Benzophenone, a versatile organic compound with the chemical formula C₆H₅COC₆H₅, is widely used in various industries, including cosmetics, pharmaceuticals, and plastics. Understanding the solubility characteristics of benzophenone is crucial for its effective utilization and processing. This comprehensive guide delves into the intricate details of benzophenone’s solubility, providing a wealth of technical information for science students and professionals.
Solubility in Water and Organic Solvents
Benzophenone is known to be practically insoluble in water, with a reported solubility of only 0.00025 g/100 g at 20°C and 0.0005 g/100 g at 40°C. This low solubility in water is attributed to the compound’s non-polar nature, which arises from the presence of two benzene rings connected by a carbonyl group.
In contrast, benzophenone exhibits excellent solubility in various organic solvents. According to the NCBI database, it is:
- Very soluble in acetone, acetic acid, and carbon disulfide
- Soluble in benzene and methanol
- Soluble in hexane, although this can lead to reduced extraction recoveries
To quantify the solubility in organic solvents, a study by Koivikko et al. (2010) found that benzophenone migrated into 95% ethanol from recycled paperboard used for food contact in Japan, with concentrations ranging from 1.0 to 18.9 ng/mL in eight out of the 21 samples collected.
Furthermore, in a study of printed board used for secondary packaging, benzophenone was detected in 61% of the samples, with concentrations varying from 0.57 to 3.99 mg/m².
Factors Affecting Solubility
The solubility of benzophenone can be influenced by various factors, including temperature, pressure, and the presence of other substances.
Temperature
As mentioned earlier, the solubility of benzophenone in water increases with temperature, from 0.00025 g/100 g at 20°C to 0.0005 g/100 g at 40°C. This trend is typical of non-polar compounds, as the increased thermal energy helps overcome the intermolecular attractions between the water molecules and the benzophenone molecules.
Pressure
The effect of pressure on the solubility of benzophenone is relatively minor, as it is a non-volatile compound. However, in certain applications, such as supercritical fluid extraction, the solubility of benzophenone may be influenced by changes in pressure.
Presence of Other Substances
The solubility of benzophenone can also be affected by the presence of other substances, such as surfactants, co-solvents, or other solutes. These interactions can either enhance or reduce the solubility of benzophenone, depending on the specific chemical properties of the system.
Theoretical Considerations
The solubility of benzophenone can be understood from a theoretical perspective by considering the intermolecular forces and the thermodynamics of the dissolution process.
Intermolecular Forces
Benzophenone is a non-polar molecule, and its solubility is primarily governed by dispersion forces, also known as London dispersion forces. These forces arise from the temporary dipole moments induced in the non-polar molecules due to the fluctuations in the electron density. The strength of the dispersion forces is proportional to the polarizability of the molecules, which is influenced by factors such as molecular size and shape.
Thermodynamics of Dissolution
The dissolution of benzophenone in a solvent can be described by the Gibbs free energy of the process, which is the sum of the changes in enthalpy (ΔH) and entropy (ΔS) of the system. The dissolution process is spontaneous when the Gibbs free energy change (ΔG) is negative, which occurs when the increase in entropy (ΔS) outweighs the increase in enthalpy (ΔH).
For the dissolution of benzophenone in water, the process is typically non-spontaneous due to the unfavorable entropy change, as the water molecules need to become more ordered around the non-polar benzophenone molecules. This results in a positive Gibbs free energy change, leading to the low solubility of benzophenone in water.
In contrast, the dissolution of benzophenone in organic solvents, such as acetone or methanol, is more favorable due to the better solvation of the non-polar benzophenone molecules by the organic solvent molecules, resulting in a more negative Gibbs free energy change and higher solubility.
Analytical Techniques for Solubility Determination
Various analytical techniques can be employed to determine the solubility of benzophenone, including:
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Gravimetric Analysis: This method involves the measurement of the mass of benzophenone dissolved in a known volume of solvent at a specific temperature.
