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1.
Fazil O. Gülaar Franois Mermound F. Johann Winkler Armand Vuchs 《Helvetica chimica acta》1984,67(2):488-501
Ammonia chemical ionization (CI) mass spectra of various open-chain, cyclic and unsaturated C5- to C10-alcohols were obtained at source temperatures ranging from 60° to 250°C. The reactivity of the ammonia adduct ion MNH and its fragmentation channels are characteristic for substrate structure. Although strongly temperature-dependent, the spectra give nevertheless information on the OH-group environment as well as on the C-skeleton at any source temperature. Primary, secondary and tertiary alcohols as well as allylic and simple olefinic alcohols can be distinguished by their spectra, which show ammonium adduct ions [MNH4]+, adduct dehydrogenation ions [MNH4-H2], ammonium substitution ions [MNH4-H2O]+ and [M-OH]+-ions as the main characteristic peaks. Moreover, konfigurational assignments of stereoisomeric alcohols are possible for larger substrate-size and source-temperature ranges than with isobutane CI mass spectrometry. Homologous M NH-ions show molecular-size control of fragmentation and linear MNH-ions are less stable than branched isomers due to incomplete energy randomization. 相似文献
2.
Alain Glangetas Fazil O. Gülacar Jean M. J. Tronchet Armand Buchs 《Helvetica chimica acta》1980,63(6):1740-1747
Electron Impact Mass Spectrometry of the 3-Desoxy-1,2: 5,6-di-O-isopropylidene-3-methylidene-δ-D -hexofuranose and Some C(3′)-Substituted Analogues The mass spectra of the 3-desoxy-1,2:5, 6-di-O-isopropylidene-3-methylidene- α-D -ribo-hexofuranose and of some C(3′)-mono- and -disubstituted derivatives have been investigated. Deuterium labelled molecules allow fragmentation modes to be proposed. 相似文献
3.
Ramajayam Govindan Mohamed El-Sherbiny Khalid Mohamed Morsy Ibraheem Srinivasan Narasimhan Mohamed EL-Dosoky Mohamed Salama Fazil Ahmad Selvaraj Jayaraman Vishnu Priya Veeraraghavan Srinivasan Vengadassalapathy Surapaneni Krishna Mohan Vidhya Rekha Umapathy Gayathri Rengasamy Shazia Fathima Jaffer Hussain Maheshkumar Poomarimuthu Senthilkumar Kalimuthu 《Molecules (Basel, Switzerland)》2022,27(3)
4.
Pierre-Alain Blane Fazil O. Gülaar Armand Buchst 《Journal of mass spectrometry : JMS》1980,15(4):198-201
The mechanisms of formation of the ionized acid and the protonated acid fragments in the electron impact induced fragmentation of the title compounds were investigated. The well known mechanisms of hydrogen transfer through mono- and bicyclic transition states that occur in the molecular ions of carboxylic esters are not the main pathways giving rise to these fragments. The major component of the m/z 172 peak corresponding formally to ionized p-toluenesulfonic acid in fact has a different structure; its formation involves a complex mechanism including a double hydrogen transfer reaction. 相似文献
5.
Deniel Braem Fazil O. Gülaar Ulrich Burger Armand Buchs 《Journal of mass spectrometry : JMS》1979,14(11):609-617
The electron impact mass spectra of 2-cyclohexen-1-ol and of several of its 2H and 13C labelled analogues show that the molecular ions lose a methyl radical by a completely different means from the mechanism described previously. Moreover, the retro Diels–Alder reaction also proceeds in a non-classical way; in addition to the elimination of an olefinic molecule from unrearranged molecular ions, a second more important route implies a formal 1,3 allylic rearrangement prior to the retro Diels–Alder reaction. The mass spectra of a series of alkyl substituted homologues show that the competition between the two processes is closely related to the size of the olefinic moiety that is expelled. 相似文献
6.
The present study reports the investigation of capillary electrophoresis (CE) for the separation of the photosynthetic pigments (chlorophyll derivatives as well as carotenoids) together. Various CE methods, such as micellar electrokinetic chromatography, capillary electrokinetic chromatography, and nonaqueous capillary electrophoresis (NACE) are tested, with coated and uncoated capillary columns to evaluate optimal separation conditions using diode array detection. The effect of different type and composition of organic solvents and surfactants on the separation is discussed. Detection limits are found in the range of 1.14-2.45 ppm. According to the system suitability results, the most effective separation is observed using NACE with Aliquat 336 as cationic surfactant in coated capillary and mixture of MeOH-ACN-THF (5:4:1, v/v/v) as solvent. Quantitative evolution is investigated, and recovery percentage values are found to be 96.7-102%. 相似文献
7.
Paul Tissot Jean-Paul Surbeck Fazil O. Gülaar Paul Margaretha 《Helvetica chimica acta》1981,64(5):1570-1574
The product distribution of compounds 2 , 3 and 4 formed in the electrohydrodimerization (EHD) of 1 was determined as function of the water content of the solvent (CH3CN). The presence of water favours the formation of the glycols 4 and reduces the relative amounts of 1,6-diketones 2 and hydroxyketones 3 , as determined by GC./MS.-analysis. 相似文献
8.
Xavier Fr. D. Chillier Gary J. Van Berkel Fazil O. Gülaar Armand Buchs 《Journal of mass spectrometry : JMS》1994,29(11):672-678
Chlorins in a sedimentary mixture were characterized, without prior isolation of individual components, using electrospray ionization combined with ion trap mass spectrometry. Collision-induced dissociation in the atmospheric sampling interface and multi-step mass spectrometry (i.e. MSn where n ? 2) were used in order to obtain structural information about the macrocycle. Fragmentation pathways are proposed for different macrocycle types based on data from model chlorins. Three unknown chlorins (RMM = 888, 844 and 790) are assigned as having bacteriochlorophyll macrocycle types esterifled to unusual side-chains (i.e. dihydrophytol for the unknown with a bacteriopheophorbide a structure, phytol and an alcohol with a molecular mass of 242 u for the two unknowns with a proposed bacteriopyropheophorbide d structure). 相似文献
9.
Pierre-Alain Blanc Fazil O. Gülaar Armand Buchs 《Journal of mass spectrometry : JMS》1978,13(3):135-140
The mass spectrometric fragmentation of a series of diols having the general formula HO? (CH2)n? OH with n = 2-11 has been studied. Extensive labelling of n-butane-1,4 diol and n-hexane-1,6 diol with deuterium allows fragmentation modes to be proposed. The labelling reveals that intramolecular exchange of H atoms often precedes the fragmentation and becomes more important when the length of the chain increases. 相似文献
10.
A CRACK PROBLEM WITH A BROKEN LINE INTERFACE 总被引:1,自引:0,他引:1
§0.IntroductionConsiderableplanecrackproblemsofcompositemediaforthecaseinwhichtheinterfaceisaninfinitestraightlinewerestudied... 相似文献