The Presence of Nitrous Oxide and Methyl Nitrite in Cigarette Smoke and Tobacco Pyrolysis Gases'
R. J. Philippe and E. J. Hackney:! Tobacco Science, 1959, 3-33, p. 139-143, ISSN.0082-4523.pdf Research Department, Liggett and Myers Tobacco Company Durham, North Carolina, U.S.A.
Relatively few nitrogenous com lose trap (Keith and Newsome, pyrolyses were t11ansferred to a ga:a1 pounds have been identified in the 1957) at -70° C and two U traps handling apparatus. It consisted gas phase of cigarette smoke. Several at liquid air temperature. The fur essentially of a fractionation and investigators ha\'e indicated the pres nace temperature was controlled by sampling high vacuum train com ence of ammonia. (Barta, 1934; Bar a powerstat. The sample temperature posed of two U traps, a manometer, ta and Toole, 1932; Bogen, 1929; in the pyrolysis chamber was meas an outlet to the infrared sample cell, Bradford et rli ., 1937; Lehmann, ured by an iron-constantan thermo all connected to ,a main manifold 1909; PreiHH, 1936; Savrilov and couple and read directly in degrees leading to a trap-protected high Koperina, 19:n; Wimusch, 1935.) centigrade on a pyrometer. Oxygen vacuum mechanical pump. This ap Hydrocyanic acid has been reported free nitrogen was forced through the paratus was used to submit the con (Lehmann and Gunderman, 1912; train at a constant one liter per min densable gases to a crude fractiona Osborne et al., 1956; Philippe and ute flow-rate. In a typical experi tion based on volatility differences. Hobbs, 1956; Scholler, 1933a; Waser ment, twenty grams of tobacco were The infrared spectra of these frac and Stahli, 1934) as well as thiocy loaded in the pyrolysis chamber and tions were recorded on a Model anie acid. (Scholler. 1938b) Toth maintained at a constant temperature 21 Perkin-Elmer spectrophotometer. (1910) has indicated the presence for three consecutive five hour peri These spectra were used for qualita of cyanogen but hh identification ods. After completion of the third tive analysis of the tobacco py has been criticized. (Kosak, 1955) period, the temperature was raised rolysis gases, and semi-quantitative Nitrogen dioxide has also been re fifty degrees. The same procedure data were obtained from absorption ported. (Haagen-Smit, 1958) We was repeated until the 25 to 900°C band intensities. ha\'e identified two additional nitro temperature range had been covered genom, compounds, namely, nitrous for a particular sample. Results and Discussion oxide and mi>thyl nitrite, in both Essentially the same appartus was ,Vitrous Oxide. Nitrous oxide was cigarette smoki> and tobacco pyroly used for flash pyrolysis experiments. identified in the gas mixture from sis gases. The furnace, however, was placed in tobacco pyrolysis after removal of a vertical position. The pyrolysis carbon dioxide by absorption on Apparatus and Experimental chamber was equipped with a sample ascarite. The infrared spectrum of Procedure dropping device at one end, and with such a gas mixture showed a band at The apparatus and experimental a perforated porcelain disc at the 2220 cm - 1 (4.5 microns) which was, technique used in eonnection with other end. In a typical experiment, prior to carbon dioxide removal, al cigarette smokP gas phase analyses five cigarettes were dropped, one at most completely hidden by the strong were reported previously. (Osborne a time, into the furnace which wa:a 2315 cm - 1 ( 4.3 microns) band of this et al., 1956; Philippe and Hobbs, held at a selected temperature. To compound. Relatively few substances 1!)56.) keep the pressure drop as low as pos absorb in the 2000-2500 cm- 1 (4 to 5 Experiment;; using- slow and flash sible, no alpha cellulose trap waF microns l region of the infrared spec pyrolyses were performed. The ap used. It was replaced in the train by trum and such absorption often indi paratmi used in thP slow pyrolyses three plain gas trnps, at liquid air cates a structure of the general type consisted of a train formed by a temperature, to collect both particu X = Y = Z. Table 1 lists a number \'ycor tube placed horizontally in a late and condensable gas phases. of compounds having this structure hinged type furnace. an alpha cellu- When pyrolysis was complete, tht! along with the frequencies and wave ' From a pa(Jer deli,•er,,l before the Tobacco gas phase was transferred to a r lengths of their chariacteristic 2000- Chrmi.rts Conference at Durliam, .1.V. C., November trap, prior to further manipulations. 1 ( 2.', 195H. 2500 cm - 4-5 microns) range '/>crrased S,pt,mher 2, 1958. The gases collected in both typ11 absorption bands. Nitrous oxide,
