Dimethylphenanthrene/anthracene

Phenanthrene, fluoranthene, and pyrene—the three abundant parent PAHs identified by GC—were confirmed by MS. The major GC peaks between phenanthrene and fluoranthene were characterized as methyl- and dimethylphenanthrene/anthracene. Four compounds, each having a nominal mass of 192 amu were dejected. Small fragment ions at masses corresponding to (M-l), (M-27)+ and M", were detected. A general feature of these spectra was loss of a methyl group from the parent ion. The spectral features are characteristic of dimethyl or ethylphenanthrene/anthracene. 

The unsigned average deviation between calculated and experimental energies is 0.36 kcal/mol for a collection of 35 benzenoid molecules. This result does not include 7,12-dimethylbenz[a]anthracene (36) the discrepancy of 16 kcal/mol between theory and experiment is in all likelyhood due in part to an error in the latter. Although certainly real, steric interactions involving the methyl group in position 12 are probably not so severe as to cause a destabilization exceeding that found in 1,8-dimethylnaphthalene and 4,5-dimethylphenanthrene—molecules that are discussed further below. 

At British American Tobacco Company (BAT) in 1966, Chakraborty and Thornton (646a) studied the effect of various additives on MSS PAHs. The changes in the per cigarette yields of a variety of PAHs were determined. They included anthracene, B[a]A, benzo[gft/]fluoranthene, benzo[ft]fluo-ranthene, B[a]P, B[c]P, chrysene, fluoranthene, fluorene, methylfluorene, phenanthrene, several alkylphenanthrenes, dimethylphenanthrene, pyrene, and several benzofluorenes.t... 

Fig. 6. GC-MS key ion plots for the alkylphenanthrene/alkylanthracene series in the unheated and pyrolyzed samples 1-7. Sum of m/z 178, 192, 206, 220 and 234 pyrolysis temperatures are indicated 1, phenanthrene 2, anthracene 3, 3-methylphenanthrene 4, 2-methylphenanthrene MA, 2-methyl-anthracene 5, 9-methylphenanthrene 6, 1-methylphenanthrene C2, dimethylphenanthrenes C3, Cs-phenanthrenes C4, C4-phenanthrenes Sg, sulfur.

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