Trimethylsilyl mass spectra

Fig. 3. (Top left) Chemical methods used to depolymerize the polyesters. (Top right) Thin-layer and gas-liquid chromatograms (as trimethylsilyl derivatives) of the monomer mixture obtained from the cutin of peach fruits by LiAlD4 treatment. In the thin-layer chromatogram the five major spots are, from the bottom, C18 tetraol, C16 triol, and C18 triol (unresolved), diols, and primary alcohol. Nx = C16 alcohol N2= C18 alcohol Mj = C16 diol M2 = C18 diol D = C16 triol D2 and D3 = unsaturated and saturated C18 triol, respectively, T4 and T2, unsaturated and saturated C18 tetraol, respectively. (Bottom) Mass spectrum of component D3 in the gas chromatogram. BSA = bis-N,O-trimethylsilyl acetamide...

Similar results have been obtained with the tetra-O-trimethylsilyl derivatives of the anomers of methyl glucopyranoside, methyl galacto-pyranoside, and methyl mannopyranoside. The 17 ev mass spectrum of the tetra-O-trimethylsilylated form of the anomers of methyl glucoside are shown in Figure 7. Again the traces are similar, but intensity differences are discernible. The ratio (377/361 )i7ev has proved most useful. 

Tris[bis(trimethylsilyl)amido]scandium(III) crystallizes from pentane as white, fragile needles, very sensitive to moisture, mp 172-174° (sealed tube). The proton NMR spectrum of a 10% solution in benzene, (TMS as internal standard) gives a single sharp resonance at r 9.66 and the mass spectrum shows a parent molecular ion corresponding to the three-coordinate monomer. Some infrared and electronic absorption spectra are given in Table II. The single-crystal X-ray... 

Tris[bis(trimethylsilyl)amido] vanadium(III) crystallizes from benzene as dark-brown, soft needles, extremely sensitive to air and moisture. This complex is paramagnetic 2.4 BM) but does not show electron paramagnetic resonance absorption at temperatures above that of liquid nitrogen. The compound is thermally unstable but gives a mass spectrum containing the parent molecular ion. Infrared spectra and electronic absorption spectra are given in Table II. The crystalline complex has the same trigonal structure as the Fe compound. ... 

A mass spectrum recorded for tris(trimethylsilyl)-8-azaguanine exemplifies the use of derivatization to increase volatility. ... 

The trimethylsilyl ether of 53 showed a mass spectrum identical to that of the trimethylsilyl ether of the naturally occurring orobanchol. 

Fig. 7, (A) El mass spectrum (70 eV) of the trimethylsilylated methyl ester of 3-Neu5Ac (B) El mass spectrum (70 eV) of the pertrimethylsilylated derivative of 3-Neu5Ac.

A (l->6)-linked disaccharide having a nonreducing 2-acetamido-2-deoxyhexose residue is characterized by a fragment at m/e 552 corresponding to m/e 583 in a per(trimethylsilyl)ated aldohexosyl-(l- 6)-aldohexose. In the mass spectrum of a-D-Glcp-(l—>6)-n-GlcNAc, the... 

Abundant Cis isoprenoid ketone, Z/E pristenal, and Z/E phytenal as well as phytol biomarker compounds were detected in the sinking particulate materials from the Yongshu Reef Lagoon and the continental shelf of the East China Sea (Figs. 5.28 and 5.29). This appears to be the first report of these compounds in China marine environment. Detection of these compounds in the studied regions is of some importance to understand the evolutional processes of acyclic isoprenoid compounds in the seawater column and their formative pathways in marine sediments. Their identifications were based on chromatographic retention time, mass spectrum features (Figs. 5.28 and 5.29), and comparison with those reported previously. The mass spectrum of phytol trimethylsilyl ether exhibits a base peak at mlz 143 and a molecular ion at mjz 368. Cig isoprenoid ketone has a base peak at mjz 58, a molecular... 

The tetrathiadiazepine (60) was obtained by chlorination of lenthionine in tetrachloromethane at 0°C, followed by cyclization with bis(trimethylsilyl)sulfurdiimide to give two products. The first was trithiadiazine (12%) and the second was an orange solid which, on the basis of its mass spectrum, was tentatively assigned structure (60) (20%) <90JCS(Pi)509> this presumably arose from incomplete sulfur-sulfur bond cleavage by chlorine (Scheme 35). 

Structure Analyses of the Product with a GC Rt of 18 min. The major methyl ester product (Rt 18 min) was purified twice by silica gel TLC. The structure was identified through GC-MS and NMR analysis. The electron impact mass spectrum (EI-MS) obtained from the methyl ester/O-trimethylsilyl ether (OTMSi) of the purified product (Fig. 2) gave a molecular ion of m/z 486 [M]+ (0.2). Typical fragment ions were interpreted as follows 396 [M-TMSiOH]+ (2), 381 [M-CH3-TMSiOH]+ (1), 355 [M-CH3CH2CHOTMSi]+ (2), 289 [M-CH2CH=CH (CH2)7C00CH3]+ (10), 265 [355-TMSiOH]+ (8), 199 [289-... 

Figure 6. Mass spectrum of penta-O-trimethylsilyl-o-glucopyranose, 34. 

Once again, furanosides can be distinguished from pyranosides. The peak at m/e 204 in the mass spectrum of ethyl /3-n-galactofuranoside tetra-O-trimethylsilyl ether 36 is drastically reduced in relative intensity compared to the mass spectra of 34 and 35 (Scheme 36). In addition. 

Figure 7. Mass spectrum of methyl 2,3,4,6-tetra-O-trimethylsilyl-a-D-glucopyranoside, 35. 

The structure of a 1 —> 4,1 —> 6 linked trisaccharide has been elucidated from the mass spectrum of its trimethylsilyl derivative (70). In addition to the peaks resulting from the independent fragmentation of each unit, the sequential arrangement of the monosaccharides can also be deter-... 

The mass spectrum of the corresponding trimethyl-silyl ether derivative is shown in Figure lb, and an important advantage of this derivatization is immediately apparent in the prominent [M —CH3] ion at m/z 173. This ion allows the estimation of the molecular weight of the derivative in cases where a molecular ion is absent. In addition, because the fragmentation pattern is characteristic of the molecule, it may be used as a mass spectral fingerprint to confirm the identity of the GC peak, and libraries of reference spectra are readily available. Trimethylsilylation is one of the most common derivatizations in GC-MS. Further details and examples are given later in the section on silylation. 

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