Butene mass spectra

Methyl-3-buten-l-ol, NMR spectrum of, 647 Methylcyclohexane, 1,3-diaxial interactions in, 123 conformations of, 123 mass spectrum of, 4H molecular model of, 123, 293... 

IR spectrum of the residue shows the disappearance of absorption peaks at 2150cm-1 and 1650cm- , 900cm-1 and 650cm- which are due to v(N=N=N) of the azido group, v(C=C) and 6(CH2) of 3-methy1-1-butene, respectively. In the mass spectrum, the parent peak due... 

The peaks in the m/z 50-57 range of the 1-butene El spectrum could be misinterpreted as a complex isotopic pattern if no formula were available on the plot (Fig. 3.8). However, there is no element having a comparable isotopic pattern and in addition, all elements exhibiting broad isotopic distributions have much higher mass. Instead, the 1-butene molecular ion undergoes H, H2 and multiple H2 losses. The m/z 57 peak, of course, results from In a similar fashion the peaks at m/z 39 and 41 appear to represent the isotopic distribution of iridium, but this is impossible due to the mass of iridium (cf. Appendix). However, these peaks originate from the formation of an allyl cation, CsHs, m/z 41, which fragments further by loss of H2 to form the CsHs" ion, m/z 39 (Chap. 6.2.4). 

Fig. 3.8. El mass spectrum of 1-butene. Adapted with permission. NIST, 2002.

Z,9Z)-3-Hexyl-5-methylindolizidine (17a) from a Solenopsis sp. exhibits characteristic peaks at miz 208 (M — CH3) and 138 (M - CgHjj, a base peak) as well as a parent peak at m/z 223 in the mass spectrum. The stereochemistry has been determined by synthesis. Racemic (5Z,9Z)-3-hexyl-5-methylindolizidine (17a) was prepared by the above-mentioned methodology, using octene-1-oxide instead of butene-1-oxide (Scheme 47) (134). 

These model studies permitted demonstration of metabolic a-hydroxylation of NPy by isolating 2-hydroxytetrahydrofuran as a metabolite of NPy. This was accoitplished by trapping 4-hydroxy-butyraldehyde as its 2,4-dinitrophenylhydrazone (DNP) derivative. For in vitvo studies, NPy-2,5-l C was incubated with rat liver microsomes, 02i and an NADPH generating system. After the incubation was complete, DNP reagent was added to the mixture and the products were extracted and examined by preparative TLC. A radioactive band corresponding to the DNP of 4-hydroxybutyralde-hyde was observed. This band was not present in controls in which NADPH was omitted or in which boiled enzyme was used. The mass spectrum was identical to that of a reference sairple. In addition, a minor metabolite with mass spectrum identical to that of the DNP of 2-butenal was also isolated. These results showed conclusively that NPy underwent metabolic a-hydroxylation in this in vitro system. 

The mass spectrum of 2-butenal shows a peak at m/z 69 that is 28.9% as intense as the base peak. Propose at least one fragmentation route to account for this peak, and explain why this fragment would be reasonably stable. 

Rees and Yelland have reported a fascinating elimination of CO2 from nonadjacent carbonyl groups that occurs both on electron impact and thermolysis Eq. (56). Cyclopentanone p5nrolysis is substantially complicated by radical chain reactions.ii > Nonetheless the three most abundant p5n olysis products, ethylene, carbon monoxide and 1-butene are all represented in the six most intense fragment ions in the mass spectrum of cyclopentanone. 

Butadiene. 100 ml. of 0.30M CoClj and 100 ml. of 1.54M KCN in an atmosphere of butadiene were employed. Injection of isopropyl iodide was followed by cyanide addition with vigorous stirring. The solution turned red. On completion of gas evolution, a gas sample was taken for analysis. It showed the presence of 19.2% propane, 33.9% propylene, 1.00% 1-butene, 1.81% fmrw-2-butene, 0.14% ci 5-2-butene the remainder was butadiene. The mass spectrum showed no C7 product. 

