- Email: [email protected]
Long chain conjugated alkadienes; a new component of plant waxes
Phytochemistry, 1971, Vol. 10, pp. 2525 to 2528. Pergamon Press. Printed in England.
SHORT COMMUNICATION
LONG CHAIN CONJUGATED ALKADIENES; A NEW COMPONENT OF PLANT WAXES B. S TOIANOVA -IV A N O V A, K. MLADENOVA and I. M ALOVA Department of Chemistry, The Kliment Ochridski University, Sofia, Bulgaria (Received 16 November 1970)
Abstract-It is shown by TLC, IR- and UV-spectra that a new component of plant waxes, conjugated alkadienes, are contained in wax, obtained from Bulgarian rose flower (Rosa dumuscena Mill.). GLC of the hydrogenated dienes indicates that they are represented in the wax as a mixture of members in the C1 i-C& range, in which C1 9, C 2p, C 27 and C z 1 are prevalent. It is suggested that there exists a biogenetic relationship between parffis, olefins and dienes, since hydrocarbons with the same number of carbon atoms are prevalent in these homologous series in the wax studied.
IN
EARLIER
INTRODUCTION works, it was established that both stearoptene from Bulgarian rose oille3
and the wax of Bulgarian rose flower concrete4-5 contain homologous series of hydrocarbons-saturated and with one double bond, as well as with odd- and even-numbered carbon atoms. These results called for further study of the interesting question about the biogenesis of normal hydrocarbons in plant waxes. To contribute towards the settlement of this question, we carried out a more detailed study on the composition of Bulgarian rose flower wax. From the work done so far, we have found the homologous series of normal acids, 6* ’ of normal primary alcohols8 and of normal ketones. g* l O Some of the experimental data, obtained when studying the hydrocarbon composition of rose flower wax, gave us grounds to believe that hydrocarbons, more unsaturated than the olefins found so far, were present in the wax. In view of this a more detailed investigation of the composition of unsaturated hydrocarbons in the wax was undertaken to establish whether it contains hydrocarbons with two or more double bonds, and to provide data on their structure. RESULTS The hydrocarbon mixture isolated from Bulgarian rose flower wax was separated into saturated and unsaturated hydrocarbons by column chromatography on silica gel impregnated with silver nitrate. After elution of the paraffins, and of tram and cis olefins, another 1 D. IVANOFF, TCH. IVANOFF, B. STOIANOVA -IVANOVA , Coopt. rend. Acud. bulg. Sci. 7, 1, 17 (1954). 2 B. STOIANOVA-IVANOVA, D. DINKOV, Rivistu Ztuliuna E. P. P. 0. S. A. 51, 7, 315 (1969). 3 B. STOIANOVA-IVANOVA, E. IGNATOVA, Rivistu Ztaliunu E. P. P. 0. S. A. 51, 8, 375 (1969). 4 D. IVANOFF, B. STOIANOVA -IVANOVA , TCH. IVANOFF, Compt. rend. Acud. bulg. Sci. 8, 2, 22 (1955). 5 B. STOIANOVA-IVANOVA, D. NIKOLOVA, V. TZVETKOVA, Compt. rend. Acad. bulg. Sci. 18, 2, 141 (1965). 6 B. STOIANOVA-IVANOVA , E. KOLAROVA, Compt. rend. Acad. bulg. Sci. 15, 2, 151 (1962). ‘I B. STOIANOVA-IVANOVA , K. MLADENOVA, Rivistu Ztuliuna E. P. P. 0. S. A. 50, 2, 72 (1968). * B. STOIANOVA-IVANOVA, P. HADIIEVA , Compt. rend. Acad. bulg. Sci. 18, 2, 145 (1965). g B. STOIANOVA -IVANOVA , P. HADIIEVA, K. MLADENOVA , Rivistu Ztaliunu E. P. P. 0. S. A. 49, 12, (1967). lo B. STOIANOVA-IVANOVA, P. HADJIEVA , S. Pomw, Phytochem. 8, 1549 (1969). 2525
B. STOIANOVA -IVANOVA , K. MLADENOVA and I. M ALOVA
2526
