It’s simple. An alcohol is a carbon chain (CH-)that ends with an hydroxyl group (-OH). Ethyl alcohol (or ethanol aka drinking alcohol) has a carbon chain length of 2. The alcohols used in a lotion or conditioner are called fatty alcohols because they have a long carbon chain. Cetyl alcohol has a carbon chain length of 16. Stearyl alcohol is 18. Behenyl is 22. The higher in carbon chain length you go, the “heavier” the molecule and “fattier” it is. Thats why ethanol is a liquid (its lighter) with a carbon chain length of 2 and cetyl alcohol is solid wax with a chain length of 16.
Source – Cosmetic Chemist
The simple answer is, the difference between the alcohols is their chemical structure. In chemistry, there is a formal naming process of molecules (IUPAC), but often for chemicals that are more prevalent in use there is a different “common name”, especially if the IUPAC name is really long or that name looks scary to a consumer. Do you want to read lauryl alcohol or 1-dodecanol. In products for bathing, the various alcohols listed are really very similar, the main difference is the carbon chain attached. Think of the alcohol having a longer tail, shorter tail or fluffier tail. The reason why these compounds are put in these type of products is because the, -OH, alcohol part of the molecule is similar to water in the way it behaves, meaning water can rinse it out.
These are usually surfactants if it’s a shampoo you’re looking at. Surfactants are the molecules that soak up grease and dirt and are found detergents. They are much different from the alcohol that you know and love.
They are alcohol ethoxylates which is a fancy way of describing a molecule which one side is a type of oily alcohol (fatty alcohol) which repels water but likes oils, fats and grease, and the other side a water loving bunch of carbons and oxygens stretched into a long chain. When this is put into water, the water repelling side attracts grease, oils and dirt, and the water loving side helps to suspend what the other half has picked up in the water, meaning you can now rinse and wash away whatever you were trying to clean. Without the alcohol ethoxylate the grease and oil wouldn’t mix with the water and it wouldn’t move. If you’ve ever had hair wax and tried to wash it out with just water you’d know what an awful mess it makes.
The ‘alcohol’ really only describes the functional group of a part of the molecule. You’d poison yourself quite badly, and you’d never get drunk on it. If you tried to substitute it for your favourite whiskey.
Why do some bodywashes dry my skin and make me itch. For example the cream ones like Nivea and dove make me itch, but Irish spring original scent body wash does not…. I narrowed it down to 2 ingredients metalozione (sp*) and another… But recently others that don’t contain those 2 ingredients still make me itch
I don’t see it in any top-level comment, so… in chemistry, “alcohol” just means a molecule has an -OH (hydroxyl) group. That’s an oxygen atom bonded to a hydrogen atom, and essentially those can travel together as a pair and attach to others things. It imparts some polarity (to small molecules especially) and can make a compound more soluble in water.
You can of course have multiple OH functional groups attached to a single molecule. Two is called a diol or 2-ol. There’s also triol (3-ol) but you don’t hear that outside scientific contexts. You can keep going with tetrol, pentol, and other Greek prefixes, or “poly-ol” more generally. You may even see the OH group named first, as hydroxy-(something). But not everything with hydroxls ends in “ol” (as others said, sugars like glucose). Some names are historical or come from biology instead.
Anyway, the differences in “alcohol” compounds you see in your toiletry products is, well… everything about their structures beyond the OH group!
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