was carried out for 4h, polyacrylamides with M = 9.4,9.2, and 10 x 10, respectively, were produced with the highest yield of 70% at 65 °C. 

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