Chemistry

T. K. Mitrofanova, A. A. Kraevskii, G. A. Serebrennikova,
V. N. Klykov, E. N. Zvonkova, G. G. Zapisochnaya, I. K. Sarycheva,
N. A. Preobrazhenskii

Complete Synthesis of the Glyceride Basis of Vegetable Oils and Animal Fats

(Presented by Academician A. N. Nesmeyanov, July 4, 1964)

The basis of vegetable oils and animal fats consists of triglycerides of higher fatty acids with an even number of carbon atoms: saturated acids (stearic, palmitic, myristic, lauric, capric, caprylic, caproic, and others) and unsaturated acids (oleic, linoleic, linolenic, arachidonic, etc.).

We have developed methods for the synthesis of these acids, obtained and studied the physicochemical properties of more than 80 triglyceride components of vegetable oils (linseed, soybean, safflower, corn, cottonseed, sunflower, and others) and animal fats (milk fat and others), and also prepared synthetic mixtures identical in their properties and glyceride composition to natural fats and oils.

Stearic, palmitic, and myristic acids were obtained starting from butadiene via the intermediates cyclododecatriene-1,5,9-cyclododecane and cyclododecanone (I) according to the following scheme:

\[ \begin{gathered} \underset{(I)}{\ce{(CH2)10< \!\!\begin{matrix} C=O \\ CH2 \end{matrix}}} \;\longrightarrow\; \underset{(II)}{\ce{(CH2)10< \!\!\begin{matrix} C(-R)(OH) \\ CH2 \end{matrix}}} \;\longrightarrow\; \underset{(III)}{\ce{(CH2)10< \!\!\begin{matrix} C-R \\ CH \end{matrix}}} \;\longrightarrow \\[4pt] \longrightarrow\; \underset{(IV)}{\ce{R-C(=O)(CH2)10COOH}} \;\longrightarrow\; \underset{(V)}{\ce{R(CH2)11COOH}} \end{gathered} \]

Cyclododecanone (I, m.p. 58.7–59.5°) was condensed with Grignard reagent from alkyl halides. In this process pairs of conformational isomers of tertiary alcohols were formed (II, \(R = C_6H_{13}, C_4H_9, C_2H_5\), overall yield 89.6–91.7%), having different \(R_f\) values in a thin layer of alumina of activity grade II in the ether–petroleum ether system, 1:2. The alcohols (II) were dehydrated to 1-hexylcyclododecene-1 (III, \(R = C_6H_{13}\), yield 83.6%, \(d_4^{20}\) 0.8745, \(n_D^{20}\) 1.4876, \(MR_D\) 81.75. \(C_{18}H_{34}\). Calculated 82.06)

Found, %: C 86.38; H 13.60
Calculated, %: C 86.34; H 13.68

1-butylcyclododecene-1 (III, \(R = C_4H_9\), yield 75.4%, \(d_4^{20}\) 0.8601, \(n_D^{20}\) 1.4833, \(MR_D\) 73.77. \(C_{16}H_{30}\). Calculated 72.82).

Found, %: C 86.44; H 13.61
Calculated, %: C 86.38; H 13.61

and 1-ethylcyclododecene-1 (III, \(R = C_2H_5\), yield 77.6%, \(d_4^{20}\) 0.8712, \(n_D^{20}\) 1.4840, \(MR_D\) 63.81. \(C_{14}H_{26}\). Calculated 63.63).

Found, %: C 86.30; H 13.39
Calculated, %: C 86.52; H 13.48

The cyclic olefins (III) were oxidized to compounds (IV): 12-ketooctadecanoic acid (IV, \(R = C_6H_{13}\), yield 63.3%, m.p. 76–77.2°)

Found, %: C 72.68; H 11.40
\(C_{18}H_{34}O_3\). Calculated, %: C 72.44; H 11.47

12-ketohexadecanoic acid (IV, R = C₄H₉, yield 67.7%, m.p. 67–69°)

Found, %: C 71.06; H 11.19
Calculated, %: C 71.20; H 11.10

and 12-ketotetradecanoic acid (IV, R = C₂H₅, yield 67.4%). The keto acids (IV) were reduced respectively to stearic acid (V, R = C₆H₁₃, yield 51.7%, m.p. 69.1–70.1°), palmitic acid (V, R = C₄H₉, yield 54.3%, m.p. 62–63°), and myristic acid (V, R = C₂H₅, yield 56.9%, m.p. 53.1–54°). Lauric and caproic acids were synthesized by cleavage of cyclododecanol and cyclohexanol, respectively, to dodecanoic and hexanoic acids (¹). Caprylic and capric acids were prepared by us analogously to the scheme described in this work, starting from cyclohexanone. Linoleic, linolenic, and oleic acids were obtained by the Grignard–Wurtz method, and arachidic acid by the Iotsich method (²).

As examples of the synthesis of the glyceride base of vegetable oils and animal fats, this work presents the results of a study of cocoa-bean oil and milk fat.

Cocoa-bean oil contains triglycerides of palmitic, stearic, oleic, and linoleic acids (³). We carried out the synthesis and studied the physicochemical properties of all 40 theoretically possible triglyceride components of this oil. Mixed-acid and single-acid triglycerides were obtained by directed synthesis from the acid chlorides of higher fatty acids and glycerol using benzylidene (scheme I, route A) and isopropylidene (route B) protections. In addition, to obtain triglycerides, the transesterification reaction of esters of glycerol and lower fatty acids with esters of higher fatty acids (route V), as well as direct esterification of glycerol with acids, their methyl esters, and acid chlorides (route G), was used.

