bluuebunny/crossref_metadata_2025 huggingface dataset:
13C NMR spectra of 1,4,5,8‐tetraazaphenanthrene derivatives
Authors: Defay N. , Maetens D. , Nasielski‐Hinkens R.
Published: May 2005

The13C NMR spectra of 1,4,5,8‐tetraazaphenanthrene (pyrazino[2,3‐f] quinoxaline), eleven of its derivatives [2‐ and 3‐chloro, ‐methoxy and ‐(1′‐piperidino), 2,3‐dichloro, ‐dimethoxy, ‐dimethyl and ‐di(1′‐piperidino) and 9‐methoxy] and of 1,4,5,8,9,12‐hexaazatriphenylene (dipyrazino[2,3‐f: 2′,3′‐h]quinoxaline) have been assigned by {1H} selective decoupling experiments, correlations and additivities of substituent‐induced chemical shifts and proton–carbon coupling patterns. Assignments of proton spectra are extended.
Proton–proton and carbon–proton spin interactions in butatriene
Authors: Kunz R. W. , Bilinski V. , von Philipsborn W. , Dreiding A. S.
Published: May 2005

The proton–proton and proton–carbon coupling constants in butatriene, measured at −50°C, are reported. Signs and relative magnitudes are in agreement with the Fermi contact interaction derived from an Extended Hückel MO calculation.
1H NMR conformational analysis of disubstituted arene tricarbonyl chromium complexes
Authors: Brocard J. , Laconi A. , Couturier D.
Published: May 2005

The positions of conformational equilibrium in disubstituted arene chromium tricarbonyl complexes, i.e. alkylanisole chromium tricarbonyl complexes and alkylbenzoate chromium tricarbonyl complexes, have been determined by1H NMR spectroscopy. It has been found that the donor effect is the dominant factor in determining the preferred conformation.
Application of the attached proton test technique in 31P NMR spectroscopy
Authors: Jancke H. , Radeglia R. , Neels J. , Porzel A.
Published: May 2005

Intensity modulated 31P NMR spectra were obtained using the pulse sequence published by Patt and Shoolery. This attached proton test (APT) technique for signal assignment could be applied to systems with long‐range heteronuclear couplings in POCH fragments. In a model system derived from the alcoholysis of P4S10 the six reaction products were assigned to the six signals in the 31P NMR spectrum.
13C NMR spectra of tricyclo[4.2.1.02,5]nonanes and tetracyclo[5.4.1.02,6.08,11]dodecanes
Authors: Ishii Yasutaka , Noda Toshimitsu , Kawahara Masakazu , Ogawa Masaya
Published: May 2005

The 13C NMR spectra of tricyclo[4.2.1.02,5]nonanes and tetracyclo[5.4.1.02,6.08,11]dodecanes and their dimethyl derivatives were measured to demonstrate the four‐membered ring annelation effects on the bicyclo[2.2.1]heptane skeleton, and the steric δ‐syn effects of the methyl groups attached to the four‐membered ring on the bridge carbons in these systems.
13C NMR spectra of p‐ and m‐substituted phenyl N‐methyl‐ and phenyl N,N‐dimethyl‐carbamates
Authors: Yamagami Chisako , Takao Narao , Nishioka Takaaki , Fujita Toshio , Takeuchi Yoshito
Published: May 2005

13C NMR spectra of p‐ and m‐substituted phenyl N‐methylcarbamates, phenyl N,N‐dimethylcarbamates and p‐ and m‐substituted phenyl propionates were recorded, and their para 13C SCS (substituent chemical shifts) were analysed by DSP (dual substituent parameters) and DSP‐NLR (non‐linear resonance) equations. It was found that the fixed substituent Y, OCONHCH3, OCON(CH3)2 and OCOC2H5, were all mild in the sense that DSP analysis gave a good correlation, leaving little room for improvement by the DSP‐NLR treatment. Further, the three series of compounds gave similar ρI and ρR values (para derivatives, 3.2–3.3 and 17.7–18.0; meta derivatives, 5.1–5.2 and 21.8–22.0). Examination of the corresponding analyses of similar compounds indicated that the ρI and ρR values and, hence, their ratio ρR/ρR = λ, depended primarily on the nature of the atom through which the fixed substituent Y (e.g. α‐C, α‐N and α‐O) was bonded to the aromatic ring when the Y substituents are mild. The extent of this tendency for compounds with active fixed substituents is also discussed.
2H, 13C shift correlation as an analytical tool for the study of deuteriated carbon compounds
Authors: Wesener Joachim R. , Schmitt Peter , Günther Harald
Published: May 2005

A chemical shift correlation experiment for 2H, 13C spin systems is described. Applications to the analysis of deuteriated carbon compounds are discussed and advantages over existing methods are pointed out.
Conformational preferences of 2‐methoxypyridine from 1H and 13C NMR and from STO‐3G molecular orbital calculations
Authors: Blonski Wayne J. P. , Hruska Frank E. , Wildman Timothy A.
Published: May 2005

Observable coupling over five formal bonds between the methoxy group protons and the ortho ring proton in 2‐methoxypyridine, coupliugs between the methoxy group carbon and ring protons, and methoxy carbon spin‐lattice relaxation times are all consistent with a preference for the planar cis conformer, in which conjugation is favoured and repulsions between the methyl group and the ortho hydrogen are reduced. Small‐amplitude torsioas about the C‐2–O bond may carry the methoxy group away from this orientation, but more distant conformations can probably be excluded. Methyl group rotation is less hindered in the cis than in the trans conformer. Molecular orbital calculations at the STO‐3G level, with complete geometry optimization, support the conduskus drawn from experimental evidence.
Deuterium isotope effects on 13C and 15N nuclear shielding in o‐hydroxyazo dyes
Authors: Lyčka Antonín , Hansen Poul Erik
Published: May 2005