(Tobacco Science 139) t N = N = 0, has this type of struc Table 1. Frequencies and Wavelengths of the 2000-2500 cm·1 ture and its spectrum has a strong Characteristic Infrared Bands for Compounds of General Struc P, R type doublet on both sides of 1 ture X=Y=Z 2220 cm- ( 4.5 microns). (Pierson Compound Frequency Wavelength 1956). et al. Name Structure in cm· 1 in microns Further verification of the identity of this compound was obtained from Carbon dioxide O=C=O 2315 4.32 the infrared spectrum of known Carbonyl sulfide O=C=S 2065 4.84 nitrous oxide prepared by decomposi Isocyanic acid 0 =C = NH 2274"" 4.40 tion of ammonium nitrate. The spec Isothiocyanic acid S = C = NH 1963* 5.10 trum, run in a 10 cm gas cell at 10 Ketene 0 = C = CH, 2155·»-:<- 4.63 mm pressure, showed bands only at 2220 and 1330-1250 cm- 1 (4.5 and Nitrous oxide N=N=O 2220 4.51 7.5-8 microns), the first being ---,- roughly twice as intense as the other. Hydrazoic acid N = N = NH 2140·X· 4.67 Many compounds absorb in the •Values from Herzberg and Reid (1950). 1330-1250 cm- 1 (7.5-8 microns) fre •*Values from American Petroleum Inst. Research. Project �Vo. 44. quency range. This low frequency Tobacco Science, 1959, 3-33, p. 139-143, ISSN.0082-4523.pdf band of nitrous oxide was therefore not detected in the spectra of our pyrolysis gases. However, the 2220 Table 2. Semi-quantitative Estimation of Nitrous Oxide in cm- 1 (4.5 microns) band was clearly Tobacco Pyrolysis Gases (Commercial Blend) shown in the gas spectra from to bacco pyrolyzed at 400 and 500° C. Corrected Microliters of N2O Slightly less nitrous oxide was found Pyrolysis absorbancies of at S.T.P. per gram Micrograms of NcO 1 at higher temperatures, namely 600 temperature the 2220 cm· of tobacco per gram of 3 and 700° C. The formation of nitrous oc N2O band x I 0 pyrolyzed tobacco pyrolyzed oxide from the nitrogen used as a 400 4.4 22 44 carrier gas in the pyrolysis experi 500 4.2 21 42 ments is not a likely possibility and 600 2.8 14 28 was ruled out. as nitrous oxide was 700 3.0 15 30 identified in experiments in which helium was used as carrier gas. The quantitative estimation of ° nitrous oxide by infrared band and 700 C. These values were used 2315 cm - 1 ( 4.3 micl'ons) band of car measurements is complicated by a to calculate the nitrous oxide concen- bon dioxide. In the cigarette smoke pressure broadPning effect which has trations and the results of these cal investigations, carbon dioxide was been observed for a number of gases. culations are also given in Table 2. not removed by absorption as it had For such gast's. the absorbancy of a These calculations are at best semi-· to be determined spectrophotometric band g-reatly depends on the total quantitative since the effect of dif.. ally. The presence of carbon dioxide pressurP of thP ga� mixture. (Ang ferent diluent gases in the calibra· and nitrous oxide in separate frac strom, 1892 and 1910; Rubem; and tion mixtures and the actual pyroly tions depended on the fractionation Laden hurry, 1905; Schaefer. 1905; sis gas mixtures was not accounted scheme adopted during a particular Von Bahr, 1909, 1910, 1911 and for; however, this effect is known to analysis. 191:1.) An example of this effect for be much less important than thE the 2200 me ' (4.5 microns) band pressure broadening. of nitrous oxide is given in Figure In previous analyses of cigarette 4.D�o<:ir 1c, , (' 1, in which the infrared band ab smoke which have been reported sorbaneies are plotted versus the (Osborne et al., 1956; Philippe and nitrous oxide partial pressures. The Hobbs, 1956) bands due to nitrous lmver nirve is for nitrous oxide oxide were observed but not identi / alone. The upper curve shows the fied at the time of publication. How 1: 0• "'"'' corresponding absorbancies for the ever, following its identification in same partial pressures of nitrous pyrolysis gases, the original Rpectra j oxide when dry, carbon dioxide-free obtained in the work on cigarette air was used to raise the total pres smoke were re-examined. Nitrous sure to 480 mm. oxide was detected in the smoke of Before an infrared spectrum was several of the cigarette types in / recorded, the total pressure of the vestigated ag shown in Table 3. In ;- pyrolysis gas mixture was adjusted this table, "not detected" is not to 480 mm with dry, carbon dioxide meant to imply that nitrous oxide free air. The pressure broadening was not present in the smoke of I � correction for the nitrous oxide band these tobacco types, but that the was then graphically estimated using fractionation scheme used in the �-� "'"' ....----___...,... the plot given in Figure 1. Table 2 analyses did not allow a definite r,---c shows the corrected values of the ab identification of the nitrous ox o ------'----�---..l..-.� �-- Cl ,u ,:, 1 ,;orbancies of the 2220 cm- (4.5 ide band in the spectra. As noted l'i ,O pre� 5Jr� microns) band of nitrous oxide for above, the major interference with 1 Figure I. Pressure broadening effect on the the gas mixtures obtained at pyroly the 2220 cm- (4.5 microns band of absorbancy of the 2220 cm-1 band of nitrous siR temperatures of 400, 500, 600, nitrous oxide was the very strong oxide.
