Propyl propionate is a propanoate ester resulting from the formal condensation of the hydroxy group of propanol with the carboxy group of propanoic acid. It has a role as a human metabolite, a rat metabolite, a biomarker and a fungal metabolite. It is functionally related to a propan-1-ol. Propyl Propionate is useful as a letdown solvent because of its low volatility, good solvent activity, and urethane grade quality. Since this product is not a HAP, it is a good choice when formulating solvent blend replacements for toluene and xylene in coating applications such as high-solids thermoset enamels. Its high electrical resistivity is beneficial in optimizing transfer efficiency in coatings applied via electrostatic spray equipment.

Safety assessment of propyl propionate

Propyl propionate was evaluated for genotoxicity, repeated dose toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity/photoallergenicity, skin sensitization, and environmental safety. Data show that it is not genotoxic. Data on propyl propionate provide a calculated margin of exposure (MOE) > 100 for the repeated dose toxicity, reproductive toxicity, and local respiratory toxicity endpoints. Data from read-across analog pentyl propionate (CAS # 624-54-4) show that there are no safety concerns for propyl propionate for skin sensitization under the current declared levels of use. The phototoxicity/photoallergenicity endpoints were evaluated based on ultraviolet (UV) spectra; it is not expected to be phototoxic/photoallergenic. For the hazard assessment based on the screening data, propyl propionate is not persistent, bioaccumulative, and toxic (PBT) as per the International Fragrance Association (IFRA) Environmental Standards. For the risk assessment, it was not able to be risk screened as there were no reported volumes of use for either North America or Europe in the 2015 IFRA Survey.[1]

Propyl propionate was assessed in the BlueScreen assay and found negative for both cytotoxicity (positive: <80% relative cell density) and genotoxicity, with and without metabolic activation (RIFM, 2013). BlueScreen is a screening assay that assesses genotoxic stress through human-derived gene expression. Additional assays were considered to fully assess the potential mutagenic or clastogenic effects of the target material.The mutagenic activity of propyl propionate has been evaluated in a bacterial reverse mutation assay conducted in compliance with GLP regulations and in accordance with OECD TG 471 using the preincubation method. Salmonella typhimurium strains TA98, TA100, TA1535, TA1537, and Escherichia coli strain WP2uvrA were treated with propyl propionate in dimethyl sulfoxide (DMSO) at concentrations up to 5000 μg/plate. Under the conditions of the study, propyl propionate was not mutagenic in the Ames test. No treatment-related mortality or clinical signs of toxicity were reported throughout the study. In addition, no treatment-related adverse effects were reported for organ weights, hematology, clinical chemistry, or urinalysis at any dose level. In females, body weight and food consumption were significantly lower in mid- and high-dose groups during the study. However, for both parameters, the decreases were <8% and therefore not considered to be of toxicological significance.

Propyl Propionate Methanolysis Kinetics

Acid-catalyzed reactions of ester transesterification by alcohols are convenient objects for a kinetics study with GC-MS and are of great practical importance. Recently, an interest in such reactions has grown due to their use for biodiesel production from vegetable oils. In the present work, the applicability of eqs 7 and 8 to the description of the process of propyl propionate transesterification by methanol is verified. For this purpose, six kinetic curves were experimentally obtained with various ratios of the reagents and different catalyst concentrations, and also the equilibrium composition of the reaction mixture was determined at 40 °C.[2]

The reaction mixtures were prepared by the weight method. In a 10 mL reaction flask with a plastic stopper, weighed methanol and propyl propionate were added for the forward reaction, and propanol and methyl propionate were added for the reverse reaction. The molar ratios of the reagents were set to be close to 2:1, 1:1, and 1:2. The values of the coefficients for methyl propionate, propanol, and propyl propionate were found to be 1.581, 1.319, and 1.501 with the correlation coefficients above 0.99. This option is directly related to the choice of pure reagents as standards. It turns out that there is a very interesting connection of kinetic and thermodynamic aspects; thermodynamics specifies a set of conditions that should be investigated by the kinetics methods in order to solve the main problem of kinetics study. The importance of this fact for chemical kinetics is difficult to overestimate, and it should become the subject of further research.

References

[1]Api, A M et al. “RIFM fragrance ingredient safety assessment, propyl propionate, CAS Registry Number 106-36-5.” Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association vol. 146 Suppl 1 (2020): 111763. doi:10.1016/j.fct.2020.111763

[2]Povarov, Vladimir G, and Andrey A Keresten. “Propyl propionate methanolysis kinetics: experiment and modeling.” The journal of physical chemistry. A vol. 117,38 (2013): 9115-9. doi:10.1021/jp403967b