Thermal Decomposition of Kitol
SEIICHI ISHIKAWA, YOSHIMORI 0MOTE,JY!ASAO KIJIMA, HIROSHI OKUDA

In 1943 Embree and Shantz1> isolated a new substance related to vitamin A
from whale liver oil and called it kitol. Their kitol was glassy yellow solid, having molecular formula of C40H5s(OH) 2 , two hydroxyl radicals and eight double
bonds.
By color reaction, absorption spectrum, analytical distillation and biologicalassay, they confirmed that kitol produced vitamin A by pyrolysis in molecular dis- ·tillation.and moreover carried on the quantitative experiment to report that 1 moleof kitol produced l mole of vitamin A. It was also ascertained by them that kitol
ester was decomposed thermally and produced corresponding vitamin A ester. 2 >After that, Baxter and others3 > isolated kitol in crystalline form, with use ofwhich they carried on the pyrolysis experiment, with a yield of less 1 mole ofvitamin A from 1 mole of kitol.
The chemical structure of kitol is still unknown. Formation of vitamin A bythermal decomposition is an important key to infer the kitol structure, so that theauthors determined to carry out the further detailed study in this respect. It must
be added that this respect is very significant for the practical method of changing
kitol of whale liver oil to valuable vitamin
A with a goo::! yield.

Isolation of Kitol from Whale
Lvier Oil.

§600~"' 500With hydrated methanol vitamin Aand cholesterol were extracted and removed 'll-~

8 400

from unsaponifiable matter dissolved in .§petroleum ether. Then petroleum ether .~JI 300solution was chromatographed to concentrate kitol. This kitol, still containinga small quantity of solvent was heated invacuo at 150° for 5 minutes to eliminate

200100the volatile fraction completely. The
absorption spectrum of kitol thus obtained
is shown in Fig. 1. As seen clearly in
it, there is a maximum peculiar to kitol at260

280

300

320
Wave length

Fig. l.

340%0(mµ.J.

Absorption spectrum of kitol.

S. ISHIKAWA, Y. 0MOTE, M. KIJIMA, If. .. OKUDA

62

290 mµ, the extinction coefficient E (!%, 1 cm) being 670, much higher than E(1%, lcm, 286mµ)==58'.> obtained by Embree, being 95%ofBa.xter'sE (lJi, lcm,290 mµ) = 707. As such an extent of purity was considered not to hinder thefollowing experiments, this kitol was used.

Change of Kitol During Molecular Distillation.
Baxter and othersO confirmed that 1 mole of kitol palmitate produced 0.65 moleor 0.75 mole of vitamin A palmitate by molecular distillation at 240° to 270°
under the vacuum of 3µ. Previously the authors2l observed that kitol was partly
decomposed to produce vitamin A in the analytical distillation of unsaponifiable matter
in whale liver oil. This tim!O, however, the authors tried to distil kitol itself
molecularly under high vacuum.
On the contrary to expectation the result was that most part of kitol was
distilled by 5 minutes' heating at 220° without decomposition; but left not distilled by 1 minute's heating at 200° or 10 minutes' heating at 160°. (Figs. 2,3 and 4)/::r600)00)00

§

400

400

~

"' 300~ 300

l"'

j200

200

100 ...

LOUl

1100

280

300

320
mp.

340)60260

I280320

HOFig. 2. Absorption spectra of molecular distillation products of kitol.
(A) 220°, 5 min. (B) 160°, 10 min. (1) kitol, (2) distillate, (3) residue, (4) total

As clearly shown in these figures, it is danger to calculate the decomposition ratio of kitol to vitamin A on the basis of the result of the experiments,
because the absorption spectrum does not change so much as it shows the clear
form3.tio:i of vitamin A. It would be noteworthy to clarify that free kitol was

Thermal Decomposition of Kitol

G3300

340
mp.

100320340}60mp.

360

Fig. 4. Absorption spectra of moleculardistillation products of kitol dissolved in
the oil, 220°, 5 min., (1) kitol, (2)distillate, (3) residue, (4) total.

