Mass spectra of some α-substituted phenyl-α,α′-dimethoxyl ketones and their derivatives

The mass spectra of some α-substituted phenyl-α,α′-dimethoxyl ketones (compounds 1) and their 2,4-dinitrophenylhydrazones (compounds 2) and semicarbazones (compounds 3) have been studied. The characteristic fragments at m/z (M ? 73) from compounds 1, m/z (M ? 253) from compounds 2 and m/z (M ? 130) from compounds 3 are abundant and proposed to be [ArCROCH₃]⁺. Fragmentations yielding [M⁺ ? 49] from compounds 2 are abnormal and probably involve the methoxyl and nitro groups. The intense peak at m/z 130 due to [CH₃OCH₂CNNHCONH₂]⁺ from compounds 3 corresponds to α-cleavage of the molecular ion. Some other fragments from these new compounds are interpreted in this paper.     

Chemical ionization and collisional activation spectra of α,β-unsaturated nitriles

A study of the chemical ionization (CI) and collisional activation (CA) spectra of a number of α, β-unsaturated nitriles has revealed that the even-electron ions such as [MH]⁺ and [MNH₄]⁺ produced under chemical ionization undergo decomposition by radical losses also. This results in the formation of M ⁺˙ ions from both [MH]⁺ and [MNH₄]⁺ ions. In the halogenated molecules losses of X˙ and HX compete with losses of H˙ and HCN. Elimination of X˙ from [MH]⁺ is highly favoured in the bromoderivative. The dinitriles undergo a substitution reaction in which one of the CN groups is replaced with a hydrogen radical and the resulting mononitrile is ionized leading to [M ? CN + 2H]⁺ under CI(CH₄) or [M ? CN + H + NH₄] and [M ? CN + H + N₂H₇]⁺ under CI(NH₃) conditions.     

Ion–molecule reaction in the gas phase 3—nucleophilic substitution of 17ξ-R-5α,14β-androstane-14,17ξ-diols under [NH4]+ chemical ionization conditions1

Under Ammonia chemical Ionization conditions the source decompositions of [M + NH₄]⁺ ions formed from epimeric tertiary steroid alchols 14 OH_β, 17OH_α or 17 OH_β substituted at position 17 have been studied. They give rise to formation of [M + NH₄? H₂O]⁺ dentoed as [MH_sH]⁺, [M_sH? H₂O]⁺, [M_sH? NH₃]⁺ and [M_sH? NH₃? H₂O]⁺ ions. Stereochemical effects are observed in the ratios [M_sH? H₂O]⁺/[M_sH? NH₃]⁺. These effects are significant among metastable ions. In particular, only the [M_sH]⁺ ions produced from trans-diol isomers lose a water molecule. The favoured loss of water can be accounted for by an S_N2 mechanism in which the insertion of NH₃ gives [M_sH]⁺ with Walden inversion occurring during the ion-molecule reaction between [M + NH₄]⁺ + NH₃. The S_N1 and S_Ni pathways have been rejected.     

Mass spectrometry of steroid systems. XXIV–The origin of [M – 28]+ and [M – 43]+ ions in equilenin and its 14β-isomer

The formation of the [M? 43]⁺ ion in equilenin is due mainly to elimination of Me radical from the [M? CO]⁺ ion and, to a lesser extent, to CO loss from the [M? Me]⁺ ion. In 14β-isoequilenin the [M? CO]⁺ ion is absent, and the formation of [M? 43]⁺ occurs via the [M? Me]⁺ ion. This makes the determination of the mode of junction of the rings C and D in the equilenin series possible, using high resolution mass spectra, even when only one stereoisomer is available.     

Anomalies in the molecular ion region in the electron impact mass spectra of α- and β-hydroxyesters

In the electron impact mass spectra of some alkyl α- and β-hydroxyesters (introduced using the gas chromatography/mass spectrometry (GC/MS) technique), the absence of the molecular ion M^+· and the presence of the [M + 1]⁺ ion instead is observed. This phenomenon is especially characteristic of C₃? C₆ glycolates and diethyl malate, and is due to chemical auto-ionization—ion-molecule reactions in the high concentration gradient at the top of the GC peak. The existence of the [M ? 2]^+·, [M ?1]⁺ and M^+· ions in the mass spectra of other β- and α-hydroxyesters is discussed.     

High resolution mass spectrometry—V: Cyclic esters of aliphatic α-hydroxy acids

The main fragmentation sequences of glycollide and its homologues are initiated by fission of a CO? O bond, leading to the formation of fragment ions of low, m/e, such as [R¹CO]⁺ and [CR¹R²CCO]⁺. When a hydrogen atom is present on a ring carbon atom, 1,3 hydrogen migration occurs to produce [CHR²OH]⁺. In case where a ring carbon atom carries an alkylchain ? C₂H₅, a McLafferty rearrangement occurs with the adjacent carbonyl group. When both ring carbon atoms are dimethyl substituted, a 1,4 hydrogen migration must be invoked to account for the observed fragmentation sequence.     