(Tobacco Science 140) ticular had the sarne characteristic Table 3. Presence of Nitrous Oxide in the Gas Phase of Cigarette shape. Comparison of the absorption Smoke band frequencies with those of methyl nitrite revealed the identity Fraction collection Presence of of the compound giving rise to these Tobacco type temperature in °C Nitrous Oxide bands. Burley -147 detected The infrared band frequencies of 50% Bright-50', Burley -136 detected methyl nitrite indicated by P. Tarte 50 % Bright-50', cased Burley -141 and -125 detected (1952) and the corresponding fre Cased Burley not detected quencies from our pyrolysis gases 1 Bright not detected spectrum, in the 5000-650 cm- (2 Turkish not detected to 15 microns) region are given in Table 4. The bands at 1445 and 1375 cm- 1 ( 6.92 to 7.27 microns) men tioned by Tarte 1·efer to the methyl group deformation vibrations and Table 4. Fundamental Frequencies of Methyl Nitrite are not particularly specific for this 1 ( from 5000 to 650 cm· ) compound. They are accordingly
in Tobacco Science, 1959, 3-33, p. 139-143, ISSN.0082-4523.pdf 1 not well defined our gas mixture Frequency values in cm· spectrum and are not recorded. The Vibration type From our pyrolysis gases other vibration frequencies, namely, From Tarte spectrum the stretching vibrations of the N •� 0 stretching 1681 (5.95 )<< 1665 (6.01) groups N = 0, C - 0 and N - 0, 1625 (6.15) 1620 (6.17) agree very well, not only in their frequency locations, but also in the CH. deformation 1445 (6.92) relative intensities and shapes of 1375 (7.27) the bands as shown in the repro C -- 0 stretching 1045 (9.57) 1045 (9.57) duced spectra. The dotted line in 993 (10.07) 990 (10.10) Figure 2 shows part of Tarte's in frared spectrum of methyl nitrite N -- 0 stretching 844 (11.85) 840 (11.90) .. uperimposed on our spectrum of 814 (12.29) 810 (12.35) the 250° C. tobacco pyrolysis gas phase. A rough estimation of the amount of methyl nitrite present in cigarette smoke was made using Tarte's infra Mrthyl Sitrit1. The second com intensity decreased rapidly in the se red spectrum as a reference standard. 1 pound identified was methyl nitrite. quence burley, cased burley, 50 per The R peak of the 810 cm- ( 12.35 Several strnng bands were observed cent bright-50 per cent burley and 50 microns) hand was chosen, which mainly in the infrared spectrum of ver cent bright-50 per cent cased bur had a calculated absorbency of 0.68 the -ll0 ° C. fraction of burley ciga ley. This band was almost absent for 10 mm pressure. The pressure rette smoke (Philippe and Hobbs, from the spectra of the smoke of broadening effect was 1�xperimentally 1956) but were not identified. One bright and Turkish tobacco ciga .;;hown to be negligible for a molecule band in particular had the char rettes. of the sizP of methyl nitrite. The aderistic P, Q, R structure with the The same strong bands were pres calculated amounts are shown in Q band at 810 cm - 1 (12.35 microns). ent in the spectrum of the 250° C. Table 5 and expres;;ed a;; micro This band was also present in the pyrolysis gases of a commercial to liters and micrograms of methyl ,;pectra of smoke fractions obtained bacco blend. These bands occurred nitrite per cigarette. Burley tobacco from cigarettes madP from other to at the same frequencies and the 810 gave roughly thirty times as much bacco types and blends. However, its cm - 1 (12.35 microns) band in par- methyl nitrite as did bright and
. _, freqency m cm 5000 3000 800 700 0
01
02
<.>� C 0 -e 03 � \.:!,• .0 04 V \' .. 05 '
10 1.5 2 4 6 8 10 12 14 woverength Jn m1cron1 Go, DhOH of 250 ° c. DY•0IYIII
° Figure 2. I c'raced socctrum ,,f the 250 C gas phase slow pyro ysis. Dotted line shows part of pu·e ncet�yl nit6te spectram h,m Tarte.
