Spectral analysis, solvents

Alkvl Azides from Alkyl Bromides and Sodium Azide General procedure for the synthesis of alkyl azides. In a typical experiment, benzyl bromide (360 mg, 2.1 mmol) in petroleum ether (3 mL) and sodium azide (180 mg, 2.76 mmol) in water (3 mL) are admixed in a round-bottomed flask. To this stirred solution, pillared clay (100 mg) is added and the reaction mixture is refluxed with constant stirring at 90-100 C until all the starting material is consumed, as obsen/ed by thin layer chromatographv using pure hexane as solvent. The reaction is quenched with water and the product extracted into ether. The ether extracts are washed with water and the organic layer dried over sodium sulfate. The removal of solvent under reduced pressure affords the pure alkyl azides as confirmed by the spectral analysis. ... 

Solvolyses of these cyclic vinyl triflates at 100 in 50% aqueous ethanol, buffered with triethylamine, lead exclusively to the corresponding cyclo-alkanones. Treatment of 176 with buffered CH3COOD gave a mixture of cyclohexanone (85%) and 1-cyclohexenyl acetate (15%). Mass spectral analysis of this cyclohexanone product showed that the amount of deuterium incorporation was identical to that amount observed when cyclohexanone was treated with CH3COOD under the same conditions. This result rules out an addition-elimination mechanism, at least in the case of 174, and since concerted elimination is highly unlikely in small ring systems, it suggests a unimolecular ionization and formation of a vinyl cation intermediate in the solvolysis of cyclic triflates (170). The observed solvent m values, 174 m =. 64 175 m =. 66 and 16 m =. 16, are in accord with a unimolecular solvolysis. 

Thermolysis-mass spectrometry is ideal for examining the amount of residual monomer and processing solvents present in polymers. In thermolysis, the polymer is heated from room temperature to 200-300 °C, and is then often held isothermally in order to drive off volatile components. Low-temperature pyrolysis (350-400 °C) of PP compounds in direct mass-spectral analysis has shown volatiles from PP at every carbon number to masses well above 1000 Da [37]. 

Because a review of previous work revealed that C02 could act as a monomer in some polymerizations catalyzed by Lewis acids [141], for our systems it was important to demonstrate that the supercritical C02 being employed as the continuous phase was not being incorporated into the backbone of the polymer chain. Spectral analysis consisting of H and 13C NMR as well as infrared spectroscopy demonstrated that no differences existed in the structure of the polymers prepared in hexane and those prepared in C02, proving that the C02 was acting as an inert solvent in these polymerizations and was not acting as a monomer [139],... 

The resultant products are slightly viscous, optically transparent (in visual area of the spectra) liquids soluble in ordinary organic solvents (benzene, toluene, acetone, etc.) and practically insoluble in water. The composition and structure of the obtained diallylsilazanes were confirmed based on the data of elemental and IR spectral analysis [6, 7] The maximums of the absorption, related to Si-NH-Si and Si-O-Si, Si-O-C groups (915-925 cm 1, 990-1000 cm 1 and 1060-1080 cm 1), also the maximums of the absorption, related to Si-CH3, CH2=CH, Si-CgHs and benzene ring (1250 cm 1,1430 cm"1,1445 cm"1,1620-1630 cm 1, 1600-1605 cm 1 correspondingly) were found in the IR spectra [6],... 

GC-MS spectral analysis. Subsequent extraction of the basified aqueous phase removed another 14% of the aqueous 1 C which contained 10 products as determined by the TLC analysis using solvents (j) and (k). HMI, which accounted for 58.8% of the extract, was the major component of this extract as determined by TLC cochromatography in solvents (j) and (k). Five other unidentified products were still present in the aqueous phase (TLC solvent (h)) after neutral, acidic and basic extraction. 

The characteristics that discourage the use of RPLC for preparative isolation of bioactive proteins favor its use as an analytical tool for studying protein conformation. Chromatographic profiles can provide information on conformational stability of a protein and the kinetics of folding and unfolding processes. Information about solvent exposure of certain amino acid residues (e.g., tryptophan) as a function of the folding state can be obtained by on-line spectral analysis using diode array UV-vis detection or fluorescence detection. 