Fig. 3. Absorption spectra of moleculardistillation products of kitol, 200°; 1~in, .(I) kitol, (2) distillate, (3) residue,(4) total.
·hardly decomposed and distilled out through molecular distillation under high vacuum
and that this was true even if oil was added a:s solvent.

Change of Kitol Heated in Sealed Tube.
After kitol dissolved in the corn oil was heated at 220° in the slender glass
tube for 1 to 16 minutes, Embree and othersll determine the produced vitamin A
by blue absorption value· E (620 m,u) with antimony trichloride and remainin~
kitol by E (286 mµ) with vitamin A correction, on the basis of which decomposition
ratio was calculated.
For the purpose of confirmation of vitamin A formation from kitol, kitol oil
sealed in the glass tube with c;i.rbon dioxide was heated at 220° , with whichabsarption spectrum at 300 to 350 mµ was persued. The curves obtained showeddearly formation of vitamin A (Fig. 5).
The result calculated by the application of the principle of AK method which
was explained in the reliminary report1 l was that in case of 8 minutes' heating 1
mole of kitol produced 1.67 mole of vitamin A.
Through the more careful experiment under the same condition change of absorption spectrum between 260 and 350 m,u was studied. The result was shown

S. ISHIKAWA, Y. 0MOTF, M. KIJIMA, H. OKUDA64310

330

350

Inµ.

Fig. 5. Absorption spectra ofdecomposed kitol heated in theCO:a sealed tube, at 220°, (1)O min., (2) l min., (3) 2min.,(4) 8 min.

Fig. 6. Absorption spectra of decomposed
kitol heated in the 002 sealed tube, at220°, (1) 0 min., (2) I min., (2) I min.,(3) 8 min.

in Fig. 6. The yield from 1 mole of kitol was 1.38 mole of vitamin A.
However, the experiment of heating for 1 minute showed that the potency ofkitol rather increased. This problem will be discussed in the future report, forthere is a· necessity for further study.

Change of Kitol Heated in Vacuum Sealed Tube.
In order to improve the yield of vitamin A, the authors ·carried on a pyrolysis
experiment about kitol under high vacuum (Fig. 7). After a thermal decompositionof kitol oil sealed under reduced pressure of 10- 4 mm, the conclusion that 1 moleof kitol produced 1.97 mole of vitamin A was derived as expected. Also in thiscase the experiment of 1 minute's ,heating showed that vitamin A formation ratio
was negative. This fact suggests us that kitol is likely to be decomposed thermallythrough the complicated process.

Properties of Vitamin A Formed from Kitol Decomposed by Heat.
It is still questionable whether or not vitamin A formed from kitol decomposedby heat is vitamin A in a strict sense. Perhaps it is possible that anhydro vitamin

Thermal Decomposition of Kitol

65

A may be formed, too. In the present
rePort, however, substances showing absorption spectrum similar to vitamin A
which were formed from kitol decomposed, were all represented by vitamin A.
-The comparative color reaction between
kitol oil and its thermally decomPosed oil
is shown in Table I.
This table shows clearly that the color
reaction of thermally decomposed kitol
oil quite agrees with that of vitamin A.
Similarly to the preliminary report, thepercentage of cis and trans vitamin A wasdetermined, 21.2% for the former and the260
280
300
320
>40mp.
Fig. 7. Absorption spectra of decomposed rest for the latter. It is interesting for thekitol heated in the vacuum sealed tube, at presumption of kitol structure that most
220°, in 10-4 mm, (1) 0 ruin, (2) l min.,of vitamin A produced from kitol is found(3) 8 min.
to be trans type.
Table I
Color Reactions of Kitol before and after Thermal Decomposition
Kitol oil

After thermal decomposition

Antimony trichloride

vivid red

blue (rather stable)

Trichloro-acetic acidred with more kitol oil,colorless with less kitol.

azure blue

Acetic anhydride and cone.
sulfuric acidred~reddish brownblue~purple-Jdark

Reagent

green

Experimental Part

Experiment I. Isolation of Kitol from Whale Liver Oil.
1 kg. of Antarctic whale live,r oil was saponified. After ether extraction about
200 g. of unsaponifiable matter was obtained, dissolved in 2 L of petrolem ether,
extracted with about 90% methanol, until the petroleum ether layer hardly gave
blue color like vitamin A with antimony trichloride reagent. The petroleum ether
solution washed with methanolic potash, then with water, was dried on sodium
sulfate. This petroleum solution was passed through the chromatographic column( 40 x 4 cm) containing alumina. Then it was developed with petroleum ether saturated

