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51.
52.
K. P. Madhusudanan Raka Jain Shubhra Mittal Susheel Durani R. S. Kapil 《Journal of mass spectrometry : JMS》1986,21(12):781-784
From a study of the reactions of nucleophiles with 1,2,3-triaryl-propenones and-butenones in a chemical ionization source it has been found that stronger nucleophiles, such as, MeO?, EtO? and MeS?, attack the α,β-unsaturated system at the β-carbon (Michael addition) or the carbonyl carbon giving rise to tetrahedral adducts, while weaker nucleophiles, such as, Cl? form the adduct ion by H-bonding with the β-hydrogen. The effect of substituents and source temperature supports the operation of these processes. The triaryl butenone did not give the adduct ion with MeO? as deprotonation leads to a stable [M ? H]? ion. 相似文献
53.
Madhusudanan KP Raj K Bhaduri AP 《Rapid communications in mass spectrometry : RCM》2000,14(10):885-896
Under electrospray ionization conditions loganic acid undergoes alkali metal (Li, Na and K) exchange and alkali metal cationization. Multiple exchanges of up to four alkali metal ions are observed. Different populations of metal exchanged species are produced during electrospray ionization. Collision-induced dissociation of ammonium cationized species is compared with that of metal cationized species to study the effect of metal cationization. Glycosidic cleavage and ring cleavages of aglycone and sugar moieties are the major fragmentation pathways observed during collision-induced dissociation. The fragmentations of the highly metal exchanged species indicate the opening of the pyran ring. Collision-induced dissociation of the various metal exchanged and metal cationized species also reveals the nature of the different populations. Copyright 2000 John Wiley & Sons, Ltd. 相似文献
54.
K. P. Madhusudanan T. S. Dhami S. Katiyar S. N. Suryawanshi 《Journal of mass spectrometry : JMS》1994,29(3):143-149
Collision-induced decompositions (CIDs) of the [M + H]+, [M + Li]+, [M + Na]+, [M + K]+ and [M + Ag]+ ions of some methyl-6-deoxy-6-bromo-α-D-glucopyranoside derivatives are discussed. Elimination of MeOH resulting in the glycosidyl cation is the predominant reaction of the [M + H]+ ion. This process is completely suppressed during CID of the metal-cationized species, which, surprisingly, show elimination of the added metal in the form of RCOO-metal and metal bromide in the case of the ester derivatives. These reactions appear to be assisted by neighbouring group participation. Because of the proximity of the C(3)-oxygen with C(6), the benzyl ether derivative is characterized by the loss of PhCH2Br from the [M + metal]+ ion. 相似文献
55.
Madhusudanan P. M. Yusuff K. K. Mohammed Nair C. G. Ramachandran 《Journal of Thermal Analysis and Calorimetry》1975,8(1):31-43
Thermogravimetric (TG), derivative thermogravimetric (DTG) and differential thermal analysis (DTA) curves of CuL2 and NiL2 (L?=diethyl dithiocarbamate anion) in air are studied. The main decomposition temperature ranges are: For CuL2, DTG 250–350°, DTA 300–320° and for NiL2, DTG 290–390°, DTA 360–400°. Mass loss considerations at the main decomposition stages indicate conversion of the complex to sulphides. Mathematical analysis of TG data shows that first order kinetics are applicable in both cases. Kinetic parameters (energy and entropy of activation and preexponential factor) are reported.
相似文献56.
K. P. Madhusudanan S. Durani D. M. Reddy R. S. Kapil Y. Itagaki K. Nojima 《Journal of mass spectrometry : JMS》1991,26(4):298-304
Substituents have been found to have a marked influence on the metastable ion decompositions and collisionally activated (CA) fragmentations of the M+˙ ion of a number of 1,2,3-triarylpropen-1-ones. An attempt has been made to confirm the structures of the rearrangement ions, [C14H10]+˙, [C13H11]+˙, [C13H9]+ and [C12H8]+˙ by comparison of their CA spectra with those of the corresponding ions produced from reference compounds. The results imply that [C14H10]+˙ and the M+˙ ions of phenanthrene and diphenylacetylene have a common structure, [C13H9]+ and the fluorenyl cation have a common structure and [C12H8]+˙ and biphenylene molecular ion have a common structure. The available data indicate that the ion at m/z 167 consists of a mixture of structures, likely possibilities being diphenylmethyl, phenyltropylium and dihydrofluorenyl cations. 相似文献
57.
K. P. Madhusudanan V. S. Murthy D. Fraisse M. Becchi 《Journal of mass spectrometry : JMS》1991,26(5):505-509
The electron impact ionization and collisional activation mass spectra of α-phenylcinnamic acid and its derivatives have been studied. The loss of a phenylic hydrogen is not an important process in these molecules, unlike the unsubstituted cinnamic acids. However, in o-chloro-α-phenylcinnamic acid and its methyl and trimethylsilyl derivatives loss of Cl resulting in the formation of 2-substituted-3-phenylbenzopyrilium ion is an important fragmentation pathway. The rearrangement ions observed at m/z 118 and 107 in the Spectrum of α-phenylcinnamic acid have been found to have the structures of the M+˙ of benzofuran and PhCH?$ \mathop {\rm O}\limits^{\rm +} $H, respectively. The ion at m/z 121 in the spectrum of the methyl ester of α-phenylcinnamic acid has been found to have the structure PhCH?$ \mathop {\rm O}\limits^{\rm +} $Me. 相似文献
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