group of products was observed. This group remains at the start on silica gel-silver nitrate TLC with light petroleum as the mobile phase, while the cis and tram olefins are mobile under these conditions. The new group, however, on a plain silica gel TLC under the same conditions of chromatography moves along with the front. These data suggest that the isolated group are hydrocarbons, containing a system of conjugated double bonds. The absence of a wide absorption band in the IR-spectrum at 1580-1650 cm-’ is an indication for the lack of a polyene chain, while the absence of absorption at 990 cm-’ and 910 cm-l is an indication for the lack of a methylene group. It follows that the compounds are alkadienes in which the system of conjugated double bonds is not at the end of the chain. Since studies on rose flower wax,l-s as well as on other plant waxes, have shown that both the paraffin and the olefin hydrocarbons are represented as homologous series, we wished to investigate whether the more unsaturated hydrocarbons isolated from rose flower wax were an equivalent series. This we achieved by hydrogenation of the product and subsequent GLC. Unfortunately, the small amount of the product which was originally available proved to have undergone a partial polymerization, which is still another proof for the presence of conjugated double bonds in it. A fresh amount of this product was isolated, following the same procedure, but in a nitrogen atmosphere, and after hydrogenation was subjected to GLC. The results obtained are given in Table 1. TABLE 1. HYDROCARBONS No. of carbon atoms (%)
X1
C11 XZ XJ C 12 X, XS X6 C 13 X7
0.4 1.2 0.2 1.2 3.2 1.1 0.8 o-3 4.5 0.5
DETECTED BY
GLC
No. of carbon atoms (%)
X3
X9 Cl4 XI0 x:: X C 15 X13 X 14 C 16
1.3 1.5 4.5 0.3 0.1 l-3 3.1 trace 0.9 4.6
IN THE HYDROGENATED
No. of carbon atoms (%I X 15 C L7 X16 C18 C 19 C 20 C 21 C 22 C23 C 24
0.8 3.1 trace 1.1 14.2 2.9 6.9 0.7 4.7 1.0
ALKADIENE
FRACTION
No. of carbon atoms (%I
CZ5 C2.5
C27 C2.9 C29 C 30 C 31 X17 C 33
6.0 1.3 8.2 2.3 9.3 1.1 2.8 trace 0.8
XI-XI, unidentified.
These results show that the product isolated is also a mixture of conjugated alkadienes, in which hydrocarbons with odd- and even-numbered carbon atoms in the Cll-C33 range are present. Moreover, the odd-numbered members prevailed in amount considerably the even-numbered in the Cr74& range. The hydrocarbons Crg, CZg, CZ7, CZ1 and C,, (arranged according to decreasing content) are in the largest amount. The unidentified paraffins, which we find almost all below Cl8 are marked X in Table 1. It is suggested that they are formed from diene hydrocarbons with a branched structure, because after hydrogenation and prior to GLC, the mixture was wholly purified from unsaturated hydrocarbons. The IR-spectrum-splitting of the peak at 1380 cm-‘-are also in favour of this assumption. To confirm that the conjugated alkadienes are contained as such in the rose flower and
Long chain conjugated alkadienes; a new component of plant waxes
2527
not formed by means of dehydration of corresponding a&glycols (so far only a,w and a$-glycols at the terminal carbon atom have been found in plant waxes”) under the catalytic action of aluminium oxide, we performed a model experiment. We transformed the unsaturated olefin hydrocarbons into a,/?-glycols by oxidation and subsequent hydrolysis. The glycols were chromatographed on a column of aluminium oxide under similar conditions. The course of the elution was followed by means of TLC. No formation of dienes was observed. DISCUSSION
