Zinc Oxide (ZnO) is an inorganic compound commonly used in various applications, including cosmetics, pharmaceuticals, and industrial products. In the cosmetics industry, it is widely used as a physical sunscreen agent due to its ability to block a broad spectrum of ultraviolet (UV) radiation. Chemical Properties of Zinc Oxide: 1. Chemical Structure: o Chemical Formula: ZnO o Molecular Weight: 81.38 g/mol o Structure: Zinc oxide consists of one zinc atom (Zn) bonded to one oxygen atom (O). It typically forms a hexagonal crystal structure, which contributes to its stability and effectiveness. 2. Physical Properties: o Appearance: Zinc oxide is a white, odorless, and powdery substance. o Solubility: Insoluble in water, but soluble in acids and alkaline solutions. o Melting Point: Approximately 1,975°C. o Boiling Point: Sublimes at about 1,800°C. 3. UV Absorption and Reflection: o Broad-Spectrum UV Protection: Zinc oxide is highly effective at blocking both UV-A (320-400 nm) and UV-B (280-320 nm) radiation. It works by reflecting and scattering UV rays, providing physical protection against sunburn and skin damage. o Opacity and Whiteness: Due to its high refractive index, zinc oxide provides excellent coverage and contributes to the whiteness and opacity of sunscreens and other products. 4. Photostability: o Zinc oxide is highly photostable, meaning it does not degrade when exposed to sunlight. This ensures long-lasting protection in sunscreen formulations. o In nanoparticle form, there are concerns about potential photocatalytic activity, which could lead to the formation of reactive oxygen species (ROS). To mitigate this, zinc oxide nanoparticles are often coated with inert materials such as silica or alumina.

Titanium Dioxide (TiO₂) is an inorganic compound widely used in various industries, including cosmetics, paints, coatings, food, and pharmaceuticals. In the cosmetics industry, it is primarily used as a physical sunscreen agent due to its ability to block ultraviolet (UV) radiation. Chemical Properties of Titanium Dioxide: 1. Chemical Structure: o Chemical Formula: TiO₂ o Molecular Weight: 79.87 g/mol o Structure: Titanium dioxide consists of one titanium atom (Ti) bonded to two oxygen atoms (O₂). It exists in different crystalline forms, the most common being rutile and anatase. 2. Physical Properties: o Appearance: Titanium dioxide is a white, odorless, and non-reactive powder. o Solubility: Insoluble in water and organic solvents, but can be dispersed in liquids. o Melting Point: Approximately 1,843°C. o Boiling Point: Sublimes at approximately 2,972°C. 3. UV Absorption and Reflection: o UV Protection: Titanium dioxide is an effective UV filter, particularly in the UV-B (280-320 nm) and UV-A (320-400 nm) ranges. It works by physically blocking and scattering UV rays, rather than absorbing them like chemical sunscreens. o Opacity and Whiteness: Due to its high refractive index, titanium dioxide provides excellent coverage and opacity, giving products a bright white color. This makes it useful as a pigment in products like paints and cosmetics. 4. Photostability: o Titanium dioxide is highly photostable, meaning it does not degrade when exposed to sunlight. This makes it a reliable ingredient in sunscreens for long-lasting protection. o However, in its nanoparticle form, there are concerns about potential photocatalytic activity, which could lead to the generation of reactive oxygen species (ROS). This is typically addressed by coating the particles with materials like silica or alumina to reduce reactivity.

