Mass spectra of chlorinated aromatics formed in pulp bleaching 2—Chlorinated guaiacols

The fragmentation of chlorinated guaiacols (2-methoxyphenols) on electron impact has been studied. The most common fragmentation processes are interpreted and in some cases the small differences between spectra of positional isomers are explained. In addition to the well-known alkyl-oxygen fission (loss of methyl radical), metastable ion studies and deuterium labelling have indicated several new fragmentation pathways. The most characteristic are the formation of [M? CH₃? HCl]⁺ and [M? CH₃? Cl]^+· ions. In general, however, the spectra of positional isomers are shown to be very similar.     

Mass spectra of chlorinated esters: 2—Methyl mono- and dichlorobutanoates

The mass spectral fragmentations of methyl mono- and dichlorobutanates have been studied. Deutrium labelling and metastable ion analysis were used to elucidate the fragmentation mechanisms. The molecular ion peaks of the esters are weak and show only in the spectra of the monochloro isomers. A McLafferty rearrangement gives the base peaks in the spectra of methyl 2-chloro-, 4-chloro- and 4,4-dichlorobutanoate; α-cleavage, [COOCH₃]⁺, in methyl 2,2- and 2,4-dichlorobutanoate; [M? Cl]⁺, in methyl 3-chlorobutanoate; [M? Cl? HCl]⁺, in methyl 3,4-dichlorobutanoate; [M? Cl? CH₂CO]⁺, in methyl 3,3-dichlorobutanoate and [M? Cl? COOCH₃]^+˙, in methyl erythro- and threo-2,3-dichlorobutanoate. The mass spectra of the stereoisomers are nearly identical, the loss of a chlorine atom and the McLafferty rearrangement giving the higher peaks in the spectrum of the threo form.     

Gas chromatographic and mass spectrometric analysis of chlorinated catechols occurring in pulp bleach liquors

Summary Chlorination step (C-step), spent bleach liquor from a kraft pulp mill and the product from the chlorination of guaiacol in aqueous solution have been investigated for their content of chlorinated catechols. After separation the samples were derivatized with diazoethane and analysed by glass capillary gas chromatography with an electron capture detector. The external standard mixture of all ethylated chlorocatechols was used in the measurements. The structures of the compounds identified were confirmed by gas chromatography/mass spectrometry. Eight chlorinated catechols were identified from a sample prepared by chlorination of guaiacol with Cl₂ in aqueous solution. However, only four of these compounds could be detected from a bleach liquor sample.     

13C NMR spectra of diazastilbenes. I—trans-styryldiazines

The ¹³C NMR spectra of all trans-styryldiazines, methyldiazines and trans-styrylpyridines have been fully assigned. Empirical shift increments were obtained for the chemical shifts of the carbon atoms; these are discussed in the light of theoretical considerations.     

Low energy,low temperature mass spectra: I—selected derivatives of n-octane

The low voltage, low temperature mass spectra of a series of octane derivatives n-C₈H₁₇X with X=CH₃, OH, OCH₃, NH₂, NHCH₃, N(CH₃)₂, CO₂H, CO₂CH₃, CO₂C₂H₅, CHO and COCH₃ are reported and discussed, using arguments involving thermochemistry where appropriate. The structures of these compounds can be uniquely assigned on the basis of such mass spectra.     