Conjugated alkadienes have not been found in natural waxes so far. Certain experimental results, obtained from the study of waxes, however, have been interpreted by their authors as an indication for the presence of alkadienes, without specifying whether they are with conjugated double bonds. l2 I3 Our results, therefore, for the first time demonstrate long chain conjugated alkadienes as components of plant waxes. Moreover, just as the other groups of compounds in the waxes they are represented as a homologous series. In addition, by comparing the results concerning the qualitative and quantitative compositions of diene hydrocarbons in rose flower wax with those obtained by us for paraffin and olefin hydrocarbons in the same wax, l4 it is seen that in all three types of hydrocarbons the odd-numbered members, C19, Czl, C2, and C&,, are present in the largest amounts. The fact that in all three types of hydrocarbons among the even-numbered members in the C17-C33 range, the C2,, hydrocarbon is in the largest amount also merits attention. If the data on the qualitative and quantitative compositions of the dienes are compared with those on the composition of the paraffins and olefins in stearoptene from Bulgarian rose oil (obtained by steam distillation), 2*3 it is also seen that the C1, hydrocarbon is represented in the largest amount as paraffin, olefin and diene. These facts give grounds to suggest that there exists a biogenetic relationship between dienes, olefins and paraffins in rose flower wax. EXPERIMENTAL Zsolation of the alkadienes. 6.5 g of wax from rose flower were chromatographed on an aluminium oxide column (activity I-II, according to Brockmann). 3 g of hydrocarbon mixture were isolated after elution with light petroleum. The hydrocarbon mixture gave a single spot at the front by TLC on silica gel G plate with light petroleum as a mobile phase. The separation of the hydrocarbon mixture into saturated and unsaturated hydrocarbons was performed by the procedure described earlier. 3 A column (20 mm dia.) with 30g silica gel impregnated with 15 % AgNO, was used. The eluents were hexane and light petroleum-lO’% peroxide free Et 20. The alkanes passed through hexane. TLC on silica gel G and silica gel G-15 % AgNOJ, they produced only a single spot at the front in light petroleum. The unsaturated hydrocarbons was eluted with the second solvent giving 41 4 ml fractions. The tirst 11 on silica gel G-15 % AgNOa produced two separate spots below the front, which by their R,-value correspond to the cis and tram oletis. 3 IR-spectrum-max. at 1575 cm-t and 966 cm-‘. In fraction 12, along with the spots for the cis and trans oletins, a new spot appeared, which remained at the start on silica gel G-l 5 % AgNO 3. Fractions 13-41 yielded only the latter, and were combined and the solvent removed under N2 giving 11.2 mg. IR-spectrum had a maxima at 1640 cm-‘, 970 cm-‘, 3020 cm-‘, as well as a slight splitting of the peak at 1380 cm-‘. The UV-spectrum in pentane gave a maximum at 221 nm (c 19,500). t1 M. S. DODOVA -ANGELOVA , Cu. P. IVANOV , Compt. rend. Acad. bulg. Sci. 22,9, 1039 (1969). I2 V. WOLLRAB , Collection 33 (5), 1584 (1968). l3 F. SORM, V. WOLLRAB , P. J AROLIMEK and M. STREIBL, Chem. Znd. (Land.), 44, 1833 (19 64). I4 B. STOIANOVA-IVANOVA, K. MLADENOVA, Compt. rend. Acad. bulg. Sci. (In press).
