Comparatively Speaking: Ether vs. Ester

In today’s competitive world, the cosmetic chemist must be a person of skill in cosmetic science. Beyond this, the formulator also must possess a great deal of artistic ability in order to formulate cosmetically elegant products at an ever increasing rate of speed.  However, the cosmetic chemist is, and remains, a scientist. 

 

 

In searching for scientific information to aid in formulating, the Internet can be a great aid – but only if used with great care. I recently read, with amazement, an Internet article warning against the use of sodium lauryl ether sulfate, since it contains ether, a material causing sleep. This was offered as science! My amazement changed to horror with the understanding that this type of misinformation can really hurt out industry.

 

How can we intelligently use good science and debunk misinformation offered as “science”?  The keys are going back to basics and communication.  At a recent conference one of my associates queried, “How many of the people present actually know the difference between an ether and an ester? “ This question and my inability to answer it led ultimately to this column.

This column will present important, fundamental concepts of chemistry.  The goal is not only to help chemists effectively use information, but to be more critical in accepting it and to question it. The format will be two questions per column, on a variety of topics, including basic science, formulation science, regulatory and legal issues. The hope is to get readers to think about, discuss the answer and get back to technical basics. Comments from readers are always welcome.

Questions:

1. What is the difference between an ether and ester?
2. What is the difference between silicon and silicone?

Answers:

1.  An ether is a compound that has a carbon oxygen carbon bond. An example of an ether is an ethoxylate. The compound below is laureth 5.

                       

CH3-(CH2)11-O-(CH2CH2O)5-H

  

 

 

This particular ether is made by the reaction of ethylene oxide and an alcohol. The ending “eth” is added to the route alcohol and the number of moles of ethylene oxide is added the name. The ether used in anesthesia shares the carbon oxygen carbon bond making it an ether, but is a very specific much more volatile material diethyl ether.

                         

CH3-CH2-OCH2CH3

 

 

Sodium lauryl ether sulfate does not contain this and consequently does not cause sleepiness.

 

An ester, on the other hand, is a compound that has a carbon-carbonyl-oxygen carbon bond. An example is lauryl stearate shown below.

 

O ||   CH3-(CH2)17-C-O(CH2)11CH3

 

 

                                                 

 

 

 

 

Esters are typically made from the reaction of an alcohol and an acid: in this case, stearic acid and lauryl alcohol. It is noteworthy that the acid name is the group which comes last to which “ate” is added and the alcohol name comes first to which the “yl” ending is added. What then is stearyl laurate?

 

2.  Silicon is an element. It does not occur in nature, but is very common in the form of an oxide, making up 25% of the Earth’s crust. You can find it in sand, quartz, rock crystal, amethyst, agate and opal. Discovered by Jöns Jacob Berzelius in in 1824, Silicon possesses an Atomic Number 14, an Atomic Weight 28 and a Melting Point 1414oC. The “silicon valley” derives its name not since the element exists in free form, but from the fact that silicon is used in computer chips.

Silicone is a polymeric compound having repeating  –Si-O-Si- bonds.  One method for production is the ring opening of cyclic silicone compounds. An example of a silicone is polydimethyl siloxane. The example below is dimethicone.

 

 

CH3   CH3           CH3                                                    |        |                |                                           CH3-Si-O-(Si-O)100-O-Si-CH3                                                    |        |                |                                                   CH3   CH3           CH3

As the number of units present increases the viscosity increases.

 All silicones contain silicon and oxygen. 

 

--Anthony J. O’Lenick, Siltech LLC

Tony O’Lenick President Siltech LLC Tony O’Lenick founded Siltech LLC, a silicone and surfactant specialty company, in 1989. He has held technical and executive positions at Alkaril Chemicals Inc., Henkel Corp. and Mona Industries and has been involved in the personal care market for over 30 years. O’Lenick has published more than 45 technical articles in trade journals, contributed chapters to five books, authored two books, and is the inventor of over 250 patents. His most recent book, Surfactants: Strategic Personal Care Ingredients, was launched in 2005 by Allured Publishing Corp.; Silicones for Personal Care was published in 2003. O’Lenick teaches continuing education courses in silicones and patent law for the Society of Cosmetic Chemists (SCC). He received a number of awards for work in chemistry including: the 1996 Samuel Rosen Award given by the American Oil Chemists’ Society; the 1997 Innovative Use of Fatty Acids Award given by the Soap and Detergents Association; and the Partnership to The Personal Care Award given by the Advanced Technology Group. O’Lenick was a member of the Committee on Scientific Affairs of the SCC.