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1.
The mass spectra of the compounds Rh2 (RCOO)4[R=C(CH3)3 (I), CH(CH3)2 (II), CF3 (III)], Pd3(RCOO)6 [R=C(CH3)3 (IV), CH(CH3)2 (V), CF3 (VI)], Os2(RCOO)4Cl2 [R=C(CH3)3 (VII)], and Ru2(RCOO)4 [R=C(CH3)3 (VIII)] have been investigated. It has been shown that in the gaseous state compounds I–III, VII, and VIII have a dimeric structure, while compounds IV–VI have a trimeric structure. The mass spectra of compounds I–VIII show peaks of the molecular ions [M]+; and the fragmentation of the molecular ions takes place mainly with the elimination of the RCOO groups. Rearrangements with the elimination of F2O have been discovered for compounds III and VI, and rearrangements with the elimination of O=C--OH have been discovered for IV and V. The migration of a fluorine atom to the metal in compound III and its absence in compound V have been explained in the framework of the principle of hard and soft acids and bases. A scheme for the fragmentation of [M]+. under the action of electron impact has been proposed.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 22, No. 3, pp. 322–330, May–June, 1986.  相似文献   

2.
The dissociative ionization of 4-azafluorene and its methyl and phenyl derivatives was investigated. The relative intensity of the [M — CH3]+ ion peak depends on the position of the CH3 group in the 4-azafluorene ring. It was established that the loss of an RCN particle (R=H, CH3, and C6H5) for unsubstituted 4-azafluorene takes place from the M+ and [M — H]+ ion, exclusively from the [M — H]+ ion for the methyl-substituted compounds, and from the [M — H]+ and [H — 2H]+ fragments for the phenyl-substituted derivatives. Randomization of the deuterium ions in the 9,9-d2-4-azafluorene molecular ion was observed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 246–250, February, 1978.  相似文献   

3.
The interactions of the sulfonium ions (CH3)3S+, (CH3)2S+CH2CO2 , and (CH3)2S+-CH2CH2CO2 with up to four water molecules have been studied by ab initio molecular orbital methods. Complexes of (CH3)3S+ with one to three water molecules involve strong electrostatic sulfur-oxygen interactions; in contrast, the sulfide (CH3)2S interacts with water molecules via weak S-H hydrogen bonds, suggesting that methyl-group transfer from (CH3)3S+ in aqueous solution involves a significant alteration of the hydration pattern around the sulfur atom. Two conformers of (CH3)2S+CH2CO2 were found that display sulfur-oxygen distances which are approximately 0.3 å less than the sum of the sulfur and oxygen van der Waals radii, indicating a strong intramolecular electrostatic interaction. For the complexes (CH3)2S+CH2CO2 ·nH2O(n =1–4), water interacts primarily with the carboxylate group via hydrogen bonds, rather than electrostatically with the sulfur atom, although in complexes with the three- and four-water complexes, the proximity of the positively charged sulfur atom to the carboxylate group significantly alters the hydration pattern compared to that in the corresponding of complexes CH3SCH2CO2 · Thus, methyl transfer from (CH3)2S+CH2CO2 to an acceptor in aqueous solution also involves substantial changes in the hydration pattern around the carboxylate group.  相似文献   

4.
The mass spectra of some (Z)α-(4-R′-phenyl)-β-(2-thienyl-5-R)acrylonitriles (R = H, CH3, Br; R′ = H, CH3O, CH3, Cl, NO2) at 70 eV are reported. Mass spectra exhibit pronounced molecular ions. The compound's where R = H, and CH3 are characterized by the occurrence of a strong [M - H]+ peak. Moreover, in all the compounds a m/z 177 peak occurs. In the compounds where R = H, [M - HS]* and [M - CHS]* ions are present except the nitroderivatives. Where R = CH3, [M - HS]+ ion occurs.  相似文献   