Deuterium isotope effects on the 13C and 15N nuclear shieldings of o‐hydroxyazo compounds are described. Both the direct and the equilibrium contributions were determined. Large direct deuterium isotope effects on 15N nuclear shieldings for 1Δ, 2Δ and 4Δ and negative Δ1J(15NH) [D] values were observed. Isotope effects on 15N nuclear shieldings, because of their magnitudes, are shown to be very useful in determining changes in the azo–hydrazone equilibrium. Isotope effects on 13C nuclear shieldings are smaller, but the effects observed at the carbon resonances of the N‐phenyl ring are likewise very useful in determining the shift in the equilibrium. Deuterium substitution leads in all cases to a shift in the equilibrium so that the content of the predominant form of the protio compound is increased.
13C NMR studies of 2,3‐dihydrofurans. Restricted rotation of bulky aryl rings in cis‐2‐aryl‐3‐methyl‐2,3‐dihydrofurans
Authors: Convert Odile , Touboul Estera , Dana Gilbert
Published: May 2005

13C NMR spectra of some 2,3‐dihydrofurans were measured. Restricted rotation of the bulky aromatic groups of cis‐2‐aryl‐3‐methyl‐2,3‐dihydrofurans is observed when these groups have substituents in both ortho positions. Barriers to rotation were deduced from the variations in line widths of the 13C NMR signals. Exchange rates are highly affected by the buttressing effect of meta‐methyl groups.
Effects of substitution on nitrogen on barriers to rotation of amides. 2—Evaluation of the importance of resonance effects
Authors: Pinto B. Mario , Szarek Walter A. , Grindley T. Bruce
Published: May 2005

Analogs of N‐acetyl‐ and N‐benzoyl‐azacyclohex‐2‐enes having an oxygen atom, a methylene‐d2 group or a carbonyl group in place of the C‐4 methylene group have been synthesized. The amide rotational barriers in these compounds have been measured by the total line‐shape analysis of variable‐temperature 1H NMR spectra. The free energies of activation for both the N‐acetyl and N‐benzoyl series decrease in the sequence O≃CD2 > CO. The barriers for the first two compounds in each series are similar to those of the corresponding saturated analogs, a result which confirms recent reports that the long accepted barrier‐decreasing effect of an α‐olefinic substituent on nitrogen is counteracted. Evidence is presented that resonance stabilization of the rotational transition state in the unsaturated compounds still obtains. It is suggested that the introduction of an α‐olefinic substituent on nitrogen has a negligible effect on the amide rotational barriers in the cases of the oxygen and methylene‐d2 analogs, since any increase in the stabilization of the transition state by resonance is offset by the accompanying decrease in the sp3 character of the nitrogen atom. In cases in which a substituent on the olefinic group can interact directly with the lone pair on nitrogen, for example in the carbonyl analogs, then the resonance stabilization of the transition state is dominant.
A 17O NMR study of the protonation of urea
Authors: Valentine B. , Amour T. E. St. , Fiat D.
Published: May 2005

17O NMR has been applied to the study of urea over a wide pH range, in fluorosulfonic acid and in magic acid (HFSO3SbF5). A 96 ppm diamagnetic chemical shift was observed on modifying the medium from an aqueous solution at pH 3 to a fluorosulfonic acid solvent. We attributed this shift to a protonation reaction at the urea oxygen having a pKa of 0.1. A 36 ppm paramagnetic shift was observed in magic acid relative to the resonance position in fluorosulfonic acid, which is consistent with the formation of a diprotonated form of urea. Values of transverse and longitudinal relaxation rates were found to be equal as a function of pH and to double on lowering the pH from 2 to −1.
Hydrogen and carbon NMR data for aminoquinolines and aminoisoquinolines
Authors: Kook Alan M. , Smith Stanford L. , Brown Ellis V.
Published: May 2005

Hydrogen and carbon chemical shifts and HH and CH couplings are reported for six aminoquinolines and six aminoisoquinolines in DMSO‐d6.
Differential effects of nerve, muscle, and fat tissue on regenerating nerve fibers in vivo
Authors: Weis Joachim , Schröder J. Michael
Published: May 2005

Axonal regeneration through silicone tubes was studied using distal nerve stumps, denervated, preatrophied muscle tissue, as well as fat tissue as a target. During the first stage of regeneration, i.e., within 2–3 weeks after surgery, a thin, filamentous structure consisting of fibrin and connective tissue‐was seen bridging the gap in all systems. Thereafter, this cord obviously served as a guideline for the outgrowth of increasing numbers of axons into distal nerve stumps as well as into muscle tissue, but not into fat tissue. These findings confirm that preatrophied muscle tissue has a similar “neurotrophic” effect on regenerating nerve fibers as distal nerve stumps. The ineffectivity of fat tissue in promoting nerve fiber regeneration could be attributed either to the absence of “neurotrophic factors” or even to an inhibitory effect.
Carbon‐13 nuclear magnetic resonance study of a new ring‐chain tautomerism of some pyridazine derivatives
Authors: Nesi Rodolfo , Chimichi Stefano , De Sio Francesco , Scotton Mirella
Published: May 2005

The 13C NMR spectra of a number of pyridazine derivatives have been recorded in DMSO‐d6 solution and analysed. Examination of the most diagnostic resonances, with particular emphasis on those arising from the pyridazine ring system, enabled the ready establishment of the presence of a ring‐chain tautomerism in 5‐(o‐aminophenylcarbamoyl)pyridazine‐4‐carboxylic acid, methyl 5‐(o‐aminophenylcarbamoyl)pyridazine‐4‐carboxylate, 5‐(o‐aminophenylcarbamoyl)‐3,6,‐dimethylpyridazine‐4‐carboxylic acid and 5‐(2‐amino‐1,2‐dicyanovinylenecarbamoyl)pyridazine‐4‐carboxylic acid. This gave rise to 3′,4′‐dihydro‐3′‐oxospiro[pyridazine‐5(2H),2′(1H)‐quinoxaline]‐4‐carboxylic acid, methyl 3′,4′‐dihydro‐3′oxospiro[pyridazine‐5(2H),2′(1′H)‐quinoxaline]‐4‐carboxylate, 3′,4′‐dihydro‐3′‐oxo‐3,6‐dimethylspiro[pyridazine‐5(2H), 2′(1′H)‐quinoxaline]‐4‐carboxylic acid and 5‐oxo‐2,3‐dicyano‐1,4,8,9‐tetraazaspiro[5.5]undeca‐2,7,10‐triene‐11‐carboxylic acid, respectively.
Intramolecular interactions and spin–lattice relaxation times of methyl groups
Authors: Ng Soon
Published: May 2005

