Mass spectroscopy carbonyls

Neutral and charged gold carbonyl species have also been observed on gold field emitter tips upon interaction with CO gas at room temperature in the presence of high electrostatic fields. The adsorbed complexes and the desorption pathways were identified using time-of-flight mass spectroscopy. [(CO)Au] species are more abundant than [Au(CO)2] species. The product distribution was rationalized by DF calculations of the electronic structure of the complexes.291... 

The initial observation is that PMMA is essentially completely degraded to monomer by heating to 375°C in a sealed tube while heating a mixture of red phosphorus and PMMA under identical conditions yields a solid, non-deqraded, product as well as a lower yield of monomer. One may observe, by 3C NMR spectroscopy, that the methoxy resonance is greatly decreased in intensity and methyl, methoxy phosphonium ions are observed by 31P NMR. Additional carbonyl resonances are also seen in the carbon spectrum, this correlates with a new carbonyl vibration near 1800 cm 1 in the infrared spectrum and may be assigned to the formation of anhydride. The formation of anhydride was also confirmed by assignment of mass spectra obtained by laser desorption Fourier transform mass spectroscopy, LD-FT-MS. 

As already mentioned, it is the volatile constituents that serve to identify fruit type and variety. Broadly speaking, qualitative analysis will identify the principal substances present in the volatiles fraction as representative of a particular fruit type, but it is the relative proportions of these substances that will reflect the variety. Alcohols, volatile acids, esters, carbonyl compounds, and low-boiling hydrocarbons are the principal groups represented. Analysis by GC-MS (gas chromatography coupled with mass spectroscopy) can be used to provide quantification and identification of the various constituents. 

Pyrolysis at 200°C of Os3(CO)j2 in a scaled, evacuated tube afforded a mixture of at least seven different carbonyl clusters which could be separated by thin-layer chromatography. In addition to some unreacted Os3(CO)i2, the new compounds, Os.i(CO)i3, Os5(CO)i6, Os6(CO)i8, Os8(CO)23, and Os8(CO)2iC, were identified by mass spectroscopy (58) the last compound was originally formulated as Oss(CO)i5C4 (61). Further pyrolysis of Os6(CO)i8 at 255°C gives the pentanuclear carbide derivative, Os5(CO)I5C, in 40% yield (59). 

We have expanded coverage of spectroscopy in several ways. Chapter 4 introduces the use of infrared spectroscopy, especially its applications to carbonyl complexes. C-13 and H-l nuclear magnetic resonance spectroscopy are emphasized in Chapter 5 and P-31 NMR is introduced in Chapter 6. New to the second edition is the inclusion of a section on mass spectroscopy in Chapter 6. Chapters 4-6 contain numerous end-of-chapter problems, where spectroscopic information is an essential part of the exercise. Subsequent chapters have additional spectroscopy problems. 

Mass spectroscopy also appears to be a valuable technique for the characterization of silyl complexes, particularly in cases where the nuclearity (or degree of association) of the compound is in question. For carbonyl complexes common fragmentation patterns consist of loss of CO, loss of silicon substituent, or, less frequently, rupture of the M-Si bond. 

Diverse spectroscopic methods have been employed to characterise triterpenes. Ultraviolet (UV) and infrared (IR) spectroscopy are not very useful techniques in elucidating the structure of triterpenes, but the former gives information about compounds with conjugated double bonds and the latter may provide some information about substituents like the hydroxyl group, ester carbonyl group or a,p-unsaturate carbonyl. Other physical data may be of interest to characterise new compounds, but the use of modem spectroscopic methods of nuclear magnetic resonance (NMR) and mass spectroscopy (MS) are essential for the structural determination. 