Doubly charged ion mass spectra: IV—chlorinated and brominated alkanes

Doubly charged ion mass spectra have been obtained for 42 chlorinated and brominated n-alkane (methyl through octyl) hydrocarbons. A double focusing Hitachi RMU-7L mass spectrometer, operated at 1.6kV accelerating voltage, has been used to measure the spectra. Molecular doubly charged ions have not been observed. Intense fragment ions have been produced from extensive H and halogen loss as well as C? C bond rupture of the parent molecule. The most abundant ions in the doubly charged ion spectra observed in this investigation resulted from reactions of [Cl]²⁺˙, [Br]²⁺˙, [CCL₂]²⁺, [C₂H₂Cl]²⁺˙, [C₃H₂]²⁺, [C₃HCl]²⁺, [C₃HBr]²⁺, [C₄H₃]²⁺˙, [C₄H₄]²⁺, [C₄H₆Br]²⁺˙, [C₄H₈Br]²⁺˙, [C₅H₂]²⁺, [C₆H₆]²⁺, [C₆H₈]²⁺ and [C₇H₈]²⁺. The prominent doubly charged fragment ions formed by electron impact of the smaller halogenated alkanes generally contained halogen, whereas ions of the type [C_nH_x]²⁺ were dominant in the spectra of higher molecular weight mono- and dihalogenated alkanes. Appearance energies of several ions have been measured. A geometry optimized quantum mechanical SCF treatment has been used to compute energies, charge densities and structures of doubly charged halogenated alkane ions.     

Mass spectra of indazolones and pyrazolones—I: Indazolones

The mass spectral fragmentations of 3-indazolone (I), 1-acetyl-3-acetoxyindazol (II), 1,2-diacetyl-3-indazolone (III), 1-methyl-3-indazolone (IV), 2-methyl-3-indazolone (V), 2-methyl-3-indazolone-N-d-1 (VI), 3-methoxy-indazole (VII), 1-ethyl-3-indazolone (VIII), 1-carbethoxy-3-indazolone (IX), 1-carbethoxy-2-methyl-3-indazolone (X), 2′-carboxyethyl-3-indazolone (XI), 1-oxo-2,3-dihydropyrazolo-(1,2-α)-3-indazolone (XII) and 1-ethyl-3-indazolone-N-d-2 (XIII) are reported. The loss of an ·N₂R radical from the parent radical ion in indazolone and the alkyl indazolones occurs more readily than the loss of a formyl radical, and no loss of HCN is observed from the parent radical ion. Mass spectral data can be used to distinguish between N-methyl and O-methyl derivatives of 3-indazolone.     

Mass spectra of steroidal alkyl ethers—I

The mass spectral fragmentation of saturated and unsaturated steroidal methyl and ethyl ethers and ethers of 4,4-dimethyl steroids are studied and compared to the fragmentation of steroidal alcohols, trimethylsilyl ethers and ethylene ketals. Unlike the trimethylsilyl ether the small fragment containing the alkoxy group is neither the base peak nor a very strong peak in the spectrum. A significant peak occurs at [M — ROH]^+·, however, sometimes even constituting the base peak of the spectrum. The fragmentations of the alkyl ethers are largely dependent on their environments. The present results also show the generalization that methyl ethers are better leaving groups than the corresponding alcohols in fragmentation processes, is not always valid.     

Mass spectra of chlorinated veratroles (1,2-dimethoxybenzenes)

The behaviour of all nine chlorinated veratroles (1,2-dimethoxybenzenes) under electron impact has been investigated. The most common fragmentation processes are interpreted using metastable ion analysis and deuterium labelled compounds. For all compounds studied, the most common fragmentation route seems to be the primary loss of a methyl radical followed by loss of carbon monoxide. The ion formed has a well-known quinonoid structure and fragments by several routes elucidated by metastable ion analysis. In general, the spectra of the positional isomers are shown to be practically similar and it is apparent that e.g. the 3- and 4-chloro isomers can be differentiated only from the abundance ratio of the [M? CH₃? CO? CH₃]⁺ and [M? CH₃? CO? H₂O]⁺ ions.     

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 spectra of 1,2,4-triazoles—II: Alkyl 1,2,4-triazoles

The mass spectra of monomethyl 1,2,4-triazoles contain fragment ions produced by specific cleavage of the heterocyclic ring. A major fragmentation from many molecular ions involves the elimination of HCN, but loss of N₂ is either very small or completely absent. No N or H scrambling occurs within the triazole ring system, as evidenced by labelling studies. The loss of a hydrogen atom from the molecular ions of 3-alkyl-1,2,4-triazoles (alkyl ? C₂H₅) originates from hydrogens attached to the β carbon and nitrogen atoms.     