5.
The complex formation of Eu(III) by bicarbonate/carbonate ions has been studied at 0.1 M ionic strength and 25°C using synergistic solvent extraction system of 1-nitroso-2-naphthol and 1,10-phenanthroline in chloroform. Concentrations of bicarbonate (5·10–3 to 1·10–1 M) and carbonate (5·10–4 to 1·10–2 M) ions in the aqueous phase have been varied in the pH range of 8.0 to 9.1 to simulate ground and natural water compositions. Under these conditions, the following species have been identified: Eu(HCO3)2+, Eu(HCO3)2 +, Eu(CO3)+ and Eu(CO3)2 . Their conditional formation constants (log ) have been calculated as 4.77, 6.74, 6.92 and 10.42, respectively. These values suggest that the carbonate complexes of Eu(III) are highly stable.  相似文献   

6.
The ionization potentials for the stereoisomers of trans-fused 1,2-dimethyl- and 1-ethyl-2-methyl-4-R-decahydroquinol-4-ols (R?C?CH, CH?CH2 or C2H5) and the appearance potentials for the [M–CH3]+ and [M–C2H5]+ ions (loss of 2-CH3 and 4-C2H5 groups potential, respectively) were measured by using the electron impact method. The ionization and appearance potential for [M–CH3]+ are always lower for the isomers with the axial 2-CH3 group. For the C-2 epimers, the difference between the appearance potentials for the [M–CH3]+ ion values is likely to be equal to the enthalpy differences between the ground states of the epimers and the dissociation energy differences between the axial and equatorial C2–CH3 bonds. The appearance potentials for [M–C2H5]+ for the C-4 epimers possessing the 4-C2H5 group were very similar. At the same time, the appearance potentials for the [M–CH3]+ ions were lower for less stable epimers which had an axial 4-C2H5 group.  相似文献   

7.
A quantum-chemical study of neutral and protonated monoalkyl sulfates RHSO4and [RH2SO4]+(where R = CH3, C2H5, iso-C3H7, and tert-C4H9) is carried out. Calculations are performed using the Hartree–Fock method in the 6-31G** and 6-31++G** basis sets taking into account electron correlation according to the Müller–Plesset perturbation theory MP2/6-31+G*//6-31+G*. Protonated tert-butyl sulfate was also calculated by the DFT B3LYP/6-31++G** method. It was found that monoalkyl sulfates are covalent compounds, and the complete abstraction of alkyl carbenium ions from them has substantial energy cost: 196.4, 161.7, 150.8 and 136.0 kcal/mol, respectively. Protonated methyl and ethyl sulfates are also covalent compounds according to the calculation. They have lower but still high energies of heterolytic dissociation (65.0 and 33.5 kcal/mol, respectively). The energy of R+abstraction from protonated isopropyl sulfate is much lower: 23.6 kcal/mol. The main covalent state and the ion–molecular pair, which is a carbenium ion [C(CH3)2H]+solvated by the H2SO4molecule, have about the same energy. The ground state of protonated tert-butyl sulfate corresponds to the ion–molecular complex [C(CH3)+ 3H2SO4] with still lower energy of carbenium ion [C(CH3)3]+abstraction, which is equal to 10.0 kcal/mol. Calculation according to the DFT B3LYP/6-31++G** method shows the absence of a minimum for the protonated tert-butyl sulfate with a covalent structure on the potential energy surface.  相似文献   

8.
The secondary-ion mass spectra of seven steroid lycotetraosides have been obtained by the SIMS method. On the use of a glycerol matrix, all the compounds of the spirostan series, including those with an additional carbohydrate substituent a C-24, formed the (M+H)+ ions, while a lycotetraoside of the furostan series formed the (M–H2O+H)+ ion. They subsequently decomposed by the alternative successive elimination of the terminal carbohydrate units of the lycotetraose. Substituents at C-25 and C-26 were ejected in the form of glucose molecules. Fragments of the aglycon and of the lycotetraoside moieties of the molecules were recorded. When NaCl was added to the same matrix, all the compounds gave preferentially the (M+Na)+ and (M+2Na–H)+ ions.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. All-Union Scientific-Research Institute of Agricultural Biotechnology, Lenin All-Union Academy of Agricultural Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 53–58, January–February, 1991.  相似文献   

