CHM 332 Fall 2020 Homework #1: Describe Intermolecular Attra

Chm 332 Fall 2020 Homework #1: Describe intermolecular attractions and analyze marketing claims

This assignment requires an exploration of various types of intermolecular interactions, their attractions, and examples of each. Additionally, it involves explaining the solubility differences between molecules, particularly propanol versus propane, and the solubility of sodium dodecanoate despite its large hydrophobic segment. Furthermore, the task includes an analysis of Garnier’s marketing claim regarding “Micellar Water” as a new and revolutionary facial cleanser, supported by chemical understanding.

Paper For Above instruction

Introduction

Intermolecular forces play a crucial role in determining the physical and chemical properties of molecules, such as boiling points, melting points, solubility, and interactions with biological systems. These non-covalent interactions include ionic attractions, hydrogen bonds, dipole-dipole interactions, and Van der Waals forces. Understanding these attractions helps explain phenomena such as solubility differences, the behavior of surfactants, and the efficacy of skincare products like micellar water.

Attractions During Intermolecular Interactions

Intermolecular attractions are the forces that occur between molecules, influencing their physical state and interactions with each other. These attractions are generally weaker than covalent bonds but are vital in dictating compound behavior. The primary attractions include ionic interactions, hydrogen bonds, dipole-dipole interactions, and Van der Waals forces. Each type varies in strength and specificity, affecting the molecules’ physical properties and behavior in different environments.

Descriptions and Examples of Intermolecular Interactions

Ionic interactions

Ionic interactions occur between oppositely charged ions. These are electrostatic attractions, exemplified by sodium chloride (NaCl), where Na⁺ ions are attracted to Cl⁻ ions. Such interactions are strong and contribute to the high melting points of salts and their solubility in polar solvents like water.

Hydrogen bonds

Hydrogen bonds are a type of dipole-dipole attraction that occurs when a hydrogen atom is covalently bonded to electronegative atoms such as oxygen, nitrogen, or fluorine, and is attracted to another electronegative atom. An example is water (H₂O), where hydrogen bonds between molecules give water a high boiling point and surface tension. In biological systems, hydrogen bonds stabilize DNA's double helix.

Dipole interactions

Dipole-dipole interactions happen between polar molecules with permanent dipoles. For example, hydrogen chloride (HCl) molecules attract each other through dipole interactions, influencing their condensation and solubility.

Van der Waals forces

Van der Waals forces (also called London dispersion forces) are weak, transient attractions due to momentary polarization of electron clouds. All molecules exhibit Van der Waals forces; however, they are particularly significant in nonpolar molecules like noble gases or hydrocarbons. For instance, methane (CH₄) relies on Van der Waals forces to condense at low temperatures.

Solubility of Propanol in Water Compared to Propane

Propanol (C₃H₇OH) is more soluble in water than propane (C₃H₈) because of its hydroxyl (-OH) group capable of forming hydrogen bonds with water molecules. This polarity enables intermolecular hydrogen bonding, enhancing solubility. Conversely, propane is a nonpolar hydrocarbon with only Van der Waals interactions, making it largely insoluble in water. The significant difference underscores the importance of hydrogen bonding and polarity in solubility phenomena.

Solubility of Sodium Dodecanoate Despite Hydrophobic Segments

Sodium dodecanoate (a surfactant) contains a long hydrophobic tail but remains soluble in water owing to its amphiphilic nature. The molecule interacts with water through its ionic carboxylate headgroup, which engages in ion-dipole interactions with water molecules. The hydrophobic tail segments tend to aggregate to minimize contact with water, forming structures like micelles. These micelles sequester the hydrophobic tails inward and expose the ionic heads to the surrounding water, thus maintaining overall solubility of the molecule in aqueous environments.

Analysis of Garnier’s Marketing Claim about “Micellar Water”

Garnier’s marketing highlights micellar water as a revolutionary, gentle, and effective facial cleanser that combines makeup removal, cleansing, and oil removal into a single product without rinsing. The active ingredients include water, hexylene glycol, glycerin, disodium cocoamphodiacetate, disodium EDTA, poloxamer 184, polyaminopropyl biguanide, and certain preservatives.

Chemically, micellar water contains surfactant molecules—such as disodium cocoamphodiacetate and poloxamer 184—that form micelles in solution. These micelles are spherical aggregates with hydrophobic tails inward and hydrophilic heads outward, capable of attracting impurities, oils, and makeup, because the hydrophobic interior dissolves oils while the exterior interacts with water. This mechanism underpins its cleansing ability.

Garnier’s claim of the product being “revolutionary” is scientifically supported by the concept of micelles enhancing cleaning efficiency without the need for rinsing, thus making it gentle on skin and convenient. It leverages surfactant chemistry to encapsulate and lift away dirt and oils, matching the description of micellar structures. Its effectiveness, gentle composition, and convenience make it a significant innovation, especially for sensitive skin types.

Disodium cocoamphodiacetate is an amphiphilic molecule with both hydrophilic and hydrophobic parts, facilitating micelle formation and cleaning action. Its presence aligns with the scientific understanding of micellar systems used in modern skin care. Evaluating Garnier’s marketing claims through the lens of chemistry shows that these claims are well-founded, grounded in the principles of surfactant chemistry and micelle formation.

Conclusion

Intermolecular interactions fundamentally influence the properties of molecules, including solubility, boiling points, and biological functions. Understanding the different types of attractions—ionic, hydrogen bonding, dipole interactions, and Van der Waals—is essential in chemistry and applied sciences. The solubility differences between propanol and propane exemplify the roles of polarity and hydrogen bonding, while sodium dodecanoate’s ability to dissolve in water despite its hydrophobic segment highlights the significance of amphiphilic behavior and micelle formation. Garnier’s marketing of micellar water as a revolutionary cleanser is chemically justified in terms of surfactant chemistry and micelle formation, illustrating how scientific principles underpin consumer products.

References

  • Chang, R. (2010). General Chemistry: The Essential Concepts. McGraw-Hill Education.
  • Tro, N. J. (2017). Chemistry: A Molecular Approach. Pearson Education.
  • Atkins, P., & de Paula, J. (2014). Physical Chemistry. Oxford University Press.
  • Miller, L. M., & Otos, A. (2019). Surfactants in Skin Care: Chemistry and Clinical Applications. Journal of Cosmetic Science, 70(4), 301-312.
  • Blum, A., et al. (2011). The Role of Micelles in Skin Cleansing. International Journal of Cosmetic Science, 33(2), 125-132.
  • Garnier USA. (2020). Micellar Water Product Information and Marketing Materials.
  • Luo, G., et al. (2012). Amphiphilic Molecules and Micelle Formation. Advances in Colloid and Interface Science, 178, 1–20.
  • Rieger, J. (2012). The Chemistry of Surfactants. A Guide for Chemists and Cosmetics Scientists. CRC Press.
  • Mathew, R. (2020). Solubility and polarity in organic molecules. Journal of Organic Chemistry, 85(12), 7624–7632.
  • Weir, S., & Wilkins, D. (2018). Intermolecular Forces and their Impact on Material Properties. Journal of Material Chemistry, 6(2), 188-204.

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