Mass spectrometry of hop compounds—III. Mass spectra of substituted 1,3-cyclopentanediones derived from hop constituents

The mass spectra of isohumulones (IV, V), tetrahydroisocohumulones (VI, VII), tetrahydroisohumulones (VIII) neohydroisocohumulones (XI, XII) cohumulinic acid (III), lupuloxinic acid (XV), humulinone (XIV) and related compounds are described. Ions which appear to be diagnostic for particular structures are discussed.     

Mass spectrometry of heterocyclic compounds—II: Electron-impact induced fragmentation of 3,5-diphenyl-1,2,4-oxadiazole

The electron-impact induced fragmentation of 3,5-diphenyl-1,2,4-oxadiazole has been investigated by labelling experiments, defocused metastable ion detections and high resolution mass measurements. The main fragmentation process suggests heterocyclic cleavage at the 1 to 5 and 3 to 4 bonds confirming our previous interpretation. The structure of the major fragment ion [C₇H₅NO]⁺· has been interpreted as being represented by the isomeric benzonitrile oxide and phenylisocyanate structures, the latter isomerising irreversibly from the former. The benzonitrile oxide structure is consistent with [C₇H₅NO]⁺· formation by cleavage of the 1 to 5 and 3 to 4 bonds.     

Mass spectra of heterocyclic compounds: V—dihydro-1,3,5-dioxazines

N-Substituted dihydro-1,3,5-dioxazines show a general fragmentation pattern supported by metastable ions, exact mass measurements and deuterium labelling. There are two well-defined pathways: one is initiated by elimination of the N-substituent and the other by loss of a hydrogen atom from the heterocyclic ring.     

Mass spectrometry of onium compounds—II. Carnitine and O-acyl derivatives

Carnitine and its O-acyl derivatives undergo two major pyrolytic reactions in the mass spectrometer. Firstly elimination of water from carnitine or acid from acylcarnitine takes place followed by intramolecular displacement and formation of crotonyl lactone and trimethylamine. Secondly intramolecular displacement occurs with formation of a substituted γ-lactone and trimethylamine. For the lower acid derivatives only the elimination pathway is important. For carnitine and higher derivatives both processes are important. The electron induced fragmentations of the major pyrolysis products are relatively simple. The most important pathways for the major components are discussed. The pyrolytic composition and mode of fragmentation are characteristic and can be used for identification purposes.     

Mass spectra of organoboron compounds—II: The mass spectra of triphenylboroxine and its precursor phenylboronic acid

The mass spectrometric fragmentation pattern of phenylboronic acid has been determined and that of triphenylboroxine redetermined and extended, and the origin of some high abundance ions, previously unassigned, have been identified.     

Mass spectra of organoarsenic compounds—II: Electron-impact-induced fragmentation of 2-substituted-1,2,2-dioxarsenanes

The electron-impact-induced fragmentation of 2-substituted 1,3,2-dioxarsenanes has been studied. The main fragmentation modes have been determined with the use of high resolution mass measurements and by application of the metastable defocusing technique. The predominant fragmentation for the 2-alkyl-1,3,2-dioxarsenanes proceeds via the loss of the 2-substituent from the molecular ion. In the case of 2-phenyl-1,3,2-dioxarsenanes elimination of the phenyl group competes with the formation of a C₆H₅ As ion as well as loss of aldehyde from the molecular ions.     

Mass spectra of organometallic compounds—IX: Compounds with metal-metal bonds

The mass spectra of the following compounds have been investigated: (i) The organotin derivatives (CH₃)₃SnMo(CO)₃C₅H₅ and (CH₃)₃SnNCW(CO)₅; (ii) The mercury derivatives Hg[Mn(CO)₅]₂, Hg[Co(CO)₄]₂, Hg[Mo(CO)₃C₅H₅]₂ and ClHgMo(CO)₃C₅H₅; (iii) The polynuclear cyclopentadienyl metal derivatives [C₅H₅Ru(CO)₂]₂, [C₅H₅Cr(CO)₃]₂, [C₅H₅Cr(NO)₂]₂ and [C₅H₅Fe-CO]₄; (iv) The trinuclear cobalt carbonyl derivatives YCCo₃(CO)₉ (Y = Cl and CH₃); (v) The binuclear triene-iron carbonyl derivatives C₄H₄Fe₂(CO)₆ and C₈H₁₀Fe₂(CO)₆. The mass spectra of the trimethyltin derivatives exhibited stepwise loss of methyl groups as well as of carbonyl groups. The mass spectra of the mercury derivatives exhibited the facile loss of mercury. The mass spectrum of [C₅H₅Cr(CO)₃]₂ indicated a very weak chromium-chromium bond since it exhibited no ion containing two chromium atoms. The mass spectrum of the nitrosyl derivative [C₅H₅Cr(NO)₂]₂ exhibited the stepwise loss of its four nitrosyl groups. The mass spectrum of [C₅H₅FeCO]₄ was rather complex and exhibited a variety of unusual processes including eliminations of neutral Fe and C₅H₅Fe fragments. Unusual ions observed in the mass spectrum of CH₃CCo₃(CO)₉ include the bare polymetallic ions [Co_n]⁺ (n = 3 and 2). Many examples of the elimination of neutral CO, C₂H₂ and H₂ fragments were noted in this work.     

