Characteristics of the mass spectra of ecdysteroids with different numbers of -OR groups

The mass spectra of 15 phytoecdysteroids and acetyl derivatives have been compared. With a decrease in the number of -OR groups, the contribution of cleavages of the bonds of the steroid skeleton increases. 20,22-Diols are characterized by the greatest significance of fragmentation at the C-20–C-22 bond. In all the spectra, clear indications of fragmentation of the side chain at the C-22–C-23, C-23–C-24, and C-24–C-25 bonds are observed.     

Features of the mass spectra of lycoctonine bases with 7,8-methylenedioxy groups

The mass-spectral properties of 21 lycoctonine bases with 1-methyoxy-7,8-methyl-enedioxy groups have been studied and generalized. An influence of a methyl-enedioxy group of the nature of the substituents at C-6 and C-10, and of a ¹⁰⁽¹²⁾ bond on the fragmentation of the alkaloids and their derivatives has been found.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Abu Ali ibn Sina [Avicenna] Tadzhik State Medical Institute, Dushanbe. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 389–397, May–June, 1987.     

Cyclic boronates in the mass spectrometry of ecdysteroids

For the structural elucidation of ecdysteroids a reaction with phenylboronic acid has been employed. This reaction takes place exclusively on the C20,C22 diol moiety, thus facilitating fast and easy detection of this moiety in the molecule od ecdysteroid. This derivatization also redirects fragmentation to C17/C20 bond cleavage with charge retention on both fragments enabling assessment of the structure both of the steroid nucleus and of the side-chain. Possible reaction of phenylboronic acid with the diol moiety of the glycosyl group of the glycoside od ecdysteroid, producing di-adduct, is demonstrated; participation of the 5β-hydroxy group of 5β,20-dihydroxyecdysone in the formation of such a di-adduct is discussed; and the role of theenol form of the 6-carbonyl group is proved.     

Common substructures in groups of compounds exhibiting similar mass spectra

Summary Principal component projections of sets of mass spectra show clusters that contain compounds with common structure properties. The similarity of structures is investigated by an automatic search for large common substructures within the compounds of a cluster. Resulting spectra-structure-relationships are helpful in interpretation of spectra.     

Photoconductivity of film composites based on branched carbazolyl oligomers with different numbers of terminal groups

Peculiarities of photoconductivity of film composites based on branched carbazolyl-containing oligomers with a branching center on a silicon atom have been studied. An increase in the photocurrent and a decrease in the photoresponse time have been found in the film composites on passing to the oligomers with larger numbers of branches (from 2 to 3 and 4). It is assumed that the increase in the photoconductivity is determined by the increase in the effective mobility of the holes. A phenomenological model describing the effects observed is proposed.     

Characteristics of the mass spectra of acetonides of some natural compounds

Summary The acetonides of alkaloids and coumarins can be identified by their mass-spectrometric properties. The intensity of the fragments characteristic for the dioxolane ring largely depends on the structure of the chain attached to it.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 336–340, May–June, 1972.     

A short way to invert configuration of the 2,3-hydroxy groups in ecdysteroids

3-epi-2-Dehydro-20-hydroxyecdysone and its 20,22-acetonide were reduced with lithium tris(secbutyl) hydridoborate selectively at the 2-oxo group with formation of 2β,3β-dihydroxy derivatives and the corresponding 2α,3α epimers which were separated by chromatography.     

Characterization of polysiloxanes with different functional groups by time-of-flight secondary ion mass spectrometry

Polydimethylsiloxane (PDMS), polyhydromethylsiloxane (PHMS), and polymethylphenylsiloxane (PMPhS) have been studied by TOF-SIMS to investigate effects of functional group changes on polymer fragmentation mechanisms. Cyclic fragments are observed in the low mass range spectra of PDMS and PHMS, but not in the spectrum of PMPhS. Effects of functional group substitution on the fragmentation mechanisms of polysiloxanes are evident in the high mass range spectra (>1000 Da). Peaks of oligomers cationized by silver dominate the high mass range of the spectra of all low molecular weight polysiloxanes. However, fragmentation patterns of these samples are different. Neutral cyclic fragments cationized by silver are identified in the high mass range of the spectra of PDMS and PHMS, but not in the spectrum of PMPhS. The major fragments of PHMS and PMPhS are [oligomer-14+Ag]⁺. The PHMS spectrum also shows peaks [oligomer-28+Ag]⁺. These distinctive fragmentation patterns can be used to identify the polysiloxanes.     

