bluuebunny/crossref_metadata_2025 huggingface dataset:
13C and 31P NMR studies of configurational and conformational effects in 1‐Phenyl‐4‐phosphorinanones and their 1‐selenides
Authors: Pietrusiewicz K. Michał
Published: May 2005

Carbon‐13 and 31P NMR data are reported for 1‐phenyl‐4‐phosphorinanone and its 1‐selenide, as well as for two anancomeric 1‐phenyl‐3,5‐dimethyl‐4‐phosphorinanones and their 1‐selenides. The conformational free energy of the P‐phenyl substituent in 1‐phenyl‐4‐phosphorinanone is estimated to be ΔG° = 0.81 kcal mol−1 (ca 80% axial) in chloroform, and this result is consistent with both 13C NMR shielding and coupling data. The γ effects of a single atom substituent on phosphorus are found to be small in the case of selenium; information in the literature indicates significant downfield‐shifting γe effects due to equatorial oxygen and sulphur substituents in phosphorinanes. In selenides, the shift for the aromatic C‐ipso carbon in the axial isomer is further downfield than in the equatorial isomer, an observation not precedented in the literature. In the discussion of P‐C coupling data a ‘second order’ Karplus‐like relationship is invoked for 3J(PC), which is dependent both on the dihedral angle and on the orientation of the phosphorus lone pair in phosphines. The one‐bond P‐C‐ipso coupling in selenides is identical for all three selenides studied, regardless of the stereochemistry at phosphorus. Similar lack of substantial differentiation is noted for one‐bond P‐Se coupling. A possible origin of this phenomenon is discussed in terms of diminution of the phosphorus charge contribution to the Fermi contact term. From 31P NMR data a high stereodependence of selenylation shifts is apparent, and greater shifts (by ca 20 ppm) are observed when selenium is bound to phosphorus in the more crowded (axial) position. In anancomeric (conformationally biased) phosphines, the isomer with the axial phenyl group has the 31P signal at lower field. This is consistent with observations made previously for rigid 1‐phenylphosphorinanes.
The carbon‐13 nuclear magnetic resonance spectra of some α‐spirocyclopropyl ketones and related cyclohex‐2‐en‐1‐ones and 2‐ethylidenecyclohex‐3‐en‐1‐ones
Authors: Helferty Patrick Hugh , Yates Peter
Published: May 2005

The 13C NMR spectra of a series of β,γ‐unsaturated α‐spirocyclopropylcyclohexanones and saturated α‐spirocyclopropylcycloalkanones have been analyzed and compared with the spectra of diethyl cyclopropanedicarboxylate and a corresponding spiro acylal. The chemical shifts of the cyclopropane methylene carbons are correlated with spiroactivation of the cyclopropane ring to nucleophilic attack. In the case of the saturated spiro ketones these chemical shifts can also be correlated with their photochemistry. In the SFORD spectra of the spiro ketones the signals of the cyclopropane methylene carbons appear as complex multiplets: this is attributed to second‐order coupling resulting from strong coupling between the vicinal cyclopropane protons. The 13C NMR spectra of a series of related cyclohex‐2‐en‐1‐ones and 2‐ethylidenecyclohex‐3‐en‐1‐ones have also been analyzed; the chemical shift assignments for the latter corroborate the configurational assignments made on the basis of 1H NMR spectroscopy.
Conformational studies on 2‐fluoro‐1,2‐disubstituted ethanes by NMR spectroscopy. Influence of electronegativity on vicinal proton–proton and fluorine–proton coupling constants
Authors: Hamman Sylvain , Béguin Claude , Charlon Claude , Luu‐Duc Cuong
Published: May 2005

The analysis of the ABKX spectra of thirteen compounds of the series RC(H‐K)(F‐X)C(H‐A)(H‐B)X gave the four vicinal proton‐proton and fluorine‐proton coupling constants. These coupling constants of conformationally mobile structures were used (i) to calculate the populations of the rotational states of the CHFCH2 bond, (ii) to calculate the vicinal trans proton‐proton J(HH)t and gauche and trans fluorine‐proton coupling constants J(FH)g and J(FH)t and (iii) to give the unambiguous assignment of protons H‐A and H‐B. The dependence of the gauche and trans coupling constants with substituent electronegativity is explored. The results extend known correlations towards smaller electronegativity values. More quantitatively, the results and those in the literature, excluding those where deformations of torsional or bond angles occur, give a good fit of the data: a linear fit for J(HH)t = 15.0‐0.77 Σ(ΔE), an exponential fit for J(FH)g = 15.35 exp [‐0.266 Σ (ΔE)] and a linear fit for J(FH)t = 65.75 ‐ 7.52 Σ (ΔE), where Σ (ΔE) is the sum of the electronegativity difference between hydrogen and the six atoms or groups on the CHCF fragment.
Use of shift reagent with MTPA derivatives in 19F NMR spectrocopy: IV—Determination of enantiomeric composition for a variety of secondary cycloalkanols. A survey
Authors: Merckx E. M. , Lepoivre J. A. , Lemière G. L. , Alderweireldt F. C.
Published: May 2005

Chiral secondary cycloalkanols (monocyclic alcohols) are derivatized to the corresponding (R)‐α‐methoxy‐α‐trifluoromethyl‐α‐phenylacetic acid [(R)‐MTPA] esters and analysed by 19F NMR in the presence of tris(6,6,7,7,8,8,8‐heptafluoro‐2,2‐dimethyl‐3,5‐octanedionato) europium(III) [Eu(fod)3]. Using this method the enantiomeric composition can be measured for several cyclopentanols, cyclohexanols and cycloheptanols, with a variety of substitution patterns. It is shown that a mixture of four stereoisomeric cycloalkanols, such as cis and trans disubstituted alcohols, can be analysed simultaneously.
High precision NMR study of 1,1‐disubstituted silacyclobutanes
Authors: Dabbitt O. , Sutcliffe L. H.
Published: May 2005