2528
B. STOIANOVA-IVANOVA, K. MLADENOVA and I. MALOVA
Hydrogenation of the diene hydrocarbons. The hydrogenation was with Adams catalyst in glacial HOAC.‘~ The hydrogenated product was purified by column chromatography on silica gel-AgN03 with hexane as eluent. After purification it gavea single spot at the front, on silica gel-AgNOJ plate with light petroleum. GLC of thk hydrogenated product. k Shimadzu GC lc chromatograph, kquipped with a flame ionization detector. was used. The column was 1.1 m long, and the 3 mm i.d. was packed with loo/, SE-30silicon on Chrimaton N (0.14425 mm). The N flow
SHORT COMMUNICATION
LONG CHAIN CONJUGATED ALKADIENES; A NEW COMPONENT OF PLANT WAXES B. S TOIANOVA -IV A N O V A, K. MLADENOVA and I. M ALOVA Department of Chemistry, The Kliment Ochridski University, Sofia, Bulgaria (Received 16 November 1970)
Abstract-It is shown by TLC, IR- and UV-spectra that a new component of plant waxes, conjugated alkadienes, are contained in wax, obtained from Bulgarian rose flower (Rosa dumuscena Mill.). GLC of the hydrogenated dienes indicates that they are represented in the wax as a mixture of members in the C1 i-C& range, in which C1 9, C 2p, C 27 and C z 1 are prevalent. It is suggested that there exists a biogenetic relationship between parffis, olefins and dienes, since hydrocarbons with the same number of carbon atoms are prevalent in these homologous series in the wax studied.
IN
EARLIER
INTRODUCTION works, it was established that both stearoptene from Bulgarian rose oille3
and the wax of Bulgarian rose flower concrete4-5 contain homologous series of hydrocarbons-saturated and with one double bond, as well as with odd- and even-numbered carbon atoms. These results called for further study of the interesting question about the biogenesis of normal hydrocarbons in plant waxes. To contribute towards the settlement of this question, we carried out a more detailed study on the composition of Bulgarian rose flower wax. From the work done so far, we have found the homologous series of normal acids, 6* ’ of normal primary alcohols8 and of normal ketones. g* l O Some of the experimental data, obtained when studying the hydrocarbon composition of rose flower wax, gave us grounds to believe that hydrocarbons, more unsaturated than the olefins found so far, were present in the wax. In view of this a more detailed investigation of the composition of unsaturated hydrocarbons in the wax was undertaken to establish whether it contains hydrocarbons with two or more double bonds, and to provide data on their structure. RESULTS The hydrocarbon mixture isolated from Bulgarian rose flower wax was separated into saturated and unsaturated hydrocarbons by column chromatography on silica gel impregnated with silver nitrate. After elution of the paraffins, and of tram and cis olefins, another 1 D. IVANOFF, TCH. IVANOFF, B. STOIANOVA -IVANOVA , Coopt. rend. Acud. bulg. Sci. 7, 1, 17 (1954). 2 B. STOIANOVA-IVANOVA, D. DINKOV, Rivistu Ztuliuna E. P. P. 0. S. A. 51, 7, 315 (1969). 3 B. STOIANOVA-IVANOVA, E. IGNATOVA, Rivistu Ztaliunu E. P. P. 0. S. A. 51, 8, 375 (1969). 4 D. IVANOFF, B. STOIANOVA -IVANOVA , TCH. IVANOFF, Compt. rend. Acud. bulg. Sci. 8, 2, 22 (1955). 5 B. STOIANOVA-IVANOVA, D. NIKOLOVA, V. TZVETKOVA, Compt. rend. Acad. bulg. Sci. 18, 2, 141 (1965). 6 B. STOIANOVA-IVANOVA , E. KOLAROVA, Compt. rend. Acad. bulg. Sci. 15, 2, 151 (1962). ‘I B. STOIANOVA-IVANOVA , K. MLADENOVA, Rivistu Ztuliuna E. P. P. 0. S. A. 50, 2, 72 (1968). * B. STOIANOVA-IVANOVA, P. HADIIEVA , Compt. rend. Acad. bulg. Sci. 18, 2, 145 (1965). g B. STOIANOVA -IVANOVA , P. HADIIEVA, K. MLADENOVA , Rivistu Ztaliunu E. P. P. 0. S. A. 49, 12, (1967). lo B. STOIANOVA-IVANOVA, P. HADJIEVA , S. Pomw, Phytochem. 8, 1549 (1969). 2525
