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KeywordsSpruce lignin Softwood lignin Carbon-carbon bonds in Thioacidolysis Desulphuration Rancy nickcl lignin SummaryThe GC-MS Identification of the main dimcrs rccovcrcd aftcr thioacidolysis, thcn dcsulphuration ovcr Rancy nickcl of sprucc lignin allowcd to charactcrizc the vurious typcs of Condensed linkagcs in softwood lignin. The major carbon-carbon bonds wcrc obscrvcd to bc rcprcscnted by the ß-5, 5-5 and ß-1 intcrunitary linkagcs cstablishcd bctwccn two guaiacyl units, in agrccmcnt with litcraturc data. Bcsidcs, minor linkagc patterns wcre rcprcscnted by dimcrs providcd with the diphcnyl cthcr, the phcnylisochroman and the tctrahydrofuran structurcs. This fingcrprint of Condensed structurcs in softwood iignin was obtaincd from a fcw milligrarns of sample, by mcans of a rcproduciblc and mild routinc proccdurc.

The dissociation dynamics of n-butylbenzene ions have been measured as a function of the parent ion internal energy. Ions were produced by dispersed synchrotron radiation and energy selected by photoelectron photoion coincidence. The branching ratio of the two fragment ions of mass 91 and 92 was measured over an ion internal energy range from 2 to 6.5 eV. This ratio, which varies from 0.05 to 8.0 is a useful thermometer for the n-butylbenzene ion internal energy. The measured dissociation rates for the production of C7H8+ were modeled with RRKM/QET calculations, from which an activation energy of 0.99 eV was derived. The assumption of a tight transition state with AS = -7 cal/K is necessary in order to account for the slow rise in the dissociation rate with ion internal energy. The small kinetic energy released in the dissociation indicates that the rate-determining step is an isomerization reaction, prior to the actual dissociation.