The hydrogen NMR spectra of 1,1‐dimethyl‐, 1,1‐dichloro‐, 1,1‐dimethoxy‐ and 1,1‐difluoro‐silacyclobutane have been analysed. A new correlation NMR instrumental technique has been used to obtain spectral parameters with very high precision.
13C nuclear magnetic resonance and conformational analysis of 5‐chloro‐2‐oxo‐1,3,2‐dioxathianes
Authors: Gorrichon Jean‐Pierre , Chassaing Gérard , Cazaux Louis
Published: May 2005

The 13C NMR chemical shifts in CDCI3 for eight cyclic sulphites, chlorinated at C‐5, are reported. The α‐and β‐deshielding effects and the γ‐shielding effects for the chlorine substituent are compared with similar effects in the 1,3‐dioxane series and with the effects arising from methyl groups in the sulphite series. The study of two conformational equilibria shows that it is difficult to use 13C NMR spectroscopy for the conformational analysis of cyclic sulphites because of the frequent participation of twist forms, with 1,4‐ and 2,5‐axes, to these equilibria.
Spectral editing for 13C NMR signals of deuterated compounds
Authors: Wesener Joachim R. , Günther Harald
Published: May 2005

J‐modulation of 13C spin echo signals is used to develop a strategy for the analysis of deuterated compounds. On the basis of 1 J(13C2H) and an experimental set‐up that allows both 2H and 1H decoupling, 13C subspectra for various groups can be produced. The application of difference methods facilitates the analysis and, finally, leads to the identification of CD, CD2, CD3, CHD, CHD2 and CH2D groups.
Empirical additive parameter and automatic assignment of 13C NMR signals of some aryl and heteroaryl groups. A new criterion for a linear relationship between 13C chemical shifts and charge densities
Authors: Bangov Ivan P. , Radeglia Reiner
Published: May 2005

The 13C NMR signals of some mono‐ and disubstituted aryl compounds were assigned by means of empirical additive substituent parameters and information taken from fully coupled spectra. This assignment was compared with that obtained with the help of the method of automatic assignment of the signals based on the linear relationship between 13C chemical shift and charge density. The results show that in the cases of XR substituents (X = O, NH and R = H, CH3, CH2CH2OH) a good correlation is observed and the automatic assignment is correct. In contrast, in the cases of CH2CH2Y substituents (Y = OH, NH2, Cl) a worsening of the correlation is observed and the automatic assignment is not correct.

It is suggested that for compounds with a preliminarily known assignment, the automatic assignment can serve as an additional criterion for the reliability of the linear relationship between 13C chemical shift and charge density.
Application of the selective 13C{1H} nuclear Overhauser effect to structure elucidation of photoadducts derived from maleic anhydrides and thiophene
Authors: Leon V. , Bolívar R. A. , Tasayco M. L. , Gonzalez R. , Rivas C.
Published: May 2005

The 13C NMR spectra of a representative series of photoadducts derived from methylmaleic anhydrides and thiophene, containing the same basic carbon skeleton, were studied in order to establish a model for future structure elucidation of similar compounds. Selective heteronuclear 13C{1H} NOE was applied to stereochemical studies on the same compounds with the dual purpose of confirming previous assignments and to gain experience in the use of this technique, rarely applied in organic chemistry. The technique was employed in two different ways, by irradiating the selected proton resonance with and without modulation [νm=½J(CH)].
Carbon‐13 magnetic resonance spectra and the stereochemistry of some substituted bicyclo[2.1.1]hexanes
Authors: Gibson Thomas
Published: May 2005

Using selective deuteriation and broad‐band and off‐resonance proton decoupling techniques, complete signal assignments are made for the 13C NMR spectra of a number of ketones and unsaturated esters with the bicyclo[2.1.1]hexane ring systems.
13C NMR spectra of 2,3‐dihydro‐1H‐benzo[b]azepines: Differentiation of diastereomers
Authors: Uriac Ph. , Huet J.
Published: May 2005

The 13C NMR spectra of 23 2,3‐dihydro‐1H‐benzo[b]azepines, including nine pairs of diastereomers separated by chromatography, [(2R*, 3R*) and (2R*), 3S*)] are hereby assigned and discussed. The relative configurations of the diastereomers were assigned by two methods. The first, based on the chemical shifts of the asymmetric carbons C‐2 and C‐3 (with regression analysis), shows that the values for (R*, R*) are approximately 1 ppm lower than those for (R*, S*) diastereomers. The second method uses the chemical shifts, δ3, of the R3(CH3) substituents. When these δ3 values are compared by means of the δ3‐δm difference (δm is the mean value obtained from compounds where R2=H), the difference is always negative for (R*, R*) and positive for (R*, S*). This is attributed to a γ‐gauche effect between R2 and R3 in the case of (R*, R*) diastereomers (R2 and R3 are cis). The results corroborate those already obtained by 1H NMR [J(23)(R*, R*)<J(23)(R*, S*)] and are a confirmation of the results of a radiocrystallographic examination carried out on two nitrogen acetylated diastereomers.
Assignment of relative configurations to acyclic diastereomeric carbinols with the lanthanide shift reagent Eu (fod)3 by 1H and 13C NMR
Authors: Ibarra C. Alvarez , Feijoo M. L. Quiroga , Perez M. S. Arias , de la Orden Parra J.
Published: May 2005

An assignment of relative configurations has been achieved for the diastereomeric racemates (1R2R,1S2S) and (1R2S,1S2R) of 3,3‐dimethyl‐1,2‐diphenylbutan‐1‐ol through the comparative analysis of the respective chemical shifts induced by Eu(fod)3 in the 1H and 13C NMR spectra, and the corresponding conformational distribution.
Barriers to internal rotation in 1,3,5‐trineopentylbenzenes: 10—13C and 19F NMR band shape studies and force field calculations
Authors: Andersson Sven , Drakenberg Torbjörn
Published: May 2005

