α-, β- et γ-Phénylchlorogermylalcools

In polar solvents, phenylchlorohydrogermanes can add onto the carbonyl group of aldehydes and ketones with formation of α-chlorogermylalcohols. This dominant reaction in the case of phenyldichlorogermane can only be observed with diphenylchlorogermane, which presents a lower Ge^δ?H^δ+ polarity, in the presence of H₂PtCl₆. In this case, the formation of α-germylalcohol is restricted by the competitive radicalar addition of the hydrogermane onto the carbonyl group, leading to a stable alkoxygermane.The dipolar 1,2-addition onto the carbonyl group, leading to α-germylalcohol, is a specific reaction of these hydrogermanes which must be related to the high electronegativity of germanium.All α-chlorogermylalcohols decompose mainly by elimination of HCl, regeneration of the starting carbonyl derivative, and formation of the corresponding germlene. They are reduced in stable α-hydrogermyl alcohols.β- or γ-chlorogermylalcohols are thermally more stable, but their dechlorhydratation leads to oxagermacycloalkanes.     

Grafting polymerization on cellulose based textiles: A C solid state NMR characterization

Grafting of methyl methacrylate and ethyl acrylate onto cellulose chains of textiles with oxidized sites has been carried out. To this aim, carboxyl and carbonyl groups have been introduced by oxidation of the cellulose and used as photosensitive agents, allowing the formation of radical sites. The copolymerization has been started irradiating the substrate with ultraviolet light for a short time. With the grafting of acrylic monomers the mechanical strength and the thermal stability of cellulose based textiles may be improved, as well as the resistance to chemical and biological agents. The method has been successfully tested performing the grafting on a naturally aged cotton sample. It is worth to note that the grafting does not affect the aspect of the material.All samples have been characterized with ¹³C solid state NMR spectroscopy. A semi-quantitative evaluation of the grafting has been performed either studying the cross-polarization dynamic process, or by direct integration of resonances in ¹³C single pulse excitation spectra.     

Substituent effects on 13C and 1H chemical shifts in 3-benzylidene-2,4-pentanediones

Substituent effects on the ¹³C and ¹H chemical shifts have been studied for derivatives of 3-benzylidene-2, 4-pentanedione. A significant correlation has been found between chemical shifts of the Z carbonyl group (C-2) and Hammett constants, while no correlation has been found for the E carbonyl group (C-4). Attempts have been made to determine the structural factors which influence these effects. The conformation of 3-benzylidene-2, 4-pentanediones has been determined by ¹³C and ¹H NMR spectroscopy.     

聚醚氨酯的红外酰胺Ⅰ.谱带分析

 通过对聚醚氨酯红外光谱酰胺-Ⅰ谱带的二级微商及傅里埃自解卷积处理,发现了位于1715cm^-1的新组分并可归属于无序的相间界面。应用差减光谱及曲线拟合对热处理试样的光谱谱带进行分析表明聚醚氨酯的加热/冷却过程是与可逆的无序/有序化过程及微相混合/分离过程有关的。新发现的1715cm^-1组分强度的变化与无序/有序化过程是一致的。     

Determination of acetaldehyde in tobacco smoke using N-methyl-4-hydrazino-7-nitrobenzofurazan and liquid chromatography/mass spectrometry

A liquid chromatography/mass spectrometry (LC/MS) method for the determination of carbonyl compounds based on derivatization with N-methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH) has been developed. Atmospheric pressure chemical ionization (APCI) in the positive mode proved the most versatile ionization technique for MNBD-hydrazones. APCI/MS spectra were recorded and the detection limits were determined for [M+H]⁺. ¹³C₂ acetaldehyde MNBD-hydrazone has been synthesized and characterized. It is applied as internal standard for the quantification of acetaldehyde. Tobacco smoke has been investigated concerning its carbonyl content. Acetaldehyde was identified as main product and quantified by LC/MS using internal standardization. The result is in good agreement to quantification data obtained with UV/vis detection.     

Mechanisms of water elimination and other degradations of 2-hydroxy-5-ketobornane cations in the gas phase

The mechanisms of water elimination in 2-hydroxy-5-ketobornanes have been investigated and compared with those in borneol and isoborneol in order to ascertain whether and how such processes are affected by incorporation of a remote second functional group of lower ionization energy. Analysis of metastable ion peak shapes and specific labelling with ²H and ¹⁸O are employed as methods for differentiating between individual reaction paths. In addition, those degradation reactions which give rise to the most prominent fragments and pattern differences in the mass spectra of the epimeric keto alcohols were scrutinized. The elimination of water is shown to exhibit entirely different features due to the presence of the carbonyl group. The other most important degradation reactions all proceed by hydrogen transfer from the hydroxyl group onto the charged product and concomitant loss of the hydroxyl oxygen in a neutral entity. The results are interpreted in terms of initial charge radical localization on the carbonyl group initiating the relevant chemical reactions. Peak shape analysis proves a very valuable, and at times the only useful way to distinguish individual reactions.     