Notiz zur protonenkatalysierten Gasphasencyclisierung von N-Benzoyl-α-aminosäremethylestern

Chemical ionization mass spectrometry of the title compounds demonstrates that the formation of the [M+H? CH₃OH]⁺ ions is strongly influenced by the degree as well as the type of alkyl substitution of the α-carbon atom. The extent of cyclization (i.e. formation of [M+H? CH₃OH]⁺) closely resembles that of the activated esters in condensed phases.     

Effect of alkali metal cationization on the collision-induced decomposition of alkyl per-O-acetyl-2-deoxy-2-halo-α-O-mannopyranosides

The effect of alkali metal cationization on the collision-induced decomposition of alkyl per-O-acetyl-2-deoxy-2-bromo-and-iodo-α-O-mannopyranosides was studied. The bromo sugars gave fairly abundant MH⁺, whereas for the iodo sugars the MH⁺ ions were insignificant. However, both the bromo and the iodo derivatives gave abundant M + alkali metal ion complexes. In contrast to the behaviour of the MH⁺ ion, the [M + Li]⁺, [M + Na]⁺ and [M + K]⁺ ions of these compounds do not decompose by loss of the C(1) substituent. Elimination of AcOH is the preferred fragmentation pathway of [M + Cat]⁺. Elimination of HX occurs only after loss of AcOH and CH₂CO from MH⁺, whereas [M + Cat]⁺ directly loses HX. The elimination of HX is more pronounced from [M + Na]⁺ and [M + K]⁺ than from [M + Li]⁺. Loss of AcOLi is an additional fragmentation route observed in the case of the decomposition of [M + Li]⁺ ion.     

Destabilized carbenium ions: α-carbomethoxy-α,α-dimethyl-methyl cations

Tertiary α-carbomethoxy-α,α-dimethyl-methyl cations a have been generated by electron impact induced fragmentation from the appropriately α-substituted methyl isobutyrates 1–4. The destabilized carbenium ions a can be distinguished from their more stable isomers protonated methyl methacrylate c and protonated methyl crotonate d by MIKE and CA spectra. The loss of I^— and Br˙ from the molecular ions of 1 and 2, respectively, predominantly gives rise to the destabilized ions a, whereas loss of Cl˙ from [3]^{+ ˙} results in a mixture of ions a and c. The loss of CH₃˙ from [4]⁺˙ favours skeletal rearrangement leading to ions d. The characteristic reactions of the destabilized ions a are the loss of CO and elimination of methanol. The loss of CO is associated by a very large KER and non-statistical kinetic energy release (T₅₀ = 920 meV). Specific deuterium labelling experiments indicate that the α-carbomethoxy-α,α-dimethyl-methyl cations a rearrange via a 1,4-H shift into the carbonyl protonated methyl methacrylate c and eventually into the alkyl-O protonated methyl methacrylate before the loss of methanol. The hydrogen rearrangements exhibit a deuterium isotope effect indicating substantial energy barriers between the [C₅H₉O₂]⁺ isomers. Thus the destabilized carbenium ion a exists as a kinetically stable species within a potential energy well.     

Electron ionization mass spectra of novel 2,3:4,5-bis-O-(1-methylethylidene)-β-D-fructopyranose derivatives and related sugar sulfamates

The electron-impact (EI) mass spectral fragmentation of ten bis-O- (1-methylethylidene)fructopyranose derivatives and three related sugar sulfamates were investigated. In particular, 2,3:4,5-bis-O - (1-methylethylidene)-β-D-fructopyranose sulfamate (topiramate), a potent anticonvulsant, was examined in greater detail. The fragmentation of the 2,3:4,5-bis-O-(1-methylethylidene) fructopyranose derivatives in general was not very dependent on the nature of substitution; the mechanisms of the common and unique fragmentation patterns are presented. These compounds showed characteristic peaks at m/z [M – 15]⁺, [M – 15 – 58]⁺, [M – 15 – 58 – 60]⁺, [M ? CH₂X]⁺ and [M ? CH₂X – 58]⁺ where X = OSO₂NR₂ (R ? H, CH₃, and/or Ph), OC (O)NHR, NH₂, CI and OH. The fragmentation of isomeric bis-O-(1-methylethylidene) derivatives of aldopyranose, ketopyranose and ketofuranose sulfamates was also investigated. The results indicate that isomeric sugar sulfamates can be easily distinguished in the EI mode. Key fragmentation pathways are discussed for these compounds.     