1,3,5‐Trineopentylbenzenes (TNB) with one or two benzylic substituents in each neopentyl group were synthesized. The substituents were F, Cl, Br, J, OCH3, OCOCH3, OSi(CH3)3 and CH3 and, in cases of disubstitution, F, Cl, Br, CH3 and Cl, CH3 and Br and SCH2CH2S. Barriers to internal Csp3Csp2 (aryl) and Csp3Csp3 rotation were estimated by 13C and 19F NMR band shape methods. Estimated barriers in the TNB series were found to be very close to those found for the corresponding mononeopentylbenzenes. For some of the compounds studied, molecular mechanics (MM) calculations were performed with the Allinger MMP1 program. Differences between calculated and experimental estimated barriers were found, and possible sources of these discrepancies in terms of parameters used in the MMP1 program are discussed.
Ab initio MO calculations and 17O NMR at natural abundance of para‐substituted acetophenones
Authors: Brownlee Robert T. C. , Sadek Maruse , Craik David J.
Published: May 2005

17O NMR chemical shifts and calculated (ab initio MO theory) electron densities are reported for a series of para‐substituted acetophenones, XC4H6COCH3, where X = NH2, OCH3, F, Cl, CH3, H, COCH3, CN, NO2. The 17O shifts are very sensitive to the para substituent and cover a range of some 51 ppm. Donors induce upfield shifts and acceptors downfield shifts. The substituent chemical shifts (SCS) correlate precisely with σI and σR+ using the Dual Substituent Parameter (DSP) method. The derived transmission coefficients ρI and ρR indicate that polar and resonance mechanisms contribute approximately equally to the observed substituent effects. The shifts also correlate well with calculated π‐electron densities (slope = 1500 ppm per electron) confirming their electronic origin. λ values are also reported, and the role of the average excitation energy, ΔE, in determining 17O SCS values is discussed. It is concluded that variations in ΔE are minor and that the local Δ‐electron density is the dominant feature controlling 17O SCS values.
Nitrogen‐15 NMR studies of 1,4‐benzodiazepines: 1
Authors: Scahill Terrence A. , Smith Stanford L.
Published: May 2005

Nitrogen‐15 NMR data are reported for ten benzodiazepines, including the chemically useful drugs diazepam, oxazepam, clonazepam, flurazepam and chlordiazepoxide. Substituent effects for neighboring groups are presented and discussed.
13C NMR assignments of nonionic and anionic ethoxylated surfactants
Authors: Figdore Phillip E.
Published: May 2005

13C chemical shift assignments have been made for the ethoxy region of nonionic and anionic ethoxylated surfactants. The lanthanide shift reagent Eu(fod)3 was used to assign the shifts of nonionics because of some ambiguities in the literature.
Conformational analysis of 7‐membered dimethyl cyclic sulphites: 2‐Oxo‐1,3,2‐dioxathiepanes and 3‐oxo‐2,4,3‐dioxathiepins
Authors: Guimaraes Afonso Celso , de Almeida Paulo Gontijo Veloso , Baltas Michel , Cazaux Louis
Published: May 2005

2‐Oxo‐1,3,2‐dioxathiepanes and 3‐oxo‐2,4,3‐dioxathiepins, including two series of three diastereoisomers, were synthesized, isolated by HPLC and characterized by 1H and 13C NMR spectroscopy. Their conformational behaviour was studied using a computer‐assisted LIS technique and, for c‐4, t‐7‐dimethyl‐2‐oxo‐1,3,2‐dioxathiepane, a 400 MHz spectral analysis. Single twist‐chair conformations or an equilibrium between them are the most stable in the dioxathiepane series while chair or twist‐boat forms, or both in equilibrium, are favoured in the dioxathiepin series. Conformations and equilibria are detailed, with and without LSR, taking into account 1H coupling constants and IR SO stretching frequencies as conformational probes.
The NMR spectra of the porphyrins: 24—The NMR spectra of some tetraarylchlorins
Authors: Abraham Raymond J. , Plant James E. , Bedford Geoffrey R.
Published: May 2005

The synthesis and complete assignment of the 1H NMR spectra of 5‐(o‐pivaloylaminophenyl)‐10,15,20‐triphenylporphyrin (PIVTPP) and its two chiral dihydro adducts 3,4‐dihydro‐(PIVPTPC‐I)‐ and 7,8‐dihydr‐ (PIVPTPC‐II)‐porphyrins are reported. The use of the zinc complexes of the chlorins as chiral shift reagents with optically active bases is discussed. Comparison of the observed shift differences between the chlorins and the parent porphyrin with those calculated by a ring current model shows that a decrease in the ring current occurs on chlorin formation, and also specific effects occur at the reduced pyrrole ring, presumably reflecting different steric constraints.
Mass spectrometry in structural and stereochemical problems. Part CLIII. Electron impact‐promoted fragmentation of n‐alkyl cyanides
Authors: Carpenter Wayne , Sheikh Younus M. , Duffield A. M. , Djerassi Carl
Published: May 2005

In spite of previous extensive studies on the mass spectrometry of alkyl cyanides, no good mechanistic insight has as yet been gained into the behavior of straight chain alky1 cyanides. For this reason the possible origins for the principal ions in the mass spectrum of a typical alkyl cyanide (n‐hexyl cyanide) have been determined using high resolution mass spectrometry anddeuterium labeling of every carbon atom. The results lead to the conclusion that most of the typical fragmentation processes of n‐alkyl cyanides proceed through cyclic intermediates.
Mass spectrometric studies of cycloalkane‐α‐glycols
Authors: Sasaki S. , Itagaki Y. , Abe H. , Nakanishi K. , Suga T. , Shishihori T. , Matsuura T.
Published: May 2005