The carbon T1 values of the alkyl substituents of various compounds have been measured. The salient observation is that the terminal methyl carbon of the n‐propyl or a three‐carbon chain bonded to an electronegative atom X(or an electron‐donating group) has a reduced T1 value. A net attractive interaction between the methyl hydrogen atoms and X in the gauche conformation is invoked to account for the observed result. In chains longer than three carbons that are not firmly anchored at one end, the γ steric interaction is suggested to be the main steric interaction that causes the reduced T1 value observed for the terminal methyl carbon.
Hindered rotation in five‐membered cyclic nitrosamines: A 13C NMR study
Authors: Haky Jerome E. , Saavedra Joseph E. , Hilton Bruce D.
Published: May 2005

The equilibrium rotamer populations and NN rotational barriers of N‐nitrosopyrrolidine (1), N‐nitrosothiazolidine (2), N‐nitrosooxazolidine (3) and their 2‐methyl derivatives, 4, 5 and 6, were determined by 13C NMR spectroscopy. While equal rotamer populations occur in 1 and 2, the E rotamers predominate in the other four compounds, with the highest percentage (92%) of E rotamer occurring in N‐nitroso‐2‐methyloxazolidine (6). The average barrier to NN bond rotation varies over a range of 4.1 kcal mol−1in these compounds, decreasing in the order N‐nitrosopyrrolidine > N‐nitrosothiazolidine > N‐nitrosooxazolidine. The compounds which contain an exocyclic 2‐methyl group have average rotational barriers which are 0.1–0.9 kcal mol−1 higher than those of the corresponding unmethylated derivatives. The results are interpreted in terms of the relative effects of steric hindrance by the 2‐methyl substituents and electron induction by the heterocyclic sulfur and oxygen atoms on both the rotamer populations and the NN rotational barriers.
Carbon‐13 NMR spectra of saturated heterocycles: XI—Tetrahydropyrans (oxanes)
Authors: Eliel Ernest L. , Manoharan Muthiah , Pietrusiewicz K. Michal , Hargrave Karl D.
Published: May 2005

The 13C NMR spectra of 62 oxanes (tetrahydropyrans) with and without methyl substituents at various ring positions, some of them bearing in addition (or instead) ethyl, vinyl, ethynyl, carbomethoxy and methylol substituents at C‐2, have been recorded, and the 294 resulting chemical shifts have been correlated by multiple linear regression analysis. Axial and equatorial α‐, β‐, γ‐, δ‐, gem‐ and vic‐parameters for shifts caused by methyl groups at all ring positions, and similar parameters for Et,—CHCH2,—CCH, CO2Me and CH2OH groups at C‐2, are reported. Standard deviations of the parameters are, in most cases, within 0.3 ppm and the agreement of calculated and experimental shifts is excellent. This is probably the largest parameter set of this type extant. 13C NMR spectra of a number of additional substituted tetrahydropyrans, and of 3,6‐dihydro‐2H‐pyrans and 3,4‐dihydro‐2H‐pyrans, are tabulated and discussed.
A revised assignment of the 13C NMR spectra of α‐ and β‐pinenes
Authors: Hall M. C. , Kinns M. , Wells E. J.
Published: May 2005

α‐Pinene and β‐pinene 13C enriched at the C‐10 position were prepared by an unambiguous synthesis. 13C NMR spectral analysis provided evidence for a revised assignment for α‐pinene at the C‐9 and C‐10 carbon atoms.
Multinuclear two‐dimensional NMR: Assignments of natural abundance polypeptide 13C, 1H and 15N chemical shifts and demonstration of isomer interconversion
Authors: Gray George A.
Published: May 2005

The polypeptide carbobenzoxy‐glycyl‐L‐prolyl‐L‐leucyl‐L‐alanyl‐L‐proline (0.2 M in DMSO‐d6) was investigated using 13C, 1H and 15N NMR in natural abundance at 4.7 tesla. The existence of cis–trans‐Gly‐Pro and ‐Ala‐Pro bonds permits up to four isomers, and all four were observed (in a 60:30:7:3 ratio). 13C shifts of the proline β‐CH2 resonances are consistent only with the 60% form being trans–trans. The 30% form is either trans–cis or cis–trans (order as above) and was tentatively assigned as cis‐trans on the basis of relaxation behavior. Refocused INEPT studies aided the 13C assignments. The 15N data were obtained using both NOE and INEPT excitation, with signals evident for the three major isomers. The spectra were analysed by starting from the 13C data, which were assigned based on known regularities in peptide spectra. A 13C1H heteronuclear two‐dimensional chemical shift correlation experiment allowed direct assignment of proton shifts for major and minor isomers. The NH proton shifts were assigned by running a homonuclear two‐dimensional chemical shift correlation experiment and noting the correlation with the previously assigned α‐CH protons. The 15N resonances were then assigned from a 15N1H heteronuclear two‐dimensional chemical shift correlation experiment, relating the 15N signals directly to the NH proton resonances. Isomer interconversion between the two major isomers was demonstrated by performing a magnetization transfer homonuclear 2D experiment. Off‐diagonal intensity was noted relating the major and minor isomer alanine NH proton, as well as for the major and minor isomer leucine NH protons.
Some INDO calculations of 1J(PC) and 1J(PF) values
Authors: Duangthai S. , Webb G. A.
Published: May 2005

INDO parameterized calculations, employing phosphorus s, p and d valence orbitals, are reported for values of 1J(PC) and 1J(PF) relating to phosphorus in formal tri‐ and pentavalent states. The 1J(PC), interactions are mainly controlled by the contact term. Thus, trivalent phosphorus compounds have negative values for 1J(PC), whereas those for pentavalent phosphorus are positive due to the s lone‐pair effect. The inclusion of phosphorus 3d orbitals is shown to be important for an understanding of the processes contributing to 1J(PF) interactions. 1J(PF) values are shown to be negative for both tri‐ and pentavalent phosphorus compounds. The contact and orbital interactions are significant for the trivalent phosphorus molecules, whereas in the pentavalent phosphorus case 1J(PF) is dominated by the orbital term.
2H and 13C NMR spectra of deuterated adamantan‐2‐ols
Authors: Duddeck Helmut , Islam Md. Rabiul
Published: May 2005