Electric field dependence of ion mobilities of aromatic compounds with different ionic mass and different functional groups

Ion mobility spectrometry with high electric fields complements the information from the spectra obtained using conventional time-of-flight ion mobility spectrometry by providing the field dependence of ion mobility. The formation and dissociation of ion clusters depending on the differences between high and low field strength is one process which has a considerable influence on the peak position in the resulting spectra. This process can be affected by the properties of substances. Therefore, one objective of our study was to determine possible influences of the nature and position of functional groups on the field dependence of ion mobilities. For this purpose, we investigated sets of compounds with different functional groups including chlorobenzenes, toluenes, anilines and phenols. Furthermore, it is known that ionic mass is an important parameter influencing the field dependence of ion mobility. Therefore, we also investigated unsubstituted aromatic hydrocarbons with different ionic masses. Although an influence of functional groups on the field dependence of ion mobilities was found, the ionic mass has a more significant influence. However, some isomers can be separated by applying high field amplitudes. Furthermore, the influence of ionic mass on the peak position is also more significant using high field amplitudes.     

Positive and negative ion mass spectra of Aryl-ONN-azoxy compounds containing electron withdrawing groups

The positive and negative ion mass spectra, at 70 eV, of p-RC₆H₄N(O)?NCOOCH₃ (R?H, Cl, Br, NO₂), C₆H₅N(O)?NCOOC₂H₅, p-RC₆H₄N(O)?NCONH₂ (R?H, Cl, Br, NO₂) and p-RC₆H₄N(O)?NCOC₆H₅ (R?H, Cl, Br, NO₂) are reported. The azoxyester derivatives show abundant molecular ions and a number of weak fragment and rearrangement ions in the positive ion mass spectra, whereas weak molecular ions and abundant low mass fragment ions are present in the negative ion mass spectra. Similar behaviour is observed in the mass spectra of the azoxyamides. Conversely, for the azoxycarbonyl compounds the positive molecular ion is absent. A ready cleavage of the N? CO bond occurs and only few fragments of low diagnostic value are formed, whereas the negative molecular ion is the base peak for all these compounds with the exception of the p-NO₂ derivative, where [M? O]^?? is the base peak and [M]^?? is the second major ion. The behaviour under electron impact of these classes of compounds is compared with that of azoxycyanides reported previously.     

Electron impact mass spectra of some acridones substituted with hydroxyl,methoxyl, alkyl and alkenyl groups

Forty-four acridones were examined by mass Spectrometry. The fragmentations were studied, and included cleavage of the carbon? oxygen bond of methoxyl groups, cleavage of the carbon–carbon bonds of γ,γ-dimethylpyranyl groups, cleavage of isoprenyl groups and the formation of doubly charged molecular ions and daughter ions. The tendency for fission of carbon? oxygen bond in the methoxyl group for acridones is about 300 : 200 : 8 : 1 for the C(2), C(4), C(5) and C(6) positions, respectively. The isoprenyl group is very sensitive to its position in fragmentation, and mass Spectrometry can be a powerful aid in distinguishing between C(2)- and C(4)-isoprenyl isomers.     

The high mass range time-of-flight secondary ion mass spectra of different polyarene films on silver

 Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to investigate thin films of poly(styrene), poly(vinyl napthalene), and poly(4-chlorostyrene) on clean silver substrate surfaces. The mass spectra were taken in the high molecular mass range (m/z>1000 amu). The different fragmentation patterns found are discussed in detail. Obviously, the fragmentation mechanisms are influenced by the electron density of the aryl rings stabilizing or destabilizing the formed cations. Received: 10 April 1996 / Revised: 12 June 1996/Accepted: 14 June 1996     

Characteristics of mass spectra of dichlorocarbene derivatives of isomeric dodecen-1-ols

The m/z of characteristic ion of the mass spectra of the dichlorocarbene derivatives of dodecen-1-ols was used as a parameter to locate the position of double bond in these isomers by a new formula.     

Electronic spectra of asym-triazinyl groups

The induction, resonance, and Hammett constants of 3-, 5-, and 6-asym-triazinyl groups were calculated from the data of¹H,¹³C,¹⁹F NMR spectra of isomeric aminophenyl-, hydroxyphenyl-, phenyl-, and fluorophenyl-asym-triazines.Deceased.Translated form Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 257–262, February, 1987.     

Interpretation of mass spectra

A computer programme is described which calculates the mass numbers and the relative intensities of each of the lines in the cluster formed in a mass spectrometer from a single type of fragment ion which contains one or more polyisotopic elements. Many elements such as B, C, S, Cl and Br possess more than one naturally occurring isotope, and the relative abundances of the various isotopes are known. A whole series of possible fragment ions may be calculated quite readily, and the results, which are printed numerically and in the form of a histogram, facilitate the interpretation of mass spectra. Trial data, a FORTRAN listing of the programme, and a sample of the output are given. The programme requires approximately 17K of fast core, and should be implemented without difficulty on any computer with a FORTRAN IV compiler.