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Introduction

Many solid-solid capillary reactions have been studied during the last many years e.g.^1-4 In the studies normally carried out so for, both the solid reactants do not have any impurities. The main motivation of the earlier work, including that of the senior author (R.A.) in this field was to obtain a better understanding of the reaction mechanism of solid-solid reactions eg.^2,5 Introduction of simple organic impurities was a step in this direction. While studying the solid-solid capillary reactions in the presence of small amounts of some organic solvent impurity, that a small amount of some substance appeared in the half occupied by one of the reactants. Thus it became clear that some of the organic substances were reacting with one of the reactants to produce a new substance which be an organo – metallic product.

Here, we discuss the formation of new products due to the presence of an organic solvent impurity in a small amount. The reactions studied are KI+HgCl₂, CuI + HgCl₂ and AgI + HgCl₂ in the presence of small amount of organic solvent impurity.

The two reactants when packed side by side in a capillary tube of a narrow diameter, say 0.5 cm after moistening with different solvent impurities and kept in an oven maintained at 80^oC showed some new product on HgCl₂ side in two cases.

In the light of the indication from capillary studies HgCl₂ was made to react with the different solvents. However, the product could be separated out only in two cases, with Cyclohexanone and Dimethylsulfoxide. A black coloured product was formed with cyclohexanone and with Dimethylsufloxide the new product was of a light greenish colour. With the other solvents like Acetophenone and Nitrobenzene, the product, if formed could not be separated out. So, we have made a preliminary study of the two new products, naming these as product A and product B respectively. The product A is formed by the reaction of Cyclohexanone solvent with HgCl₂ and product B is formed by the reaction of Dimethylsufloxide solvent with HgCl₂, both at 80ºC, for 5 hours.

Experimental

Method of Preparation

We take 4 gms of well ground HgCl₂(99.9% Merck) reactants, moistened with about 0.4 ml of Cyclohexanone solvent (99% Merck) on a watch glass. Then it is put in an oven at constant temperature of 80º C, for 5 hours. In this way,a black coloured product is formed,this is called product A Same procedure is adopted for the Dimethylsulfoxide solvent (99% Merck). HgCl₂ is moistened with 0.4 ml of the double distilled solvent and the same procedure is followed in this case also. A light greenish coloured product is formed, this is called product B. Powdered crystals of the new products are taken for observation, measurement and other studies with simple techniques for finding out their physical properties etc. These are given in Table 1.

Measurement of Molecular Weight (By Elevation of Boiling Point Method)

The equation relating the boiling point elevation with the molecular weight of the solute is given as

where M₂ is the molecular weight of the solute, W₂ is the mass of solute, K_b is the molal elevation constant, W₁ is the mass of the solvent and T_b is the boiling point elevation due to the presence of the solute. THF is used as solvent.

Table 1: Physical Properties of New Products  Click here to View table

Table 2: Result of the Measurements of the Molecular Weight of the Products with Thf as Solvent Click here to View table

T_b is measured by a digital electronic thermometer.

Benzoic acid and Acetanilide are taken as standard solute. A known small amount of the solute is added to known amount of THF solvent and the elevation of boiling point is found out. All chemicals used are 99% purity Merck chemicals.

The K_b occurring in the formula for the determination of molecular weight is found out using Benzoic acid and Acetanilide as solute. The mean value of K_b using Actanilide as solute is used for the determination of molecular weight. The mean value of K_b for THF is 191.45. These molecular weights are given in Table 2.

Measurement of Some Other Properties of this New Product Such as Ionicity, XRD, FTIR etc

The kinetics of the reaction is studied by placing 400 mgms of HgCl₂and about the same amount of CuI in close contact near the middle, first without any impurity, and then after mixing with the two new products formed, as impurities, taken turn by turn. Both the reactants are 99.9% purity Merck chemicals. The internal diameter of the pyrex glass tube is 0.5 cm and about 5 cm length. These are kept in an air thermostat oven, controlled upto 0.5º C to 1ºC at 80ºC. The product thickness is measured with a traveling microscope having a least count of 0.01mm at equal intervals of time (15 min). The results are given in Fig. 1 and the corresponding digital data are given in Table 3.