9.
The main fragmentation pathways of the N-1, C-2 and C-4 stereoisomers of the 1,2-dimethyl-4-R-transdecahydroquinoline-4-ol N-oxides (R=C?CH, CH?CH2 and C2H5) under electron impact are discussed. The correlation between the mass spectrometric chromatographic behaviour and the configuration of polar groups in the N-oxides examined is discussed. The mass spectra of the N-1 stereoisomers may be subdivided into two groups, depending only on the orientation of N→O group and not of the 4-OH group. The spectra of N-oxides with the axial N-oxide group reveal less intense ions and much more intense [M? CH3]+, [M? O]+, [M? OH]+ and ions, whereas in the spectra of their equatorial epimers the abundance of the ions exceeds the intensities of the latter ions.  相似文献   

10.
Unlike micelles of straight hydrocarbon chain-surfactants, isoprenoid surfactants, CH3 [CH(CH3)CH2CH2CH2]3 CH(CH3)CH2–R (R=CH2N+ (CH3)3 Br, CH2OPO3H Na+, CH2OSO 3 Na+, CO 2 Na+), gave large globular and cellular assemblies in water which could be observed directly by transmission electron microscopy; critical micelle concentration of 0.31.4×10–3 M at 20°C, aggregation number of 215×104, and diameter of 200–2000 Å. A basic structure of the assemblies was a thin layer with a thickness (about 30 Å) which was close to the molecular length of the surfactants. The assemblies were decomposed during gel column chromatography; viz., they were not as stable as the liposomes of lecithins. The morphology was discussed in conjunction with a steric effect of the isoprenoid chain.  相似文献   

11.
The title ion–molecule reaction has been proposed to play an important role in interstellar chemistry if it yields acrylonitrile ions CH2CH–CN+. This question was probed by examining the formation of HCCH+ and HCN from low-energy ions CH2CH–CN+ and related isomers, using tandem mass spectrometry based experiments (D and 13C labelling) in conjunction with model chemistry calculations (CBS-QB3/APNO). We conclude that the title reaction is a barrierless multistep rearrangement that may not effectively compete with the straightforward formation of stable distonic ions HCCH–NCH+ from HCCH+(ion)–HCN(dipole) encounter complexes.  相似文献   

12.
29Si NMR peaks due to species with the double four-membered ring siloxane backbone composed of both Si(O)4/2 and CH3Si(O)3/2 units, (CH3) n Si8O 20 – n /(8 – n) – (n=1–3), formed by co-hydrolysis of tetraethoxysilane and methyltriethoxysilane in the presence of tetramethylammonium ions in methanol have been assigned. It has been found that 29Si NMR peaks due to Si(OSi)3(O) units shift to lower frequencies by replacement of the adjacent Si(O)4/2 units by CH3Si(O)3/2 units, in other words, with increasing m value in Si[OSi(O)3]3 – m [OSi(CH3) (O)2] m (O) (m=0–2). Peaks from CH3 Si(OSi)3 units in the species have also appeared as separated due to the kind of neighbor structural units. On the basis of the assignments, positions of CH3Si(O)3/2 units in the cubic octameric siloxane framework of (CH3) n Si8O 20 – n /(8 – n) – (n=2, 3), for both of which three isomers are present, have been estimated.  相似文献   

13.
The mass spectra of 53 alkaloids and their derivatives are considered. It is known that the presence of a C6(OCH3)-C7(OH)-C8 (OH) grouping in C19-diterpene alkaloids leads to a high intensity of the (M - 15)+ ions at the expense of the C6(OCH3) group and considerably suppresses the competing processes of forming the [M - OH (OCH3)]+ ions in the alkaloids and the (M - 56)+ ions in the anhydroxy bases. When the above-mentioned grouping is absent, the (M - 15)+ ions are formed mainly by the splitting out of a H3 from a N-ethyl group.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii. No. 4, pp. 525–536, July–August, 1985.  相似文献   