The composition of a mixture of adamantan‐2‐ol and its two epimeric 4‐deuterio derivatives was determined by 2H NMR spectroscopy with the aid of Eu(fod)3. In addition, unambiguous assignments of the two H‐4 signals and the two δ carbon signals were possible; these assignments had previously been speculative.
13C NMR shifts and conformations of substituted indans
Authors: Agrawal Pawan Kumar , Schneider Hans‐Jörg , Malik Mangel S. , Rastogi Shri Nivas
Published: May 2005

13C NMR spectra of indan derivatives bearing substituents in the 1, 2, 5 and 6 positions are reported and assigned by LIS measurements and other techniques. Epimeric indanes bearing vicinal oxygen and phenyl or benzyl substituents show ring carbon shielding in the cis relative to the trans isomers, which is compared with corresponding cyclopentane shifts, and indicates the predominance of envelope conformations with pseudoaxial oxygen substituents for the cis isomers. Acetylation shifts show consistently larger shielding at C‐β for the trans compounds. Introduction of oxygen at C‐5 leads to asymmetric shielding effects at the ortho carbon atoms as soon as there is a substituent in the para position which can participate in mesomeric forms.
Rotational isomerism about the C‐αC‐β bonds in sulphur‐containing amino acids and their non‐sulphur‐containing isoesters
Authors: Picur B. , Siemion I. Z.
Published: May 2005

The conformation of the methionine side‐chain in methanolic solution does not differ from that of norleucine; some differences, however, were observed for S‐methylcysteine and norvaline derivatives. It was also shown that the temperature coefficients of the CH2 group resonances could be used for the assignment of the HR‐β and HS‐β signals.
Dynamic stereochemistry of imines and derivatives: 15—Carbon‐13 NMR studies of aryl‐substituted imines and oxaziridines
Authors: Jennings W. Brian , Wilson Valerie E. , Boyd Derek R. , Coulter Peter B.
Published: May 2005

13C chemical shifts for several series of cis‐ and trans‐N‐alkylimines and oxaziridines bearing para‐substituted C‐phenyl rings are reported and correlated with dual substituent parameters. The 13CN and oxaziridine ring carbon shifts correlate primarily with the inductive/field parameters, σ1, whereas both resonance and inductive terms generally contribute about equally to the long‐range substituent effects on alkyl side‐chain chemical shifts. Correlations on diastereoisomeric imines show that the transmission of substituent effects can be significantly affected by the E–Z configuration. Aromatic carbon chemical shifts in imines are discussed in relation to the E–Z configuration and the conformation around the aryl—imino bond.
13C1H coupling constants in 9, 10‐dihydroanthracene
Authors: Holak T. A. , Aksnes D. W. , Syguła A.
Published: May 2005

The 1H and 13C NMR spectra of 9,10‐dihydroanthracene have been obtained at 2.1 and 9.4 T using selective decoupling of the methylene protons. Complete spectral analyses of the experimental spectra have provided the chemical shifts and coupling constants. The 13C1H coupling constants in 9, 10‐dihydroanthracene and biphenylene have been well accounted for by MNDO theoretical calculations of the molecular geometries and bond orders in these compounds.
Some calculations of the solvent dependences of phosphorus nuclear shielding
Authors: Nalamphun B. , Webb G. A.
Published: May 2005

Some CNDO/S parameterized calculations of phosphorus shielding, as a function of the dielectric constant of the medium, are presented. Pople's SOS perturbation approach together with the solvaton model are employed. For trivalent phosphorus compounds a shielding decrease by up to 15 ppm is predicted as ε increases from 1 to 80. For pentavalent phosphorus a much smaller shielding variation, in the opposite direction, is predicted. In general, a consideration of changes in phosphorus charge density is insufficient to account for the variation in nuclear shielding.
Oxygen‐17 nuclear magnetic resonance study of some oxirane derivatives
Authors: Sauleau A. , Sauleau J. , Monti J. P. , Faure R.
Published: May 2005

The 17O chemical shifts of seventeen variously substituted oxiranes have been measured in CDCI3 solution. Deviations of δo from additivity have been interpreted in terms of steric effects and loss of conjugation. Moreover, in the case of certain cis‐ and trans‐dimethyl‐substituted compounds, 17O NMR allows a differentiation between the different molecular configurations.
1H and 13CNMR data of C‐6 epimeric iridoids
Authors: Bianco Armandodoriano , Passacantilli Pietro , Polidori Giovanna , Nicoletti Marcello
Published: May 2005

The NMR data of epimeric pairs of iridoids are reported.
Some INDO/SSOS calculations of the effects of hydrogen bonding on the nitrogen shielding of some heterocycles
Authors: Lamphun B. Na , Webb G. A. , Witanowski M.
Published: May 2005

Some INDO/S parameterized SOS shielding calculations are reported for the nitrogen nuclei of some N‐heterocycles. Hydrogen bonding with H2O and CF3CH2OH is incorporated in a supermolecule approach. The calculated effects of hydrogen bonding are found to be in satisfactory agreement with observed nitrogen shielding variations upon a change of solvent.
Carbon‐13 NMR spectra of Δ4(20).11‐ taxadiene derivatives
Authors: De Marcano Deanna , Méndez Bernardo , De Méndez Jeannette , Monasterios José , Rojas Aníbal C. , Halsall Thomas G.
Published: May 2005

The 13C NMR spectra of a series of some Δ4(20),11‐taxadiene derivatives are reported. A detailed analysis of their assignments is presented.
29Si chemical shifts and additivity in pertrimethylsilylated O‐methyl, O‐benzyl, O‐benzoyl and O‐acetyl methyl β‐D‐xylopyranosides
Authors: Schraml J. , Petráková E. , Pihar O. , Hirsch J. , Chvalovský V.
Published: May 2005

