Molecule of the Day

The vast majority of molecules you will ever see here don’t contain a metal ion. And so it goes for many chemists - myriad possibilities exist with just carbon, hydrogen, nitrogen, and oxygen - add in sulfur and the halogens and you have lifetimes of work for armies upon armies of chemists. The chemistry of metal compounds merits its own subfield, inorganic chemistry, which encompasses essentially the rest of the periodic table (plus the aforementioned atoms).

The number of possible molecules, as you can imagine, goes up sharply as you start putting other atoms in there, so many inorganic compounds are only known to inorganic chemists and those who work routinely with them. There are a few inorganic all-stars that every chemist will recognize, though. In synthesis, Grignard reagents are amazing compounds that are generated by the addition of magnesium (metal - you actually use bits of metal!) to alkyl halides. These are workhorses in organic chemistry, as are Grubbs’ Catalysts, a series of ruthenium complexes which won Grubbs the 2005 Nobel.

In biochemistry (and laundry science - more on that in a minute), the inorganic-complex forming hero is EDTA, or ethylenediaminetetraacetic acid:

EDTA posesses just the right shape and size to complex with most common multivalent metal ions (calcium, iron, magnesium, and many others). Its electronegative atoms (nitrogen and oxygen) have electrons that can be donated into complexes with positively charged metal ions.

The net result is that we have a water-soluble compound that can effectively take metal ions out of commission. This can be very useful in biochemistry; many enzymes depend on metal ions. Put in some EDTA to mop them up, and you can often take the enzyme out of commission. In detergents, it can be quite useful, too. Toss a little EDTA in, and your water isn’t so hard anymore (water hardness usually coming from magnesium and calcium walts). This, as we’ve discussed in the past, can increase the effectiveness of soaps.

Finally, EDTA’s appetite for metals (and relative lack of toxicity) makes it useful for removing toxic metals from the body (although more effective compounds than EDTA exist for most toxic metals).

In one memorable case, a man named Harold McCluskey was exposed to a large dose of a radioactive Americum isotope in an explosion. Chelation with DTPA, an EDTA relative, removed a good chunk of the radioactive metal from his body!