May 2004

Aluminum chloride, AlCl3, is a major industrial CATALYST, meaning it speeds up the rates of certain chemical reactions important in manufacturing. Catalysts are very useful because they reduce the amount of energy required for chemicals to react, allowing reactions to proceed quickly. And catalysts are economical: they are chemically unchanged by the reactions they accelerate, so they may be used again and again.

Organic chemists are the
"architects" who link
carbon-hydrogen chains
together at the molecular

The Organic Compound Connection

Aluminum chloride is used in the production of rubber, lubricants, wood preservatives, medicines and paints. These substances are made of ORGANIC COMPOUNDS-compounds whose molecules resemble chains of carbon atoms surrounded by hydrogen atoms. For example, propane, familiar as the gas used to fire up the backyard grill, is a simple organic compound consisting of a straight chain of three carbon atoms surrounded by eight hydrogen atoms: 

A Simple Organic "Chain" Molecule
Propane (in the red tank) 
fuels the backyard grill.

Living things--plants and animals--are composed of organic compounds. Many of these are highly complex links of carbon "chains," including rings and branching chains--much more complicated than propane. Organic chemists study the structures of natural organic molecules and look for ways to design and produce new organic compounds, such as new medicines to cure diseases, and other products to improve our lives. Aluminum chloride is one catalyst that plays a role in speeding up the process of combining and rearranging organic molecules into new compounds.

Building Molecules With the Help of Aluminum Chloride

Linky Chainsworth,
organic chemist,
in her laboratory
To help us understand how aluminum chloride acts as a catalyst in organic chemical reactions, organic chemist, Linky Chainsworth agreed to be interviewed for this article. In her tidy lab, Linky explains how organic chemists use aluminum chloride to attach two molecules together to form a new molecule. "Aluminum chloride is a great 'chain buster,'" she states excitedly. "It helps me open up links in organic chains, forming spots where I can attach new chains. Using aluminum chloride I can design new complex molecules that function in very special ways, whether in medicines, paints, or lubricants."

Linky Chainsworth is clearly a fan of catalysts. "Catalysts are widely used both in chemical manufacturing and in chemical research," she says. "They are incredibly handy chemicals. And they're recyclable!"

AlCl3: Keeping us Dry and Odor-Free
As if being an important catalyst isn't enough, a hydrated form of aluminum chloride--aluminum chlorhydrate (AlCl3 . 6H2O), is the active ingredient in antiperspirants. (This compound is said to be hydrated because there are water molecules in its structure--note the "6H2O" in the chemical formula.) This compound closes sweat ducts in the skin, reducing perspiration. It also kills bacteria in perspiration, eliminating body odor. We've probably all been grateful for the properties of aluminum chlorhydrate at some time in our lives!

For a list of previous "Chlorine Compound of the Month" features, click here.


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