29Si chemical shifts in pertrimethylsilylated O‐methyl, O‐benzoyl, O‐benzoyl and O‐acetyl methyl β‐D‐xylopyranoside derivatives are reported. The chemical shifts in monotrimethylsilyl derivatives with the same O‐substituents are in the order: δ(Si‐2) > δ(Si‐4) > δ(Si‐3). When the chemical shifts in bis (trimethylsilyl) and tris(trimethylsilyl) derivatives are assigned according to this rule, all the chemical shifts agree well with a direct additivity rule. The only significant deviation from additivity occurs for methyl 2,4‐di‐O‐benzoyl‐3‐O‐trimethylsilyl‐β‐D‐xylopyranoside, which has a different average conformation from the other compounds studied.
Dynamic1H NMR spectroscopy of η2‐ethylene transition metal complexes
Authors: Benn Reinhard
Published: May 2005

The low‐temperature1H NMR spectra of bis(ethylene)trimethylphosphinenickel (1), η5‐cyclopentadienyl(ethylene)methylnickel (2a), bis(ethylene)‐η5‐cyclopentadienylcobalt (2b), [bis(1‐ethyl‐2,4,6‐triphenylphosphorinyl)nickel]P,P′‐nickel(ethylene) (3) and η5‐cyclopentadienyl(ethylene)hydrido(triphenylphosphine)ruthenium (4) exhibit {AA′B′B} (1) {ABB′A} (2a and 2b), {ABA′B′} (3) or {ABCD} (4) spin patterns, respectively, for the complexed ethylene. A full line shape analysis including all the proton couplings was performed for the ethylene rotation in 1, 2a and 2b. In addition to olefin rotation, a reversible intramolecular β‐H‐elimination was confirmed for 4 by magnetization transfer experiments.
Mass spectral correlations for some fluorinated alkanes
Authors: McCarthy E. R.
Published: May 2005

The cracking patterns of thirty‐three fluorinated methanes, ethanes and propanes have been tabulated. For many of the compounds molecular ions were not observed. A comparison has been made of some of the halomethyl ion abundances with stabilization energies that have recently been derived from appearance potential measurements. Rearranged halomethyl ions occur frequently in the fluoroethane spectra. Their intensities often exceed those resulting from simple carbon bond rupture.
The mass spectra of metal complexes of dibenzoylmethane
Authors: Lacey M. J. , Macdonald C. G. , Shannon J. S.
Published: May 2005

The mass spectra of a series of metal complexes of dibenzoylmethane have been rationalized. The paths of novel rearrangement reactions involving both hydrogen and oxygen migration may differ according to the type of metal atom in the complex. Further examples are proposed of the effect of metal valency changes in ion reactions.
The mass spectrum of 1‐(2‐thienyl) hexane‐1‐13C
Authors: Foster Norman G. , Higgins Robert W.
Published: May 2005

The mass spectrum of 1‐(2‐thienyl) hexane‐1‐13C is reported. The principal fragmentation routes ofthe parent ion are delineated. Beta cleavage of the alkyl chain predominates, and the label retention indicates that the alpha carbon atom remains with the charged ring moiety. A substantial part of the m/e 97 ion undergoes a ring expansion to a six membered ring. A small amount of alpha cleavage of the alkyl chain occurs with the expected loss of the label. Further fragmentation of the ions from initial alpha or beta cleavage produces similar fragment ions. It is noted that many of the neutral particles lost in the formation of the fragment ions are typical of those encountered in the alkylbenzenes or other aromatic ion systems.
Organic ions in the gas phase. Part XX. Mass spectra of phenylthiophenes
Authors: Meyerson Seymour , Fields E. K.
Published: May 2005

The mass spectra of 2‐ and 3‐phenylthiophenes and their phenyl‐d5 counterparts reveal that the thienyl ring is markedly more reactive than the phenyl ring under electron impact. In one process, that leading to loss of C2H2S, the atoms lost are apparently derived solely from the thienyl ring, quite probably from the original molecular configuration.
High resolution mass spectrometry—I. Some substituted δ‐lactones
Authors: Millard B. J.
Published: May 2005

The mass spectra of some δ‐lactones substituted in various positions by methyl groups have been studied both by accurate mass measurements at high resulution and by deuterium labelling. The loss of carbon dioxide has been shown to be important only for a mono‐substituted lactone. A fragmentation mode common to all the lactones studied is the elimination of the ring oxygen atom, plus the adjacent carbon atom with its substituents, as a neutral carbonyl molecule such as formaldehyde, acetaldehyde or acetone. Deuterium labelling has uncovered the existence of a rearrangement involving hydrogen transfer in an even‐electron ion, and a mechanism involving a six‐membered transition state is proposed for this. The bond fissions, common to all the lactones, by which the principal ions in the mass spectra arise, are summarised.
High resolution mass spectrometry.—II Some substituted benzothiazoles
Authors: Millard B. J. , Temple A. F.
Published: May 2005

The mass spectra of nineteen substituted benzothiazoles have been recorded and the identity of the various ions in the mass spectra has been established by high resulution (accurate) mass measurement. Deuterium labelling has been used to elucidate the fragmentation processes of these compounds. The parent compound of the series, benzothiazole, exhibits the loss of hydrogen cyanide and carbon monosulphide from the parent ion as the most important decomposition pathways. The hydrogen atom concerned in the loss of hydrogen cyanide is shown to originate from the 2‐position of benzothiazole, while in 2‐substituted benzothiazoles, different mechanisms are apparent for the loss of hydrogen cyanide, and these are clarified by deuterium labelling. Some substituted benzothiazoles can lose sulphur from their molecular ions, a process which does not occur in benzothiazole itself. The substituted benzothiazoles undergo many other types of fragmentations, in some cases retaining the substituent, and in other cases losing it prior to collapse of the thiazole ring.
The mass spectra of some chlorinated pesticidal compounds
Authors: Damico J. N. , Barron R. P. , Ruth J. M.
Published: May 2005

The mass spectra of nine bridged polycyclic chlorinated pesticidal compounds have been investigated, and fragmentation modes to account for the more abundant ions are postulated. The principal features of the spectra are ions corresponding to a set of retro‐Diels‐Alder decompositions, ions resulting from successive losses of Cl, HCl, or both, ions produced by combinations of a retro‐Diels‐Alder process with a preliminary or subsequent loss of Cl or HCl, and ions whose processes of formation more specifically involve the epoxide group.
Mass spectometry of aralkyl compounds with a functional group—VI1: Mass spectra of 1‐phenylethyanol‐1, 2‐phenylethanol‐1 and 1‐phenylpropanol‐2
Authors: Nibbering N. M. M. , De Boer Th. J.
Published: May 2005

Mass spectra of 1‐phenylethanol‐1 and its analogues, specifically deuterated in the aliphatic chain, suggest that the [MCH3]+ ion is represented partly by an α‐hydroxybenzyl fragment. Moreover, the molecular ion loses successively—after scrambling of all hydrogen atoms, except those of CH3a hydrogen atom and C6H6, generation the CH3CO+ ion.

