The Use Of Fluorochemical Compounds In Organic Chemistry

Generally, the major uses of fluorochemical compounds fall into three major categories at the turn of the 21st century. The first are the rather stable halocarbon compounds used in medicine such as several types of inhalation anesthetics for anaesthesia. A very major industrial use is in the form of heat tolerant and inert synthetic oils and metalworking lubricants. However, there are many fluorochemicals and halocarbon chemicals that are used extensively, albeit carefully, in organic (meaning carbon containing) chemistry. The unique nature of fluorine, even among other halogen elements, grants halocarbon fluoro compounds unique properties that are indispensable in organic chemical work.

Since the discovery of hydrofluoric acid (HF) from calcium fluoride and sulphuric acid in the 17th century, it has been well known to generations of chemists that certain fluorochemical compounds have very unusual properties. The etching of glass has been performed commercially with HF since the 18th century. Despite being a weak acid, it has an unparalleled ability to corrode silicon and calcium. Much of the pure and quite toxic elemental fluorine (F) is produced from HF by electrolysis.

Trifluoroacetic Acid (TFA) is another very commonly used halocarbon compound. TFA is a relatively simple organic molecule and is a colorless liquid that is a powerful carboxylic acid in solution. It can be produced by "electro-fluorinating" plain old acetic acid. Though similar to the much more familiar acetic acid (better known as the business end of vinegar), it is a strong acid in this form, stronger than acetic acid by at least 3 orders of magnitude.

On the other hand, Trifluoroacetic Anhydride (TFAA) is a very similar substance that is often used in creating free trifluoro methyl groups in organic reactions. It is a handy relative to TFA that can be stored indefinitely as long as it doesn't get wet. When it does come in contact with water it reverts back to TFA. It can be made by chemically dehydrating TFA. However, TFAA is also very highly corrosive, and dangerous to work with under anything but the strictest of conditions. Even just inhaling fumes from a TFAA reaction can cause permanent lung injury, as many reactive fluorochemicals do in their gaseous state.

The use of 2,2,2-Trifluoroethanol (TFE), sometimes known by its old school name trifluoroethyl alcohol, in organic chemistry for many years has been to dissolve nylon. A colourless liquid that smells like everyday ethanol, trifluoroethanol is very often used as a solvent since it is more acidic than water given the highly negative nature of the fluorine end of the molecule. This characteristic also makes it possible for useful hydrogen bridging to occur in solution, making it a useful intermediary step in the creation of more stable and non-toxic fluorochemical compounds with heterocycles such as the amino acid pyridine.

More recently, TFE has been used as part of a solvent capable of selectively cleaving bits of folded proteins off their parent molecule. TFE is also notable for being the source of trifluoroacetaldehyde and TFA when oxidized. Though TFE doesn't reach a gaseous state until temperatures exceed 70C, the liquid has a flash point of only 33C. Controlled lab conditions are absolutely necessary when handling TFE.

Trifluoroacetyl Chloride (or TFAC) is perhaps the most difficult of these to work with. It is a gas at room temperature (down to below the freezing point of water) and one that doesn't smell very good, at that. TFAC is almost always delivered to labs and vendors in pressurized cylinders that are handled very carefully since the contents are toxic and acidic when released into the air. Contact with the skin is not recommended under any circumstances, since the contents will readily hydrolyze into TFA and hydrochloric acid.

TFAC is highly advantageous when used as an intermediate substance in the synthesis of organic molecules. Pesticides and herbicides also use TFAC in the manufacturing process.

Though fluorochemical compounds are very often dangerous or toxic themselves, they very strongly bond to many organic molecules and provide the properties that make many of the wonders of modern medicine possible. That said, research into testing the stability of the novel halocarbon compounds that are introduced every year continues in the interest of public health.

Any client who wishes to utilize halocarbon chemicals in a lab or manufacturing capacity is advised to make themselves fully aware of the MSDS data sheet for each fluoro-chemical since so many of them are corrosive in their native state and some are even explosive when improperly handled. It is of the highest and utmost importance to use care and consider safety first when using fluorochemicals in any environment.