PROCEEDINGS
OF THE TOMSK POLYTECHNIC INSTITUTE
NAMED AFTER S. M. KIROV,
HOLDER OF THE ORDER OF THE OCTOBER REVOLUTION
AND THE ORDER OF THE RED BANNER OF LABOR

Vol. 214 1977

PHOSPHORYLATION OF MODEL LIGNIN COMPOUNDS.

COMMUNICATION 2. INFRARED SPECTRA

OF CERTAIN THIOPHOSPHATES

G. G. Lykhina, L. A. Pershina

(Presented by the scientific seminar of the Faculty of Chemical Technology)

IR spectra are a reliable method for investigating the structure of organic compounds. In the present work IR spectra were used to determine the position of the phosphoryl group in model lignin compounds.

In the reaction of O-methyl-O-ethyl chlorothiophosphate with 1-guaiacyl-1-propanol, both the phenolic hydroxyl group and the alcoholic hydroxyl group may react:

Vanillin oxime can react with O-methyl-O-ethyl chlorothiophosphate in two directions.

Studying the IR spectra of the phosphorylation products of model lignin compounds, we found that, when O-methyl-O-ethyl chlorothiophosphate acts on 1-guaiacyl-1-propanol in acetone medium in the presence of pyridine, only the alcoholic hydroxyl group is phosphorylated. Phosphorylation of the phenolic hydroxyl group occurs in the case when the initial phenolic alcohol is taken in the form of its sodium phenolate. Dithiophosphate

\[ \text{vanillin oxime} + \mathrm{Cl{-}P(=S)(OCH_3)(OC_2H_5)} \longrightarrow \begin{cases} \text{vanillin } O\text{-}[methoxy(ethoxy)thiophosphoryl] oxime,}\\ \text{vanillin oxime phenyl } O\text{-}[methoxy(ethoxy)thiophosphate].} \end{cases} \]

chlorothiophosphate with the Na salt of 1-guaiacyl-1-propanol in the presence of pyridine. 1-Guaiacyl-1-propanol is obtained by the reaction of O-methyl-O-ethyl-[[unclear: continuation cut off]].

From vanillin oxime, the thiophosphate can be obtained at the oxime hydroxyl group in absolute ether, in the presence of triethylamine at 5–7°C; if an excess of the acid chloride is taken, the dithiophosphate is obtained.

The structure of the thiophosphates obtained was demonstrated by IR spectra [2]. Figure 1 shows the IR spectra of guaiacol (a) and guaiacol thiophosphate (b). In the IR spectra of the thiophosphate, bands disappeared in the region

Fig. 1. IR absorption spectra: a—guaiacol, b—guaiacol thiophosphate.

1375 cm\(^{-1}\) and 3550 cm\(^{-1}\), responsible for the deformation vibrations of phenolic hydroxyl groups and hydroxyl groups involved in hydrogen bonding; bands appeared in the region of 1050 cm\(^{-1}\) \((\mathrm{P—O—C}_{\text{aliph.}})\) and 1180 cm\(^{-1}\) \((\mathrm{P—O—C}_{\text{arom.}})\).

In the IR spectra of the thiophosphate of 1-veratryl-1-propanol (Fig. 2b), bands responsible for vibrations of secondary hydroxyl groups are absent,

Fig. 2. IR absorption spectra: a—1-veratryl-1-propanol; b—thiophosphate of 1-veratryl-1-propanol.

groups, and a very strong band appeared in the region of 1050 cm\(^{-1}\), corresponding to the \(\mathrm{P—O—C}_{\text{aliph.}}\) bond.

The structure of the thiophosphate of 1-guaiacyl-1-propanol, phosphorylated at the aliphatic hydroxyl group, is demonstrated by the disappearance of the absorption band in the region of 1030 cm\(^{-1}\) (Fig. 3b), by a decrease in the absorption band in the region of 3550 cm\(^{-1}\), by the retention of phenolic hydroxyl groups (1375 cm\(^{-1}\)), and by the appearance of a band at 1050 cm\(^{-1}\). In the IR spectra of the dithiophosphate of 1-guaiacyl-1-propanol (Fig. 3c), bands characteristic of hydroxyl groups are absent, but strong bands are present in the region of 1050 cm\(^{-1}\) \((\mathrm{P—O—C}_{\text{aliph.}})\) and 1180 cm\(^{-1}\) \((\mathrm{P—O—C}_{\text{arom.}})\).