Determination of microtacticity of poly(vinylketones) and their derivatives by NMR spectroscopies of carbon-13 and proton

Sequence distribution of atactic poly(phenylvinylketone) (PPVK) has been determined by [¹³C]-[¹H]NMR spectroscopy. Quantitative analysis of the carbonyl pattern allows resolution into pentads with intensities fitting a first order Markov process. The carbonyl pattern of highly isotactic PPVK, initiated by diethylzinc, deviates strongly from Bernoullian statistics, as in the case of highly isotactic polymethylvinylketone (PMVK). For n-butyl-lithium initiated poly(isopropenylphenylvinylketone) (PIPK), the carbonyl pattern practically agrees with a Bernoullian distribution. Atactic PMVK, analyzed from the methylene and the carbonyl pattern in [¹³C] or [¹H]NMR, shows that the polymerization process is purely Bernoullian and quite different from that for poly(isopropenylmethylketone). Except for poly(methylallylalcohol) for which the tacticity can be determined, the resolution is too poor to allow a quantitative sequence distribution of poly(allylalcohols) or poly(allyltrifluoroacetates). [¹H] and [¹⁹F]NMR spectroscopies of these compounds do not give better results.     

13C and 1H chemical shifts in 2-benzylidene[3]ferrocenophane-1,3-diones. Elucidation of the substituent dependence of carbonyl chemical shifts in different carbonyl derivatives

The ¹³C and ¹H chemical shifts of the ferrocene moiety, as well as the carbonyl carbons and styrene moiety, of substituted 2-benzylidene[3]ferrocenophane-1,3-diones have been assigned. Correlations of ¹³C substituent chemical shifts of both carbonyl carbons with the Hammett constants have been found, and the effect of the transmission of substituent effects on these chemical shifts through the styrene moiety is discussed. An explanation is given for the different sensitivities of the carbonyl carbon chemical shifts to the electronic effect of substituents in mono- and dicarbonyl derivatives.     

纳米铝粉促进羰基化合物水相烯丙基化反应

氮气保护条件下,纳米铝在0.1 N NH₄Cl溶液中,能有效地促进羰基化合物与烯丙基溴进行Barbier-Grignard型烯丙基化反应,得到相应高烯丙醇。芳香族醛或酮的烯丙基化产率较高,而脂肪族羰基化合物反应产率低,反应产率受羰基空间位阻影响大,在同样条件下,邻羟基羰基化合物烯丙基化产物主要是赤式-邻二醇。     

Solid Phase Derivatizations in HPLC: Borohydride/Silica Reductions for Carbonyl Compounds

Abstract

Sodium borohydride adsorbed onto silica gel has now been utilized for on-line, pre-and post-analytical column chemical derivatizations via reductions of various organic carbonyl compounds. These on-line reactions have been performed using normal phase HPLC conditions, involving conventional silica gel packings, organic mobile phases, and commercially available HPLC equipment and instrumentation. This approach for on-line HPLC derivatizations has been evaluated for a large number of organic carbonyl compounds, at a variety of temperatures for aldehydes and ketones. The overall rates of such carbonyl reductions via sodium borohydride/silica are sufficiently different as a function of temperature of the reaction to permit for compound/class identifications. Analyte identification can be both qualitative and quantitative, even wherein an analyte co-elutes with a non-carbonyl compound. In-house prepared borohydride/silica gel reactors can be characterized via standard iodine titration procedures along with inductively coupled plasma (ICP) elemental boron analysis. These normal phase derivatization approaches have been applied to certain standard vitamins, and to cinnamaldehyde found in a commercial spice product. Such approaches to on-line HPLC derivatizations     

Mesomere Kationen: III—13C-Fourier-Transform-NMR-Spektren von Harnstoffen,Thioharnstoffen und Guanidinen

The ¹³C-chemical shifts of methyl substituted ureas, thioureas and related compounds are reported and discussed. π-Electron densities, as obtained by simple HMO calculations, do not reproduce the ¹³C-chemical shift trend. A correlation has been found for the carbonyl and thiocarbonyl resonances which has been discussed as being mainly influenced by the mean excitation energy in the paramagnetic screening term.     

A Facile Ester Homologation of Carbonyl Compounds Via Ketene-O,S-Acetals

A usefull extension of the available methods for the conversion of carbonyl compounds into ketene-O,S-acetals^1,2,3 has been found in the Peterson olefination with methoxyphenylthiotrimethylsilyl-methyllithium 1 of aldehydes and ketones. The starting material for this reagent 1 was prepared by reaction of methoxyphenylthio-methyllithium^4,5 with chlorotrimethylsilane at -80°C in THF. Deprotonation of the obtained methoxyphenylthiotrimethylsilyl-methane with n-butyllithium at -80°C in THF gave 1 and subsequent addition of the carbonyl compound at -80°C gave mixtures of Z and E ketene-O,S-acetals 2.     