S. ISHIKAWA, Y. 0M01'E, :M. KIJIMA, H. OKUDA

66

with methanol, when narrow orange band appeared at the bottom. This seemed tobe anhydro vitamin A. When this layer eluted, alumina was nearly colorlessand showed vivid red color peculiar to kitol with antimony trichloride reagent.
The adsorbent was taken out and eluted with lL of petroleum ether and 50 cc. of
methanol. This petroleum ether solution was washed with water and dried, chromatographed again. After extracting the adsorbent, thepetroleum ether solution was evaporated to concentrate kitol asresidue. It was heated in the micro molecular still shown in
Fig. 8, at 150°, under 10- 4 mm for 5 minutes. The residue wasFig. 8.
:Micromolecularstill.

glassy solid of orange color, showing vivid red with chloroform
solution of antimony trichloride (30%), same but lighter color
with 20% chloroform solution of trichloro-acetic acid andsimilarly red and soon reddish brown with acetic anhydrideand cone. sulfuric acid. The absorption spectrum of finallyobtained kitol was shown in Fig. 1.

Experiment 2. Molecular Distillation of Kitol (I).
(1) Kitol obtained in the experiment 1 was ·heated at 220°, for 5 minutes
under vacuum of 10-'1 mm in the apparatus shwon in Fig. 8 connected w.ith Hickman'soil diffusion pump. After. reaction, evaporating surface was separated from condenser both being washed with. isopropanol, the washing accurately diluted to acertain volume and' the extinction. was measured by Beckman ..spectrophotometer.
Extinction· coefficient was obtained by extinction divided by gram of sample per
lOOcc. Thus obtained extinction coefficient was figured in Fig. 2.
(2) The result of experiment with 10 minutes' heating at 160° was also
shown in Fig. 2. The sum of extinction coefficient of the distillate and the residue
is far smaller than that of the sample (control). This being likely to be effectedby weighing and diluting errors, the same experiment was carried on with somesolvent in order to reduce errors.

Experiment 3. Molecular Distillation of Kitol (2).
(1) Evaporating benzine from the petroleum solution of kitol in vacuo, the residue gave viscous oil. Similar experiment to Exp. 1 was made with this oil.
(Fig. 3).
(2) Molecular distillation of kitol oil.
Kitol and cod liver ·oil were distilled in order to make an experiment under
the same condition as molecular distillation of natural liver oil. The cod liver oil

Thermal Decomposition of Kitol

67

was the residue after 5 minutes' distillation at 150° under 10-4 mm in the apparatus shown in Fig. 7 with use of cod liver oil which had lost the. vitamin A
reaction through the preliminary heating at 200° and stirring mixed with Japaneseacid clay. The kitol oil was prepared from 6::> mg. of kitol obtained in the experiment 1 and 1.1 g. of the above refined cod liver oil fully mixed. This kitol oil
was used in the following experiments. Moreover, since the absorption spectrumof oil itself was affected by heat, the same cod liver oil whicq did not contain kitol
was distilled under the same condition as above. (blank test). The reimlts areshown in Fig. 4. Heating condition was: at 220° for 5 minutes under 10- 4 mm.

Experiment 4.

Thermal ·Decomposition of Kitol in Carbon
Dioxide Sealed Tube (1).

Kitol oil was weighed in a small test tube and the air in it was displaced by·carbon dioxide. Instantly. after, it was sealed and heated. When reaction wasfinished, sealed tube was cut off, the content dissolved in isopropanol to measure
its extinction. The result was shown in Fig. 5. It was heated at 220° for 1, 2and 8 minutes.
Now, in order to find the amount of vitamin A and kitol from this result withAK method, for convenience's sake, extinction coefficients at 330 mµ and 310 mµwere analyzed. As spectrum of pure vitamin A were used the same date as in thepreliminary report, while that of kitol was based on the spectrum obtained in Exp.
1 in the present report. Hence, the following equations are obtained.
A(330)= l.439 E (330)-0.5175 E(3l0)K(310) = 1.439 E(310)-1.218 E(330)A(328) =1.018 A(330), K (290) = 1.362 K(310)The equation to calculate decomposition ratio of kitol based on A (328) andK(290), was mentioned in the preliminary rep::>rt. 5 1 The result was as follows.
i min.