In the IR spectra of the dithiophosphate of vanillin oxime, absorption bands in the regions of 1375 cm\(^{-1}\) and 3550 cm\(^{-1}\) disappeared; absorption bands appeared in the regions of 1050 cm\(^{-1}\) \((\mathrm{P—O—C}_{\text{aliph.}})\) and 1180 cm\(^{-1}\) \((\mathrm{P—O—C}_{\text{arom.}})\).

In the IR spectra of the thiophosphate of vanillin oxime, obtained at the oxime hydroxyl group, the band in the region of 1375 cm\(^{-1}\) (OH phenolic) was retained and the absorption band in the region of 3550 cm\(^{-1}\) decreased; an absorption band at 1050 cm\(^{-1}\) \((\mathrm{P—O—C}_{\text{aliph.}})\) appeared.

Fig. 3. IR absorption spectra: a — 1-guaiacyl-1-propanol, b — thiophosphate of 1-guaiacyl-1-propanol, c — dithiophosphate of 1-guaiacyl-1-propanol.

Experimental Part

Preparation of thiophosphates:

O-methyl-O-ethyl thiophosphate of guaiacol, O-methyl-O-ethyl thiophosphate of 1-veratryl-1-propanol, and O-methyl-O-ethyl thiophosphates of 1-guaiacyl-1-propanol at the phenolic hydroxyl group and at the alcoholic hydroxyl group were obtained by the method we proposed earlier [1].

Dithiophosphate of 1-guaiacyl-1-propanol was obtained under the following conditions: into a three-necked flask equipped with a reflux condenser with a calcium chloride tube, a dropping funnel, and a stirrer were introduced 3.64 g (0.02 M) of 1-guaiacyl-1-propanol and 10 ml of methanol; then 0.46 g (0.02 M) of metallic sodium in methanol solution was added. The alcohol was distilled off, and 15 ml of benzene was added to the dry Na salt of 1-guaiacyl-1-propanol. At 75°C, 0.8 g (0.02 M) of pyridine was added and, dropwise, 8.7 g (0.05 M) of O-methyl-O-ethyl chlorothiophosphate. The reaction mixture was kept at 80°C for 4 hours. The precipitated hydrochloride ...

The sodium was filtered off; yield 95%. The filtrate was poured onto ice, extracted with benzene, and dried over Na₂SO₄. The benzene and unreacted O-methyl-O-ethyl chlorothiophosphate were distilled off under vacuum; the residue in the flask was dissolved in benzene and passed through an Al₂O₃ column, and the benzene was distilled off. The residue in the flask was a slightly yellowish, very viscous liquid that decomposed on heating. Yield 70%. Found, %: P 12.55. Calculated for C₁₆H₂₈O₇P₂S₂, %: P 12.75.

Preparation of O-iminothiophosphates of vanillin

20 g of vanillin oxime was placed in a three-necked flask equipped with a reflux condenser, dropping funnel, and stirrer; 100 ml of absolute diethyl ether and 12.2 g of triethylamine were added. The mixture was cooled to +5—+7°C, and O-methyl-O-ethyl chlorothiophosphate was introduced over 30 min. The reaction mass was kept at this temperature for 1 h. The precipitated triethylamine hydrochloride was filtered off and washed with ether; its yield was 97% of theoretical. From the filtrate, the ether and unreacted O-methyl-O-ethyl chlorothiophosphate were distilled off under vacuum. The residue in the flask was a colorless, very viscous liquid that decomposed at 90°C.

At a ratio of vanillin oxime : O-methyl-O-ethyl thiophosphate = 1 : 1, a product was obtained with a sulfur content of 10.6%; calculated, on the basis of one thiophosphoryl group for C₁₁H₁₆O₅NPS: 10.5%; yield 85%; at a ratio of 1 : 2, a product was obtained containing 14.3% sulfur; calculated for two thiophosphoryl groups for C₁₄H₂₃O₇NP₂S₂: 14.45%; yield 80%.

The IR spectra of the initial model lignin compounds and their thiophosphates were recorded on a UR-10 double-beam automatic spectrophotometer. All compounds were examined in CCl₄ solution; concentration, 5%.

Conclusion

The structures of thiophosphates of guaiacol, 1-veratrylpropanol-1, 1-guaiacylpropanol-1, and vanillin oxime have been proved by means of IR spectra.

References

1. L. A. Pershina, G. G. Lykhina, V. N. Shvacheva. Izv. TPI, 1968.
2. L. Bellamy. Infrared Spectra of Complex Molecules, Foreign Literature Publishing House, Moscow, 441, 1963.