Synthesis and Structure of Borane Complexes with 3-Hydroxyflavone

Conclusions have been made regarding the structure of the complexes formed between flavonol and boranes of different structures on the basis of the analysis of their ¹H, ¹³C, and ¹¹B NMR spectra, IR and electronic spectra, and also from the results of quantum-chemical calculations. In all of the complexes, independently of the structure and acceptor properties of the boranes, it was found that the donor acceptor bond is formed between the boron atoms and the oxygen of the carbonyl group in the flavonol. Despite the lowered electron-donor ability of the carbonyl group oxygen atom after the formation of the bond to the boron atom it is likely that the hydrogen bond between the carbonyl and the 3-hydroxy group of the flavonol is retained. It was found that the carbonyl group of the flavonol has a lower electron-donor ability than the analogous group of aliphatic and aromatic ketones.     

Comment on “Maximum Interaction Model of Force Constant Calculation of the MLx(CO)6-x Type Molecule”

Since the introduction of non-mechanical coupling model proposed by Cotton and Kraihanzel^1-3) for the calculation of nonrigorous carbonyl force constants of metal carbonyls, several criticisms^4-3) and modifications^6-13) on this simplified CO-factored force field has been reported. Recently, a different approach of so-called “maximum interaction model” was proposed by Chen and Hsiang¹⁴⁾. However, we found that basic assumptions of this model are very shaky and questionable since three serious abnormal results could be noted as a result of maximum interaction between carbonyl groups. Here we would like to make some comments on this model.     

252Cf-Plasma desorption mass spectrometry using polymer surfaces

The adsorption of molecules onto a specially designed polymer surface is a new sample preparation technique for ²⁵²Cf-plasma desorption mass spectrometry (²⁵²Cf-PDMS) where an analyte is adsorbed from a solution onto the surface of a thin film that has been modified to have a particular attraction for the analyte. The adsorbed layer is directly analyzed by ²⁵²Cf-PDMS. Mass spectra of pepsin (mol. wt. 35 000) adsorbed onto nitrocellulose and highly-charged heparin fragments adsorbed onto an immobilized cationic surfactant film are some of the recent applications to difficult analytical problems.     

The mechanism of elimination of an H2O molecule in desmethylencecalin under electron impact

The mass spectrum of desmethylencecalin has been measured and a fragmentation mechanism for the loss of a water molecule from the [M? CH₃]⁺ ion is proposed on the basis of isotope labelling and metastable peak observations. The eliminated water has been shown to involve the carbonyl oxygen and hydrogen atoms of the hydroxyl and acetyl groups.     

The mechanism of borohydride reductions. Reactions of gas phase borohydride ion with carbonyl groups by ion cyclotron resonance spectroscopy.

The reaction between BH₄^? and CH₂O has been investigated in the gas phase using ion cyclotron resonance spectroscopy. No hydride transfer from BH₄^? to the carbonyl group is observed, however a novel reaction between enolate ions and diborane has been observed.     

Highly Porous Zirconium Aryldiphosphonates and Their Conversion to Strong Bronsted Acids

Porous inorganic-organic hybrids have been prepared by the reaction of 4,4′-biphenylbis(phosphonic acid) with Zr(IV) in organic solvents. The resultant products consist of α-zirconium phosphate-type layers crosslinked by biphenyl pillars. By using an excess of Zr in the synthesis, surface areas of ∼400 m²/g have been obtained and the pores can be controlled to be the micro-type with diameters of 10-20 Å and a relatively narrow pore size distribution. The aromatic rings are readily sulfonated by SO₃ under pressure to produce very strong Bronsted acid catalysts. An NMR procedure, utilizing the shift of the carbonyl carbon of acetone-2-¹³C sorbed onto the sulfonated products, indicated an acid strength for the Bronsted acid sites equal to that of 100% sulfuric acid. Unpillared Zr(O₃PC₆H₄SO₃H)₂ has a somewhat lower acid strength, but still has a higher acid strength than zeolites HX and HY. The particles of this layered acid exfoliate in water and light-scattering data show that they are in 5 nm size range. They also exhibit high proton conductivity as solid membranes. These sulfonated materials have a potential as strong acid catalysts for a variety of reactions at a low temperature.     

Thermische disproportionierung von (η5-C5H5)2V2(CO)5. Tetrakis[carbonyl(η5-cyclopentadienyl)vanadium], (η5-C5H5)4V4(CO)4

The novel vanadium cluster tetrakis[carbonyl(η⁵-cyclopentadienyl)- vanadium has been prepared in 32% yield by thermal disproportionation of μ-dicarbonyltricarbonylbis(η⁵-cyclopentadienylvanadium) (V-V) in boiling tetrahydrofuran.     

13C?C13 coupling constants in dimethyl phthalate and phthalic anhydride. Determination of signs—III

Relative signs of ¹³C? ¹³C coupling constants between ring carbons and carbonyl carbons in dimethyl phthalate and phthalic anhydride, ¹³C-labelled in both carbonyl groups, have been determined. The two-and three-bond coupling constants are shown to be positive, whereas four-bond coupling constants are negative. Substituent effects on carbon-carbon couplings due to a carboxyl group have been determined and effects of 5-membered ring formation in phthalic anhydride have been observed.