Table 4: XRD of Pure HgCl2 Click here to View table

The X-ray diffractogram of HgCl₂ and the two products are obtained. These are given in Figs. 2-4. The corresponding digital data are given in Tables 4-6. The digital data of some of the most prominent diffraction peaks is given in Table 7. The near – matching normal mode frequencies of HgCl₂and the two products are given in Table 8 (a) and the remaining ones are given in Table 8 (b). The FTIR spectrum of HgCl₂ and the two products are given in Figs. 5-7.

Discussion

We see from Table 7 that the prominent peaks of product A are very nearly at the same place as that of HgCl₂. This means that HgCl₂ molecule remains more or less as such in product A, with some organic group getting attached to the HgCl₂ molecule, consistent with the molecular weight of product A. This proposal is consistent with observations because the organic group is expected to diffract X-rays very-very scantily.
 

Table 5: XRD of product A  Click here to View table

On the other hand, for product B, the 100% intensity is diffracted for d=8.0289 which is a totally new d-value. Also there is a new peak of 34.8% intensity at d=3.4618. There is also a new peak of intensity 15% at d=2.7696. Rest of the prominent d values for product B are more or less same as for HgCl₂ From this, we may conclude that at least one chlorine is replaced by an organic group consistent with the observed molecular weight. This should account for the observed X-ray data.
 

Table 6: XRD of product B Click here to View table

From Table 8 (a), we also notice many near matching between the normal mode frequencies of HgCl₂ and those of product A. There are fewer near matching between the frequencies of HgCl₂ and those of product B. This is consistent with our proposal regarding the new products.
 

We may tentatively suggest the following structures for the new products. Then one should have a very close look at the FTIR and other supporting data to eliminate many of the proposed structures to hopefully arrive at the best choice.
 

Table 7 Click here to View table

Table 8 (a) and (b) Click here to View table

Figure 2: X- Ray diffractogram of HgCl2 Click here to View figure

Figure 3: X- Ray diffractogram of Product A Click here to View figure

Figure 4: X- Ray diffractogram of Product B Click here to View figure

Figure 5: FTIR of HgCl2 Click here to View figure

Figure 6: FTIR of product A Click here to View figure

Figure 7: FTIR of product B Click here to View figure

The above are merely examples and these are not even good examples. Out of the many proposals, that one may make, one should be able to arrive at the correct structure, mainly on the basis of the FTIR and other supporting data. That is not being done here.

The normal mode frequencies of the two solvents, Cyclohexanone and Dimethylsulfoxide can be seen from Fig. 8 and 9, where the frequencies are noted in digital form over the spectrum.

Concluding Remark

One structure for product A and one for product B are tentatively proposed. More such structures have to be proposed and assessed against the observed molecular weighty and the spectra etc. Only then one may arrive at a unique structure for each of the two products.

Figure 8: FTIR of Cyclohexanone  Click here to View figure

Figure 9: FTIR of Dimethy lsulfoxide Click here to View figure

Acknowledgements

We wish to express our thanks to Prof. M.A. Wahab, HOD Department of Physics, JMI, New Delhi for X-ray measurement. Thanks are also due to Prof. Kamaluddin, Department of Chemistry, IIT Roorkee for X-ray and FTIR measurements. We would also like to thank Prof. Amir Azam for FTIR measurements. Special thanks are due to the Ex-Head of the Chemistry Department Prof. Kishwar Saleem, for extending to us the facilities of the Department. We are also thankful to Prof. Sharif Ahmad, Head Department of Chemistry, JMI, New Delhi.

Referenecs
 

1. Beg M.A., Ansari S.M., J. Solid State Chem. 20: 103 (1977).
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5. Rahman R., Ph.D. Thesis, Aligarh Muslim University, Aligarh (1984).
6. Maron S.H. and Prutton C.F., Principles of Physical Chemistry, 4th ed, Amerind Publishing Co. New Delhi, Bombay, Calcutta, New York (1965).