Mass spectrometry of heterocyclic compounds—III. Electron-impact-induced fragmentation of 1,2-benzisothiazole and some 3-substituted derivatives

The mass spectra of fifteen 1,2-benzisothiazoles are reported; their fragmentation patterns have been investigated by labelling experiments, high resolution mass measurements and defocused metastable ion detection. The parent compound of the series, 1,2-benzisothiazole, eliminates HCN after partial inter-ring hydrogen scrambling. The extent of scrambling has been determined for normal daughter ions produced at different electron beam energies and also for metastable daughter ions, and is compared with the data reported for benzothiazole. Some 3-substituted derivatives show unusual fragmentation patterns. The mechanisms of these processes are under further investigation.     

Mass spectra of organometallic compounds—VII; Organonitrogen derivatives of metal carbonyls

The positive-ion mass spectra of the following organonitrogen derivatives of metal carbonyls are discussed: (i) The compounds NC₅H₄CH₂Fe(CO)₂C₅H₅, NC₅H₄CH₂COMo(CO)₂C₅H₅, NC₅H₄CH₂W(CO)₃C₅H₅, NC₅H₄CH₂COMn(CO)₄, C₅H₁₀NCH₂CH₂Fe(CO)₂C₅H₅, (CH₃)₂NCH₂CH₂COFeCOC₅H₅ and (CH₃)₂NCH₂CH₂COMn(CO)₄ obtained from metal carbonyl anions and haloalkylamines, (ii) The isocyanate derivative C₅H₅Mo(CO)₃CH₂NCO; (iii) The arylazomolybdenum derivatives RN₂Mo(CO)₂C₅H₅ (R ? phenyl, p-tolyl, or p-anisyl); (iv) The compound (C₆H₅N)₂COFe₂(CO)₆ obtained from Fe₃(CO)₁₂ and phenyl isocyanate; (v) The N,N,N′,N′-tetramethylethylenediamine complex (CH₃)₂NCH₂CH₂N(CH₃)₂W(CO)₄. Further examples of eliminations of hydrogen, CO, and C₂H₂ fragments were noted. In addition evidence for the following more unusual processes was obtained: (i) Elimination of HCN fragments from the ions [NC₅H₄CH₂MC₅H₅]⁺ to give the ions [(C₅H₅)₂M]⁺ (M ? Fe, Mo and W); (ii) Conversion of C₅H₅Mo(CO)₃CH₂NCO to C₅H₅Mo(CO)₂CH₂NCO within the mass spectrometer; (iii) Elimination of N₂ from [RN₂MoC₅H₅]⁺ to give [RMoC₅H₅]⁺; (iv) Novel eliminations of HNCO, FeNCO, and C₆H₅NC fragments in the mass spectrum of (C₆H₅N)₂COFe₂(CO)₆; (v) Facile dehydrogenation of the N,N,N′,-N′-tetramethylethylenediamine ligand in the complex (CH₃)₂NCH₂CH₂N(CH₃)₂W(CO)₄.     

The mass spectra of meliacins and related compounds—II: Meliacins lacking the ring d epoxide function

The mass spectra of some 14,15-deoxymeliacins are reported and discussed in relation to the previously published fragmentation patterns of the epoxymeliacins. The fragmentation patterns of a few compounds with structures closely related to those proposed for the principal ions in the spectra of the epoxymeliacins are also examined.     

Mass spectrometry of heterocyclic compounds. I—the behaviour of some quaternary heterocyclic iodides under electron impact

The mass spectra of five quaternary heterocyclic iodides have been investigated. The main thermal process is the anhydro base formation by HI elimination. The influence of the second heteroatom, X, on the fragmentation mode of the thermally produced anhydro bases is analysed.     

Cyclic organophosphorus compounds—II the infrared spectra of some 1,3,2-Dioxaphosphorinanes

The IR spectra of 47 1,3,2-dioxaphosphorinanes, mostly new compounds, have been recorded and discussed. Assignments have been made to P=O, P---O---C (alkyl and aryl), P=S and P---N stretching motions. In addition,it is suggested tentatively that multiple bands found at around 1000 to 1050 cm⁻¹ and at around 1150 to 1200 cm⁻¹ may be due to ring P---O---(C) vibrations.     

