Structural and stereochemical factors in the mass spectrometry of mono‐ and dimethylbicyclo[3.3.1]nonanes

Abstract

The mass spectra of mono-and dimethylbicyclo[3,3,l]nonanes have been studied. In addition to the fragmentation of the bicyclic form of the molecular ion, the latter appears to dissociate from its monocyclic form. Structural isomers and stereoisomers with essential differences in thennodynamic stability may be identified by the quantitative differences in their mass spectra. Stereoisomers with a 'boat' conformation of one of the cyclohexane rings have been showu to differ from the stereoisomers with a 'chair' conformation of both rings by virtue of higher intensity of odd-electron ions for the former.Continuing our studies of the application of mass spectrometry to structural and stereochemical problems in the chemistry of saturated cyclic hydrocarbons,' we have investigated the mass spectra of monoand dimethylbicyclo[3.3. llnonanes. The stereochemistry and equilibrium correlations of these hydrocarbons have been studied p r e v i o~s l y .~~~ 1: R, = R, = R, = R,= R, = R 6 = H 2: R,= CH,; R, = R, = R, = R, = R 6 = H 3: R, = CH,; R, = R, = R, = R , = R , = H 4 R, = CH,; R, = R, = R, = Rs = R,=H 5: R, = CH,; R, = R, = R, = R, = R,= H 6: R, = R, = CH,; R, = R, = R,= R,=H 7: R, = R, = CH,; R, = R, = R, = R, = H 9 ' i.;.; R, 3

Structural Identification of Petroleum Acids by Conversion to Hydrocarbons and Multidimensional Gas Chromatography-Mass Spectrometry

“…Three peaks, eluting the latest of the C 10 hydrocarbons had mass spectra comparable with those of four methylbicyclo[3.3.1]­nonane isomers (Chart , XI and XII) reported by Golovkina et al (Figure and Figure S-6 in the Supporting Information). This corresponds with previous observations of bicyclo[3.3.1]­nonane-1- and 3-carboxylic acids identified previously in commercial NA as the methyl esters .…”

“…Examples of mass spectral identification of bicyclic hydrocarbons from the reduced acid methyl esters by comparison with literature mass spectra including (A and B) bicyclo[4.4.0]­decanes, (C and D) bicyclo[4.3.0]­nonanes, (E and F) bicyclo[3.3.1]­nonanes, (G and H) bicyclo[2.2.2]­octanes, (I and J) bicyclo[3.3.0]­octanes, and (K and L) bicyclo[3.2.1]­octanes. Reference mass spectra plotted from tabulated values previously reported. ,,− …”

Understanding the Mechanisms of Decalin Hydroprocessing Using Comprehensive Two-Dimensional Chromatography

“…Therefore, literature references were used in order to collect 79 additional spectra, which were added to the MS database. This allowed us to tentatively identify the following decalin derivatives (the corresponding chemical groups are presented in Figure with their abbreviated name): methylbicyclo­[4.3.0]­nonanes, 17 isomers (Figure -I) dimethylbicyclo­[3.3.0]­octanes, 12 isomers (Figure -II) methylbicyclo­[3.3.1]­nonanes, 6 isomers (Figure -III) ,, dimethylbicyclo­[3.2.1]­octanes, 25 isomers (Figure -IV) trimethylbicyclo­[2.2.1]­heptanes, 5 isomers (Figure -V) , dimethylbicyclo­[2.2.2]­octanes, 14 isomers (Figure -VI) …”

“…Computer Language for Identifying Chemicals (CLIC) expressions were used for identification of compound families, and the NIST MS database (version 2.0) was used for the identification of 25 C10 molecules. The database was complemented with 148 mass spectra reported in the literature (see discussion below). − …”