14.
Reactions of [Ru{C=C(H)-1,4-C6H4C≡CH}(PPh3)2Cp]BF4 ([ 1 a ]BF4) with hydrohalic acids, HX, results in the formation of [Ru{C≡C-1,4-C6H4-C(X)=CH2}(PPh3)2Cp] [X=Cl ( 2 a-Cl ), Br ( 2 a-Br )], arising from facile Markovnikov addition of halide anions to the putative quinoidal cumulene cation [Ru(=C=C=C6H4=C=CH2)(PPh3)2Cp]+. Similarly, [M{C=C(H)-1,4-C6H4-C≡CH}(LL)Cp ]BF4 [M(LL)Cp’=Ru(PPh3)2Cp ([ 1 a ]BF4); Ru(dppe)Cp* ([ 1 b ]BF4); Fe(dppe)Cp ([ 1 c ]BF4); Fe(dppe)Cp* ([ 1 d ]BF4)] react with H+/H2O to give the acyl-functionalised phenylacetylide complexes [M{C≡C-1,4-C6H4-C(=O)CH3}(LL)Cp’] ( 3 a – d ) after workup. The Markovnikov addition of the nucleophile to the remote alkyne in the cations [ 1 a–d ]+ is difficult to rationalise from the vinylidene form of the precursor and is much more satisfactorily explained from initial isomerisation to the quinoidal cumulene complexes [M(=C=C=C6H4=C=CH2)(LL)Cp’]+ prior to attack at the more exposed, remote quaternary carbon. Thus, whilst representative acetylide complexes [Ru(C≡C-1,4-C6H4-C≡CH)(PPh3)2Cp] ( 4 a ) and [Ru(C≡C-1,4-C6H4-C≡CH)(dppe)Cp*] ( 4 b ) reacted with the relatively small electrophiles [CN]+ and [C7H7]+ at the β-carbon to give the expected vinylidene complexes, the bulky trityl ([CPh3]+) electrophile reacted with [M(C≡C-1,4-C6H4-C≡CH)(LL)Cp’] [M(LL)Cp’=Ru(PPh3)2Cp ( 4 a ); Ru(dppe)Cp* ( 4 b ); Fe(dppe)Cp ( 4 c ); Fe(dppe)Cp* ( 4 d )] at the more exposed remote end of the carbon-rich ligand to give the putative quinoidal cumulene complexes [M{C=C=C6H4=C=C(H)CPh3}(LL)Cp’]+, which were isolated as the water adducts [M{C≡C-1,4-C6H4-C(=O)CH2CPh3}(LL)Cp’] ( 6 a–d ). Evincing the scope of the formation of such extended cumulenes from ethynyl-substituted arylvinylene precursors, the rather reactive half-sandwich (5-ethynyl-2-thienyl)vinylidene complexes [M{C=C(H)-2,5-cC4H2S-C≡CH}(LL)Cp’]BF4 ([ 7 a – d ]BF4 add water readily to give [M{C≡C-2,5-cC4H2S-C(=O)CH3}(LL)Cp’] ( 8 a – d )].  相似文献   

15.
Ion-molecule reactions with the trimethylsilyl ion were used to distinguish between cis- and trans-1,2-cyclopentanediol isomers. The ion kinetic energy of [Si(CH3)3]+ was varied from 0 eV to 15 eV (center of mass frame of reference). At low ion kinetic energies (<4 eV), there are significant differences in the relative stabilities and decomposition behavior of the adduct ions [M + Si(CH3)3]+. The cis-1,2-cyclopentanediol isomer favors decomposition of [M + Si(CH3)3]+ to yield the hydrated trimethylsilyl ion [Si(CH3)3OH2]+ at m/z 91. For the trans isomer, the formation of the hydrated trimethylsilyl ion is an endothermic process with a definite threshold ion kinetic energy.  相似文献   

