Nicotine is a naturally occurring compound found primarily in the tobacco plant. It exists in several chemical forms that affect how it is delivered and experienced by the user. While the compound itself remains the same, how it is chemically processed dictates its physical properties in products like cigarettes and e-liquids. One specific form, known as freebase nicotine, has historically been the standard for nicotine delivery across various products.
The Chemical Basis of Freebase Nicotine
Freebase nicotine refers to nicotine in its pure, deprotonated state, meaning it is not bound to a salt or a proton. The nicotine molecule is naturally a weak base, and this freebase form is achieved by treating the nicotine extract with an alkaline substance, such as ammonia. This chemical process, often called “freebasing,” raises the pH level of the nicotine solution, typically to a highly alkaline range of around 8 to 9.
This high alkalinity defines freebase nicotine and gives it unique properties. By increasing the pH, the nicotine is converted from a charged, protonated state (a salt) into an uncharged, neutral molecule. This neutral state makes the molecule more volatile and able to cross biological membranes more easily, a concept known as increased bioavailability. The uncharged form is significantly more potent because it is readily absorbed into the bloodstream.
How Freebase Nicotine Differs from Nicotine Salts
Freebase nicotine is structurally different from its main alternative, nicotine salts, which are the form nicotine exists in naturally within the tobacco leaf. Nicotine salts are created by chemically bonding the nicotine molecule with an organic acid, such as benzoic acid, which lowers the pH of the solution significantly. This addition of acid results in a less volatile and more chemically stable compound compared to the freebase form.
The resulting nicotine salt solution is more neutral or slightly acidic, typically with a pH around 5, which is closer to the body’s natural pH. The chemical stability of nicotine salts means they do not degrade as quickly and can be used in different product formulations. Conversely, the high alkalinity of freebase nicotine makes it less stable and more prone to oxidation over time.
These chemical differences also dictate how the two forms are used in delivery systems. Nicotine salts are fully protonated, allowing them to deliver high concentrations of nicotine effectively at lower temperatures and with lower-powered devices. Freebase nicotine requires higher temperatures and more powerful devices to vaporize efficiently.
Rate of Absorption and Physiological Effects
The high alkalinity and uncharged molecular structure of freebase nicotine have direct consequences for how the body absorbs it. The neutral molecule is lipophilic, meaning it easily passes through the fatty cell membranes in the lungs and nasal passages. This characteristic allows the nicotine to be absorbed rapidly into the bloodstream, leading to a quick onset of its effects.
However, the high pH of the vapor or smoke is also responsible for a distinct physical sensation upon inhalation. This high alkalinity creates a noticeable “throat hit,” which is a feeling of irritation or harshness in the throat and lungs. Because this sensation becomes uncomfortably intense at high concentrations, freebase nicotine e-liquids are generally limited to lower nicotine strengths, typically below 12 milligrams per milliliter.
Despite the quick initial absorption, freebase nicotine is metabolized more slowly than nicotine salts, which can contribute to a more prolonged presence in the body. The physical experience of the harsh throat hit influences a user’s nicotine consumption, as it acts as a self-regulating mechanism that limits the amount that can be comfortably inhaled.
Where Freebase Nicotine is Used
Freebase nicotine has been the long-standing standard in both traditional and modern nicotine products. In the mid-20th century, tobacco companies began adding ammonia to traditional cigarettes to convert the naturally occurring nicotine salts into the more potent freebase form. This process enhanced the bioavailability of the nicotine in the smoke, effectively increasing its perceived strength without increasing the actual amount of tobacco.
In the vaping industry, freebase nicotine was the original and sole form of nicotine used in e-liquids from the inception of e-cigarettes until around 2016. It remains the dominant form for e-liquids intended for use in high-wattage, lower-resistance devices, often referred to as sub-ohm devices. These devices generate more heat and vapor, which is necessary to effectively atomize the less stable freebase molecule.
As a result, freebase e-liquids are commonly associated with higher-VG (vegetable glycerin) formulas, which are designed for producing large vapor clouds. Because of the harshness at higher concentrations, these liquids are typically sold in lower nicotine strengths, such as 3 milligrams or 6 milligrams per milliliter.