Comparatively Speaking: Dimethicone vs. Methicone

August 5, 2009 | Contact Author | By: 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.

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!



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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