Title: Decamethylcyclopentasiloxane
CAS Registry Number: 541-02-6
Additional Names: D5
Molecular Formula: C10H30O5Si5
Molecular Weight: 370.77
Percent Composition: C 32.39%, H 8.16%, O 21.58%, Si 37.87%
Literature References: Cyclic siloxane. Isolated from the hydrolysis product of dimethyldichlorosilane: W. Patnode, D. F. Wilcock, J. Am. Chem. Soc. 68, 358 (1946). HPLC determn and GC-MS characterization of metabolites in urine: S. Varaprath et al., Drug Metab. Dispos. 31, 206 (2003). Physicochemical properties: M. Palczewska-Tulinska, P. Oracz, J. Chem. Eng. Data 50, 1711 (2005).
Properties: Colorless volatile liquid. mp -38°. bp760 210°; bp20 101°. d 0.9593. nD20 1.3982. Soly in water: 17 ppb. Vapor pressure (50°): 2 mm Hg.
Melting point: mp -38°
Boiling point: bp760 210°; bp20 101°
Index of refraction: nD20 1.3982
Density: d 0.9593
Use: Intermediate in the mfr of high mol wt siloxane polymers. Carrier ingredient in personal care products; dry cleaning solvent.
Decamethylene Glycol Decamethyltetrasiloxane Dechlorane?Plus Decimemide Decoquinate

Skeletal formula of decamethylcyclopentasiloxane
CAS number 541-02-6 YesY
PubChem 10913
ChemSpider 10451 YesY
EC number 208-764-9
MeSH Decamethylcyclopentasiloxane
RTECS number GY5945200
Beilstein Reference 1800166
Jmol-3D images Image 1
Image 2
Molecular formula C10H30O5Si5
Molar mass 370.77 g mol−1
Appearance Colourless liquid
Density 0.958 g cm-3
Melting point −47 °C; −53 °F; 226 K
Boiling point 210 °C; 410 °F; 483 K
Viscosity 3.74 cP
MSDS External MSDS
EU classification Irritant Xi
R-phrases R36/37/38
S-phrases S23, S24/25
NFPA 704
NFPA 704.svg
Flash point 73 °C; 163 °F; 346 K
Related compounds
Related Organosilicon compounds tetramethylsilane, silabenzene
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Decamethylcyclopentasiloxane (D5) is a silicone fluid commonly used in cosmetics such as deodorants, sunblocks, hair sprays and skin care products. It is becoming more common in hair conditioners, as it makes the hair easier to brush without breakage. It is also used as part of silicone based personal lubricants. It can be found in other cosmetics such as sunless tanning lotion and underarm deodorants. D5 is an emollient.

D5 is contained in the mixture cyclomethicone (INCI name).