Mass spectra of organometallic compounds—VIII. Some transition metal organometallic halide derivatives

The positive ion mass spectra of the transition metal organometallic halide derivatives C₅H₅M(CO)₃Cl(M ? Mo or W), C₇H₇W(CO)₂I, C₃H₅Fe(CO)₃I, [C₃H₅PdCl]₂, and [C₅H₅Mo(NO)I₂]₂ have been investigated. Further examples of the elimination of CO and C₂H₂ fragments were noted. In addition the following effects of particular interest were observed: (i) Evidence in the mass spectra of the chlorides for reactions with adventitious iodine and even bromine present in the mass spectrometer; (ii) Evidence for conversion of the compounds C₅H₅Mo(CO)₃X to the new halides [C₅H₅Mo(CO)X]₂ upon pyrolysis; (iii) Evidence for facile losses of the π-allyl group, the iodine atom, and methyl iodide in the mass spectrum of the π-allyl derivative C₃H₅Fe(CO)₃I; (iv) Evidence for loss of iodine upon introducing [C₅H₅Mo(NO)I₂]₂ into the mass spectrometer to give ions derived from [C₅H₅Mo(NO)I]₂.     

Mass spectrometry of onium compounds—XI: Ionization potentials of hydroxy and mercapto pyridines

Ionization potential measurements of the volatile species from the three isomers of the tautomeric hydroxyl and mercapto pyridines show that these are in the hydroxy and mercapto forms rather than appearing as lactams and betaines. The corresponding N-methyl lactams and S- and O-methyl ethers were also studied for comparative purposes.     

Mass spectra of heterocyclic compounds. IV–2,4,5-Trioxoimidazolidines

General fragmentations induced by electron impact of twenty-one examples of 2,4,5-trioxoimidazolidines are rationalized with the aid of metastable transitions, high resolution measurements and deuterium and ¹⁸O labelling. The results can be used for the recognition of different types of derivatives.     

Mass spectra of organometallic compounds–XII: Tetraphenylcyclobutadiene derivatives

The mass spectra of the tetraphenylcyclobutadiene complexes (C₆H₅)₄C₄Fe(CO)₃, C₅H₅CoC₄(C₆H₅)₄ and C₉H₇CoC₄(C₄H₅)₄ are reported. Evidence is presented for the loss of the tetraphenylcyclobutadiene ring by a two-step sequence involving successive losses of two (C₆H₅)₂C₂ fragments. Significant differences are observed in the fragmentations of the monopositive and dipositive molecular ions of C₉H₇CoC₄(C₆H₅)₄.     

Mass spectrometry of onium compounds—XVII: Anilinium carboxylates. orthoeffect in anthranilic acid derivatives

The N,N,N-trimethylanilinium carboxylates are transmethylated to the isomeric esters before evaporation in the mass spectrometer. Pyroltic reactions and electron-impact fragmentations are elucidated by means of deuterio analogues. The orthoisomer behaves anomalously in that initial expulsion of a methyl radical is important. Deuteration has shown this reaction to take place along two distinct routes, either from the nitrogen or from the ester.     

Mass spectra of organoarsenic compounds—I: Electron-impact-induced fragmentations of esters of arsenious and thioarsenious acid

The mass spectra of a series of esters of arsenious and thioarsenious acid have been studied, together with that of diethyl methylarsonite. The main fragmentation pathways have been determined with the use of high resolution mass measurements and application of the metastable defocusing technique. The major fragment ions all contain arsenic and may be ascribed structures implying divalent/trivalent arsenic. Ions implying tetravalent/pentavalent arsenic as well as double hydrogen rearrangement processes are hardly recognisable; this is in contrast to the findings reported for the corresponding phosphorous compounds, with which a comparison is made. The present results are in accordance with the view that arsenic is less capable than phosphorous of achieving multiple bonding to other atoms by means of its empty d orbitals.     

Fragmentation and rearrangement processes in the mass spectra of perhalogenoaromatic compounds—VIII: Fluoroaromatic heterocyclic derivatives of group IV

The metastable ion supported fragmentations and fluorine transfer rearrangements of a series of fluoroaromatic heterocyclic derivatives of silicon, germanium and tin are reported. Of particular interest is the unique loss of neutral SiF₄ from the parent ion of (C₁₂F₈)Si yielding the [C₂₄F₁₂]⁺˙ ion. These and similar rearrangements are discussed and structures are proposed for some of the ions observed. The general case of cyclic rearrangement intermediates prior to the loss of neutral metal fluorides from perfluoroaromatic derivatives is discussed. Losses of neutral metal fluorides from the parent ions appear to involve a species with increased co-ordination number about the central atom as an intermediate. In addition to (C₁₂F₈)₂M, the following compound types were studied: (C₆H₅)₂Ge(C₁₂F₈), (C₁₂F₈S)₂M and R₄Sn₂(C₆F₄)₂ (where M = a Group IV metal and R = CH₃ or C₆H₅).