The mass spectral fragmentations of stereoisomeric cyclohexane‐1,2‐diols, p‐menthane‐2,3‐diols, 1‐hydroxycarvomenthols and 4‐hydroxymenthols are discussed.
Skeletal rearrangements in mass spectra. Part I. Bis‐aryl compounds
Authors: Wszolek P. C. , McLafferty F. W. , Brewster J. H.
Published: May 2005

Examination of a large number of spectra indicates that bis‐unsaturated compounds commonly undergo a skeletal rearrangement in which part or all or the bridging moiety is eliminated, often with concomitant loss of hydrogen atoms. The spectra of labeled azobenzene, diphenyl sulfide, and their p,p′‐dimethyl derivatives show that scrambling of hydrogen atoms precedes or accompanies such rearrangements, in contrast to the loss of a p‐methyl group from the latter derivatives. These results are rationalized in terms of the radical site formed on one unsaturated functional group attacking the polarizable π‐electrons of the other unsaturated group.
‘Mass spectrometry of vitamin B6: Different forms of the vitamin, its metabolites, antimetabolites, and analogs’
Authors: Dejongh D. C. , Perricone S. C. , Gay M. L. , Korytnyk W.
Published: May 2005

The mass spectra of the different forms of vitamin B6, some metabolites and antimetabolites, and some analogs are reported. The free bases are suitable for study, but the 5‐phosphates are not sufficiently volatile. The hydrochloride salts dissociate thermally in the inlet system into the free base and HCl and give the spectrum of the free base with the spectrum of HCL superimposed on it. The compounds studied are: pyridoxol, pyridoxamine and pyridoxal, which are different forms of vitamin B6; 4‐pyridoxic acid and its lactone, 5‐pyridoxic acid lactone, isopyridoxal, 5‐formyl‐3‐hydroxy‐2‐methylpyridine‐4‐carboxylic acid, and 3‐hydroxy‐2‐methylpyridine‐4,5‐dicarboxylic acid, which are vitamin B6 metabolites; α4‐and α5‐deoxypyridoxol, 3‐deoxypyridoxol, and 4‐ and 5‐ norpyridoxol, which are antimetabolites and analogs of vitamin B6.
Amino‐acid sequence study in peptides by mass spectometry—III Investigation of ethyoxycarbonyl‐peptide methyl esters
Authors: Kamerling J. P. , Heerma W. , Vliegenthart J. F. G.
Published: May 2005

The utility of ethoxycarbonyl‐peptide methyl esters for mass spectrometric analysis is described. The ethoxycarbonyl group has important advantages over other protecting groups which are in use. The derivatives have high intensity; this greatly facilitates the interpretation of the fragmentation pattern. The spentra of the methyl esters of the ethoxycarbonyl derivatives of pro‐val, trp‐gly, gly‐ser, (cys)2, glutation (GSH), glu‐his‐phe, val‐tyr‐pro and val‐lys‐val‐tyr‐pro are given.
Effects related to Stevenson's rule in mass spectral intensity correlations
Authors: Bursey Maurice M. , Wolfe Edward S.
Published: May 2005

According to Stevenson's rule, there is a possibility that the chloromethyl and bromomethyl ions in the spectra of alkylhalides may not be formed from the molecular ion by processes described by electronic ground states alone. Since ion intensities at 75 eV are generally considered to be governed by appearance potentials, the operation of Stevenson's rule should influence correlations of intensity data according to the kinetic approach to mass spectra. Deviations from linearity were obtained in correlations of CH2Br+ intensities, but not in those of CH2CL+. Stevenson's rule is of help in explaining the deviations, but by its nature it is not absolute in predicting their occurrence with certainty. Consequently caution must be exercised in the interpretation of new data, particularly for aliphatic compounds.
The mass spectra of some C‐19 modified cholesteryl derivatives
Authors: Kirkien‐Konasiewicz Alijca M. , Moriarty Robert M. , Loudon Alexander G. , Cardnell Peter M.
Published: May 2005

The mass spectra of twenty one C‐19 modified cholesteryl derivatives have been determined and compared with results for related systems. In the case when the hydrogen(s) of the C‐19 group have been replaced by other groups the metastable evidence shows that in those molecules with a C‐3 hydroxyl group the loss of water followed by the loss of the C‐19 group gives rise to an intense ion at m/e 353, whereas the loss of the C‐19 group with hydrogen transfer to the ion, followed by the loss of water gives rise to the large ion at m/e 354. In contrast in the case of the C‐3 acetates the main fragmentation is the loss of acetic acid followed by the loss of the C‐19 group to give the ion at m/e 353. This is rationalised on the basis of results observed in other systems. In the case of the C‐3 tosylates evidence for pyrolysis before electron impact fragmentation is presented. The subsequent fragmentation of the large ions at m/e 354, 353 and other m/e values in the high mass region is shown to be in line with earlier work.
Computer‐aided interpretation of mass spectra
Authors: Venkataraghavan R. , McLafferty F. W. , van Lear G. E.
Published: May 2005

A system is described in which computer techniques are used to carry out major steps in the procedure for interpretation of high‐resolution mass spectral data. These steps include identification and evaluation of the molecular ion, neutral fragments lost from the molecular ion, and characteristic ion series, followed by elucidation of specific structural details using a sub‐routine for the particular compound class selected. The technique shows promise of not only increasing the interpreter's efficiency, but of providing more specific and detailed structural information from the spectral data.
Mass spectra of indazolones and pyrazolones—I: Indazolones
Authors: Desmarchelier J. M. , Johns R. B.
Published: May 2005