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Spectrophotometry: Ultraviolet-visible (UV-Vis) spectrophotometry can be used to quantify the concentration of benzophenone in a solution by measuring the absorbance at a specific wavelength.
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High-Performance Liquid Chromatography (HPLC): HPLC is a powerful analytical technique that can separate and quantify benzophenone in complex mixtures, providing accurate solubility data.
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Gas Chromatography-Mass Spectrometry (GC-MS): GC-MS can be used to identify and quantify benzophenone in various samples, including those with low concentrations.
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Differential Scanning Calorimetry (DSC): DSC can be used to study the phase transitions and thermal properties of benzophenone, which can provide insights into its solubility behavior.
The choice of analytical technique depends on the specific requirements of the study, such as the concentration range, the presence of interfering compounds, and the desired level of accuracy and precision.
Applications and Implications
The solubility characteristics of benzophenone have important implications in various applications, including:
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Cosmetics and Personal Care Products: Benzophenone is commonly used as a UV absorber in sunscreens and other personal care products. Its solubility in organic solvents is crucial for formulation and product performance.
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Pharmaceutical Formulations: Benzophenone is used as a photostabilizer in some pharmaceutical preparations. Understanding its solubility is essential for ensuring the stability and efficacy of these formulations.
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Polymer and Plastics Industry: Benzophenone is used as a photoinitiator in the production of certain polymers and plastics. Its solubility in the polymer matrix affects the curing and crosslinking processes.
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Environmental Monitoring: Benzophenone is a ubiquitous environmental contaminant, and its solubility in water and organic solvents is important for understanding its fate and transport in the environment.
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Food Packaging: Benzophenone can migrate from printed board used for secondary food packaging into the food, and its solubility in food simulants is a crucial factor in assessing the potential for migration and exposure.
By understanding the comprehensive details of benzophenone’s solubility, scientists and engineers can optimize its use in various applications, ensuring safety, efficacy, and environmental sustainability.
Conclusion
The solubility of benzophenone is a complex and multifaceted topic, with numerous factors influencing its behavior in different solvents and environments. This comprehensive guide has provided a detailed exploration of the solubility characteristics of benzophenone, covering its solubility in water and organic solvents, the factors affecting its solubility, the theoretical considerations, and the analytical techniques used for its determination. The applications and implications of benzophenone’s solubility have also been discussed, highlighting the importance of this knowledge in various industries and research fields. By understanding the intricacies of benzophenone’s solubility, science students and professionals can make informed decisions and develop innovative solutions that leverage the unique properties of this versatile compound.
Reference:
- Koivikko, R., Pastorelli, R., Rodríguez-Bernaldo de Quirós, A., Paseiro-Cerrato, R., Paseiro-Losada, P., & Simoneau, C. (2010). Analytical methods for the determination of benzophenone in food and beverages. Analytical and Bioanalytical Chemistry, 397(3), 1173-1181.
- NCBI. (n.d.). Benzophenone. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK373188/
- PubChem. (n.d.). Benzophenone. Retrieved from https://pubchem.ncbi.nlm.nih.gov/compound/Benzophenone
- Thermo Fisher Scientific. (n.d.). Determination of Benzophenone in Cereal Using QuEChERS and HPLC-UV. Retrieved from https://assets.thermofisher.com/TFS-Assets/CMD/Application-Notes/an-20639-quechers-benzophenone-cereal-an20639-en.pdf
- Course Hero. (n.d.). Lab 1 Solubility. Retrieved from https://www.coursehero.com/file/68741337/Lab-1-Solubilitydocx/
- Course Hero. (n.d.). Compare the solubility results of biphenyl and benzophenone. Explain why you think the results are different. Retrieved from https://www.coursehero.com/file/p7pvarae/1-Compare-the-solubility-results-of-biphenyl-and-benzophenone-Explain-why-you/
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