Translational energy release and stereochemistry of steroids. VIII-The mechanism of the elimination of water from metastable ions in epimeric 3-hydroxy steroids of the 5α-series

The mechanism of water elimination from metastable molecular, [M ? CH₃˙]⁺ and [M ? ring D]⁺˙ ions of epimeric 3-hydroxy steroids of the 5α-series has been elucidated. Deuterium labelling, the measurement of the translational energy released during the loss of water, and collision-induced decomposition mass-analysed kinetic energy spectrometry were the techniques used. It was found that the mechanisms of water loss from metastable M⁺˙ and [M ? ring D]⁺˙ ions is different from that from [M ? CH₃˙]⁺ ions.     

Photodissociation of protonated β-diketones in the gas phase

The gas phase photodissociation spectra of four protonated β-diketones were obtained and compared with the absorption spectra of the corresponding ions in solution. Protonated 2,4-pentanedione was observed to undergo the photodissociation process [C₅H₉O₂]⁺ +hν → [CH₃CO]⁺ +C₃H₆O with a λmax at 276±10 nm compared with a solution absorption maximum at 286 nm. Protonated 2,4-hexanedione was observed to undergo the photodissociation processes [C₆H₁₁O₂]⁺ +hν → [CH₃CO]⁺ +C₄H₈O and [C₆H₁₁O₂]⁺ +hν → [C₂H₅CO]⁺ +C₃H₆O with a λmax at 279±10 nm compared with a solution absorption maximum at 288 nm. Protonated 3-methyl-2,4-pentanedione was observed to undergo the photodissociation process [C₆H₁₁O₂]⁺ +hν → [CH₃CO]⁺ +C₄H₈O with a λmax at 295±10 nm compared with a solution absorption maximum at 305 nm. Protonated 1,1,1-trifluoro-2,4-pentanedione was observed to undergo the photodissociation process [C₅H₆F₃O₂]⁺ +hν → CF₃H+[C₄H₅O₂]⁺ with a λmax at 273±10 nm compared with a solution absorption maximum at 288 nm. The [CH₃CO]⁺ and [C₂H₅CO]⁺ produced photochemically with the first three ions react to regenerate the protonated β-diketone leading to a photostationary state. Photodissociation of the protonated alkyl β-diketones is believed to occur from the protonated keto form, whereas photodissociation of protonated 1,1,1-trifluoro-2,4-pentanedione is believed to occur from the protonated enol form. Mechanisms for the observed photodissociation processes are proposed and comparisons with results from related techniques are presented.     

Collision-induced dissociation study of cyclization of α-diazo-ω-arylsulphonylaminoalkan-2-ones

The collision-induced dissociation mass-analysed ion kinetic energy (CID MIKE) spectra (electron impact and chemical ionization) of five α-diazo-ω-arylsulphonylaminoalkan-2-ones and corresponding N-arylsulphonylazetidin-3-ones and N-arylsulphonylpyrrolidin-3-ones were studied. The [M ? N₂]⁺˙ and [MH ? N₂]⁺ ions of two types of the diazo ketones provide CID MIKE spectra similar to those of the corresponding M⁺˙ and MH⁺ of the heterocyclic compounds, i.e. a cyclization analogous to that in solution takes place. For the other three types of diazo compounds the Wolff rearrangement prevails in both the gas and liquid phases. The effect of the substituents on the cyclization process was studied. The data obtained permit the results of acid-catalysed cyclization of similar diazo ketones to be predicted on the basis of their CID MIKE spectra. Chemical ionization provides a closer similarity with reactions in solution than electron impact ionization, which can be rationalized by the protonation of the diazo ketone molecule being the driving force of the cyclization reaction either in solution or in the ion source of a mass spectrometer.     

Hydrogen transfer in the retro diels–alder fragmentation of oxygen-containing heterocyclic compounds. II—Chromones

Mass Spectra of unsubstituted, 2-methyl-, 3-methyl and 2,3-dimethylchromones were examined. These compounds showed [RDA]⁺˙ and [RDA + H]⁺ ions as characteristc ions, together with [M? H]⁺,[M? CO]⁺˙,[M? CHO]⁺ and [RDA? CO]⁺˙ ions. Based on deuterium labelling experiments and measurement of metastable peaks by the ion kinetic energy defocusing technique, the origin of transferred hydrogen in the [RDA + H]⁺ ion was clarified. The mechanism of the [RDA + H]⁺ ion formation is discussed.     

