LECTURE NOTES:

Organic chemistry is the study of chemical compounds that have carbon as the principle element. (Inorganic chemistry covers all the other types of chemistry.) This may seem odd—after all, what is the big deal about carbon? The answer is that most known chemical compounds are organic compounds.

A few examples include: all forms of alcohol, gasoline and most other fuels, many paints, all oils, fats, plastics, foods, vitamins, most flavorings, most drugs. Millions of organic compounds are known, and thousands more are discovered each year.

What makes carbon so special is that each carbon atom has four electrons available for bonding (or four "hands"). Each carbon atom can bond with up to four other atoms (including other carbons) to form long and complex molecular chains.

In this class we are going to have only a very quick survey of organic chemistry, and learn what some of the mysterious names mean on the sides of cans. We will also meet some of the chemicals that we will be seeing again in biology, nutrition, and cooking. Some of these chemicals are also used in the fabrication of semiconductors and other industrial processes.

Hydrocarbons: On basic type of organic chemical is the hydrocarbon. This family of organic compounds is made of only two elements: hydrogen and carbon. What is important to see here is the grammar of naming.

This is the basic grammar for simple chains of carbons: we have a number ("oct") followed by the "ane," which means "single bond".

Just like in English, though, more parts can be added. For example, if we have a double bond between carbons at some point, the "ane" becomes "ene": ethane becomes ethene. Finally, if we have a triple bond, the "ane" becomes "yne": ethane—ethene—ethyne.

The important thing to note here is that unsaturated hydrocarbons could have more hydrogens added, by opening up the double bonds and adding more hydrogen. (See the blue box on p. 328). This is the same "saturated" and "unsaturated" that we talk about when we speak of saturated fats or unsaturated fats!! Saturated fats are saturated with hydrogen—they don’t have any more "hands." These fats are more likely to be solid at room temperature (like lard, or Crisco). Unsaturated fats are more likely to be liquid at room temperature, like Wesson oil.

Unsaturated fats and oils can be made saturated by adding more hydrogen until all the possible "hands" are used up on the carbon chain. This how we have "partially hydrogenated vegetable oil": it is liquid that has been at least partially "lardified" so that it will be less liquid at room temperature. Note that when this happens, the benefits of using vegetable oil over animal fat decreases. The more the oil is hydrogenated, the more fat-like it becomes—and the more likely it is to clog up our arteries!!

Another use for oils is of course for gasoline. Gasoline is a mix of molecules ranging from 5 to 12 carbons long. The "ideal" gasoline, however, is 100% octane. This would give us an octane number of 100 on the side of the pump. (Regular gas is about 87, or the equivalent of 87% octane, while premium is about 93.)

The other 13% of our gasoline is equivalent to heptane (7 carbons). If we had some really, really bad gasoline, its octane number could be ZERO. This means that it would be equivalent to burning pure heptane. It would also "knock" in our engines like crazy!

The reason that low-octane gas knocks is that it is so light that it ignites in the cylinders too soon. Longer molecules like octane take longer to burn, though they pack more power when they actually do ignite.

Kerosene is longer, about C12 to C15. It is used in old-time lamps, and also in jet aircraft fuel and some rocket fuel. Diesel fuel is longer yet (about C15 to C18), and motor oil is about the same. Asphalt, used for paving roads, is C40 or more.

Hydrocarbons are used as fuels. Alcohols are another important class of organic compounds. These all have a "hydroxyl" group (-OH) somewhere in the molecule.

These also have the organic chemistry "grammar."

Ethanol is the only alcohol that humans can consume in some amount without serious ill effects. The other alcohols are supposedly even more intoxicating, but they are also extremely poisonous, and can cause violent illness, blindness, neurological damage, and death!! This is why bad "moonshine" or can be quite poisonous.

Lets talk now a bit more about ethanol, the alcohol that we can drink.

Ethyl alcohol is, of course, produced by yeast during the fermentation process. Both beer and wine "top out" in alcohol content at around 12%; above that level, the yeast die off and fermentation stops. If we are very careful, we may be able to gradually add sugar and get up the 20% alcohol, but this is a special technique.

To get an alcohol concentration significantly above 12%, we must distill the drink. Brandy is basically distilled wine, while whiskey is distilled beer. Rye grain, if fermented and distilled, makes rye whiskey, sometimes just called "rye."  (Gin is rye whiskey flavored with juniper berries, which is where the name "gin" comes from.) Fermented and distilled molasses makes rum.

