Hans-Friedrich Grützmacher

Sodium Phosphaethynolate as a Building Block for Heterocycles

Phosphorus-containing heterocycles have evolved from laboratory curiosities to functional components, such as ligands in catalytically active metal complexes or molecular constituents in electronic devices. The straightforward synthesis of functionalized heterocycles on a larger scale remains a challenge. Herein, we report the use of the phosphaethynolate (OCP)(-) anion as a building block for various sterically unprotected and functionalized hydroxy substituted phosphorus heterocycles. Because the resulting heterocycles are themselves anions, they are building blocks in their own right and allow further facile functionalization. This property may be of interest in coordination chemistry and material science.

Massenspektrometrische untersuchungen : XIX. Mitteilung. Kombination von gaschromatographie und massenspektrometrie zur analyse partiell methylierter zuckerderivate. Die massenspektren von partiell methylierten methylglucosiden

Some partially methylated methyl glucosides were investigated by the gas chromatography-mass spectrometry method. The main properties of their mass spectra can be derived from the fragmentation scheme of permethylated pyranoses by a consideration of the effects of the different substituents. Apart from a shift of the ion masses, due to replacement of methoxyl by hydroxyl groups, the main effect of the substituent is a variation of the inductive stabilisation of the positive charge of the fragments. Furthermore, the derivatives having methoxyl groups at the 1,2,3-, 1,2,3,6-, 1,3,4-, or 1,3,4,6-positions produce a very characteristic peak at m/e 161. The stereochemistry of the partially methylated methyl glucosides has no significant effect on their mass spectra, but the effect of the position of the substituent is important. The type of substitution can thence be deduced from the mass spectra. The gas chromatography-mass spectrometry method is much more appropriate for the identification of a mixture of monosaccharides obtained from a permethylated polysaccharide by solvolysis than the gas-chromatographic method alone.

A fourier transform-ion cyclotron resonance study of steric effects on proton transfer reactions of polyalkyl benzenes

Abstract The rates of deprotonation, MH + + B → M + BH + (M = 1 , 2 ), and the rates of protonation, M + BH + → MH + + B (M = 2 , 3 , 4 ), have been measured by Fourier transform-ion cyclotron resonance (FT-ICR) spectrometry for the increasingly sterically crowded alkyl benzenes ethylbenzene, 1 ; 1,3,5-trimethylbenzene (mesitylene), 2 ; 3,5-di( t -butyl)toluene, 3 ; 1,3,5-tri( t -butyl) benzene, 4 ; and a series of n-bases B. In addition, the gas phase basicities of 3 and 4 were determined by proton transfer equilibrium measurements using FT-ICR. The efficiencies of deprotonation and protonation are always large (> 50%) for exoergic reactions and increase with increasing exoergicity, but never reach unit efficiency. For each of the alkylated benzenes 1 – 4 the efficiency decreases steeply at the border between exoergic and endoergic reactions. This is the “normal” behaviour of proton transfer reactions and shows the absence of steric effects for proton transfer to and from alkylated benzenes even in the case of 3 and 4 substituted by bulky t -butyl groups, and is in complete contrast to the behaviour of t -butylated pyridines. This difference is explained by different geometries of the transition state for the proton transfer reactions in the case of the alkylated pyridines and alkylated benzenes, and by the critical role of π-complexes in proton transfer reactions of benzene derivatives.

Die Konstitution der Kondensationsprodukte von Catechinen mit Phloroglucin

Kurze Originalmitteilungen Die Natur-wissenschaffen chloromercury derivatives]; their discussions and various calculations will be published separately in J. Amer. Chem. Soc. Im Zusammenhang mit unseren Untersuchungen ~) fiber eine strukturchemische Systematik anorganischer Verbin-dungen ergab sich, dab die Morphotropiebeziehungen yon GOL~SCH~IDT ~) als zum Tefl fiberholt anzusehen sind. Die bet den Verbindungen vom Typ A~BX~ auftretenden Struktur-typen h~ingen sowohl yon dell Radien (rA, rB, rx) der Gitter

