On the nature of so-called “Khimdu”

Talattta, 1972, Vol. 19, pp. 1665 to 1669. Pcroamon Press. Printed In Northern Ireland

AN-NOTATIONS

On the nature of so-called “Khimdu” (Received 24 April 1972. Accepted 18 May 1972) THE methyliminodiacetic acid derivative of chromotropic acid (disodium salt of 1 ,I-dihydroxynaphthalene2N,N-dicarboxymethylaminomethyl-3,6-disulphonic acid, so-called ‘Xhimdu”) was tirst reported by Basargin et al. as a calorimetric reagent for titanium(IV).l As we have been interested in this type of reagent, we tried to repeat their work carefully, but found some doubts about the nature of the reported compound. According to the result of our investigation, it is very likely that the reported reagent is a mixture of various reaction products, and not the pure compound having the proposed chemical structure(I). OH

-o*s’

60

co

OH

’

,CH,COOH ,CH*N \CH#ZOOH ‘so,-

EXPERIMENTAL Reagents Buffer solutions of hydrochloric acid/potassium chloride (pH 2). hexamethylenetetraamine/ hydrochloric acid (pH 3) and potassium acetate/acetic acid (pH 5) were used. * Metal ion stock solutions (O-01M) were prepared from analytical grade ferric nitrate and metallic titanium, and their strengths were determined by EDTA titration. The stock solutions were diluted with distilled water before use. Apparatus A column 16 mm in diameter and 500 mm long was used for the gel chromatographic separation of the reaction mixture. The column was tilled with a Sephadex LH-20 gel which had been swollen in the eluent (80% aqueous methanol) for 24 hr before use. Electronic spectra were observed with a Hitachi 124 double-beam recording spectrophotometer. Synthesis of kY/dmdu Xhimdu was synthesized according to the method of Basargin.” A mixture of 4.37 g (0.12 mole) of chromotropic acid (disodium salt) and 1.6 g (0.012 mole) of iminodiacetic acid was placed in a lOO-ml reaction flask. After addition of 20 ml of water, the mixture was heated on a water-bath until dissolution was complete. The solution was cooled to about 50”, and the pH adjusted to 2.0-3.0 with 1M hydrochloric acid. Then 0.87 ml (0.012 mole) of 37 % formaldehyde was added while stirring for several minutes. The reaction mixture was kept at room temperature for 3 hr. then transferred into a 300~ml beaker, and 120 ml of acetone were added to precipitate the product. The solution at first, gave a white suspension, from which a reddish-brown heavy oil separated. After collection, the oily product was treated with acetone to yield a brown powder. The product was carefully pulverized under acetone, then filtered off, washed with acetone and ether successively, and finally dried over phosphorus pentoxide. The yield of the crude product was 5-25-5-88 g (86-96 %) (product ICA). In an alternative procedure, the mole ratio of the reagents was altered to 1:2:3, and the reaction was carried out at 50” in an atmosphere of nitrogen for 14 hr. The reaction product was treated in a similar fashion to that described above, and a reddish brown powder (product ICB) was obtained (yield: 73 %). 1665 12

Annotations

1666

Chromatographic fractionation of the reaction products In order to purify the crude reaction products, samples of KA and KB were subjected to chromatographic fractionation on a Sephadex LH 20 gel column at an elution speed of 0.3 ml/mm. The effluents were fractionated into three or four fractions according to their relative differences in ultraviolet absorption spectra. Each fraction was concentrated to a small volume under reduced pressure, and pure product precipitated with acetone. The isolated product was washed with acetone and ether, and vacuum-dried. The yields of fractions obtained were as follows: 100 mg of KA gave 8.2 mg of KA-(1), 44.4 mg of KA-(2) and 9-l mg of KA-(3), and 150mg of KB gave l*Omg of KB-(1), 66.5mgof KB-(2). 7-4 mg of KB-(3) and 10.5 mg of KB-(4). The purified sample as well as the crude products were subjected to the absorption spectral analysis and elemental analysis. RESULTS

AND

DISCUSSION

Our original purpose was to reproduce Basargin’s results, and the samples obtained were found to have spectral characteristics identical with those of Khimdu. It is seen from Figs. 1, 2 and 3, that the crude product KA gave an absorption spectrum which is very close to that of Khimdu, and the visible absorption spectra of iron and titanium(W) complexes of the product KA also showed identical characteristics with those of Khimdu. A continuous variation study of the iron(II1) complex was also made in order to obtain an additional proof of identity of our sample with Khimdu. The results, as shown in Figs. 4 and 5, again confirmed the identity of our crude product with the material called Khimdu by Basargin, and the different metal ligand ratios obtained in the studies at different wavelengths also imply that more than one complex-forming species is present. However, as the result of elemental analysis on the crude sample showed discrepancies from the expected value for Khimdu, the sample was puritied. The sample was rather unstable, becoming darker at elevated temperature, and was very slightly soluble in most common organic solvents, so that purification by recrystallization did not seem to be feasible. Of the chromatographic separations investigated, gel chromatography on Sephadex LH-20 column with 80% methanol as an eluent was found to give best separation. However, contrary to expectation, the absorption spectra of the fractionated samples became more divergent from those

0.8 -

Wavelength,

Fro. l.-Visible

nm

absorption spectra of “Khimdu,” the reaction products andchromotropic acid (reference water, l-cm cells) 1. Khimdu 8 x lo-‘M (reproduced from ref. 1); 2, KA; 3, KA-(2); 4. KB-(2); 5, chromotropic acid (all 1 x lOAM).

