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Comparatively Speaking: Dimethicone vs. Methicone

Contact Author Anthony J. O'Lenick, Jr., Siltech LLC
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Dimethicone refers to a silicone compound that has “D” units, meaning only silicon atoms with two methyl groups attached. Dimethicone compounds are common and this term encompasses silicone fluids, PEG-8 dimethicone, cetyl dimethicone and many others (see Figure 1).

The presence of the “D” unit, written in parenthesis with an “a” subscript, makes a compound a dimethicone. The “D” unit is shown in Figure 2.

A methicone, on the other hand, completely lacks the “D” unit. In place of a "D" unit are organofunctional groups. An example is cetyl methicone, which conforms to the structure shown in Figure 3.

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If any “D” units are present, the compound is a dimethicone. Consequently, the molecule shown in Figure 4 is cetyl dimethicone. Strangely enough, cyclomethicone has four "D" units in cyclic form, yet it is called cyclomethicone not cyclodimethicone. No one ever said the names would be logical!

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Figure 1. Dimethicone

Figure 1

Dimethicone refers to a silicone compound that has "D" units.

Figure 2. "D" Unit

Figure 2. "D" Unit

The presence of a "D" unit makes a compound a dimethicone.

Figure 3. Cetyl methicone

Figure 3. Cetyl methicone

Cethyl methicone conforms to this structure.

Figure 4. Cetyl dimethicone

Cetyl dimethicone

This molecule is cetyl dimethicone.

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