(Tobacco Science 141) Turkish tolian·os. Casing with 10 per cent dextrose seem8 to reduce Table 5. Semi-quantitative Estimation of Methyl Nitrite in the amount of methyl nitrite pro Cigarette Smoke and Tobacco Pyrolysis Gases duced on smoking. Together with the low nitrate nitrogen content of Total absorbancy Methyl nitrite in smoke bright and Turkish tobaccos, their Number of of the R peak Microliters Micrograms high .�ugar content may account for cigarettes of the 810 at STP per per the low rnncentration of methyl Tobacco type smoked cm- 1 band cigarette cigarette nitrite in the cigarette smoke of these tobaccP types. Burley 99 0.72, 172 4Gis Bright 6 Hi The precurso1·s of nitrous oxide 99 0.02. . Turkish 0.01,. G Hi and methyl nitrite in cigarette smoke 60 Cased Burley 45 G9 188 and tobacco pyrolysis gases cannot 0.13, 50% Bright- be deduced from the information at 45 0.11 58 158 hand. Hov.;eyer, general types of re 50% Burley 0 actions may be proposed for their Methyl nitrite in 250°C origrn. Nitrous oxide has special pyrolysis gases properties among the oxides of nitro Microliters gen. While th(• other oxides are easily Tobacco Science, 1959, 3-33, p. 139-143, ISSN.0082-4523.pdf intPrconwrtible, nitrous oxide. al Weight of at STP per Micrograms though it may be obtained from the tobacco gram of per gram of higher oxides, cannot be directly oxi pyrolyzed tobacco tobacco dized to them. In other words, in grams pyrolyzed pyrolyzed nitrous oxide, once formed, is rela Commercial tinly stable. The reduction of more blend 20 0.72::, 156 424 highly oxidized nitrogen compounds as well as th<· dehydration of sub stances of the general formula nitric oxide, nitrogen dioxide and N O • nH,O. ma;v account for the Acknowledgment 0 methyl nitrite but no methanol. This prPsence of nitrous oxide in ciga The authors wi,;h to thank Dr. M. seems to indicate a quite easy and rettf:' smoke and tobacco pyrolysis E. Hobbs, of Duke University, for complete reaction. gasf:',;. (Ephraim, 1948) Although his permission to use data obtained Several reasons may be found for we were unable to directly identif.v in his laboratories several years ago. the difficulty of direct identification other nitrogen oxides, it is possible They would also like to acknowledge that they ma�· be present in ciga of nitrogen dioxide and nitric oxide the assistance of Mr. Henry Moore rette smoke and tobacco pyrolysis in cigarette smoke and tobacco py 111 part of this work. rolysis gases. Assuming the mech gases. The pre,;ence of nitrogen anism outlined above to be correct. dioxide in cigarette smoke has been Literature Cited rppor1Pd in a l'PCPnt paper. (Ha:1
(Tobacco Science 142} Kosak, A. I., in "The Biologic Effects ( 1956). (1938"). of Tobacco" by E. L. Wynder, Preiss, W., Pharm. Zentralhalle, 77, Spaeth, C. P. (to E. I. du Pont de Little Brown and Co., Boston, 437 and 453 (1936). Nemours and Co.), U.S, 2,831,882, 1955. p. 21. Preiss, W., Z. Untersuch. Lebensen, April 22, 1958. C. A., 5:>.', 15565d Lehmann, K. B.. ,4rch. Hyg., 68, 319 72, 189 and 196 (1936). (1958). (1909). Rubens, H., and Ladenburg, E., Tarte, P., J. Chem. Phys., 20, 1570 Lehmann, K. B., and Gundermann, Verh. d. D. Phys. Ges., 7, 170 ( 1952). K., Ibid., 76, 98 (1912). (1905). Toth J., Chem. Ztg., 34, 298 (1910). Osborne, J. S., Adameck, S., and Savribov, N. J., and Koperina, A. Von Bahr, E., Ann. d. Physik, 29, Hobbs, l\1. E.. Anal. Chem., 28, W., Biochem. Z., 231, 25 ( 1931). 780 (1909); 33, 585 (1910); Phys. 211 (1956). Schaefer, CL, Ann. der Physik., 16, Zeits., 12, 1167 (1911); Vern. d. D. Philippe, R. J., and Hobbs, M. E., 93 (1905). Phys. Ofes., 15, 673, 710 (1913). Ibid., 28, 2002 (1956). Scholler, R., Fachl. Mitt. Osterr. Ta Waser, E., and Stahli, l\L, Z. Unter Pierson, R. H., Fletcher, A. N., and bakregie (1938a) June, pp. 7 to 10. such. Lebensen., 67, 280 (1934). St. Clair Gantz, E., Ibid., 1218 Scholler, R. Ibid., October, pp. 1 to 4 Wenusch, A., Ibid., 70, 201 (1935). Tobacco Science, 1959, 3-33, p. 139-143, ISSN.0082-4523.pdf
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(Tobacco Science 143)