A historical note: Distilling makes possible a much higher alcohol content; in fact, the spread of distilled liquor in Europe among the common people in the 1700's contributed to a massive upsurge of alcoholism. Before this time, distilled spirits such as brandy were mainly available to the well-off, since brandy requires (expensive) wine for its base. However, after Columbus and the Spanish (and later the Dutch, and then the French, and finally the British) began slave-based sugar production in the Caribbean, mollassas was produced as a waste product in large amounts. When fermented and distilled, this produced vast quantities of cheap rum, with alcoholism following in its wake.  Over time, the quest for sugar, the forced importation of huge numbers of Africans, rum production, and ensuing alcoholism would change the face of the Americas. In the U.S. it would lead to slavery, the Civil War, and to the rise of Methodism and the Salvation Army (both "temperance churches" which avoided alcohol) in the U.S. and in England.  But back to chemistry...

A very deep understanding of distillation is beyond the scope of this course. One key point to remember, however, is that there is more to making hard liquor than simply distilling wine or beer. Only the "middle" portion of distillation should be used; the "foreshots" and "aftershots" contain large amounts of fusel oils. These are ethyl alcohol's evil cousins (see p. 486 in McGee), such as methanol, propyl alcohol, and amyl alcohol. Traces of these chemicals in wine make a wine harsh. Large quantities, which can be concentrated by the distilling process, can cause serious poisoning, blindness, or even death. This is what makes moonshine, especially poorly-made moonshine, dangerous.

The "proof" of a liquor is based on the ethanol concentration. It approximately twice the concentration of alcohol: something that is 100 proof, for example, is about 50% alcohol. Denatured alcohol is usually ethanol with other things (like acetone or jet fuel) added to make it undrinkable. These contaminants are difficult to get rid of through further distillation.

So far we have talked about naming organic compounds, fuel, and alcohol. We are now going to talk more about the chemicals of life—the stuff that humans, plants, and animals are made of—as well as the food that we eat. The material in the book is good, but there is a lot of it! Here is the stuff that you really need to know:

There are three basic classes of food/life molecules. The first of these is the Carbohydrates. The name comes from the early (and not entirely accurate) notion that they are all made of carbon and water.

Sugars are one type of carbohydrate. They store energy, which is later released through oxidation. There are lots of different kinds of sugars.

Glucose ("blood sugar"), fructose (found in fruit and honey), and galactose are simple sugars (monosaccharides).

Table sugar (which has a chemical name of sucrose) is a disaccharide, (which means "two sugars") because it is made of a molecule of glucose and molecule of fructose hooked together.

Lactose is another disaccharide. It is found in milk. A lactose molecule is made of a molecule glucose and a molecule of galactose hooked together, and is not very sweet. While table sugar (sucrose) is probably the most familiar type of sugar to us, there are many, many other varieties. Much of the structures of DNA and RNA, for example, are made of a sugar called "ribose."

Starch, our second type of carbohydrate, is probably the most important carbohydrate in terms of cooking. It is basically a long chain of sugar molecules. Starch is also how plants store energy. A potato, for example, is mostly starch.

Cellulose, our third carbohydrate, makes up plant cell walls. Cellulose is the main structural component of plants, and allows vegetables, fruits, and grasses to hold their shape, even when dried. Even though cellulose is a long chain of glucose (sugar) molecules, it isn't sweet. In fact, it cannot be digested by humans.

Fats and oils are a second type of food molecule. These are also known as lipids. Oils are liquid at room temperature, while fats are solids.

Fat has two major functions in us. First, it used for energy storage--it contains about twice as much energy per pound as carbohydrates. Secondly, it is used for insulation.

In cooking, fats lubricate food and aid in heat transfer. It also carries flavors. Finally, they can help give food a smooth and/or moist texture.

The smoke point is the temperature at which a specific fat or oil starts to break down.

Protein is our third and final food molecule type. Proteins are incredibly important to us: they help form our skin, our nails, our muscles, and our vital organs. Hemoglobin, which carries oxygen, is mostly protein. Finally, all of our enzymes (organic catalysts which help carry out the chemical reactions in our body) are proteins.

In our bodies, all proteins are made from about 20 amino acids.Of these 20, 8 are "essential" amino acids, which means that our bodies cannot make them. The other 12 can be made by our bodies. Children, however, need 9 or 10 essential amino acids.

One thing that makes amino acids (and proteins) chemically special is that--unlike fats or carbohydrates--amino acids all contain nitrogen. When proteins start to break down (or rot), they produce compounds like ammonia and related compounds which smell really bad.

One central concept that will come up over and over again is protein denaturization. Protein denaturization can occur through heating (cooking), drying (salting), and exposure to acid. Basically, it means that the protein's structure is permanently changed. Examples of this are cooking meat and frying eggs. In each case the proteins are being modified. The contents of an egg are mostly protein, and turn white and gel when heated, or when placed in acid. Cooked proteins are often more easily digested than raw ones.