16.
Viscosities for aqueous NH4Cl and tracer diffusion coefficients for22Na+,36Cl, HTO, and CH3OH, acetone and dimethylformamide (all14C-labelled) in NH4Cl supporting electrolyte are reported for 25°, together with tracer diffusion coefficients for22Na+,36Cl, and14CH3OH in 1M KI, and for14CH3OH in 1M MgCl2. The diffusion coefficient of HTO in NH4Cl solutions is slightly larger, for most of the concentration range investigated (0.05 to 4.5 M), than the value for pure water and is almost unaffected by the supporting electrolyte up to about 4M. Similar behavior is shown by CH3OH, acetone and dimethylformamide in NH4Cl solutions. Onsager limiting law behavior is approached by Cl at NH4Cl concentrations in the 0.05–0.1M region but at much lower concentrations by Na+.  相似文献   

17.
Cyclic polysulfides isolated from higher plants, model compounds and their electron impact induced fragment ions have been investigated by various mass spectrometric methods. These species represent three sets of sulfur compounds: C3H6Sx (x=1?6), C2H4Sx (x=1?5) and CH2Sx (x=1?4). Three general fragmentation mechanisms are discussed using metastable transitions: (1) the unimolecular loss of structural parts (CH2S, CH2 and Sx); (2) fragmentations which involve ring opening reactions, hydrogen migrations and recyclizations of the product ions ([M? CH3]+, [M? CH3S]+, [M? SH]+ and [M? CS2]); and (3) complete rearrangements preceding the fragmentations ([M? S2H]+ and [M? C2H4]). The cyclic structures of [M] and of specific fragment ions have been investigated by comparing the collisional activation spectra of model ions. On the basis of these results the cyclic ions decompose via linear intermediates and then recyclizations of the product ions occur. The stabilities of the fragment ions have been determined by electron efficiency vs electron energy curves.  相似文献   

18.
The CH4 chemical ionization (CI) spectra of several keto-steroids are reported as well as the H2 and C3H8CI spectra of a few keto-steroids. [M + H ? H2O]+ is an abundant ion in the CH4CI spectrum of 5α-androstane-17-one and the water loss from the [M + H]+ ions does not involve the hydrogens on C-18 and only involves the C-16 hydrogens to about 10%. The major loss process has not been determined.3-Keto and 17-Keto steroids are readily distinguished by their CH4CI spectra. The effectiveness of substituents for directing attack by [CH5]+ and [C2H5]+ can be estimated:carboxyl > methoxy ? carbonyl > bromo ? chloro > hydroxy. Significant differences are observed in the H2CI spectra of two 5α-vs. 5β-steroids. Propane CI Spectra are similar to methane CI spectra, but show generally less fragmentation.  相似文献   

19.
The concentration dependence of the205Tl chemical shifts of Tl+ and of (CH3)2Tl+ ions was determined in several solvents with NO 3 and ClO 4 counterions. In general, increased ion pairing caused a low-frequency shift of the205Tl resonance, with the exceptions of (CH3)2TlNO3 inn-butylamine and TlNO3 in N,N-dimethylformamide (DMF) and in hexamethylphosphorotriamide (HMPA). In HMPA,205Tl linewidths of both Tl+ and (CH3)2Tl+ increased dramatically with dilution below 0.1M. Analysis of the data allowed ion-pair formation constants and205Tl chemical shifts for the ion-paired cation and for the free (solvated) cation to be estimated for some of the solvents.  相似文献   

20.
The major dissociation pathways of the [M-H]+ (loss of NH3 or CH4) and the [M+H]+ (loss of NH3 or CH3) ions from dimethylpyrroles have been determined to occur from isomeric parent ions. For the [M-H]+ ion (formed by loss of a methyl hydrogen), loss of NH3 leads to the formation of the phenylium ion and is preceded by consecutive carbon ring expansions followed by a ring contraction to form protonated aniline. Loss of CH4 occurs after the first carbon ring expansion, which forms protonated picoline. The relative partitioning between the two dissociation paths depends upon the internal energy content of the parent ion; the highest point on the potential energy surface is the second ring expansion step. The [M+H]+ ion reacts through a similar pathway via dihydro analogs of picoline and aniline. The proposed reaction pathways are supported by results of semiempirical molecular orbital calculations.  相似文献   

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