Carbonyl Linkage Research Articles

Synthesis and properties of polyaryletherketones

Crystalline polyarletherketones of high molecular weight have been prepared previously by polycondensation of aroyl fluorides such as 4-phenoxybenzoyl fluoride in liquid HF, but not by polyether synthesis because these polymers are not soluble in the recommended (see Farnham et al., J. Polym. Sci., Al, 1967, 5, 2375) dipolar aprotic solvents such as dimethyl sulphoxide or sulpholane. We find that tough, crystalline polyaryletherketones and copolyaryletherketone-sulphones can be obtained by polycondensation of bis-4-halogenophenyl ketones (plus bis-4-halogenophenyl sulphones for copolymers) with the potassium salts of bis-4-hydroxyphenyl ketones at 280°–340°C using certain diaryl sulphones as solvents for the reactions. There is no evidence for structural anomalies in the polyetherketone made by polycondensation of bis-4-fluorophenyl ketone with the bis-phenoxide from bis-4-hydroxyphenyl ketone, but synthesis of this polymer by polycondensation of the potassium salt of 4-fluorophenyl 4-hydroxyphenyl ketone gave products containing some gel and soluble polymer in which the chains appear to be branched. Several different polyaryletherketones give almost identical X-ray diffraction patterns, and in the unit cells of these polymers (fibre repeat distance 10.0Å) ether and carbonyl linkages are interchangeable; Tg and Tm for these polymers are recorded.

Substituent effects in heterogeneous catalysis: VIII. Reactions of 2-methyl- and 2-ethylcyclohexanone with deuterium catalyzed by platinum metals

2-Methyl and 2-ethyl derivatives of cyclohexanone were allowed to react with deuterium in tBuOD using platinum group metals as catalysts. The product alcohols and the remaining ketone were examined by mass spectrometry. Over Ru, Os, and Ir, the simple addition of two deuterium atoms to the carbonyl linkage was predominant, accompanied by little isotopic exchange. Over Pt, however, isotopic exchange was significant and over Rh and Pd quite extensive. The samples obtained over Rh and Pd were further analyzed by NMR spectroscopy to determine the loci of the incorporated deuterium atoms. Deuterium exchange over Pd was almost entirely confined to the C(2) and C(6) positions, while that over Rh was smeared beyond these positions. These results can be accounted for by assuming the intermediacy of π-absorbed π-oxaallylic species on Pd and of αβ-diadsorbed species on Rh.

The crystal and molecular structure of 1-bromobenzocymantrene, (η 5-C 9H 6Br)Mn(CO) 3

The crystal and molecular structure of tricarbonyl [1–4: 9-η-(1-bromo)indenyl]manganese (III) prepared by reaction of bromo(pentacarbonyl)manganese (II) with diazoindene (I) (“diazo method”) has been determined by X-ray diffraction methods. III belongs to the monoclinic space group P2 1/ c with unit cell constants a 12.953(9), b 7.627(5), c 13.098(9) Å, and β 110.53(5)°. Full-matrix least-squares refinement converged with a conventional R factor of 0.052 based on 1505 observed reflections. The molecule contains an essentially planar indenyl-π-ligand which is coordinated to the manganese atom through its cyclopentadienyl-like moiety. The bromine ligand is attached to the C(1) position of the indenyl system and has only a very slight influence on the characteristics of the indenyl skeleton. The change from cyclopentadienyl (in cymantrene) to indenyl (in III) produces essentially no disturbance in the normal manganese—carbonyl linkage.

Ester and keto carbonyl linkages in chlorophyll a, pyrochlorophyll a, and protochlorophyll a

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEster and keto carbonyl linkages in chlorophyll a, pyrochlorophyll a, and protochlorophyll aFrancis K. FongCite this: J. Am. Chem. Soc. 1975, 97, 23, 6890–6892Publication Date (Print):November 1, 1975Publication History Published online1 May 2002Published inissue 1 November 1975https://doi.org/10.1021/ja00856a062RIGHTS & PERMISSIONSArticle Views55Altmetric-Citations13LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (383 KB) Get e-Alerts Get e-Alerts

Crystal and molecular structure of titanocene dicarbonyl, ( h5-C 5H 5) 2Ti(CO) 2

The first X-ray structural determination of a complex with a Ti—carbonyl linkage is reported. The Ti—C(carbonyl) bond length is 2.030(11) Å, and the average TiC(cyclopentadienyl) distance is 2.347(9) Å.

Catalytic deuteration of cyclohexanone and allied reactions over platinum metals

In order to gain some insight into the mechanism of ketone hydrogenation to alcohol, cyclohexanone was deuterated over platinum metal catalysts under elevated pressure at 80 °C. The straightforward addition of two deuterium atoms to the carbonyl linkage was predominant over the heavy triad (Os, Ir, Pt). In contrast, the deuteration over the light triad (Ru, Rh, Pd) was accompanied by considerable isotopic exchange at the C-2 or C-6 position, leading to substantial proportions of the polydeuterated alcohols. A mechanism for cyclohexanone hydrogenation is presented which consists of three interlinked hydrogenation paths each having a different half-hydrogenated intermediate. The deuterium incorporation into the C-2 or C-6 position is attributable to alternation between the 1-monoadsorbed and 1,2-di-adsorbed intermediates.

Raney cobalt hydrogenation catalysts. III. Applications and promoter effects

AbstractA description is given of the use of Raney cobalt for the hydrogenation of unsaturated and carbonyl linkages under mild conditions. The results are compared with those obtained with Raney nickel catalysts.A study has also been made of the promoter effects of triethylamine, chloroplatinic acid and combinations of these, on the activity of the Raney cobalt catalyst for the hydrogenation of carbonyl compounds. As in the case of Raney nickel, such effects are highly specific for the compound under investigation. The most notable effect occurred in the hydrogenation of benzaldehyde, where the use of triethylamine chloroplatinate as promoter resulted in a cobalt catalyst having an activity several times greater than an unpromoted catalyst.

293. The vibration frequency of the carbonyl linkage

293. The vibration frequency of the carbonyl linkage

Spectroscopic Evidence for Hydrogen Bonds: Effects of Chelation on the Carbonyl Frequency

The vibrational band characteristic of the carbonyl linkage was measured for o-hydroxyacetophenone, o-methylaminobenzoate, o-methylsalicylate, o-hydroxybenzaldehyde and for compounds similar to these but lacking an adjacent proton-donor group. Chelation through hydrogen bonding was found to shift the C=O band to longer wave-lengths by about 0.15μ to 0.20μ, or 40 cm—1 to 53 cm—1, and to increase its intensity. Similar effects were observed for the carbonyl band of the enol forms of acetyl-acetone, ethyl malonate, ethyl acetoacetate. The magnitude of the effects of hydrogen bonding on the carbonyl band shows that energy changes in the proton-acceptor groups cannot be neglected in the computation of the energy of the hydrogen bond from spectroscopic data. The results also show that measurements on the proton-acceptor group can often be used as criteria for the presence of hydrogen bonding when experimental difficulties prevent accurate measurements of the effects on the vibrational band of the proton-donor group. Smaller effects were noted for ethylenic linkages of some of these compounds.