Tobacco Documents Online

~ 'i""!~,. '. Toba,cco. Pyrolysis Chemistry Stud~e:s.. Review papers 01 ~he thermal d,egra,datio:n of carbohyd~rates, particularly, the simple sugars (Fagerson, 1969),. and on the pyrolytic olrigins of smoke constitu.en.ts (Da'w.son, 1970; Chortyk, 1973;~Green" 1!97.7; Brunnemann, 1982)i emphasize the complexity of char.ac- terizing thee intermed!~ate reactions an~d elu,cidating the. mecha- nisms leadin,gl to the ~ormatioln of the many compounds found ~n

smoke. Th,ese: a~thors sugg!est the difficulty of equating pyrolys!is studies! of pu!re compounds with studies of .cigarette smoke formation and its composition, particularly in regard to th,e relative amounts of the products formed. Sugars are noln~olatile and therefore a~re subject to. pyrolytic degradation during the ~smoking process. Only trace: lev.els of suglars have been found in. the mainstream' smoke. For example, in one, reported study, glu,cose, arabinose and xylo.se were foundi in the smoke: of four lots of unblended cigarettes made from tobacco type:s: inclu~ding American, an~di Japanese flue-cured toba~cco, Japanese s~n-cured, tobacco~, an~d' b~rley tobacco cultured in J~apan. Fru~ctose was found in. smoke from. thee American and Japanese flue-cured cigarettes. To~tal red~cin,gl suqars in. the smoke of American a~nd J~apanese flue- cured cigarettes were 562 a,nd 77.5 microgr.am:s per cig!a,rette, resp,ecti~ely (Koba,sh~i,. 1959:). ~ In tracer studfes using radioactive: glucose o~r ~& sucrose a,dded to: the burley portion of 'experimental cig,a- ~.~ reties, small amounts of thes.e sug.ars, in the ran,ge, o.f ~ 0.4~-0'.8%, h~ave been foundi to transfer to the smoke unchange,dl ~i (Gager, 19711)i. Carbo~n, dioxidie was the major pyroilysis product of the radiolabeled su~gars! in the smoke. Su~glars contrib~tedi to the levels o!f 5-(hydirolxymeth.yl)-2--fura]]dehyde and 5-methyl-2- furalde~hyde in th,e neutral fra,ction of the sm,o~e, and th,~rteen compounds were idlen.tified in the gas-pha.sle mainstream, smo~e which comprised less than 0,.5% of th,e to~tal radioactivity.

Acetone and acetaldehyde were among the produ.cts formed in h,igh~est rad~och,emical yields, but these c~ompounds a~e_ formed! n,aturally in larger amounts during the pyro~lysis of pure toba.cco. The relative con,tributions to the smoke from, the added sugars were grea,test for the furans. Glu~cose and sucros:e were found to contribute to the: n~on~ola,tile basic, acidic,, and phenolic~ fractions a,s well as the neutral fractioln, (Gager, 1971; Da'wson, 1970)~. ~In an extensive study of the water-soluble portions of cigarette smoke, twenty n,ew compoundls classified as sugar anhydrides or sugar dianhydrides were is~olate.d (Schumacher, ~977). Su,gars were not identifiedi as th,e direct precur.sors of these anhyd~rides, although th,e dehydrated! sugars have: been considered by some, investigato~rs as ~ntermedia~tes in carbohy-- dirate pyrolysis inclu,diing pyrolysis of cellulose. Cigarette:s made f!rom burley tobacco contain,ingl differen:t levels of! added fructo:se and glu~cose (101.5.-17.81%')i were smoked a~nd compared to control cigarettes without added su~gars. There was virtually no chanig,e in the d.eliv.eries of aldehydes and carbonyl constituents (Thornton,. i~975!),. Phill- ~ that total aldehyd,e yield in ~! ports (1975) found similarly tobacco, smoke is. not related to either sugar content or the G~I equilibrium mo{s.ture content of th,e tobaccos. The delivery of furfu~ral wa,s increased,, especially when fructose was the added s~gar (Thornton, 1975.).: The a:ddition of gluco.se and fructose. reducedl the delivery o~f nicotin.e: by apparentIy .in,creasing the • "filtration efficiency in the tobacco rod (.Tho~rnton~, 19175).

Studies by Kaburaki a:nd co-workers (K.aburaki, 19~69) with smoke from cigarettes with added: cellulose and with smoke fr.om: cigarettes with varying~ levels of sug:a~rs indiicated that simple smoke carb,onyls in the vapor ph,ase w, ere glenerated from, the skeletal substances in the tobacco leaf. Addition of glu.cose, fru, ctose or su,crose to cigarette:s resulted in a~, increase of 2-methyl~.fura,n and 2,5-d;~methyl.furan in the vapor phase smoke fraction,. Non-Tobacco Pyrolysis Chemi.stry Studies. Pyrolysis of sucrose at atmosph,eric pressu~res gave 7.8% yield of vo]~atile chloroform sloluble products!. Th,e major pr.o,duct in th,e hig~her boil.~ng fraction was 5-(,hydroxy~methyl)-2-fu!raldehyde and furfural was the major component of th,e iowe~r boiling fraction. Fifteen. compounds were isolated and id~entified in~cluding m- and p-cresols (Johnson,. Ii969). Thee mech,anism for formation of twelve of the c:ompounds of su.crose pyrolysis were correlated to pro:dUcts formed from glucose by reactions occurring in strongly reducing aqu,eous acid systems.. Tw,enty semi-volatile pyrolysis produ.cts of dextri'n and suc~rose h,ave been identified,. Th,e relative amounts of these pyrolysis products have been: compared to cellulose and toba,cco l~gnin, pyrolysis products. Th,ere are some qu.alitative O a,nd quantitative: similarities in the products from dextrin, ~' sucrose and cellulose:. The lignin produced few' of the same ~i compounds formed~' by the thermal degradation, of the carbohy- . ~ drates (Schlotzhauer, 19815.) ....

- 20 - aromatic h'ydrocarbonsl, fu!rfurals a~nd ph,enols (~Higman, 1.970). ~evels: of benzo[a]pyrene prod,ced on. pyrolysis o~ glu.c:o~se, f:ruct:o:se and ce1.1ulos:e: were 47...5, 98.5. and 288.8: ug/g of / compound pyrolyzed respectiv,ely.