Mass spectrometry dianhydrides

The treatment of sucrose with anhydrous HF89 results in the formation of a complex mixture of pseudooligo- and poly-saccharides up to dp 14, which were detected by fast-atom-bombardment mass spectrometry (FABMS). Some of the smaller products were isolated and identified by comparison with the known compounds prepared86 88 a-D-Fru/-1,2 2,1 -p-D-Fru/j (1), either free or variously glucosylated, was a major product, and this is in accord with the known stability of the compound. The mechanism of formation of the products in the case of sucrose involves preliminary condensation of two fructose residues. The resultant dianhydride is then glucosylated by glucopyranosyl cation.89 The characterization of this type of compound was an important step because it has permitted an increased understanding of the chemical nature of caramels. 

Defaye, K. and Garcia Fernandez, J.M., Protonic and thermal activation of sucrose an the oligosaccaride composition of caramel. Carbohydrate Res., 256, Cl, 1994. Ratsimba, V. et al.. Qualitative and qnantitative evaluation of mono- and disaccharides in D-fructose, D-glucose and sucrose caramels by gas-liquid chromatography-mass spectrometry di-D-fructose dianhydrides as tracers of caramel authenticity, J. Chro-matogr. A, 844, 283, 1999. 

The product of mass 178 from pyromellitic dianhydride is tentatively pictured as anthracene, and that from mellophanic dianhydride as phenanthrene, although we have not been able to distinguish between the two compounds by either mass spectrometry or gas chromatography. These products are formed by two 1,4-additions of the benza-diyne to benzene phenylnaphthalene results from an addition and an... 

CH2CI2 and aniline were obtained from Fischer Scientific Co. and distilled from CaH2 (Aldrich Chemical Co.). 3,4,9,10-perylenetetracarboxylic dianhydride, 2-chloro-5-nitrobenzoic acid, sodium borohydride, copper (II) acetyl-acetonate, trifiuoroacetic acid (TFA), tetrabutylammonium hexafluorophosphate (TBAPF6), dimethylacetamide (DMA), and N-phenyl-l,4-phenylenediamine were purchased from Aldrich Chemical Co. and used as received. Quinoline and triethylamine (TEA) (Aldrich Chemical Co.) were distilled in vacuo. IR spectra were obtained on a Bruker Equinox 55 Spectrometer. NMR spectra were obtained on a Bruker 250 multiprobe spectrometer. Elemental andyses were performed by Atlantic Microlabs. Mass spectrometry data were provided by the Auburn Mass Spectrometry Laboratory. 

Thermal stability of PEI is significantly deteriorated by the use of unpurified monomers. PEI obtained using unpurified dianhydride A possesses poorer molecular-mass characteristics even if all production conditions are maintained (PEI 7, Table 2). Mass-spectrometry analysis of dianhydride A allowed detection of three admixtures bisphenol A, nitrophthalic anhydride (initial monomers for dianhydride A synthesis), and phthalic anhydride. Moreover, PEI thermal stability may be definitely reduced by solvent traces (PEI 8) increased Cf ion content at insulficient washing off of methylene chloride. As known, inorganic admixtures (metal ions) may occur in the polymer both from raw materials (monomers and solvents) and directly from the equipment. In case of iron increments, PEI thermal stability is decreased by its 10-fold exceeding of the permissible level only (PEI 3 compared to PEI 2). 

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