Carbonyl compound , acidity mass spectrometry

A systematic investigation of the free amino acids of the Leguminosae led to the isolation of a novel ninhydrin-positive compound from the leaves of Derris elliptica Benth. (Papilionidae) (93). This substance was analyzed as C6H,3N04 (microanalysis and high resolution mass spectrometry) and was shown to be an amino alcohol. The absence of a carbonyl in the 1R, the loss of 31 mass units in the mass spectrum, and a positive periodate cleavage reaction were best embodied into a dihydroxydihydroxymethylpyrrolidine structure. The relative simplicity of the NMR spectra (three peaks in the 13C spectrum four spin-system in the H spectrum) pointed out a symmetrical structure. Inasmuch as the material was optically active ([a]D 56.4, c = 7, H20), meso structures were ruled out, and the 2R, 3R, 4R, 5R relative configuration was retained (93). This structure (53) was further confirmed by an X-ray determination (94). 

The special type of carbonyl-group derivatization is aimed for gas chromatography-mass spectrometry (GC-MS) determination of double-bond C = C positions in the unsaturated long-chain acids. The analytical derivatives for the solution of this problem are nitrogen-containing heterocycles. These compounds can be synthesized by condensation of carboxylic acids with 2-amino-2-methyl-l-propanol (2-substituted 4,4-dimethyloxazolines), 2-aminophenol (2-substituted benzoxazoles), and so forth. 

LMW organic compounds produced by irradiation of DOM cover a wide range of compound classes, but are generally carbonyl compounds such as aldehydes and carboxylic acids, compounds readily available to aquatic microbes [26-28,30,33,35,38,95-111]. These compounds appear to arise from the degradation, or fragmentation, of larger humic structures into its component molecules by either direct photolysis or indirect secondary reactions discussed in Section 6.3. Measurement of these photoproducts usually involves gas chromatography/mass spectrometry of derivatized compounds or capillary ion electrophoresis (e.g., [37,38,52,112-114]). 

Similar to the examples discussed in CHEC-II(1996) <1996CHEC-II(6)637>, condensation reactions remain the primary methods for the synthesis of benzothiazines. 1,2,3-Benzothiazine-l,1-dioxides were synthesized successfully via intramolecular condensation of a thiophene sulfonic acid hydrazide with a carbonyl group in moderate to high yields (Schemes 2 and 3) <1995USP5464831>. The products 19 and 22 were characterized using mass spectrometry and proton NMR spectroscopy. These compounds are important in the treatment of glaucoma (see Section 9.04.12). 

Volatiles from red pepper or chills (Capsicum annuum and . frutescens) were isolated by steam distillation-solvent extraction methods. Compounds identified by gas chromatography-mass spectrometry are 17 alcohols, 20 carbonyl compounds, 14 carboxylic acids, 21 esters, 6 pyrazlnes, 14 terpene hydrocarbons, and 10 miscellaneous compounds. Only ten of these components have been reported previously in volatiles from peppers. Although the odor threshold method was applied, the characteristic red pepper odor was not fully correlated with identified constituents. The green bell pepper compound, 2-methoxy-3-lsobutylpyrazine, was found in both annuum and C. frutescens. 

Combined glc and mass spectrometry provide the capability to deal with the complex mixtures of closely related compounds often found in plant cuticles. Even though identification of new compounds solely by their mass spectra cannot be considered reliable, mass spectrometry has become an invaluable tool in identifying known types of compounds in cuticular lipids. For example, methyl branches in alkanes can be located by cleavage on both sides of the substituted carbon (Fig. 5). Mass spectrometry is also the most suitable technique for identifying branched fatty acids (Tulloch, 1976 Jack-son and Blomquist, 1976 Nicolaides and Apon, 1977). Functional groups such as carbonyl groups and hydroxyl groups in the aliphatic chain can be... 

Esters are carboxylic acid derivatives, and the spectrum of ethyl acetate is shown in Figure 14.19D. The carbonyl absorption does not distinguish this compound from an aldehyde or a ketone, but there is the C-O absorption at about 1200 cm 1. Because this is in the fingerprint region, however, its position can be difficult to identify. This is clearly the case for methyl pentanoate, where the C-0 absorption can easily be missed or misidentified. Based only on the infrared, it may be difficult to distinguish an ester from an aliphatic aldehyde or ketone. If the formula is known, however (from mass spectrometry), the identification is easier because an ester has two oxygen atoms, whereas the aldehyde or ketone has only one. 

An efficient method for palladium(II) catalytic desulfitative conjugate addition of arylsulfinic acids with a, -unsaturated carbonyl compound has been developed. Experimental evidences for the key reacting intermediates including aryl Pd(II) sulfinic intermediate, aryl Pd(II), and C=0-Pd complexes were provided. The mechanism of the dehydrosulfenylation of 2-arylsulfinyl esters for furnishing enoates has been determined to be a homolytic process. The interception of the radical intermediate using a nitroxyl radical and mass spectrometry techniques were useful for identification of the intermediates involved in the dehydrosulfenylation of 2-arylsulfinyl esters. These data indicated that a radical-mediated process is operative. Tetrabutylammonium iodide has been found to promote deselenylation reaction of ) -chloro- and -oxyselenides to afford alkenes efficiently with formation of selenenyl iodides. A catalytic version of the transformation has also been developed. 

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