Mercury isotope pattern

For organometailic compounds, the situation becomes even more complicated because the presence of elements such as platinum, iron, and copper introduces more complex isotopic patterns. In a very general sense, for inorganic chemistry, as atomic number increases, the number of isotopes occurring naturally for any one element can increase considerably. An element of small atomic number, lithium, has only two natural isotopes, but tin has ten, xenon has nine, and mercury has seven isotopes. This general phenomenon should be approached with caution because, for example, yttrium of atomic mass 89 is monoisotopic, and iridium has just two natural isotopes at masses 191 and 193. Nevertheless, the occurrence and variation in patterns of multi-isotopic elements often make their mass spectrometric identification easy, as depicted for the cases of dimethylmercury and dimethylplatinum in Figure 47.4. 

The isotope patterns for two simple organometallic compounds in the molecular ion region (a) dimethylmercury and (b) dimethylplatinum. The seven isotopes of mercury show clearly and appear quite different from the six isotopes of platinum. Since there are only two carbon atoms, the contribution from C is negligible. 

Two radioactive isotopes of mercury are used in medicine mercury-197 and mercury-203. Both isotopes are used to study the brain and the kidneys. The isotopes are injected into the body where they travel to the brain and the kidneys. Inside these two organs, the isotopes give off radiation that is detected by instruments held above the body. The pattern of radiation provides information about how well the brain and kidneys are functioning. 

Phenyl Mercuric Chloride, An organomercury compound was believed responsible for a large fish kill in Boone Lake, Tennessee in 1968. Residue obtained from empty, unlabeled drums found in the lake was analyzed by MS using the direct probe method. Mercury has six isotopes of enough abundance to be observed by mass spectrometry (5). The mercury isotope pattern was observed in the molecular ion region of the spectrum (M" 314, Figure 3) where it is distorted by the chlorine isotope... 

Mercury has a relatively even distribution of its seven stable isotopes (196, 0.15% 198,10.0% 199, 16.7% 200,23.2% 201,13.2% 202,29.8% 204,6.8% Friedlander et al., 1981 Lauretta et al., 2001). This pattern presented cosmochemists with a formidable task when mercury isotopic distributions in meteorites were examined (e.g., Jovanovic and Reed, 1976 Thakur and Goel, 1989). Analytical difficulties apparently resulted in inaccurate determinations of the bulk abundance and isotopic composition of some meteorites, leading to the so-called mercury problem examined meteorites did not show the same bulk abundance and isotopic distribution as terrestrial material (Grevesse, 1970 Lauretta et al., 1999). Subsequent advances in mass spectrometry, and especially the development of multi-collectors. 

Mercury as an environmental pollutant is sometimes found as dimethyl mercury. Look up the natural abundance of the mercury isotopes and calculate the pattern to be expected in the molecular-ion region. The methyl group in acetophenone can be deuterated by refluxing a mixture of acetophenone and D2O with a little base catalyst. 

---