Diffuse peaks, found in the spectra of of 2‐phenylethanol‐1 and its analogues, specifically deuterated in the aliphatic chain and in the phenyl ring, show that the molecular ion loses C2H4O, possibly via a four‐center mechanism, after an exchange of aromatic and hydroxylic hydrogens.

Mass spectra of 1‐phenylpropanol‐2 and its analogues, specifically, deuterated in the aliphatic chain, demonstrate that in the molecular ion exclusively the hydroxyl hydrogen atom is transferred to one of the ortho‐positions of the phenyl ring via a McLafferty rearrangement, generating the [M  C2H4O]+ ion. Furtherore, an eight‐membered ring structure is proposed for the [M  CH3]+ ion to explain the loss of H2O and C2H2O from this ion after an extensive scrambling of hydrogen atoms.
Pharmacologically interesting compounds—I: High resolution mass spectra of phenothiazines
Authors: Gilbert J. N. T. , Millard B. J.
Published: May 2005

The mass spectra of twenty‐six commercially available medicinal phenothiazines have been determined at high resolution. In each compound, the side chain attached to the 10‐position of the phenothiazine ring contains nitrogen and fission of the CC bond α to this nitrogen gives in most cases the base peak. Some of the compounds are also substituted at the 2‐position and this substituent generally remains intact, though some substituents such as acetyl, propionyl, methoxyl and methylthio can undergo fragmentation. Fragmentations fall into three groups; those which give ions representing a part of the side chain; those which give ions representing the intact phenothiazine ring with part of the side chain attached; those which give ions representing a partially fragmented ring system.
Electron‐impact fragmentation of aliphatic polynitro compounds
Authors: Larkins J. T. , Saalfeld F. E. , Kaplan Lloyd
Published: May 2005

The mass spectra of two series of aliphatic polynitro compounds are reported and discussed. The fragmentation patterns of aliphatic nitro and polynitro compounds are similar in that no appreciable molecular ion current is observed; however, there are several other features in the fragmentation of aliphatic polynitro compounds which differ from that of nitroalkane spectra. Both series of compounds studied‐C(NO2)x(CH3)4−x, where x = 4 to 0 and C2(NO2)x(CH3)6−x, where x = 6,4,2‐show a decrease in the number and intensity of alkylions with an increase in the NO+ and NO2+ ion current as x increases. The main ions resulting from the more nitrated compounds are [NO]+, [NO2]+, [CO2]+. and [CH3CO]+, whose noncharged counterparts are the principal species produced in the detonation of these compounds. This similarity of the products of the two processes suggests the use of mass spectroscopy for the investigation of the initial explosive processes. The principal fragmentation pathways of the polynitroalkanes have been elucidated by exact mass measurements and the observation of metastable ion transitions.
Mass spectrometry and organic analysis—XIII. The mass spectra of doubly unsaturated carbonyl compounds
Authors: Thomas A. F. , Willhalm B. , Müller Regula
Published: May 2005

In 2,6‐di‐unsaturated carbonyl compounds, two successive, site‐specific hydrogen transfers are necessary to account for the loss of carbon atoms 1, 2, 3 and 4, together with one hydrogen from C‐8. The deuterated methyl geranate required for this study was readily converted to pseudo‐ionone, in which a similar fission was shown to occur. Previous predictions about the β‐ionone mass spectrum2 have been shown to be substantially correct, and its similarity to the mass spectra of benzylidence acetones is pointed out.
Ionisation et fragmentation en spectrometrie de masse—I: Sur la répartition de la charge positive entre fragments provenant de mêmes ruptures
Authors: Audier H. E.
Published: May 2005

Lors d'une rupture en spectrométrie de masse, la charge positive demeure préférentiellement sur le fragment de potentiel d'ionisation le plus bas. Ce critère, qui fut mis en évidence sur les alcanes, a été généralisé à divers types de fragmentations.
The mass spectra of dunnione and hydrodunnione diacetate
Authors: Buckle D. R. , Waight E. S.
Published: May 2005

The synthesis of dunnione (II) from 2‐hydroxynaphtha‐1,4‐quinone has been improved and used to prepare three deuteriated analogues. The mass spectra of these compounds and of the products of their reductive acetylation and deuterioacetylation have been measured and used to interpret the mass spectrum of atrovenetin.
Die β,γ‐Spaltung von Carbonylver‐Bindungen und derivaten als Allgemeingültige Hauptabbau‐Reaktion IM Massenspektrometer
Authors: Kraft M. , Spiteller G.
Published: May 2005

Aliphaten mit polarisierten Doppelbindungen (I) zeigen bei Elektronenbeschuß im Massenspektrometer häufig eine vorzugsweise Spaltung einer zur funktionellen Gruppe β,γ‐ständigen CC Bindung. Das dadurch Entstehende heteroatomhalitige Fragment ist mit einer konjugierten Doppelbindung als (IV) zu formulieren. Es entsteht im Zuge einer doppelten Wasserstoffumlagerung (I)→(II)→(III)→(IV). Deuteriummarkierung, Hochauflösung und metastbile Ionen beweisen, daß dieses Ion (IV) durch McLafferty‐Umlagerung weiter abgebaut werden kann.
The mass spectra of 1,1,1,2‐Tetrafluoroethane and 1,1,2,2‐Tetrafluoroethane
Authors: MacKnight S. D. , Teng Lei , Jones W. E.
Published: May 2005