A study of gaseous benzenium and toluenium ions generated from 1,4- dihydro- and 1-methyl-1,4-dihydro-benzoic acids

Gaseous benzenium C6H7+(1) and toluenium C7H9+(2) ions have been generated by mass spectrometric loss of ˙CO2H from the corresponding 1,4-dihydrobenzoic acids (3) and (4), and their fragmentations after ca. 10 µs have been investigated by means of mass-analysed ion kinetic energy (MIKE) spectrometry of some 2H and 13C labelled analogues. Metastable C6H7+ ions eliminate H2 after proton randomization, whereas metastable C7H9+ ions expel both H2 and CH4 after incomplete proton equilibration. In particular, 40% of C7H9+ ions randomize all their carbon and hydrogen atoms prior to loss of CH4, and 60% of C7H9+ ions lose the original methyl group along with a hydrogen atom from the (proton-equilibrated) benzenium ring, accompanied by a slow and incomplete exchange between the hydrogen atoms of the ring and the methyl group. It is suggested that loss of both CH4 and H2 occur via the (ipso-)toluenium ion (2). The role of a non-classical C7H9+ isomer, phenylmethonium ion (6), is discussed since striking similarities are found compared with [C6H6·CH3+]* adducts from ion–molecule reactions described in the literature.

Polycyclic Aromatic Hydrocarbon Solute Probes. Part VII: Evaluation of Additional Coronene Derivatives as Possible Solvent Polarity Probe Molecules

Fluorescence emission spectra are reported for dinaphtho[8,1,2abc; 2′,1′,8′klm]coronene, naphtho[8,1,2abc]coronene, naphth[2′,1′,8′,7′: 4,10,5]anthra[1,9,8abcd]coronene, dibenzo[bc,ef]coronene, benzo[1,2,3bc;4,5,6b′c′]dicoronene, anthra[2,3a]coronene, dinaphtho-[8,1,2abc;2′,1′,8′jkl]Coronene, and tetrabenzo[de,hi,mn,qr]naphthacene dissolved in n-hexadecane, butyl acetate, dichloromethane, and acetonitrile. Results of these measurements are used to screen PAHs for potential solvent polarity probe behavior. Of the eight PAHs studied, only naphtho[8,1,2abc]coronene, dinaphtho[8,1,2abc;2′,1′,8′klm]-coronene, and anthra[2,3a]coronene were classified as probe molecules. The fluorescence spectra of the first two PAHs show selective enhancement of the I band emission intensity in polar solvents. For anthra-[2,3a]coronene, the measured ratio of emission intensities of bands I and II decreased systematically with increasing solvent polarity.

Unimolecular and bimolecular reactions of the β-distonic ion CH2CH2OCH+2 and its deuterated derivatives

Abstract The unimolecular and bimolecular reactions of the β-distonic ion + CH 2 OCH 2 CH 2 ( a ) and its deuterated analogues b and c have been studied by tandem mass spectrometry and by Fourier transform ion cyclotron resonance (FT-ICR) spectrometry. The spontaneous reactions of metastable a are the loss of H and CO respectively. H and D are eliminated from metastable b and c irrespective of the position of the D atoms, suggesting an oxetane radical cation d as an intermediate for this process. However, a careful examination of the collisional activation (CA) spectra of a—c reveals that the CH 2 groups of a do not scramble by a mutual interconversion of a and d , in line with previous results. The reactions of a and the isotopomers b and c with pyridine and acetonitrile respectively have been investigated by FT-ICR spectrometry using an external ion source. Besides the elimination of an H atom which is very probably a collision-induced process, a reacts with pyridine by charge exchange, by protonation, and by the formation of an N -formyl pyridinium ion but not by the transfer of C 2 H + 4 . All six H atoms of a take part in the protonation. A mechanism involving a rearrangement of a into CO and C 2 H + 6 in the collision complex with pyridine and subsequent transfer of a proton from C 2 H + 6 is suggested. The generation of the N -formyl pyridinium ion occurs specifically from the CH 2 O moiety of a and corresponds to an electrophilic reaction of the β-distonic ion. In addition to the known transfer of C 2 H + 4 from a to acetonitrile a proton transfer has been observed. However, the energetically allowed formation of an N -formyl nitrilium ion is not detected. The mechanistic origin of this diverse behaviour of the two nulceophiles pyridine and acetonitrile towards the β-distonic ion a is discussed.