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.
The elimination of small neutral molecules and fragments in mass spectra—II: 2‐substituted 8‐hydroxyquinolines
Authors: Stevenson Robert L. , Wacks Morton E. , Scott Ward M.
Published: May 2005

The mass spectra of a series of 2‐substituted 8‐hydroxyquinolines and related compounds are reported. Fragmentation pathways based upon interpretation of spectra and metastable transitions for 8‐quinolinol; 2‐methyl‐8‐quinolinol; 4‐methyl‐8quinolinol; 2‐hydroxymethyl‐8‐quinolinol; 2‐aminomethyl‐8‐quinolinol; 8‐quinolinol‐2‐carboxaldehyde; 8‐quinolinol‐2‐carb‐oxaldehyde oxime; and 8‐quinolinol‐2‐carboxaldehyde tert‐butylimine are discussed, as are dissociations in the related compounds 2‐hydroxymethyl quinoline and quinoline‐2‐carboxaldehyde oxime. It is suggested that the molecular ions of 2‐substituted‐8‐quinolinols undergo rearrangement to a substituted azatropylium ion prior to dissociation. An ion of m/e 89 has been observed in these spectra and is considered to be characteristic of the quinoline nucleus bearing an X‐substituent in any position, where X  OR, SR, NH2 etc. (R  H, CH3, etc).
Mass spectra of isomeric monoalkylanisoles and monoalkylphenols with straight alkyl chains
Authors: Gorfinkel M. I. , Ivanovskaia L. Yu. , Koptyug V. A.
Published: May 2005

An analysis of the mass spectra of ortho, meta and para isomers of monoalkylanisoles and monoalkylphenols, the alkyls being n‐amyl, n‐octyl and n‐undecyl, has been performed. The regularities found allow determination of the structure of such compounds by inspection of the mass spectrum only. It was shown that Hammett's equation may be used for evaluating a ration of intensities of peaks originating formally from the simple β‐cleavage and that accompanied by hydrogen migration of the resulting fragment ions.
Electron‐impact induced fragmentation of 2‐substituted 2H‐cyclopenta[D]pyridazines
Authors: Forkey David M.
Published: May 2005

The mass spectra of the non‐benzenoid aromatic heterocycles 2H‐ and 2‐methyl‐2H‐cyclopenta[d]pyridazine and several deuterated analogs have been analyzed. The majority of the nitrogen lost from these heterocycles occurs as HCN OR H2CN. The deuterium labeling suggests a rearrangement of the molecular ion prior to fragmentation.
The loss of water from molecular ions of aliphatic ketones in electron‐impact mass spectra
Authors: Yeo Adrian N. H. , Williams Dudley H.
Published: May 2005

In a series of straight chain aliphatic ketones which has been studied, it has been shown that the structural requirement for loss of water from the molecular ions produced by electron‐impact is an alkyl group of seven or more carbon atoms attached to the carbonyl function.
Some aspects of the high resolution mass spectra of toluene‐p‐sulphonamides
Authors: Aftalion S. , Proctor G. R.
Published: May 2005

The cracking patterns of twenty five toluene‐p‐sulphonamides have been studied. In certain cases an abundant [M  SO2] ion is detected: the structural features associated with this phenomenon are discussed.
Mass spectra of organometallic compounds—VII; Organonitrogen derivatives of metal carbonyls
Authors: King R. B.
Published: May 2005

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.
Massenspektrometrie herausgegeben von Hermann Kienitz, verfaßt von Fritz Aulinger, Gerhard Franke, Karleugen Habfast, Hermann Kienitz und Gerhard Spiteller. Verlag Chemie, Weinheim/Bergstraße, 1968. 883 Seiten mit 342 Abbildungen und 52 Tabellen im Text und einem Tabellenteil. Ganzleinen DM 195
Authors: Grützmacher H.‐Fr.
Published: May 2005

Structure elucidation of organic compounds is only one of the applications of mass spectrometry to chemistry. Important subjects are also mass spectrometric quantitative analysis of mixtures of inorganic and of organic compounds, determination of isotopes and related problems. In ‘Massenspektrometrie’, edited by H. Kienitz, all these applications are discussed together with an excellent introduction to the function of mass spectrometers and the techniques of measurement. This book contains a lot of information and stimulation for mass spectroscopists and chemists, and is especially recomended for use in analytical laboratories.
Fragmentation of organic compounds on electron‐impact—V: 1,1‐Dichlorocyclopropanes
Authors: Weinberg D. S. , Stafford C. , Scoggins M. W.
Published: May 2005

The mass spectral fragmentation reactions of twenty‐one 1,1‐dichlorocyclopropanes prepared from various isomeric octenes are discussed. The most characteristic reaction may be represented as follows:
magnified image

The importance of this fragmentation and the distribution of the positive charge between the species produced is a function of the degree of branching in the molecule. The more highly branched isomers produce less characteristic fragmentation patterns.

The identification of isomeric octenes from the fragmentation patterns of the corresponding 1,1‐dichlorocyclopropanes is discussed.
Substituent effects in the fragmentation reactions of acetanilides and phenyl acetates
Authors: Shapiro Robert H. , Tomer Kenneth B.
Published: May 2005

The mass spectra of a group of m‐ and p‐substituted acetanilides were measured to determine the effect of the substituents, if any, on the rate of C2H2O expulsion (rearrangement) vs. the rate of [CH3CO]+ formation (simple cleavage). Our results agree with observations of others in that substituents which raise the ionization potential of the aromatic ring appear to localize, on the average, less charge density on this locus, and conversely. The atomic composition of the substituent, however, irrespective of its position, seems to determine the relative rates of the competing reaction. Although in several cases Zm/Zp values were close to unity, rearrangement of isomeric molecular ions to a common species is shown not to occur.
Electron‐impact studies—XLVII: The mass spectra of 2‐aryl‐1,3‐dithianes and ‐1,3‐dithiolanes
Authors: Bowie J. H. , White P. Y.
Published: May 2005

