The Chemistry Of Mdma

David Nichols, Ph.D.

When I asked Dr. Holland what she wanted me to present in this chapter, she replied, "Explain the molecule to the masses. . . . Keep it elementary." That is a somewhat daunting task, because for many people who attended college or university, organic chemistry is a subject that is best forgotten. Those of you who have never had the experience of a basic organic chemistry course may still have heard horror stories about the subject or you are at least aware that it instills a kind of instinctive fear into most non-chemistry majors. In my opinion, chemistry itself is beautiful, and legendary accounts of its difficulty are greatly exaggerated. I hope to prove that here and even to instill a basic understanding of chemistry into those formerly thought to be immune to such attempts.

Acids and Bases

Where to start? Our discussion probably should begin with acids and bases. Most people are familiar with these terms. For example, the acid in most car batteries is a solution of sulfuric acid. It will burn the skin, eat through cotton clothing, and dissolve many kinds of metals that are placed into it. Acid rain is rainfall that has absorbed diluted sulfuric acid vapors from polluted air. It would have the same effect as battery acid if it were it to be concentrated to the same strength. Sulfuric acid, as well as hydrochloric acid and nitric acid, are known as inorganic, or mineral, acids, because they lack the presence of carbon atoms, and things containing carbon atoms are generally referred to as "organic"molecules. There are, however, a great many organic

acids. Perhaps one of the most common is ordinary vinegar. Vinegar is a dilute (about 3%) solution of acetic acid. There are a number of other common acids that the reader will recognize. For example, aspirin is acetylsali-cylic acid, and vitamin C is ascorbic acid. Although these are much weaker acids than mineral acids, they nevertheless have the same essential property—that is, they give off hydrogen ions, or protons (positively charged atoms), and it is these protons that lead to the unique chemistry of acids.

Figure 1. Ionization of a prototypical acid by loss of a proton (H+). Lines indicate chemical bonds.

At the left of figure 1 is shown an idealized acid, where the sphere can represent any sort of organic molecule or a group of inorganic atoms. On the right is shown the loss of the proton from the acid, with a positive charge on the hydrogen atom (H+) and a balancing negative charge on the oxygen atom (Or) of the acid molecule. Each chemical bond consists of two electrons, and normally one electron is contributed to the bond by each of the bonding partners. When the proton left the acid, however, it left both electrons with the oxygen atom. It is therefore one electron short of being electrically neutral (and hence has a positive charge, +). The oxygen atom is one electron in excess of neutrality and hence carries a negative electric charge (-). This process of the proton leaving the acid, because it creates charges in the groups involved, is called ionization.

For the purposes of this discussion, we are not really as interested in acids as we are in their chemical counterparts, bases, because many drug substances, including MDMA, are organic bases. Bases have the property of being attracted to protons, the H+ shown in figure 1. Since acids give off H+ and bases are attracted to, and interact with, H+, when the two are mixed together there is an "acid-base" reaction. If the proportions of the two species are exacdy equivalent, we say that "neutralization" has occurred. That is, we have neutralized the acid with the base or vice versa.

There are very strong and caustic inorganic bases, such as sodium hydroxide (lye), employed commonly in a drain cleaner marketed as Drano, which has the ability to chemically react with and dissolve greases and fats. More relevant to our interests, however, are the weaker organic bases, which are ultimately chemically related to ammonia. The gas ammonia has a structure where a nitrogen atom (N) is attached (bonded) to three hydrogen atoms. Everyone has no doubt smelled a bottle of household ammonia. That product is, in fact, a weak solution of ammonia gas dissolved in water, but the smell of ammonia gas is quite pungent.

Figure 2. Ammonia accepts a proton to become an ammonium ion. Lines indicate chemical bonds. The two dots between the Nand H also denote a completely equivalent bond, which is indicated this way only to show that the two electrons in one of the bonds both came from the nitrogen atom.

Figure 2 illustrates ammonia reacting with a proton (from an acid) in a neutralization reaction to become an ammonium ion, or ammonium salt. This reaction occurs because organic bases (amines) have a pair of electrons that are not normally involved in the formation of a chemical bond. These electrons are represented in figure 2 as the pair of black dots adjacent to the central nitrogen (N) atom. There is a strong attraction between the negative character of these electrons and the proton, which bears a positive electronic charge (+) because it does not possess enough electrons to make it electrically neutral. After the neutralization reaction, the central nitrogen atom has four hydrogen atoms attached to it as well as the positive charge brought by the proton, shown as the + sign. Organic molecules that bear a positive charge are often given names ending in "onium." Because this new product was derived from ammonia, it is called ammonium. Thus, if the proton came from sulfuric acid, the final compound would be called ammonium sulfate. If

Figure 2. Ammonia accepts a proton to become an ammonium ion. Lines indicate chemical bonds. The two dots between the Nand H also denote a completely equivalent bond, which is indicated this way only to show that the two electrons in one of the bonds both came from the nitrogen atom.

the proton came from acetic acid, the product would be called ammonium acetate.

If one replaces the H atoms of ammonia with small organic groups (units that contain carbon atoms), these resulting molecules are called organic bases, or amines. The low-molecular-weight amines have an ammonia-like, or fishy, smell. In fact, the smell of fish is due to the formation of very small amounts of these amines as the fish slowly decomposes. Amines behave much like ammonia in that they react with protons to form salts. Salts of organic bases are most often white crystalline substances, which possess a bitter taste and are usually water-soluble. Salts of amines with complex structures are typically named after the amine itself, followed by the name of the acid that was used to prepare the salt. That is, while the neutralization of ammonia with hydrochloric acid gives ammonium chloride, neutralization of a more complex base, such as amphetamine, would give a salt with the name amphetamine hydrochloride.

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