The mass spectrum of the GC/MS experiment with an empty reactor provided us with the fragmentation pattern of i3C-labelled 1-butene. Subsequently, isomerization experiments were carried out using fresh and spent HS-FER catalysts. The MS spectra corrected for the fragmentation pattern of the butene in question provided us with the label distribution in butenes. In Fig. 4 the results of the label distribution for isobutene, as obtained from isomerization at 350°C over the catalysts, are displayed. The scrambling of 13C over isobutene as observed with the fresh HS-FER after correction for natural abundance of 3C, is close to the values expected from complete (statistical) scrambling. Clearly, with the spent Ferrierite catalyst, which is still active for butene isomerization, scrambling has not taken place either in isobutene, or in the other butenes. Very similar results were obtained using i3C-labelled isobutene instead of 1-butene. 

Alkenes characteristically show a strong molecular ion peak, most probably formed by removal of one tt electron from the double bond. Furthermore, they cleave readily to form resonance-stabilized allylic cations, such as the allyl cation seen at tniz 41 in the mass spectrum of 1-butene (Figure 14.8). 

There are other fragmentation reactions that resemble solution chemistry. For example, an important peak in the mass spectrum of 1-butanol is at m/z = 56. High-resolution analysis of this peak shows that its formula is C4H8. Apparently, the parent ion eliminates water to give a butene radical cation (Fig. 15.13). This behavior is typical for alcohols and has clear roots in the solution chemistry described in our sections on elimination reactions (p. 298). 

Reaction scheme of a ruthenium benzylidene complex showing the formation of a reactive intermediate (compound 2) and final product (compound 3), along with the mass spectrum obtained after isolation of compound 2 and subsequent reaction with 1-butene. Adapted with permission from [12]. Copyright 1998 John Wiley Sons. 

Example The base peak at m/z 88 in the mass spectrum of ethyl hexanoate results from butene loss from the molecular ion, M, m/z 144, via McLafferty rearrangement. This product ion may then undergo ethene loss to yield the fragment ion at m/z 60. The remaining fragments can be rationalized by propyl loss via y-... 

Figure 1.8 Mass spectrum derived from a PTR-MS instrument containing a time-of-flight mass analyser. This spectrum was recorded using a gas mixture containing methanol, acetaldehyde, trans-2-butene, acetone, methacrolein, cyclohexanone and p-pinene. Spectrum (a) shows a survey scan while (b) shows an expanded view of part of the mass spectrum in (a). Data were accumulated for 20 s and the vertical scale expresses the signal as the total number of Ions detected In that 20 s period for a given m/z. The higher mass resolving power of a time-of-flight mass spectrometer compared with a quadrupole mass spectrometer is evident from comparison of this mass spectrum with that in Figure 1.7.

Figure Bl.7.5. (a) MIKE spectrum of the iinimoleciilar decomposition of 1-butene ions (m/z 56). This spectrum was obtained in the second field-free region of a reverse geometry magnetic sector mass...

The mass spectra of oxyphenbutazone is reproduced in Figure 5. According to Locock et al (7) the drug undergoes McLafferty rearrangement to give a radical ion at m/e 268. A metastable ion is present in the spectrum to indicate that this ion is a direct fragmentation from the molecular ion with the loss of the elements of butene (Scheme I). 

Fig. 3. Daughter-ion spectrum of the products from the gas-phase reaction of mass-selected [Cp2Zr(CH3)]+ (m/z=235) and 1-butene...

When 1 -butene was used as reaction partner and thermalization gas in the first octopole, a new signal with the mass corresponding to the propylidene complex 17 appeared in the spectrum, indicating that an olefin metathesis reaction had occurred. This reactivity was confirmed by mass-selecting either 15 or 16 in the first quadrupole and reaction with 1-butene in the collision cell. The... 

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