Early Chemistry of Nicotine Degradation in Heat-Not-Burn Smoking Devices and Conventional Cigarettes: Implications for Users and Second- and Third-Hand Smokers

Molecular conformational effects on the overall rate constant and the branching ratios of the n-heptane + OH reaction: an ab initio and variational transition state theory study

The oxidation of fuels by hydroxyl radical (OH) is a crucial initiation step in both combustion and atmospheric processes. In the present work, we explore the site-specific hydrogen atom abstraction reactions by OH from n-heptane through high level ab initio and sophisticated kinetic calculations. Rate constants for each of the four distinct abstraction sites were computed, for the first time, over a wide temperature range (200-3000 K) and using multistructural torsional variational transition state theory (MS-T-VTST) with small curvature tunneling (SCT) corrections. Optimized geometries, vibrational frequencies and minimum energy paths (MEPs) were determined using the M06-2X/aug-cc-pVTZ level of theory, with single-point energy refinements performed at the CCSD(T)/aug-cc-pVTZ level of theory to refine the energy of the optimized stationary points whose energy is up to 1 kcal mol-1 of their respective global minimum conformer. Our findings reveal that the overall rate constants obtained from our site-specific calculations align closely with experimental data, with a maximum deviation factor (kexp/ktheory) of 1.5 at 1000 K. More importantly, we provide branching ratios that are based on first-principles calculations, identifying the secondary site neighboring the primary site as the dominant abstraction channel-data not previously reported in the literature, thereby adding value to our kinetic study. Moreover, we demonstrate that, as long as multi-structural torsional anhamonicity effects are implemented, appropriate density functional methods with large enough basis sets can yield rate constants that are comparable to those from much more computationally demanding levels of theory that are based on wave function methods. The demonstrated protocol, in which we have also tested the effect of different energy cuttoffs for the computationally intensive single-point energy refinements, effectively handles large and conformationally complex chemical systems, offering a reliable framework for future investigations in this field involving similar chemical systems whose kinetics is barely known or simply based on estimations.

Sensitivity of Mouse Lung Nuclear Receptors to Electronic Cigarette Aerosols and Influence of Sex Differences: A Pilot Study

The emerging concern about chemicals in electronic cigarettes, even those without nicotine, demands the development of advanced criteria for their exposure and risk assessment. This study aims to highlight the sensitivity of lung nuclear receptors (NRs) to electronic cigarette e-liquids, independent of nicotine presence, and the influence of the sex variable on these effects. Adult male and female C57BL/6J mice were exposed to electronic cigarettes with 0%, 3%, and 6% nicotine daily (70 mL, 3.3 s, 1 puff per min/30 min) for 14 days, using the inExpose full body chamber (SCIREQ). Following exposure, lung tissues were harvested, and RNA extracted. The expression of 84 NRs was determined using the RT2 profiler mRNA array (Qiagen). Results exhibit a high sensitivity to e-liquid exposure irrespective of the presence of nicotine, with differential expression of NRs, including one (females) and twenty-four (males) in 0% nicotine groups compared to non-exposed control mice. However, nicotine-dependent results were also significant with seven NRs (females), fifty-three NRs (males) in 3% and twenty-three NRs (female) twenty-nine NRs (male) in 6% nicotine groups, compared to 0% nicotine mice. Sex-specific changes were significant, but sex-related differences were not observed. The study provides a strong rationale for further investigation.

A review of the characteristic properties of selected tobacco chemicals and their associated etiological risks

OBJECTIVES

Despite the quantum of research findings on tobacco epidemic, a review on the formation characteristics of nicotine, aldehydes and phenols, and their associated etiological risks is still limited in literature. Accordingly, knowledge on the chemical properties and free radical formation during tobacco burning is an important subject towards unravelling the relationship between smoking behaviour and disease. This review investigates how scientific efforts have been advanced towards understanding the release of molecular products from the thermal degradation of tobacco, and harm reduction strategies among cigarette smokers in general. The mechanistic characteristics of nicotine and selected aldehydes are critically examined in this review. For the purpose of this work, articles published during the period 2004-2021 and archived in PubMed, Google Scholar, Medley, Cochrane, and Web of Science were used. The articles were selected based on the health impacts of cigarette smoking, tobacco burning kinetics, tobacco cessation and tobacco as a precursor for emerging diseases such as Covid-19.

