Ethylenes mass spectra

The mass spectrum of 1-torr ethylene in 20-torr He is also shown in in Figure 14. Remembering that the (electron impact) ionization cross-section for ethylene is 20 times higher than that for He, we expect almost... 

Application to Ethylene Radiolysis. The predominant ions in the mass spectrum of ethylene (1) are ethylene, vinyl, and acetylene ions, which together account for over 85% of the total ionization. A total of 38% of all ions are C2H4+, and since kF(ethylene) = 25.9 e.v./ion pair, the parent ion should be produced with a yield of at least 1.5 ions/100 e.v. absorbed in ethylene. Similar calculations for the probable yields of the other major ions lead to estimates of 0.96 vinyl ions/100 e.v. and 0.94 acetylene ions/100 e.v. Successive dissociations are relatively unimportant in ethylene. 

The fact that only ethylene and tetramethylethylene are evolved from exp-[8]rotane 168 and permethyl-exp-[6]rotane 173 upon thermal decomposition leads to the conclusion that the spirocyclopropane moieties in these expanded [n]rotanes fragment only externally and leave carbene moieties behind. Indeed, the MALDI-TOF mass spectra of several exp-[ ]rotanes show fragment ions with M minus 28. Thus, if this fragmentation in an exp-[n]rotane were to continue n times, a cyclic C carbon cluster would be left over. So far, however, a fragment ion with m/z = 480 corresponding to 182 has not been recorded in the mass spectrum of exp-[8]rotane 168 and it remains to be seen whether a Cgo cluster 183 will be detected in the mass spectrum of exp-[12]rotane 171 (Scheme 35). 

Compound 37a showed the absence of an aldehydic proton and the singlet around 8.15 ppm was assigned to the ethylenic proton located p with respect to the electron-withdrawing cyano and ester groups. The benzofuranyl coumarins 38 exhibited the carbonyl-stretching band around 1690 cm in the IR spectra (Table 6). PMR data for 13 compounds are given in Table 2. The El mass spectrum of 36a showed a molecular ion peak at m/z 324 (41%). 

Dougherty159) reported in 1968 that the peak at m/e = 300 in the mass spectrum of hexahelicene (C26H16) is due to the ion of coronene (C24H12+), formed by an internal Diels-Alder reaction, followed by a fragmentation yielding ethylene. Indeed, traces of coronene were detected on heating hexahelicene at 485 °C for 2 h in an evacuated tube. 

Loss of ethylene and subsequent formation of the stable 3//-pyrrolinine cation dominates the mass spectrum of 2,3,4,5-tetrahydro-l//-l-benzazepine <75OMS(10)992). Biphenylene (m/e 152), acridinium cation (m/e 179) and fluorene cation (m/e 165) are the major fragments in the mass spectra of dibenz[T>,/]azepines (74CJRV101). 

The mass spectra of some cyclopentadienylrhodium olefin complexes have been investigated 80>. The molecular ion in the mass spectrum of the ethylene complex CsHsRh H undergoes fragmentation to the bare metal ion by the following sequence ... 

The ethylene groups are thus lost stepwise much like the carbonyl groups in metal carbonyls. The relative abundance of the molecular ion in the mass spectrum of CsHsRh EU is only about 10% of that of the strongest rhodium ion CsH5Rh+ similar to the relative abundance of the molecular ions in similar metal carbonyl derivatives. 

From the field desorption mass spectra of standard samples, a table for identification of poly(oxyethylene) alkylphenyl ethers and determination of the degree of polymerisation of ethylene oxide was constructed as shown in Table 6.1 n is the number of alkyl carbon atoms and m is the degree of polymerisation of ethylene oxide. When the field desorption mass spectrum having a peak pattern with the difference of 44m/z was obtained such as the peaks at 484, 528, 572, 616 and 660m/z, Table 6.1 would show that those peaks are due to poly(oxyethylene) nonylphenyl ethers with the degree of polymerisation of 6-10 of ethylene oxide. Table 6.2 also shows the identification of poly(oxyethylene) dialkylphenyl ethers and determination of the degree of polymerisation of ethylene oxide based on calculations of the molecular weight. 