Reaction of Carbon Anions With Iron α,β-Unsaturated Ketimine Complexes

Complexes (η⁴-PhCH=CHCR=NPh)Fe(CO)₃, where R=H(1a) and CH₃ were synthesized in excellent yield from the reaction of the corresponding α,β-unsaturated ketimines with excess Fe₂(CO)₉. Reaction of la with (Ph)₂CHLi and (CH₃)₂(NC)CLi at ?78°C or ambient temperature followed by acid quenching gave trans-PhCH=CHCHRNHPh, where R=CHPH₂ and C(CH₃)₂CN, respectively, in good yield. In the presence of 1 atm. of CO the reaction of 1a with (CH₃)₂(NC)CLi, followed by CuCl₂ oxidation resulted in the formation of a carbamyl choride, trans-PhCH=CHCH[C(CH₃)₂CN]N(Ph)COCl. This species was converted to a carbamate compound trans-PhCH=CHCH[C(CH₃)₂ - CN]N(Ph)COOCH₃ in MeOH in the presence of Ag⁺.     

Variation of fragmentation with ring size in cyclic α-amino acids

High resolution mass measurements, defocused metastable ion detection and deuterium labeling experiments have been employed in an investigation of the electron-impact induced decomposition of a series of carbocyclic amino acids, which varied in ring size from three to eight carbon atoms. About 50 per cent of the total ion current is carried by [M ? COOH]⁺ ions in the spectra obtained from compounds with five to eight carbon atoms in the ring. This is analogous to the fragmentation of the open chain naturally occurring amino acids. The behavior of the compounds with the two smallest rings is anomalous, reflecting to a larger extent the influence of the ring itself. Special attention has been given the loss of H₂O and NH₄ from ionized species of 1-aminocyclopropanecarboxylic acid.     

Mass spectra of some (Z)-α-Phenyl-β-(2-thienyl)acrylonitriles

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.     

Convenient Access to α‐Fluorinated Alkylammonium Salts

A series of novel α‐fluoroalkyl ammonium salts was obtained from the corresponding cyano compounds or nitriles by reaction with anhydrous HF. Room‐temperature stable trifluoromethyl ammonium salts were obtained in quantitative yield in a one‐step reaction at ambient temperature from the commercially available starting materials BrCN or ClCN. The novel cations [CF₃CF₂NH₃]⁺, [HCF₂CF₂NH₃]⁺, and [(NH₃CF₂)₂]²⁺ were obtained from CF₃CN, HCF₂CN, and (CN)₂, respectively, and anhydrous HF. The aforementioned fluorinated ammonium cations were isolated as room temperature stable [AsF₆]^? and/or [SbF₆]^? salts, and characterized by multi‐nuclear NMR and vibrational spectroscopy. The salts [HCF₂NH₃][AsF₆] and [CF₃NH₃][Sb₂F₁₁] were characterized by their X‐ray crystal structure.     

Addition des O'Donnell Reagenzes [Ph2C=NCHCO2Me]– an π-koordinierte,ungesättigte Kohlenwasserstoffe in [(C6H7)Fe(CO)3]+, [(C7H9)Fe(CO)3]+, [(C7H7)M(CO)3]+ (M = Cr,Mo) und [(C2H4)Re(CO)5]+. α-Aminosäuren mit metallorganischen Seitenketten

Metal Complexes of Biologically Important Ligands. CXVII [1] Addition of the O'Donnell Reagent [Ph₂C=NCHCO₂Me]^– to Coordinated, Unsaturated Hydrocarbons of [(C₆H₇)Fe(CO)₃]⁺, [C₇H₉Fe(CO)₃]⁺, [(C₇H₇)M(CO)₃]⁺ (M = Cr, Mo), and [(C₂H₄)Re(CO)₅]⁺. α-Amino Acids with Organometallic Side Chains The addition of [Ph₂C=NCHCO₂Me]^– to [(C₆H₇)Fe(CO)₃]⁺, [(C₇H₉)Fe(CO)₃]⁺, [(C₇H₇)M(CO)₃]⁺ (M = Cr, Mo) and [(C₂H₄)Re(CO)₅]⁺ gives derivatives of α-amino acids with organometallic side chains. The structure of [(η⁴-C₆H₇)CH(N=CPh₂)CO₂Me]Fe(CO)₃ was determined by X-ray diffraction. From the adduct of [Ph₂C=NCHCO₂Me]^– and [(C₇H₇)Mo(CO)₃]⁺ the Schiff base of a new unnatural α-amino acid, Ph₂C=NCH(C₇H₇)CO₂Me, was obtained.     

Mass spectra of transition metal π-complexes. VI—The metastable ion mass spectrum of (η1-Toluene)-tricarbonylchromium

First field free region metastable fragmentations of (η⁶-PhCH₃)Cr(CO)₃ have been examined by means of the linked scan technique. The molecular ion is shown to fragment exclusively by single and multiple CO loss. The ion [C₇H₈Cr(CO)₂]⁺? also fragments directly to [C₇H₈Cr]⁺?.