The fragmentation patterns in the spectra of 2‐aryl‐1,3‐dithianes and ‐1,3‐dithiolanes have been elucidated by deuterium labelling studies. Ortho effects are observed in the spectra of 2(o‐alkoxyphenyl)‐1,3‐dithianes. The molecular ions of the 1,3‐dithianes eliminate S2H· and metastable kpeaks substantiate these eliminations. The hydrogen involved in this elimination randomises (C‐4, 5 and 6) Prior to elimination in the spectrum of 2‐phenyl‐1,3‐dithiane, but originates mainly from C‐5 in that of the bis propane‐1,3‐dithioacetal of terephthaldehyde.
Mass spectra of organometallic compounds—IX: Compounds with metal‐metal bonds
Authors: King R. B.
Published: May 2005

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 [Con]+ (n = 3 and 2). Many examples of the elimination of neutral CO, C2H2 and H2 fragments were noted in this work.
Electron‐impact studies—L: Skeletal‐rearrangement fragments in the mass spectra of diphenylpyrazoles and ‐isoxazoles
Authors: Simons B. K. , Kallury R. K. M. R. , Bowie J. H.
Published: May 2005

The mass spectra of all diphenylpyrazoles and ‐isoxazoles contain rearrangement peaks at m/e 165 [C13H9]+. In addition, the spectra of 3,5‐diphenylisoxazoles contain peaks at m/e 180 [C13H10N]+, which are produced by specific phenyl migrations. The mechanisms of both rearrangement processes have been studied by deuterium labelling.
Oxygen rearrangement processes in mass spectrometry
Authors: MacLeod J. K.
Published: May 2005

The recent publication1 concerning oxygen rearrngement process in the mass spectra of aromatic and unsturated esters parallels an investigation by the auther on similar compounds. Some further definitive aspects of this study are reported here.
The mass spectra of amino‐acid and peptide derivatives—III:. A comparison of the utility of various N‐protecting groups
Authors: Aplin R. T. , Eland I. , Jones J. H.
Published: May 2005

Comparison of the acetyl‐, trifluoroacetyl‐, benzyloxycarbonyl‐, methoxycarbonyl‐, ethoxycarbonyl, methylaminocarbonyl, phenylaminocarbonyl‐, phthanoyl‐, and stearoyl‐derivatives of glycylleucylphenylalanine methyl ester has shown that acetyl derivative is the most volatile. The relative abundances of the sequence ions in the mass spectra od these compounds have been determined and compared: the acetyl derivative provides the best combination of volatility and abundance of sequence ions. Evidence is presented to show that the use of acid‐catalysed esterification procedure for the chemical modification of peptides prior to mas spectrometric investigation can lead to degraded derivatives.
Massenspektrometrische Untersuchungen an Heterocyclen—IV: Zur Wasserstoffabspaltung aus Xanthen und Thioxanthen
Authors: Heiss J. , Zeller K.‐P.
Published: May 2005

Die struktur der [M — 1]‐Ionen von Thioxanthen (I) und Xanthen (II) wird mit Hilfe der 9,9‐Dideuteroderivate (Ia und IIa) untersucht. Das Auftreten eines [M — 1]‐Ions auch bei Ia und IIa zeigt, daß neben einer einfachen Abspaltungsreaktion eine Umlagerung zu einem Troppyliumkation beteilligt ist. Eine wietere derartige Umlagerungsreaktion tritt auch bei der Fragmentierung von Thioxanthen‐S,S‐dioxid (III) auf.
Electron‐impact induced rearrangement of N‐acetyl‐O‐aryl carbamates
Authors: Blessington B.
Published: May 2005

Electron‐impact induced rearrangements of a series of agriculturally important carbamates and N‐acyl carbamates are described. High resolution and metastable evidence supporting this is presented.
Electron‐impact studies of organometallic molecules—XI:. Some polyfluoroaromatic derivatives of ferrocene
Authors: Bruce M. I.
Published: May 2005

The mass spectra of eight ferrocene derivatives containing C6F5, C6F5CO, C6F5CH2 or p‐CH3OC6F4 groups attached to one or both cyclopentadienyl rings are described and discussed. In addition to features normally found in the mass spectra of ferrocene compounds, the migration of fluorine to the iron atom leads to the formation of ions such as [C5H4COFeF]+. The elimination of neutral FeF2 or C5H5FeF molecules is also found.
The mass spectra of aluminum isopropoxide
Authors: Daasch Lester W. , Fales H. M.
Published: May 2005

The mass spectra of aluminum isopropoxide show that polymers, [Al(OC3H7)3]x where x = 1 to 7, can be present in the vapor and are, therefore, probably present in the bulk sample. The polymeric composition of the vapor depends on the previous history of the sample. Exact mass measurements on many of the ions along with data on a number of metastable peaks support the proposed fragmentation mechanisms. Loss of 102 mass units between intense peaks in the mass range above 500 a.m.u. leads to the suggestion that the higher polymers may be used as high mass marking substances.
Mass spectrometry in structural and stereochemical problems—CLXXVIII: The electron‐impact promoted fragmentation of 1,2‐cyclohexene oxide
Authors: Strong M. Karen , Brown Peter , Djerassi Carl
Published: May 2005

The mass spectra of 1,2‐cyclohexene oxide and three deuterium labeled analogs are discussed and mechanistic rationalizations are given for the major fragmentation processes observed. Multiple mechanisms are required to explain the indicated peak shifts in the labeled analogs for many of these ions, thus demonstrating again the care that needs to be exercised in the interpretation of the mass spectra of relatively simple molecules.
The mass spectra of cinnolines and their N‐oxides
Authors: Palmer M. H. , Russell E. R. R. , Wolstenholme W. A.
Published: May 2005

