Column chromatography characterization

Polymeric -peroxides (3) from hydrogen peroxide and lower carbon ketones have been separated by paper or column chromatography and have been characterized by conversion to the bis(p-(nitro)peroxybenzoates). Oligomeric peroxides (3, R = methyl, R = ethyl, n = 1-4) from methyl ethyl ketone have been separated and interconverted by suitable treatment with ketone and hydrogen peroxide (44). 

Careful chromatographic and detailed HNMR spectroscopic analysis of the products from the thermolyses of ethyl azidoformate in o-, m- and p-xylene revealed in all cases a mixture of 1 //-azepines.80 In o-xylene, only two of the four possible isomers were separated and characterized, namely, ethyl 4,5-dimethy 1-1 //-azepine-1 -carboxylate (9 %) and ethyl 3,4-dimethyl-l H-azepine-1-carboxylate (7 %). w-Xylene yielded a 2 3 mixture of ethyl 3,5-dimethyl-l//-azepine-1-carboxylate and ethyl 2,4-dimethyl-l//-azepine-l-carboxylate. The 2,4-dimethyl isomer (20 %) can be isolated from the mixture by removal of the 3,5-dimethyl isomer as its Diels-Alder cycloadduct with ethenetetracarbonitrile. p-Xylene gave a mixture of the two possible isomeric azepines which were partially separated by column chromatography. A pure sample of ethyl 2,5-dimethyl-1//-azepine-1-carboxylate (26%) was obtained from the mixture by selective decomposition of the 3,6-dimethyl isomer with refluxing alcoholic potassium hydroxide. 

The di-t-butyl-substituted silanols 40 and 41 result from hydrolysis during column chromatography of the corresponding triflates and have also been structurally characterized (240). The adamantyl compound... 

Synthesis of Allylic Alcohol Xa. A 3.84 g sample of olefin VII was treated with m-chloroperoxybenzoic acid (MCPBA) in dichloromethane for 1.5 hours at 0°C and 2.5 hours at 20°C. The NMR spectrum of the crude product indicated a mixture of approximately 75% epoxide VIII and 25% IX (structural assignments based upon assumed epoxidation preferentially from the less hindered side). Purification by column chromatography furnished 0.61 g of IX and 2.58 g of VIII. The separation was performed for characterization purposes the crude epoxidation mixture was suitable for subsequent transformations. 

Recently, Mascal and Ceron Bertran <2005JA1352> reported the preparation and characterization of 35 (aza-analogue anions of triquinacenes) which are stable enough in THF solution (in the absence of acid). Moreover, the hexachloro anion 35b could be isolated as tetraethylammonium salt by column chromatography on alumina. As expected, anion 35a was more nucleophilic than 35b. Indeed, only the former could be benzylated leading to 36a. However, 35b reacts easily with molecular bromine at low temperature yielding the corresponding a,a,a-tribromide 37b or dibrominated ether 37 b when this bromination was conducted in THF. 

A variety of procedures were utilized to analyze this reaction mixture and to characterize a,10-diaminopolystyrene. Thin layer chromatographic analysis using toluene as eluent exhibited three spots with Rf values of 0.85, 0.09, and 0.05 which corresponded to polystyrene, poly(styryl)amine and a,w-diaminopolystyrene (see Figure 1). Pure samples of each of these products were obtained by silica gel column Chromatography of the crude reaction mixture initially using toluene as eluent [for polystyrene and poly(styryl)amine] followed by a methanol/toluene mixture (5/100 v/v) for the diamine. Size-exclusion chromatography could not be used to characterize the diamine since no peak was observed for this material, apparently because of the complication of physical adsorption to the column packing material. Therefore, the dibenzoyl derivative (eq. 5) was prepared and used for most of the analytical characterizations. 

Prbpy, 5-(2-MePr)bpy and 5-(2,2-Mc2Pr)bpy have been prepared and characterized. The mer-and /uc-isomers of each complex have been isolated by use of cation-exchange column chromatography as the steric requirements of the R group increase, the percentage of the /uc-isomer decreases. Enantiomers of [Ru(5-Prbpy)3] + were separated on SP Sephadex C-25. Electro-kinetic chromatography has been used to separate the enantiomers of [Ru(104)3] " anionic carboxymethyl-/ -cyclodextrin was employed as the chiral mobile phase additive. ... 

Boron trifluoride-mediated acylation of pyrrolidine-2,4-dione 68 led to the isolation of the neutral boron difluoride complex 2, which was sufficiently stable to be purified by column chromatography (Equation 18). This compound has been characterized crystallographically as noted above <1990J(P1)1959>. 

When the linear trans-[Pt(PEt3)2Cl2] was used to connect the bis (alkyne) ligand 15a-c, a mixture of different sizes of chiral metallocycles [trans-(PEt3)2Pt(15a-c)] , (rt = 3-8,19-24) was obtained [26], Each of the chiral molecular polygons 19-24 was purified by silica-gel column chromatography and analytically pure 19-24 was obtained in yields (%) of 5,18,16,10,5, and 4, respectively (Figure 4.12). Compounds 19-24 have been characterized by H, and P H NMR spectroscopy,... 

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