For purification of the triglycerides, adsorption chromatography on silicic acid was employed. The purity of the compounds was monitored by paper partition chromatography, thin-layer chromatography, IR and UV spectroscopy, and X-ray structural analysis. The physicochemical characteristics of the cocoa-bean-oil components are given in Table 1.

Routes of triglyceride synthesis
Scheme I

                                  CH2OH
                                    |
                                   CHOH
                                    |
                                  CH2OH
                         A        ↓ Б                         В
                      ↙           |                         ↘
              CH2O              CH2OH                         CH2OCOR
                \                 |                              |
                 CH—CHC6H5       CHO—C(CH3)2                    CHOCOR
                /                 |                              |
              CH2O              CH2O                             CH2OCOR
                |                 |
                ↓                 ↓
              CH2OH             CH2OCOR'
                |                 |
              CHOCOR''          CHOH
                |                 |
              CH2OH             CH2OH
                |              ↙     ↘
                ↓             /       \
          CH2OCOR'      CH2OCOR'     CH2OCOR'
             |             |            |
          CHOH          CHOH         CHOH
             |             |            |
          CH2OCOR'      CH2OCOR'     CH2OCOR''
             |             |            |
             ↓             ↓            ↓
          CH2OCOR'     CH2OCOR'    CH2OCOR'
             |             |            |
          CHOCOR''     CHOCOR''    CHOCOR'''
             |             |            |
          CH2OCOR'     CH2OCOR''   CH2OCOR''
                                                   Г ↘ ↓ ↓
                                                     CH2OCOR'
                                                       |
                                                     CHOCOR'
                                                       |
                                                     CH2OCOR'

Along with the synthesis and study of the properties of individual triglycerides, synthetic glyceride mixtures have been obtained which, in their composition and physicochemical indices, are identical to vegetable oils and animal fats. Table 2 gives the characteristics of natural cocoa-bean oil and of a glyceride mixture prepared by transesterification—

Table 1

Physicochemical constants of the triglyceride components of cocoa-bean oil

* The letters denote acid residues: P—palmitic, S—stearic, Ol—oleic, L—linoleic.
** For identification of the polymorphic forms of triglycerides, X-ray structural analysis was used.

—of glycerol esters and lower fatty acids with mixtures of esters of stearic, palmitic, oleic, and linoleic acids, taken in ratios corresponding to the composition of the natural oil.

In milk fat about 60 acids have been found, of which the major part consists of butyric, caproic, caprylic, capric, lauric, myristic, palmitic, stearic, oleic, linoleic, and linolenic acids (⁴). On the basis of the molar ratios of these acids in the natural fat, we prepared a mixture of synthetic triglycerides:

tributyrin (b.p. 121–125° (0.27 mm), \(d_4^{20}\) 1.0328, \(n_D^{20}\) 1.4359, \(MR_D\) found 76.53. \(\mathrm{C}_{15}\mathrm{H}_{26}\mathrm{O}_6\). Calculated 76.43), tricapronin (b.p. 155–160° (0.25 mm), \(d_4^{20}\) 0.9821, \(n_D^{20}\) 1.4428, \(MR_D\) found 104.29. \(\mathrm{C}_{21}\mathrm{H}_{38}\mathrm{O}_6\). Calculated 104.14), tricaprylin (b.p. 160–165° (0.03 mm), m.p. 8.5–9.5°, \(d_4^{20}\) 0.9568, \(n_D^{20}\) 1.4481, \(MR_D\) found 131.72. \(\mathrm{C}_{27}\mathrm{H}_{50}\mathrm{O}_6\). Calculated

Table 2

131.85), tricaprinin (b.p. 230–235° (0.09 mm), m.p. 30–31°, \(n_D^{40}\) 1.4444), trilaurin (m.p. 48–48.5°), trimyristin (m.p. 56–56.5°), tripalmitin, tristearin, triolein, trilinolein and trilinolenin (m.p. \(-(26–24)^\circ\), \(-(46–44)^\circ\), \(d_4^{20}\) 0.9591, \(n_D^{20}\) 1.4975, \(MR_D\) found 266.0. \(\mathrm{C}_{57}\mathrm{H}_{92}\mathrm{O}_6\) [\(^9\). Iodine value 256.5, calculated 261.6). After transesterification of this mixture, a preparation was obtained with characteristics close to those for milk fat (Table 3).

Table 3

Data from thin-layer chromatography and paper chromatography, as well as IR spectroscopy, indicate that both the process of transesterification of mixtures of monoacid triglycerides and the transesterification of glycerides of lower fatty acids with mixtures of esters of higher fatty acids lead to preparations analogous in their glyceride structure to vegetable oils and animal fats.

Moscow Institute of Fine Chemical Technology
named after M. V. Lomonosov

Received
4 VII 1964

REFERENCES CITED

1. G. G. Zapesochnaya, I. A. Kovtun, I. K. Sarycheva, N. A. Preobrazhenskii, ZhOKh, 33, 2552 (1963).
2. A. A. Kraevskii, Yu. B. Pyatnova, G. I. Myagkova, I. K. Sarychev, N. A. Preobrazhenskii, DAN, 146, 1349 (1962).
3. C. R. Scholfield, H. J. Dutton, J. Am. Oil Chem. Soc., 36, 325 (1959).
4. E. L. Jack, C. P. Freeman, L. M. Smith, J. B. Mickle, J. Dairy Sci., 46, 284 (1963).