CONTENT

The toxicity of cigarette smoke is directly correlated with its chemical composition derived from the pyrolysis of tobacco stem and leaves. Most of the harmful toxic substances are generated by pyrolysis during smoking and depends on pyrolysis conditions. Detailed studies have been conducted on the kinetics of nicotine by use of robust theoretical models in order to determine the rate constants of reactions in nicotine and those of nicotine dissociation via C-C and C-N scission, yielding pyridinyl and methyl radicals, respectively. Research has suggested that acetaldehyde enhances the effect of nicotine, which in turn reinforces addiction characteristics whereas acrolein and crotonaldehyde are ciliatoxic, and can inhibit lung clearance. On the other hand, phenol affects liver enzymes, lungs, kidneys, and the cardiovascular system while m-cresol attacks the nervous system.

SUMMARY AND OUTLOOK

The characteristics of chemical release during tobacco burning are very important in the tobacco industry and the cigarette smoking community. Understanding individual chemical formation from cigarette smoking will provide the necessary information needed to formulate sound tobacco reform policies from a chemical standpoint. Nonetheless, intense research is needed in this field in order to prescribe possible measures to deter cigarette smoking addiction and ameliorate the grave miseries bedevilling the tobacco smoking community.

Enhancing the Photo and Thermal Stability of Nicotine through Crystal Engineering with Gentisic Acid

The use of crystal engineering to convert liquids into crystalline solids remains a powerful method for inhibiting undesired degradation pathways. When nicotine, a liquid sensitive to both light and air, is combined with the GRAS-listed compound, gentisic acid, the resulting crystalline solid, exhibits enhanced photo and thermal stability. Despite a modest ΔT_m of 42.7 °C, the melting point of 155.9 °C for the nicotinium gentisate salt is the highest reported for nicotine-containing crystalline solids. An analysis of the crystal packing and thermodynamic properties provides context for the observed properties.

Effects on Health of Passive Smoking and Vape on Terraces in the COVID-19 Pandemic: A Review

The health damage caused by passive smoking is well known in closed public spaces such as workplaces, inside homes and restaurants. However, at present, the number of smokers in open public spaces such as terraces has increased and consequently a loss of the quality of the air breathed, increasing the concentration of particles and other contaminating agents, affecting the health of workers and customers, of these spaces. Multiple studies show that high exposure to tobacco smoke in these environments augments the risk of developing cardiorespiratory diseases, especially in the vulnerable population, but also respiratory infections. Tobacco smoke can be an excellent vehicle for transmitting viral particles, favoring coronavirus disease 2019 (COVID-19).

Rapid Gas-Phase Autoxidation of Nicotine in the Atmosphere

Nicotine is the most abundant alkaloid chemical in smoke emission. In this work, we investigated the gas-phase oxidation mechanism of nicotine initiated by its reactions with the OH radical and ozone. Both initiation reactions start dominantly by hydrogen atom abstractions from the C1, C3, and -CH₃ groups of the methylpyrrolidinyl group and form radicals nicotinyl-1, nicotinyl-3, and nicotinyl-6, respectively. The nicotinyl radicals would recombine rapidly with O₂, forming RO₂ with rapid intramolecular hydrogen-atom transfers (HATs) with rate coefficients from 4 s^-1 to greater than 10⁴ s^-1. The rapid HATs in peroxy radicals suggest rapid autoxidation of nicotine in the gas phase. Formation of HCNO and HC(O)NH₂, being observed in previous studies, arises likely from secondary reactions or photolysis of intermediate products.