0 min.

Beated for-A (328)0.265

II·0~~1-K (290)

Ii

5.05

Mole of vitamin A
per I mole of kitol

9.40
-0.09

I

2 min.

8 min.

5.79

7.225

----______,.

6.18-4.21

1.77

I

1.67

IExperiment 5. Thermal Decomposition of Kitol in Carbon
Dioxide Sealed Tube (2).
Almost similarly to Exp. 4, carbo::l dioxide displacement was rrtade with special.care and the range of the absorption spectrum was 260 to 350 m,u (Fig. 7). :68

S. ISHIKAWA, Y. 0MOTE, M. KIJIMA, H. OKUDA

AK equation was as follows:A(328)=1.018x{l.115 E(330)-0.2942 E(290)}
K(290)=1.115 E(290)-0.4350 E(330)
The result of calculation was:Heated for0 min.

I min.

8 min.

A (328)-0.248-0.238

7.17

K (290)

10.87

14.25

6.64-0.02

1.38

mole of vitamin A
per 1 mole of kitol

Experiment 6. Thermal Decomposition of Kitol in Vacuum Sealed Tube.
Similar to Exp. 5, excepting that sample was sealed under vacuum of I0- 4mm.
The result of calculation was as follows.
Heated forO min.

I min.

8 min.

A (328)-0.248-0.0825

7.225

K (290)

10.87

11.24

7.89

-0.3611.97

mole of vitamin A
per 1 mole of·kitol

Experiment 7. Reaction Velocity of Maleic Anhydride withVitamin A Produced.
In the same method as the preliminary reports> maleic anhydride reagent reactedwith vitamin A obtained by 8 minutes' heating of kitol oil in carbon dioxide. After
16 hours at 25°, the recovery was 20%. Since it is known that recovery ofvitamin 'A and neovitamin A under the same condition is respectively 3% and 83%,
the percentage of neovitamin A in the sample is calculated as follows.
% of neovitamin A=~~=~ x100=21.2%
Namely, the vitamin A obtained by the decomposition of kitol was found to consist -of 21.2% of cis- type and 78.8% of trans type.
Summary(1) Kitol was distilled nearly without decomposition, through molecular distillation under I0-4 mm.

Thermal Decomposition of Kitol

69(2) When kitol was heated at 220° for 8 minutes, sealed in carbon dioxide
or vacuum, the absorption spectrum changed to show the formation of vitamin A.
Analysis of the spectrum ascertained that 1 mole of kitol decomposed to produce 1.4
to 2.0 mole of vitamin A.
(3) Vitamin A obtained by thermal decomposition of kitol consisted of 80%
of trans type and 20% of cis type.
In conclusion, the authors express their cordial thanks to Mr. T .. Yamakawa
and Mr. Hirao for accordance of facilities for measurement of absorption spectrum
and Mr. T. Tawara for his assistance of obtaining the material and kitol extraction.
References
1) N. D. Embree, E. M. Shantz, J. Am. Chem. Soc., 65, 910 (1943).
2) N. D. Embree, E. l.VI. Shantz, Brit. P. 568, 607 (1945), U.S.P. 2, 414, 457 (1947).
3) F. B. Clough, H. M. Kascher, C. D. Robeson, J. G. Baxter, Science, 105, 436 (1947).
4) S. Ishikawa, Y. Omote, Y. Soma, Sci. Rep. Whales Research Institute, No. 2, 35 (1948).
5) S. Ishikawa, Y. Omote, H. Okuda, Sci. Rep. Whales Research Institute, No. 5,53 (1951).
(1) C. D. Robeson, J. G. Baxter, J. Am. Chem. Soc., 69, 136 (1947).