The mass spectra of cinnoline and various alkyl derivatives, and their 1‐ and 2‐mono‐oxides and 1,2‐dioxides and a quaternary salt have been investigated. The spectra are interpreted in the light of experiments with deutero and 15N labelled derivatives whose syntheses are described. The major fragmentation path for cinnoline is loss of nitrogen molecule while that for its homologues is loss of nitrogen plus a hydrogen atom in some instances. Various initial fragmentations occur with the N‐oxides, and deoxygenation appears to be the dominant process; in both 4‐methylcinnoline 1‐oxide and 1,2‐dioxide an important path is formation of a 3‐methyl‐anthranil cation by loss of HCN and HCNO respectively.
Electron‐impact fragmentation of the bicyclo[4.1.0]heptane‐2‐one system: Correlations with photochemistry
Authors: Fenselau Catherine , Shaffer G. W. , Dauben W. G.
Published: May 2005

The low resolution and complete high resolution mass spectra of a series of methyl and deuterium substituted bicyclo[4.1.0]heptane‐2‐one derivatives have been measured. An attempt has been made to test the operation of a fragmentation process analogous to the known photochemical rearrangement, and to determine if the substitution effects critical to the photorearrangement also influence the electron‐impact process. The fragmentation pattern of these conjugated cyclopropyl ketones is detailed and the influence of the cyclopropyl ring is discussed. It is suggested that electron‐impact‐induced rearrangements which are analogous to photochemical transformations will be relatively low energy processes and will remain prominent at low ionizing voltages.
Electron‐impact fragmentation of some secondary aliphatic nitramines. Migration of the nitro group in heterocyclic nitramines
Authors: Bulusu Suryanarayana , Axenrod T. , Milne G. W. A.
Published: May 2005

The mass spectra of a series of nitramines, including the explosives RDX and HMX, are reported. The nature of the major fragment ions is established by labeling with 15N or13C and by high resolution mass spectrometry. Electron‐impact‐induced fragmentation pathways including the migration of the nitro group in the heterocyclic nitramines, RDX and HMX, are postulated.
Identification of the aromatic hydroxylamine group by mass spectrometry
Authors: Coutts R. T. , Mukherjee Gita
Published: May 2005

The mass spectra of aromatic hydroxylamines are diagnostic; [M], [M – 2], [M – 16] and, in most instances, [M – 17] ions are observed.
Zum Mechanismus Massenspektrometrischer Fragmentierungsreaktionen—IV: Zur Bildung von Phenonium‐Ionen bei der Elektronenstoß‐Fragmentierung von ß‐Phenyläthylbromiden
Authors: Grützmacher Hans‐Friedrich
Published: May 2005

Die von N. M. M. Nibbering et al.3 aufgrund von Deuteriummarkierungen nachgweisene scheinbar gleichartige Bindung aller 9 H‐Atome in [C8H9]+‐Ionen, die durch Br‐Abspaltung aus β‐Phenyläthylbromid im Massenspektrometer entstehen, konnte bestätigt werden. Dieser Befund ist durch eine cyclooctatrienyl‐Struktur (a) erklärt worden. Ein Vergleich der Bildungsenthalpien von [C8H9]+‐Ionen verschiedenen Ursprungs beweist jedoch, daß dies für die aus ß‐Phenyläthylbromid im Grundzustand entstehenden [C8H9]+‐Ionen nicht zutrifft. R. H. shapiro et al.4 leiten aus dem Einfulß von substituenten am Phenylkern ovn ß‐Phenyläthylbromid auf die Intensität von [M  Br]+‐Ionen eine Phenonium‐Struktur (c) für die [C8H9]+‐Ionen ab. Der substituenteneffekt auf die Intensitäten und AP der [M  CH2Br]+‐Ionen substituierter ß‐Phenyläthylbromide ist jedoch deutlich anderer Art und läßt sich viel besser mit einer ‘Klassischen’ Struktur der [C8H9]+‐Ionen vereinbaren. Für diese Struktur spricht auch ein Vergleich der IP und AP der [M  Br]+‐Ionen von Benzyl‐, ß‐Phenyläthyl‐ und γ‐Phenylpropylbromid.
Massenspektrometrische Untersuchungen an Heterocyclen—V Fragmentierungsverhalten Einiger Purine
Authors: Heiss Jürgen , Zeller Klaus‐Peter , Voelter Wolfgang
Published: May 2005

Die Massenspektren von 9 Purinen werden diskutiert. Purine vom Xanthintyp spalten HNCO und anschließend CO, während 3‐Methylhypoxanthin HCN und CO verliert. Im Fall des 3‐Methylxanthins entsteht os ein Ion, dessen Stabilisierung durch Umlagerung diskutiert. wird. Das Fragmentierungsverhalten von 3‐Methyl‐2‐thioxanthin und 3‐Methyl‐thiohypoxanthin weicht von dem der entsprechenden Sauerstoffanaloga ab. 6‐Methyl‐mercaptopurin und 6‐Methoxypurin eliminieren HCS· bzw. HCO·. Für diese Reaktion wird ein Mechanismus vorgeschlagen.
Massenspektren von Metallkomplexen des 2‐n‐Butyl‐8‐Hydroxychinolins
Authors: Budzikiewicz H. , Plöger E.
Published: May 2005

Das Fragmentierungsmuster der Metallkomplexe des 2‐Butyl‐8hydroxychinolins hängt im wesentlichen davon ab, ob das Metall‐Ion unter Aufnahme eines Elektrons in eine stabile einwertige Form übergehen kann oder nicht. Im ersten Fall entsteht das Hauptfragment durch Verlust eines Moleküls 2‐n‐Butyl‐8hydroxychinolin, im zweiten durch Abspaltung eines Äthyl radikals.
Mass spectrometry in structural and stereochemical problems—CLXXXVII A study of skeletal rearrangements in chromans by combined 13C and deuterium labeling
Authors: Trudell J. R. , Woodgate S. D. Sample , Djerassi Carl
Published: May 2005