Mass spectra of indazolones and pyrazolones—II: 5-pyrazolones

The mass spectral fragmentations of 3-methyl-5-pyrazolone (I), 3-methyl-5-pyrazolone-1-d₁ (II), 3-methyl-5-pyrazolone-1,4,4-d₃ (III), 1-acetyl-3-methyl-5-pyrazolone (IV), 3-methyl-5-ethoxy-pyrazole (V), 3,4-dimethyl-5-pyrazolone (VI), 1,3-dimethyl-5-pyrazolone (VII), 1-acetyl-5-acetoxy-3,4-dimethylpyrazole (VIII), 1,2,3-trimethyl-5-pyrazolone (IX), 3,4,4-trimethyl-5-pyrazolone (X), 3,4,4-trimethyl-5-pyrazolone-1-d₁ (XI), 3-phenyl-5-pyrazolone (XII), 2-acetyl-3-phenyl-5-pyrazolone (XIII) and 5-acetoxy-3-phenylpyrazole (XIV) are reported. Comparison is made between the mass spectra of 5-pyrazolones and 3-indazolones. As for the latter compounds initial loss of ·N₂R is preferred to loss of ·CHO, and is followed by loss of CO. The [M ? 1]ions are intense in the C-methyl substituted pyrazolones, and unlike the 3-indazolones, the pyrazolones do not show any significant loss of HCN from these ions. The mass spectra distinguish between certain isomeric 5-pyrazolones.     

Mass spectrometry of hop compounds—II: Mass spectra of related oxygen heterocyclic compounds

Mass spectra have been determined of a number of phloroglucinol derivatives and closely-related compounds encountered in chemical studies of hop components. Initial fission involving acyl, alkyl or alkenyl side-chains gives predominantly even-electron ions which then fragment their oxygen heterocyclic rings by elimination of neutral molecules, whilst gem-dialkenyl centres show preference for loss of an alkenyl group. The fragment ions induced by electron-impact may be correlated to a useful extent with molecular structure.     

Carbon-13 nuclear magnetic resonance spectra. I—Monosubstituted adamantanes and adamantanones

The chemical shifts of 4_ax and 4_eq substituted adamantanones are compared with those calculated with the aid of a given additivity rule. It is found that both δ carbons are shielded with respect to the substituent. In contract to the situation for the y-atoms, however, the δ_syn atom is less shielded than the δ_anti atom. In most cases the additivity rule predicts the chemical shifts with an accuracy of approximately 1 ppm. Exceptions are carbon atoms 4 and 9 of the 4_eq substituted adamantanones. In both cases the measured values are 4 to 6 ppm upfield. This can possibly be explained by an electronic interaction between the carbonyl group and the substituent.     

o-Nitrobenzylidene compounds. I—Competitive ortho interactions in the mass spectra of n-o-nitrobenzylidene-o-substituted anilines

The intense [M – 17]⁺ ion, which is a characteristic feature of the mass spectra of N-o-nitrobenzylideneaniline and its simple derivatives, may be substantially reduced in intensity when the aniline-derived ring is also ortho substituted: the intensity is lowest when this ortho substituent has a nucleophilic character and can itself interact with the CH?N group. The ortho substituents examined are Br, CH₃, OH, NH₂, SH, SC₆H₄CH₃(p), CO₂CH₃ and CO₂C₂H₅.     

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.     

Studies in mass spectroscopy—II Mass spectra of substituted furans

The mass spectra of 29 furans, variously substituted with alkyl, aldehyde, ketone, ester, nitrile and nitro groups are reported and discussed. The spectra are generally quite simple and amenable to analysis. Not only do the characteristic m/e values give information as to the type of substituents, but also the operation of certain ortho-effects permits conclusions as to the relative location of functional groups. A number of rearrangement process have been investigated by high resolution measurements and deuterium labelling.     

Mass spectra of liquid crystals. III—phenylpyrimidine derivatives

The 70 eV electron impact mass spectra of 34 1-phenyl-2,5-pyrimidine derivatives are presented. Based on the observed mass shifts by the various substituents, the nature of the main fragment ions is rationalized.     

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.