Comparatively Speaking: Guerbet Alcohol vs. Linear Fatty Alcohol

By: Anthony J. O'Lenick, Jr., Siltech LLC

Posted: March 16, 2010

Linear Alcohols
Natural fatty alcohols are linear materials with an even number of carbon atoms. They have the following structure: CH₃(CH₂)_nOH The physical properties of linear primary fatty alcohols are shown in Table 1. 

Guerbet Alcohols
Guerbet alcohols are a class of highly branched alcohols. They were first developed in the 1890s by Marcel Guerbet, who synthesized them. The reaction sequence, which bears his name, is related to the Aldol Reaction and occurs at high temperatures under catalytic conditions. The overall reaction is represented by Figure 1. Guerbet alcohols have significantly lower melting points than the linear alcohols with the same number of carbon atoms. The melting point of Guerbet alcohols vs. linear alcohols is shown in Figure 2. This makes them highly desirable in the personal care market.

Only two approaches are possible to obtain alcohols with a high molecular weight and liquidity:

The first is the introduction of unsaturation. Stearyl alcohol (C₁₈ saturated) is a waxy solid at ambient conditions and oleyl alcohol (C₁₈ with one double bond) is liquid. The problem with this approach is the degraditive process of rancidity attacks the unsaturation, producing color and odor.

The second approach is the introduction of branching. Methyl branched products are slightly more liquid than their linear counterparts. Longer branches, like those obtained by Guerbet technology, are liquid to far lower temperatures than either the linear of methyl branched products, making them outstanding candidates for use as emollient oils.