Formation of New Products in a Solid-Solid Reaction in the Presence of Organic Solvent Impurity

We discuss the formation of new products in a solid – solid reaction in the capillary as in well as in bulk in the presence of an organic solvent impurity in a small amount. Three reactions namely KI + HgCl2, CuI + HgCl2 and AgI + HgCl2 were studied. It was found for some of the organic solvent impurities, a small amount of some substance appeared in the half occupied by HgCl2. Thus it became clear that some of the organic substances were reacting with HgCl2 to produce a new substance which be an organo-metallic product. In this light HgCl2 was made to react with the different solvents. However, the new product could be separated out only in two cases, with Cyclohexanone and Dimethylsulfoxide. A black coloured product was formed with Cyclohexanone and with Dimethylsulfoxide 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 a preliminary study of the two products naming these as product A and product B formed with Cyclohexanone and Dimethylsulfoxide respectively has been done. The product A is formed by the reaction of Cyclohexanone solvent with HgCl2 and product B is formed by the reaction of Dimethylsulfoxide solvent with HgCl2 both at 80oC, for 5 hours. The preliminary studies carried out were measurement of molecular weight (by elevation of boiling point method), ionicity, XRD, FTIR etc.

In the light of the indication from capillary studies HgCl 2 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 HgCl 2 and product B is formed by the reaction of Dimethylsufloxide solvent with HgCl 2 , both at 80ºC, for 5 hours.

Method of preparation
We take 4 gms of well ground HgCl 2 (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).HgCl 2 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 e.g 6 .
where M 2 is the molecular weight of the solute, W 2 is the mass of solute, K b is the molal elevation constant, W 1 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.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 HgCl 2 and 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 The results are given in Fig. 1 and the corresponding digital data are given in Table 3.
The X-ray diffractogram of HgCl 2 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 nearmatching normal mode frequencies of HgCl 2 and the two products are given in Table 8 (a) and the remaining ones are given in Table 8 (b).The FTIR spectrum of HgCl 2 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 HgCl 2 .This means that HgCl 2 molecule remains more or less as such in product A, with some organic group getting attached to the HgCl 2 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.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 HgCl 2 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.From Table 8 (a), we also notice many near matching between the normal mode frequencies of HgCl 2 and those of product A. There are fewer near matching between the frequencies of HgCl 2 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.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.