Oxybenzone (also known as Benzophenone-3) is an organic compound commonly used as an active ingredient in sunscreens and other personal care products. It primarily functions as a UV filter, absorbing ultraviolet light to protect the skin from the harmful effects of sun exposure, including sunburn, premature aging, and an increased risk of skin cancer. Chemical Properties of Oxybenzone: 1. Chemical Structure: o IUPAC Name: (2-Hydroxy-4-methoxyphenyl)phenylmethanone o Chemical Formula: C14H12O3 o Molecular Weight: 228.24 g/mol o Structure: Oxybenzone is a benzophenone derivative with a hydroxyl group (-OH) and a methoxy group (-OCH3) attached to the benzene rings. The compound's structure allows it to absorb UV radiation effectively. 2. Physical Properties: o Appearance: Oxybenzone is a pale yellow, crystalline powder. o Solubility: It is moderately soluble in organic solvents like ethanol and oils and slightly soluble in water. o Melting Point: Approximately 62-65°C. o Boiling Point: Decomposes before boiling. 3. UV Absorption: o Maximum Absorption Wavelength (λmax): Around 288 nm. Oxybenzone absorbs both UV-A (320-400 nm) and UV-B (280-320 nm) radiation, making it effective in broad-spectrum sun protection. 4. Stability: o Photostability: Oxybenzone is relatively photostable, meaning it does not significantly degrade when exposed to sunlight. However, its stability can be enhanced when combined with other UV filters and antioxidants.

Avobenzone (also known as Butyl Methoxydibenzoylmethane) is an organic compound widely used as an active ingredient in sunscreen formulations. Its primary function is to absorb ultraviolet A (UV-A) radiation, which is crucial for protecting the skin from long-term damage such as premature aging and skin cancer. Chemical Properties of Avobenzone: 1. Chemical Structure: o IUPAC Name: 1-(4-Methoxyphenyl)-3-(4-tert-butylphenyl)propane-1,3-dione o Chemical Formula: C20H22O3 o Molecular Weight: 310.39 g/mol o Structure: Avobenzone is a dibenzoylmethane derivative with a methoxy group (-OCH3) and a tert-butyl group attached to aromatic rings. These groups are essential for its ability to absorb UV radiation. 2. Physical Properties: o Appearance: Avobenzone is a yellow crystalline powder. o Solubility: It is soluble in organic solvents such as ethanol and oils but is poorly soluble in water. o Melting Point: Approximately 81-86°C. o Boiling Point: Decomposes before boiling. 3. UV Absorption: o Maximum Absorption Wavelength (λmax): Around 357 nm. Avobenzone is highly effective at absorbing UV-A rays, particularly in the 320-400 nm range, which are the longer wavelengths that penetrate deeper into the skin. 4. Stability: o Photostability: Avobenzone is known to degrade when exposed to sunlight, losing its effectiveness as a UV filter over time. This photodegradation can be mitigated by combining it with other stabilizing agents or photostable UV filters in sunscreen formulations.

Octinoxate (also known as Octyl Methoxycinnamate or OMC) is a widely used organic compound found in many sunscreen and cosmetic products. It is used for its ability to absorb UV-B rays from the sun, which helps in protecting the skin from sunburn and other harmful effects of UV radiation. Chemical Properties of Octinoxate: 1. Chemical Structure: o IUPAC Name: Ethylhexyl Methoxycinnamate o Chemical Formula: C18H26O3 o Molecular Weight: 290.40 g/mol o Structure: Octinoxate is an ester formed from methoxycinnamic acid and 2-ethylhexanol. It has a methoxy group (-OCH3) attached to the benzene ring, which is part of the cinnamate backbone, providing UV absorption properties. 2. Physical Properties: o Appearance: It is a clear, colorless, or pale yellow liquid. o Solubility: Soluble in organic solvents like alcohols and oils, but insoluble in water. o Melting Point: Approximately 65-67°C. o Boiling Point: Approximately 198°C at 3 mmHg. 3. UV Absorption: o Maximum Absorption Wavelength (λmax): Around 310-315 nm. Octinoxate effectively absorbs UV-B rays in this range, preventing them from penetrating the skin. 4. Stability: o Octinoxate is relatively stable when exposed to UV light but can degrade over time, leading to reduced efficacy. It may be combined with other UV filters to enhance stability. 5. Reactivity: o Octinoxate can undergo photodegradation when exposed