An Acid-Base Chemistry Example: Conversion of Nicotine

Abstract

Much of the traditional general chemistry class focuses on the nuts and bolts of chemical calculations. As a result it is often difficult to infuse the class with timely chemistry topics. This Journal has provided some excellent applications over the years (1-8).The current government interest in nicotine conversion by cigarette companies (9) provides an example of acid-base chemistry that can be explained to students in the second college semester of general chemistry. The discussion of acid-base chemistry tends to coincide with the students' preregistration for the next semester's organic chemistry class. Organic chemistry has a notorious reputation. Thus students tend to be anxious about this future class. One result of this anxiety is that although the explanation for nicotine conversion relies on organic acid-base chemistry, the students are particularly interested because organic chemistry is already on their minds. This example is also suitable for an AP high school chemistry class, but is probably too advanced for an introductory high school course.The weak base ammonia is often added to cigarette tobacco (10). The U.S. Food and Drug Administration (FDA) has argued that this added ammonia enhances the delivery of nicotine into the smoker's bloodstream. In contrast, tobacco companies argue that it is important to know as much as possible about nicotine chemistry in order to provide smoker satisfaction, and this knowledge is the underlying reason for their interest in ammonia as an additive (11).

Possible Role of Ammonia on the Deposition, Retention, and Absorption of Nicotine in Humans while Smoking†

“…Some cigarette manufacturers add ammonia-forming ingredients as flavorants and processing agents ( − ), which can ( , ), but does not always (), increase the amount of ammonia in mainstream (MS) 1 smoke. Various hypotheses have been proposed that cigarette manufacturers add ammonia to the tobacco to increase ammonia in the smoke, thereby enhancing nicotine's bioavailability to smokers; the total amount and relative proportions of free base, nonprotonated nicotine ( 1 ) relative to its protonated forms 2 and 3 present in MS smoke are widely believed to control the amount and rate of nicotine uptake in smokers and the amount and rate of nicotine delivered to the central nervous system ( 7 , 10 , − .

…”

Nicotine aqueous solutions: pH-measurements and salting-out effects - analysis of the effective Gibbs energies of hydration and ionic strengths of the solutions

“…12,27,[38][39][40] The first protonation (pK b = 5.99 or pK a = 8.01 occurs on the nitrogen atom (Nsp 3 ) of the nicotine N-methylpyrrolidine ring, while the second one occurs on the nitrogen (Nsp 2 ) in the pyridine ring (pK b = 10.59 or pK a = = 3.41). 12,27,[38][39][40] The first protonation (pK b = 5.99 or pK a = 8.01 occurs on the nitrogen atom (Nsp 3 ) of the nicotine N-methylpyrrolidine ring, while the second one occurs on the nitrogen (Nsp 2 ) in the pyridine ring (pK b = 10.59 or pK a = = 3.41).…”

“…12,27,[38][39][40] The first protonation (pK b = 5.99 or pK a = 8.01 occurs on the nitrogen atom (Nsp 3 ) of the nicotine N-methylpyrrolidine ring, while the second one occurs on the nitrogen (Nsp 2 ) in the pyridine ring (pK b = 10.59 or pK a = = 3.41). 39 However, it was also emphasized that the percentage of protonated nicotine is dependent on the pH of the solution. 39 However, it was also emphasized that the percentage of protonated nicotine is dependent on the pH of the solution.…”

Using "Basic Principles" To Understand Complex Science: Nicotine Smoke Chemistry and Literature Analogies

“…There has been a tendency to assume that tobacco and tobacco smoke are sufficiently similar to aqueous systems, such that the use of pH and pK a values will provide meaningful predictions (6)(7)(8). Aqueous ammonia and other compounds that can form ammonia during the smoking process are known to be added to cigarette blend (9).…”