Figure 10 shows a spectrum of butyl rubber gum stock obtained on the solid at 80°C using normal pulsed FT techniques. Clearly it could be identified as a component in fabricated materials by direct nmr spectral analysis. Figure 11 shows spectra obtained from various portions of typical rubber products. These samples were cut from the rubber product, placed in an nmr tube without solvent, and spectra obtained at an elevated temperature. The data show how polyisoprene, a polyisoprene/polybutadiene blend and a polyisobutylene/polyisoprene/polybutadiene rubber blend are quickly identified in the materials. Figure 11a shows processing oil was present, and which was confirmed by solvent extraction. 

The dipole moments of oxepin and benzene oxide have been calculated to be in the range 0.76-1.36 D and >1.5 D respectively using the ab initio SCF and MINDO/3 methods (80JA1255). The lower calculated dipole moment would be in accord with experimental observations where the equilibrium was found to favor oxepin (7) in less polar solvents. Coordination between the oxirane oxygen atom and polar solvent molecules would also strengthen the C—C bond of the epoxide and thus lead to a preference for the benzene oxide isomer <72AG(E)825). Thus the proportion of oxepin (7) was found by UV spectral analysis to be higher in isooctane solvent (70%) than in water-methanol (10%). 

Fraction D. After removing the nonaqueous solvents from this fraction, a thin, light yellow oil separated. The yield in Table II is the weight of this oil. Infrared spectral analysis indicated a fatty alcohol ester of phthalic acid. 

The starting material (2 mmol) was added to the finely powdered urea-hydrogen peroxide adduct (376 mg, 4 mmol) in a glass test tube, and the reaction mixture was placed in an oil bath at 85 °C. After completion of the reaction, monitored by TLC, the reaction mixture was extracted into ethyl acetate and the combined extracts were washed with water and dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure to afford the crude product, which was purified by chromatography to deliver pure product, as confirmed by the spectral analysis. 

The 13C-NMR spectral analysis of ajaconine in nonionic and ionic solvents indicated that in hydroxylic solvents the ether linkage of ajaconine ionizes and covalent solvation takes place (87). This observation accounted for the formation of the Schiff salt, with the resultant high pA a value (11.8) of ajaconine in aqueous solution—behavior which parallels that of atisine (pKa 12.5) and veatchine (pA a 11.5). These results suggested that ajaconine may be rearranged by refluxing in an ionic solvent to a compound in which the C-7-C-20 ether linkage is absent. 

Rico, Chou and his team undertook a number of large-scale runs in our Union, New Jersey, pilot plant using Puerto Rico intermediate I and their new batch of DBDMH (a batch not yet used by Puerto Rico) received from our normal supplier. Chou observed, in all of the pilot plant runs, that the yield of epoxide was as expected but was puzzled by the purity number (99%), which was consistently 0.5% lower than typically found. Chou Tann and his team undertook many laboratory reactions with different lots of intermediate I, different lots of DBDMH, and different solvents in an attempt to resolve their quality finding. This led them to undertake a mass spectral analysis of the new DBDMH which revealed the presence of the fire-retardant, octabromobiphenyl (IV), as a trace contaminant. 

The direct attack of proton from the solvent on the intermediate dihydropyridine as well as the over-all mechanism of the reduction received support from the extent and position of deuterium labeling in the product from the reduction of l-methyl-4-phenyl-pyridinium iodide (7) with sodium borohydride in dimethylformamide and deuterium oxide. The l-methyl-4-phenyl-l,2,3,6-tetrahydropyridine (9) formed was shown by nuclear magnetic resonance (NMR) and mass spectral analysis to contain approximately one deuterium atom located at the 3-position.13,14 This is the result to be expected from the pathway shown in Eq. (3) if the electrophile were a deuteron. 

The spectral analysis is carried out manually because automatic interpretation and library programs are normally not available. Difficulties in NMR and automatic interpretation are (a) high spectral background in spectra recorded from environmental samples, often leading to resonance overlap, (b) solvent dependence of chemical shifts (8), which with couplings affects the appearance of the spectrum, and (c) in the case of H NMR spectra, the complexity. The other spectra, particularly 13C H, are simple, but low sensitivity is then a problem. 

Polymorphism is customarily monitored by melting point or infrared spectral analysis. However, other methods, such as X-ray diffraction, thermal analytical, and solid-state Raman spectroscopy, also can be used. It is expected that the sponsor will conduct a diligent search by evaluating the drug substance recrystallized from various solvents with different properties. Either the basis for concluding that only one crystalline form exists, or comparative information regarding the respective solubilities, dissolution rates, and physical/chemical stability of each crystalline form should be provided. 

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