1667

Annotations

O-

4ob

I

I

500

600

Wavelength, nm FIG. 2.-Visible absorption spectra of titanium(IV) CompIexes (reference rageat blank, l-cm cells, pH 2) I, Khimdu, 4 x lo-*Mand Ti 4 x lo-‘M (reproduced from ref. 1); 5, chromotropicacid (all 1 x IO-Wand Ti 4 x 10m5M). 2, KA; 3, KA-(2); 4, m(2);

06

% Ei c) g

0.4

9

0.2

C

500

650

Wavelength,

nm

Fro. 3.-Visible absorption spectra of iron complexes (reference reagent blank, l-cm cells, pH 5). I, Khimdu 2.5 x lO+Mand Fe 23 x l(rM (reproduced from ref. 1); 2, KA; 3, KA-(2); 4, KR(2); 5, chromotropic acid (all 23 x lo-*M and Fe(III) 2.5 x 10-w).

I 2

R

I 4 6

I

FIG. 4.-Continuous variation study on iron(II1) complex at 400 nm. Total corcentration 1.0 x lo-‘M; l-cm cells; 1, Khimdu, at 395 nm and pH 3.0 (reproduced from ref. 1); 2, KA, at 403 nm and pH 20.

0

I

2

I

R

Fe

I

I 6

I 4

0

FIG. 5.-Continuous variation study on iron complex at 650 nm Total concentration 2.0 x 1O-4M, 5-cm cells; I, Khimdu, at 650 run and pH 3.0 (reproduced from ref. 1); 2, KA, at 630 MI and pH 2.0.

0

I

I 2

I 4

1669

Annotations

of Khimdu. Moreover, the results of elemental analyses on the fractionated samples deviated more and more from the calculated values for Khimdu, as shown in Table I. In the case of KB, where the TAB= I.-E=NTAL

ANALYSES

OF THE

CRUD8

PRODUCTS

AND

TIE

CHROMATOQRAPHBD

FRACTIONS

Sample S-(l) U-(2) a-(3) KB-(1) KB-(2) KB-(3) KB-(4) Caicd. value for Khimdu (C,,H,,NO,,S,Na,) Chromotropic acid (sodium salt) (CJ-bO&Na,) Dimethylol deriv. of chromotropic (CIIHlOGlOSINa~)

C%

H%

N%

Na%

36.0 34.6 347 33.4 37.8 35.2

3.2 3.1 2.6 2.8 3.6 3.3

2.0 0.7 0.0 0.2 3.1 2.6 I.6 0.5

88:; 95 10.5 6.0 9.3 -

35.37

2.57

2.75

9.03

0.00

12.62

0.00

10.84

1.66 32.97 acid (sodium salt) 2.38 33.97

mole-ratio of the reactants was 1:2:3, the nitrogen content in the product as well as in the chromatographed fractions was higher than for KA. However, none of the results for the fractions agree with the calculated value for Khimdu. Generally, as the fractionation goes on, the nitrogen content becomes lower. For example, the fraction KA-(2) does not contain nitrogen and the analytical value is rather close to that of the dimethylol derivative of chromotropic acid. Although we do not want to give any decisive conclusion, as Basargin et al. did not show the analytical results for their sample, it is very likely that the product called “Khimdu” is not acompound with well-defined structure, but is a mixture of various reaction products. YONQ &XJN bI3+ KYIJ JA W-f Ksmm UENO

Deptment of Organic Synthesis Facdty of Engineering Kyushu University Fukuoka 812, Japan REFERENCES 1. N. N. Basargin, M. K. Akhmedli and M. M. Shirinov, Zh. Analit. Khim., 1968,23,1813. 2. N. N. Basargin and M. I. Starostina, U.S.S.R. Patent 175514 (Cl. CO7c). Oct. 9,1965. Snnnnary-The reagent called “Khimdu” has been investigated and evidence found to show that it is not a pure compound but a mixture of several reaction products. Zusammenfassun8-Das Reagens “Khindu” wurde untersucht und Hinweise darauf erhalten, da13 es sich nicht um eine reine Verbindung, sondem um ein Gemisch mehrerer Reaktionsprodukte handelt. Rknn~ a examine le r&&if nomme “Khimdu” et trouv6 de-s preuves montrant que ce n’est pas un cornpod pur mais un m&nge de plusieurs produits de reaction. l Colombo Project Fellow; present address: Department of Chemistry, College of Science and Engineering, Yonsei University, Seoul 120, Korea. t Present address: Department of Manufacturing Pharmacy, College of Pharmacy, Sookmyung Women’s University, Seoul 140, Korea