Mass spectra of the two compounds 1,1,1,2‐Tetrafluoroethane and 1,1,2,2‐Tetrafluoroethane are presented.
Formation of [M — C2H4]+· in O‐d1‐butyric acid
Authors: Fairweather R. B. , McLafferty F. W.
Published: May 2005

The mass spectrum of CH3CH2CH2COOD shows no observable loss of C2H3D. This indicates for this compound that either the McLafferty rearrangement is concerted, or that the second step (olefin loss) is very fast in comparison to the reverse transfer of hydrogen back to the methylene radical.
Evidence for aryl participation in mass spectrometric fragmentation processes
Authors: Richter W. J. , Vetter W.
Published: May 2005

While heterolysis of oxonium ions generated upon electron‐impact in the mass spectrometer is a well documented phenomenon in the fragmentation of aliphatic ethers, little analogy exists for structurally comparable immonium ions. Exceptions are ions of the latter class in which dissociation is facilitated by the presence of proper substituents in position allowing satabilization of daughter ions. Two main types of subtitution were explored providing(1) resonance stabilization of the product ions by aryl substituents in benzylic,heterolysis,and (2) aryl neighboring group participation in homobenzylic heterolysis, possibly yielding phenonium ions (or isometric ions via further rearrangement) as stable products in the gas phase. In the discussion emphasis will be placed on Case 2.
Massenspektrometrische Untersuchungen an Heterocyclen—III: Thioxanthen, Thioxanthon und Phenothiazin Sowie deren S‐oxide
Authors: Heiss J. , Zeller K.‐P.
Published: May 2005

Das massenspektrometrische Fragmentierungsverhalten schwefelhaltiger Dibenzoheterocyclen und deren S‐oxide wird mit Hilfe exakter Massenmessungen untersucht. Die Stabilität der Molekülionen und der Zerfall hängen stark von der Art der Zweiten Atomgruppe im zentralen Sechsring ab. Für die Ketenabspalutung aus den N‐Acetylderivaten von Phenothiazin und dessen S‐Oxiden werden Mechanismen diskutiert.
Cortisol‐eine ausgezeichnete Testsubstanz für die Qualitätsprüfung von Einführsystemen
Authors: Spiteller‐Friedmann Margot , Spiteller Gerhard
Published: May 2005

Cortisol ist thermisch instabil. Es zersetzt sich leicht unter Verlust von Keten und Wasser, Das Spektrum das entstehenden 11β‐Hydroxy‐Δ4‐androsten‐3,17‐dions überlagert sich dem Cortisolspektrum, das man frei von Zerstezungsprodukt nur unter sorgfältiger Einhaltung der Aufnahmebedingungen erhält Das thermische Zersetzungsprodukt läßt sich leicht an seinem Molekül‐Ion der Masse 302 und einem Schlüsselbruchstück der Masse 163 erkennen, die im Cortisolspektrum nahezu völlig fehlen, so daß Cortisol eine ausgezechnete Testsubstanz zur Qualitätsprüfung vonEinlass‐Systemen darstellt.
Mass spectra of alditol trifluoroacetates
Authors: Chizhov O. S. , Dmitriev B. A. , Zolotarev B. M. , Chernyak A. Ya. , Kochetov N. K.
Published: May 2005

The trifluoroacetyl derivatives of alditols are convenient compounds for mass spectrometric investigation as they are easily obtainable and highly volatile. They show simple fragmentation patterns with intensive peaks in the high mass range. Trifluoroacetates of alditols may be used for detection and location of deoxy groups in the molecule.
Substituent effects on ion abundances and energetics in substituted acetophenones
Authors: Chin Margaret S. , Harrison A. G.
Published: May 2005

Based on the quasi‐equilibrium theory of mass spectra it is shown that the intensity ratio [A]+/[M]+, where [A]+is a fragment ion and [M]+is the molecular ion, is given by [A]+/[M]+= f′ (k1/kt) ((1/f) − 1), where f is the fraction of molecular ions with insufficient energy to fragment, f′ is the fraction of [A]+ions with insufficient energy to fragment, and k1/ktis the fraction of fragmenting molecular ions which form [A]+. For substituted acetophenones it is shown that f depends on the substituent present and that f′ k1/ktis also substituent dependent for formation of both [CH3CO]+and [YC6H4CO]+. It is also shown that no direct information concerning the effect of a substituent on the rate of a particular fragmentation reaction can be obtained from intensity studies.

The ionization potentials of the parent molecules and the appearance potentials of the [YC6H4CO]+fragment ions have been measured for fifteen substituted acetophenones and the correlations with substituent constants are discussed.
The electron‐impact‐induced fragmentation of n‐alkyl cyanides
Authors: Heerma W. , De Ridder J. J. , Dukstra G.
Published: May 2005

The mass spectra of the alkyl cyanides up to n‐pentyl cyanide were studied. Using metastablel ion transitions, appearance potentials and deuterium labelling, the fragmentation patterns, spectral characteristics and trends for this series can be given. The investigation of labelled compounds demonstrates the specificity of rearrangement and normal decomposition processes. Alkyl ions in nitriles are produced by simple cleavage of the carbon‐carbon bond, while ions of the type [M –alkyl]+, which at the first sight could originate in the same way, are presumably formed via cyclic intermediates and are in fact rearrangement ions.