B. STOIANOVA -IVANOVA , K. MLADENOVA and I. M ALOVA
2526
group of products was observed. This group remains at the start on silica gel-silver nitrate TLC with light petroleum as the mobile phase, while the cis and tram olefins are mobile under these conditions. The new group, however, on a plain silica gel TLC under the same conditions of chromatography moves along with the front. These data suggest that the isolated group are hydrocarbons, containing a system of conjugated double bonds. The absence of a wide absorption band in the IR-spectrum at 1580-1650 cm-’ is an indication for the lack of a polyene chain, while the absence of absorption at 990 cm-’ and 910 cm-l is an indication for the lack of a methylene group. It follows that the compounds are alkadienes in which the system of conjugated double bonds is not at the end of the chain. Since studies on rose flower wax,l-s as well as on other plant waxes, have shown that both the paraffin and the olefin hydrocarbons are represented as homologous series, we wished to investigate whether the more unsaturated hydrocarbons isolated from rose flower wax were an equivalent series. This we achieved by hydrogenation of the product and subsequent GLC. Unfortunately, the small amount of the product which was originally available proved to have undergone a partial polymerization, which is still another proof for the presence of conjugated double bonds in it. A fresh amount of this product was isolated, following the same procedure, but in a nitrogen atmosphere, and after hydrogenation was subjected to GLC. The results obtained are given in Table 1. TABLE 1. HYDROCARBONS No. of carbon atoms (%)
X1
C11 XZ XJ C 12 X, XS X6 C 13 X7
0.4 1.2 0.2 1.2 3.2 1.1 0.8 o-3 4.5 0.5
DETECTED BY
GLC
No. of carbon atoms (%)
X3
X9 Cl4 XI0 x:: X C 15 X13 X 14 C 16
1.3 1.5 4.5 0.3 0.1 l-3 3.1 trace 0.9 4.6
IN THE HYDROGENATED
No. of carbon atoms (%I X 15 C L7 X16 C18 C 19 C 20 C 21 C 22 C23 C 24
0.8 3.1 trace 1.1 14.2 2.9 6.9 0.7 4.7 1.0
ALKADIENE
FRACTION
No. of carbon atoms (%I
CZ5 C2.5
C27 C2.9 C29 C 30 C 31 X17 C 33
6.0 1.3 8.2 2.3 9.3 1.1 2.8 trace 0.8
XI-XI, unidentified.
These results show that the product isolated is also a mixture of conjugated alkadienes, in which hydrocarbons with odd- and even-numbered carbon atoms in the Cll-C33 range are present. Moreover, the odd-numbered members prevailed in amount considerably the even-numbered in the Cr74& range. The hydrocarbons Crg, CZg, CZ7, CZ1 and C,, (arranged according to decreasing content) are in the largest amount. The unidentified paraffins, which we find almost all below Cl8 are marked X in Table 1. It is suggested that they are formed from diene hydrocarbons with a branched structure, because after hydrogenation and prior to GLC, the mixture was wholly purified from unsaturated hydrocarbons. The IR-spectrum-splitting of the peak at 1380 cm-‘-are also in favour of this assumption. To confirm that the conjugated alkadienes are contained as such in the rose flower and
Long chain conjugated alkadienes; a new component of plant waxes
2527
not formed by means of dehydration of corresponding a&glycols (so far only a,w and a$-glycols at the terminal carbon atom have been found in plant waxes”) under the catalytic action of aluminium oxide, we performed a model experiment. We transformed the unsaturated olefin hydrocarbons into a,/?-glycols by oxidation and subsequent hydrolysis. The glycols were chromatographed on a column of aluminium oxide under similar conditions. The course of the elution was followed by means of TLC. No formation of dienes was observed. DISCUSSION