An independent determination of the isotope effect could be derived from the mass spectrum of the 3-trimethylsiloxycyclohexene-retro Diels-Alder fragmentation (m/e = 142). 

The intramolecular isotope effect on the loss of a hydrogen atom as manifested in the El mass spectrum of trideuteroethylene has been observed to rise from 1.53 at an electron energy of 20 eV to 3.0 close to threshold [331]. Isotope effects in the El mass spectra of all the deuterated ethylenes have recently been re-examined [865]. The effects were found to be in accord with the predictions of QET and the calculated mass spectra agreed well with the experimental. 

In the 20 eV El mass spectrum of CHD = CHD and CD2CDH, the isotope effects IhJIhd and IHd/Id2 were found to be 1.76 and 1.53, respectively [331]. With the metastable ion decompositions, isotope effects of about 30 were obtained [331, 645]. Isotope effects on loss of molecular hydrogen from all ethylene isomers have been recently... 

Telluriranes were detected as short-lived species, but have not yet been isolated. Flash photolysis of a mixture of dimethyl tellurium and propene produced methyltellurirane that decayed in 0.5 sec and was detected by mass spectrometry. Tellurirane, formed by flash-photolysis of ethylene and dimethyl tellurium, was detected by UV-spectromctry1. An ion corresponding to benzotellurirene was present in the mass spectrum of benzotellurophene2. 

The mass spectrum of diethyl ether appears in Figure 14-5. The four most abundant ions correspond to the molecular ion, loss of an ethyl group, a cleavage, and loss of an ethylene molecule combined with a cleavage. All these modes of cleavage form resonance-stabilized oxonium ions. 

The mass spectrum of butyraldehyde shows the expected ions of masses 72, 57, and 29. The base peak at m/z 44 results from the loss of ethylene via McLafferty rearrangement. 

Treatment of 6.38 with Na-Hg followed by reaction with ethylene gives a product with a molecular ion peak in the mass spectrum at 42. What could be concluded from this ... 

Diaminocarbene, H2N-C-NH2 (26), was prepared by collisional reduction of the corresponding cation-radical that was in turn generated by dissociative ionization of aminoguanidine [102]. Carbene 26 gives an abundant survivor ion in the +NR+ mass spectrum and is clearly distinguished from its more stable isomer formamidine. Amino(hydroxy)carbene, H2N-C-OH, has also been prepared by NRMS [103]. Hydroxy-thiohydroxy-carbene cation-radical, HO-C-SH+ (27+ ), is formed somewhat unexpectedly by ethylene elimination from ionized S-ethylthioformate and O-ethylthioformate instead of the expected thioformic acid. Carbene ion 27+ was characterized by a +NR+ mass spectrum that showed a dominant survivor ion of reionized carbene [104]. The energetics of neutral and ionic HO-C-SH have been addressed by ab initio calculations [105]. Di-(thiohydroxy)carbene, HS-C-SH, is also known [106]. 

Finally, Hinderling and Chen used ESMS to screen the activity of a small library of eight Brookhart-type palladium(II) complexes in the solution-phase polymerization of ethylene [62]. The crude reaction mixture was quenched with DMSO, diluted, and electrosprayed in order to analyze the growing polymers chains. Upon CID in the gas phase, the polymer chain was fragmented from the catalyst by /J-hydride elimination, thus facilitating the identification of the most active catalysts in an otherwise dauntingly complex mass spectrum of a polymer mixture. Since this analysis can be performed simultaneously for a whole catalyst library, ESMS was hereby proven the method of choice for an assay of multiple, competitive and simultaneously occurring catalytic reactions. 

The mass spectrum of pyrrolidine (55) contains the base peak (peak of highest intensity) at mass 43 (Budzikiewicz,11 p. 98). This fragment is formed by cleavage of one C—C bond adjacent to the nitrogen with subsequent elimination of ethylene, (55)->[56]->[57]4Z ... 

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