Apart from the known γ and δ‐hydrogen rearrangements, there is novel evidence for a β‐hydrogen rearrangement via a five‐membered ring transition state.
Das Massenspktroskopische Fragmentierungsverhalten von Derivaten des Benzisothiazol‐S‐dioxids
Authors: Hettler H. , Schiebel H. M. , Budzikiewicz H.
Published: May 2005

Das Fragmentierungsverhalten von Derivaten des Benzisothiazol‐S‐dioxids wird diskutiert. Es läßt sich für die Verbindungsklasse eine Reihe von typischen Zerfallsreaktionen erkennen, deren relatives Gewicht jedoch stark von der Art der substitution abhängt. Soweit dies energetisch günstig ist, tritt bevorzugt Abbau des Substituenten (evtl. gefolgt von Verlust von SO2) auf, Anderenfalls Zerfall des heteroaromatischen Ringes. (u.U. erst nach Umlagerung im Bereich der SO2‐Gruppe). parallelität zwischen thermischen und elektronenstoßinduzierten Umlagerungen wird nicht beobachtet.
Variation of relative ion abundances with accelerator potential in the mass spectrometer: The importance of source penetration
Authors: Howe Ian , Williams Dudley H.
Published: May 2005

Calculations have been carried out, using the Quasi‐Equilibrium Theory of Mass Spectra to show that a decrease in penetration of the accelerating field intol the ion source of a mass spectrometer may significantly increase the number of primary daughter ions [A]+ produced from a molecular ion [M]+ in the source. The calculations show that this effect appears to be more important than the decay of [M]+ between source and collector in implementing an increase in [A]+/[M]+ at the collector with decreasing accelerator potential.
The mass spectra of small‐ring hetero‐cycles—II. Aziridinones (α‐lactams)
Authors: Baumgarten Henry E. , Parker Richard G. , Von Minden David L.
Published: May 2005

The mass spectra of six aziridinones (α‐lactams) are presented. The six aziridinones exhibit the same general fragmentation pattern, the primary processes being loss of the N‐t‐butyl group, loss of carbon monoxide and loss of t‐butyl isocyanate. Several additional rearrangement or fragmentation processes are observed with specific α‐lactams.
Ionization and dissociation of cyclic ethers and thioethers by electron‐impact. A comparison between 1,4 dioxane, 1,4 dithiane and 1,4 oxathiane
Authors: Condé‐Caprace G. , Collin J. E.
Published: May 2005

The various modes of fragmentation of 1,4 dithiane and 1,4 oxathiane under electron‐impact have been discussed using variation of their mass spectra with electrons energy, high resolution and AP of the main ions. It is shown that they are qualitatively very similar, but differ considerably from those of 1,4 dioxane.
Electron‐impact induced fragmentation of substituted pyrazolone azomethine dyes
Authors: Maier D. P. , Happ G. P. , Regan T. H.
Published: May 2005

The mass spectra of 18 substituted 1‐(p‐R2‐phyeyl)‐3‐R3‐4‐(p‐R1‐phenylimino)‐2‐pyrazolin‐5‐ones have been obtained. The major cleavages under electron bombardment take place in the pyrazoline nucleus, producing four major fragment ions whose abundance is related primarily to the electronic properties of R1. These ions appear to be produced from the molecular ion via an intermediate formed by the loss of CO. In most instances metastable ions are observed for the overall decomposition of the molecular ion to the four major fragment ions. A mechanism is proposed for these cleavages.
The mass spectra of substituted cyclobutanones
Authors: Weiss D. S. , Gagosian R. B. , Turro N. J.
Published: May 2005

The low resolution mass spectra of several di‐, tri‐and tetra‐methylated cyclobutanones were determined at high and low ionizing voltages. The spectra are discussed in terms of the competition between loss of CO or loss of a ketene from the molecular ion of the cyclobutanone. The mass spectral results are correlated with the known photochemical behavior of the cyclobutanones and possible mechanistic implications are discussed.
Mass spectra of chloro‐, aminochloro‐ and ethylaminochloro‐s‐triazines
Authors: Ross James A. , Tweedy B. G.
Published: May 2005

The mass spectra of cyanuric chloride and all of the possible amino‐and ethylaminochloro‐s‐triazines have been investigated. The simpler compounds provide evidence for the structures of low mass fragment ions found in the spectra of the more complex derivatives. Fragmentation patterns are presented which account for most of the major ions. These pathways involve either the initial loss of a chlorine atom (important for the simple aminochlorotriazines) or ring cleavage with expulsion of cyanogen chloride (important for cyanuric chloride). The ethyl derivatives undergo cleavage of the side chain prior to either ring cleavage or chlorine expulsion.
Carbon‐oxygen bond formation in electron‐impact ions of acetylenic sulfoxides and sulfones
Authors: Kinstle T. H. , Oliver W. R. , Ochrymowycz L. A.
Published: May 2005

Migration of the ethynyl group, from sulfur to oxygen in acetylenic sulfoxides and sulfones leads to several documented examples of carbon‐oxygen bond forming rearrangement reactions.
Zum Mechanismus Massenspektrometrischer Fragmentierungsreaktionen—V: Substituenteneffekte auf Intramolekulare Substitutionen des Phenylrestes in den Massenspektren von N,N‐Dimethyl‐N′‐Phenylformamidinen
Authors: Grützmacher Hans‐Friedrich , Kuschel Heinz
Published: May 2005

Das Massenspektrum des N,N‐Dimethyl‐N′‐phenylformamidins(I) besitzt einen großen Peak von [M  H]⊕‐Ionen. Durch Deuterierung wird gezeigt, daß bei dieser Reaktion ebenso wie bei der entsprechenden Fragmentierung von Thioformanilid (V) eines der beiden ortho‐städigen H‐Atome des Phenylkerns abgespalten wird und Benzimidazolium‐Ionen (a) entstehen.

Der Einfluß von Substituenten am Phenylkern auf die Intensität und das AP dieser Ionen und auf das IP der Molekü‐Ionen wird gemessen. Aufgrund dieser Ergebnisse wird ein Mechanismus für die Cyclilsierungsreaktion vorgeschlagen.
Kinetic studies in mass spectrometry—IV. The [M — Cl] reaction in substituted chlorobenzenes and the question of molecular ion isomerization.
Authors: Brown Peter
Published: May 2005

The [M]+˙ → [M  Cl]+ reaction in a series of m‐ and p‐X substituted chlorobenzenes has been studied, utilizing a simple kinetic approach, comparison of metastable ion relative abundances, and by measurement of ionization and appearance potentials. All evidence obtained is consistent with rearrangement prior to cleavage in the molecular ions, in which substituent position becomes effectively randomized. These findings are related to known hydrogen randomization reactions occurring in either the molecular ion or [M  Cl] ion of chlorobenzenes. Mechanisms involving carbon scrambling via such species as ionized benzvalenes or prismanes, or ring‐opening to isomeric acyclic molecular ions in which hydrogen randomization might occur can be entertained, but mechanisms involving simple hydrogen shifts in the intact benzene ring appear less likely.