What is the difference in chemical composition between D4 and D5


The differences in chemical composition between D4 (octamethylcyclotetrasiloxane) and D5 (decamethylcyclopentasiloxane) are mainly reflected in molecular structure, molecular weight, physical properties, and application fields. The following is a specific analysis:


molecular structure
D4: The chemical formula is C ₈ H ₂₄ O ₄ Si ₄, which is a tetracyclic octamethylsiloxane containing 4 silicon atoms in its molecule and belongs to cyclic organosilicon compounds.
D5: The chemical formula is C ₁₀ H ∝₀ O ₅ Si ₅, which is a pentacyclic compound of decamethylsiloxane containing 5 silicon atoms. It also belongs to cyclic organosilicon compounds.
molecular weight
D4: The molecular weight is 296.62.
D5: The molecular weight is 370.770.
physical property
Appearance: D4 is a colorless, transparent or milky white liquid; D5 is a colorless transparent oily liquid.
Melting point: The melting point of D4 is 17-18 ° C; the melting point data of D5 is not explicitly mentioned, but the melting point of cyclic siloxanes usually changes with the increase of silicon atoms in the molecule.
Boiling point: The boiling point of D4 is 175 ° C (74 ° C, 2.66kPa); The boiling point of D5 is not explicitly mentioned, but generally the boiling point of cyclic siloxanes also increases with the increase of the number of silicon atoms in the molecule.
Relative density: The relative density of D4 is 0.9558 (20/4 ° C); The relative density data of D5 is not explicitly mentioned.
Volatility: D5 has excellent room temperature volatility (lower heat of evaporation and vapor pressure), while D4 also has some volatility, but its volatility may be slightly weaker compared to D5.
application area 
D4: It is an important intermediate in the organic silicon industry, mainly used for the preparation of organic silicon polymers such as methyl silicone oil. It is also one of the important raw materials for organic silicon softeners in textiles, and can be used for insulation and moisture resistance of wireless components, as well as surface deactivators for gas chromatography glass capillary columns.
D5: Widely used in cosmetics and human care products, it has good compatibility with most alcohols and other cosmetic solvents, and is one of the main components of "silicone oil" commonly found in cosmetics.