Dissociation of proton-bound complexes and proton affinity of benzamides

Proton-bound heterodimers of substituted benzamides 1–15 and N,N-dimethyl benzamides 16–30, respectively, with a series of reference bases were generated under chemical ionization conditions. Their dissociation into the protonated amide AH+ and protonated reference base BH+ was studied by metastable ion techniques and by collision-induced dissociation (CID) to examine substituent effects on the proton affinity (PA) of the benzarnides and to elucidate some aspects of the dissociation dynamics of proton-bound clusters. The PAs of the substituted benzarnides were determined by bracketing the amide by a pair of reference bases to give rise to more and less abundant signals of the protonated base in the mass-analyzed ion kinetic energy (MIKE) spectra of the proton-bound heterodimers. The substituent effects observed agree with O-protonation in both the primary and the tertiary benzamides. However, the susceptibility of the benzamide to polar substituent effects is remarkably small, which indicates a “resonance saturation”), of the amide group. The relative abundances of AH+ and BH+ in the MIKE and collisional activation (CA) mass spectra depend strongly on the pressure of the collision gas during CID, and in certain cases a reversal of the relative abundances with increasing pressure that favors the formation of BH+ from a less basic reference base is observed. Although this effect underlines the limited possibilities of the “kinetic method” for PA determination by CID of proton-bound heterodimers, it uncovers important kinetic effects during the dissociation of proton-bound heterodimers and of proton transfer reactions in the gas phase.. In the case of the protonated amide clusters, the observed intensity effects in the CA mass spectra are explained by a double-well potential energy surface caused by solvation of the protonated base by the polar amide in the protonated heterodimer.

Dithia-diaza[n.2]paracyclophane-enes

Abstract The dithia-diaza[n.2]paracyclophane-enes 3a - 3h (n = 6 - 14) were synthesized starting from p-hydrazotoluene by using the rigid group prinziple and the high dilution technique. 3a - 3c exist only in the cis -azo configuration, while 3d and 3e are obtained as mixtures of the cis -and trans -isomers. 3f - 3h are formed as pure trans -azoarene derivatives. A thermal cis/trans -isomerisation is observed only for 3e , but 3d - 3f can be transformed into pure cis -azoarene derivatives by photoisomerizacion. The 1H-NMR- and UV/VIS spectra of 3a - 3h are discussed. Both types of spectra show characteristic differences for the cis - and trans -isomers.

Remote fragmentations of protonated aromatic carbonyl compounds via internal reactions in intermediary ion-neutral complexes

Protonated aromatic aldehydes and methyl ketones 1a–10a, carrying initially the proton at the carbonyl group, are prepared by electron impact-induced loss of a methyl radical from 1−arylethanols and 2−aryl−2−propanols, respectively. The aryl moiety of the ions corresponds to a benzene group, a naphthalene group, a phenanthrene group, a biphenyl group, and a terphenyl group. respectively, each substituted by a CH3OCH2 side-chain as remote from the acyl substituent as possible. The characteristic reactions of the metastable ions, studied by mass-analyzed ion kinetic energy spectrometry, are the elimination of methanol, the formation of CH3OCH2+ ions, and the elimination of an ester RCOOCH3 (R = H and CH3) . The mechanisms of these fragmentations were studied by using D-labeled derivatives. Confirming earlier results, it is shown that the ester elimination, at least from the protonated aryl methyl ketones, has to proceed by an intermediate [acyl cation/arylmethyl methyl ether]-complex. The relative abundances of the elimination of methanol and of the ester decrease and increase, respectively, with the size of the aromatic system. Clearly, the fragmentation via intermediate ion-neutral complexes is favored for the larger ions. Furthermore, the acyl cation of these complexes can move unrestricted over quite large molecular distances to react with the remote CH3OCH2-side-chain, contrasting the restricted migration of a proton by 1,2-shifts (“ring walk”) in these systems.