Juvabione, the compound responsible for this activity, was isolated from the balsam fir, Abies balsamea (L.) Miller, and identified as the methyl ester of todomatuic acid, (+)-4(i )-[ 1 R)-S -dimethyl-3 -oxohexyl]-1-cyclohexene-1-carboxylic acid [87]. This compound is a sesquiterpenoid (Fig. (6)) with a cyclohexene group and an a,(3-unsaturated methyl ester group the chemical data for this compound are summarized in Appendix II, Table 1. The IR spectrum suggests that there is a carbonyl ester group present in conjunction with a double bond (1722 and 1645 cm 1) and also an isolated carbonyl group (1712 cm 1) [87]. Mass spectroscopy confirms... 

The aging of hulk epoxy networks has been studied by various techniques such as FTIR spectroscopy [1-4], gravimetric analysis [1, 3, 5, 6], mass spectroscopy [1], DSC [2], or XPS [6]. The aging conditions applied vary broadly from thermo-oxidation at elevated temperature (100-250 °C) [1-3, 5, 6] or photo-oxidation [1, 2] to humid or environmental conditions [4, 7]. FTIR investigations [1-4] show the rise of new IR bands at 1660-1670 cm and 1720-1730 cm in an oxidized region near to the sample surface. The bands are explained by amide and carbonyl formation due to radical oxidation mechanisms initiated by the elevated temperature or UV irradiation [1, 2, 4]. Also, backbone cleavage is held responsible for the observed decrease in glass transition temperature [2]. 

The principal use of the carbonyls is that of obtaining pure metals. The Mond process for refining nickel and the preparation of pure iron for special pui oses, such as magnet cores, involve the formation of a volatile carbonyl, transport of the vapors away from impurities in the original metal, and subsequent decomposition to obtain the pure metal. The carbonyls of chromium, molybdenum, and timgsten have been used in mass spectroscopy to determine the stable isotopes of the respective metals. Nickel carbonyl has been used to obtain metallic mirrors and to coat objects with a thin film of metal. Iron carbonyl has been used as an antiknock agent in gasoline. 

The evolved gas analyses were conducted on FTIR and mass spectroscopy (MS) devices, coupled to the TG apparatus. The main volatile compounds released below 350 °C were carbon dioxide and water vapours, which increased during the whole thermal decomposition process. Alcohol traces and aromatic structured compounds were also identified. Volatile structures containing carbonyl groups were found in the gaseous mixture at temperature values above 350 °C. Ammonia evolvement was also found in the gaseous mixture. The MS spectra were in good correlation with the findings from the FTIR spectra data. 

Another rheniim carbonyl tetrahedron is the deep red powder Hi+Rei (CO) 12 which is prepared by pyrolysis of [HRe(C0)ij]3 in boiling decalin for 30 min followed by precipitation with benzene (340). Very recently (224a) Hi Reii (CO) 12 was also obtained by reaction of Re2(CO)io with hydrogen at 150-160° and 1 atm. The formula Hi Rei (CO) 12 was confirmed by mass spectroscopy (340). The four hydrogen atoms in Hi Re (CO) 12 exhibit a characteristic high-field NMR at xl5.08. The v(CO) frequencies in HijRe (C0)i2 resemble closely those in Ir (C0)i2 which likewise has a metal tetrahedron. 

Ephedra spp. roots are known as major source of ephedrine and derivatives alkaloids, but this plant species also contains an imidazole derivative, feruloylhistamine (12), which was identified in methanolic extract of the drug in 1983 [19, 20]. After column chromatography and crystallization procedures, feruloylhistamine was characterized by and NMR and mass spectroscopy. A molecular ion peak was observed at miz 287 consistent to a C15H17N3O3 fragment, and the NMR spectrum revealed signals for aliphatic and aromatic carbons and also one carbonyl group. The synthetic derivative was also obtained and afforded the same physical data as the natural compound [19]. 

The imidazole alkaloid 4,6-dehydro-l,2,4,5-tetrahydro-2,5-dioxopilocarpine (34) was isolated from P. grandiflorus Engl, stems, as a yellowish oil. Its structure was determined by high-resolution mass spectroscopy miz 238) and and NMR that indicated a change in the structure of pilocarpine due to the signals at 177.7, 162.4, 152.4, 132.2, and 112.3 ppm, associated to two additional carbonyl groups and a double bond [33]. 

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