Conjugated alkadienes have not been found in natural waxes so far. Certain experimental results, obtained from the study of waxes, however, have been interpreted by their authors as an indication for the presence of alkadienes, without specifying whether they are with conjugated double bonds. l2 I3 Our results, therefore, for the first time demonstrate long chain conjugated alkadienes as components of plant waxes. Moreover, just as the other groups of compounds in the waxes they are represented as a homologous series. In addition, by comparing the results concerning the qualitative and quantitative compositions of diene hydrocarbons in rose flower wax with those obtained by us for paraffin and olefin hydrocarbons in the same wax, l4 it is seen that in all three types of hydrocarbons the odd-numbered members, C19, Czl, C2, and C&,, are present in the largest amounts. The fact that in all three types of hydrocarbons among the even-numbered members in the C17-C33 range, the C2,, hydrocarbon is in the largest amount also merits attention. If the data on the qualitative and quantitative compositions of the dienes are compared with those on the composition of the paraffins and olefins in stearoptene from Bulgarian rose oil (obtained by steam distillation), 2*3 it is also seen that the C1, hydrocarbon is represented in the largest amount as paraffin, olefin and diene. These facts give grounds to suggest that there exists a biogenetic relationship between dienes, olefins and paraffins in rose flower wax. EXPERIMENTAL Zsolation of the alkadienes. 6.5 g of wax from rose flower were chromatographed on an aluminium oxide column (activity I-II, according to Brockmann). 3 g of hydrocarbon mixture were isolated after elution with light petroleum. The hydrocarbon mixture gave a single spot at the front by TLC on silica gel G plate with light petroleum as a mobile phase. The separation of the hydrocarbon mixture into saturated and unsaturated hydrocarbons was performed by the procedure described earlier. 3 A column (20 mm dia.) with 30g silica gel impregnated with 15 % AgNO, was used. The eluents were hexane and light petroleum-lO’% peroxide free Et 20. The alkanes passed through hexane. TLC on silica gel G and silica gel G-15 % AgNOJ, they produced only a single spot at the front in light petroleum. The unsaturated hydrocarbons was eluted with the second solvent giving 41 4 ml fractions. The tirst 11 on silica gel G-15 % AgNOa produced two separate spots below the front, which by their R,-value correspond to the cis and tram oletis. 3 IR-spectrum-max. at 1575 cm-t and 966 cm-‘. In fraction 12, along with the spots for the cis and trans oletins, a new spot appeared, which remained at the start on silica gel G-l 5 % AgNO 3. Fractions 13-41 yielded only the latter, and were combined and the solvent removed under N2 giving 11.2 mg. IR-spectrum had a maxima at 1640 cm-‘, 970 cm-‘, 3020 cm-‘, as well as a slight splitting of the peak at 1380 cm-‘. The UV-spectrum in pentane gave a maximum at 221 nm (c 19,500). t1 M. S. DODOVA -ANGELOVA , Cu. P. IVANOV , Compt. rend. Acad. bulg. Sci. 22,9, 1039 (1969). I2 V. WOLLRAB , Collection 33 (5), 1584 (1968). l3 F. SORM, V. WOLLRAB , P. J AROLIMEK and M. STREIBL, Chem. Znd. (Land.), 44, 1833 (19 64). I4 B. STOIANOVA-IVANOVA, K. MLADENOVA, Compt. rend. Acad. bulg. Sci. (In press).
2528
B. STOIANOVA-IVANOVA, K. MLADENOVA and I. MALOVA
Hydrogenation of the diene hydrocarbons. The hydrogenation was with Adams catalyst in glacial HOAC.‘~ The hydrogenated product was purified by column chromatography on silica gel-AgN03 with hexane as eluent. After purification it gavea single spot at the front, on silica gel-AgNOJ plate with light petroleum. GLC of thk hydrogenated product. k Shimadzu GC lc chromatograph, kquipped with a flame ionization detector. was used. The column was 1.1 m long, and the 3 mm i.d. was packed with loo/, SE-30silicon on Chrimaton N (0.14425 mm). The N flow