Chroman (I), 2,2‐dimethylchroman (II), flavan (III) and 2,2‐diphenylchroman (IV) were labeled with 13C or deuterium at every position of importance. The mass spectra of these labeled compounds make possible a detailed interpretation of some very complex carbon skeleton rearrangements. The combination of deuterium and 13C‐labeling revealed that loss of CH3, C2H5 and C7H7 fragments from chroman (I), 2,2‐dimethylchroman (II) and 2,2‐diphenylchroman (IV) respectively, occurs by multiple pathways involving aryl or alkyl migrations with little hydrogen randomization prior to fragmentation. Although ejection of C7H7 from flavan (III) occurs to a small extent by a route similar to those mentioned above, its [M  C7H7] fragment can also be formed by a pathway involving no phenyl migration but extensive hydrogen scrambling. The validity of the schemes proposed on the basis of the 13C labeling data was checked by using them to predict the spectra of the deuterium labeled compounds.
Charge participation in the fragmentation of functionalized steroids
Authors: Vetter W. , Meister W. , Richter W. J.
Published: May 2005

A series of steroidal model compounds specifically designed to allow maximal as well as minimal charge localization at certain functional groups was subjected to mass spectrometric analysis. The results indicate that electron deficiency at the potentially reactive site is a prequisite for any fragmentation reaction to occur to an appreciable extent. The amount of charge density required at such a site seems to vary substantially for different types of fragmentation processes.
The mass spectra of acetylenic ketones and their secondary amine adducts
Authors: Aplin R. T. , Mestres R.
Published: May 2005

The mass spectra of a number of alkyl and aryl acetylenic ketones of the type RCO·CC·CC·R′ have been examined. All the spectra exhibit molecular ions together with the expected intense fragments arising from cleavage α‐to the carbonyl group. The most striking feature of the ketone spectra is the loss of CO from the molecular ion. This process dominates the spectra of the aryl ketones, the spectra below [M – 28]+˙. being virtually identical to those of the corresponding phenylacetylenes. The spectra of the piperidene and/or morpholine adducts of the alkyl ketones are very similar to those of the parent ketone whereas those of the aryl ketones are dominated by the loss HO˙ from the molecular ion. Deuterium labelling has established the site of the hydrogen involved as being the carbons α‐ to the nitrogen of the heterocyclic ring.
Aldehyde and ketone spectra from bisulfite adducts
Authors: Fenselau Catherine , Young John L. , Landis William R.
Published: May 2005

The use of bisulfite derivatives of liquid aldehydes and cyclic ketones is reported to facilitate sample handling in mass spectral analysis of these compounds. The carbonyl compounds can be regenerated from their sulfinate derivatives in the direct probe. Precautions must be taken to avoid back exchange of enolizable deuterium atoms in labeled carbonyl compounds.
Mass spectrometry of the 11H‐dibenzo[c,f][1,2]‐diazepine system
Authors: Popp F. D. , Dubois R. J. , Potts K. T. , Brugel E.
Published: May 2005

The mass spectra of 3,8‐dichloro‐11H‐dibenzo[c,f] [1,2]diazepine, the corresponding diazepin‐11‐01 and diazepin‐11‐one and their dihydro and N‐oxide derivatives have been recorded. The most important fragmentation of the molecular ions of all diazepines studied was an initial loss of m/e 28, with further fragmentation depending on the 11‐substituent. No general pathway was observed for the corresponding N‐oxides and dihydro compounds.
Mass spectra of organometallic compounds–XI: Pyrrolyl, indenyl and fluorenyl derivatives of manganese carbonyl
Authors: King R. B. , Efraty A.
Published: May 2005

The positive ion mass spectra of the π‐pyrrolyl derivatives C4H4NMn(CO)2L (L = (C6H5)3E or CO; E = P, As, or Sb), the π‐indenyl derivatives C9H7Mn(CO)2L (L = (C6H5)3E or CO; E = P, As, or Sb) and the π‐fluorenyl derivatives C13H9Mn(CO)2L (L = (C6H5)3P or CO) have been investigated. The relative tendencies of ions of the type [QMnE(C6H5)3]+ (Q = π‐pyrrolyl, π‐indenyl, or π‐fluorenyl; E = P, As, or Sb) to fragment by losses of the Q ring system and the (C6H5)3E ligand are compared. Phenyl transfers from phosphorus, arsenic, or antimony to manganese to form relatively high abundances of [C6H5Mn]+ are also observed. Other processes typical of metal carbonyl derivatives (CO losses), aromatic derivatives (C2H2 eliminations) and (C6H5)3E derivatives (phenyl losses, conversion of [(C6H5)3E]+ directly to [C6H5E]+, and formation of [C12H8E]+ 9‐heterofluorenyl ions) are observed in these mass spectra and are supported in many cases by the presence of appropriate metastable ions.
Mass spectral studies of some β‐diketones and their beryllium complexes
Authors: Patel Kantilal S. , Rinehart Kenneth L. , Bailar John C.
Published: May 2005

Detailed comparison of the fragmentation behavior of a series of beryllium β‐diketonates with that of the corresponding series of β‐diketones reveals a number of striking differences. A‐typical fragmentations are observed for diketones and diketonates with trifluoromethyl and α‐phenyl substituents.
The mass spectra of 2,4,7‐trihydroxypteridines and their trimethylsilyl derivatives
Authors: Haug Pat , Urushibara Toshiyuki
Published: May 2005

The mass spectra of a series of 2,4,7‐trihydroxypteridines and their trimethylsilyl derivatives have been determined. Fragmentation mechanisms are supported by high resolution, deuterium labeling and metastables.