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Topic: Why is Hydroxyethyl cellulose not an alcohol?  (Read 414 times)

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Offline roastchicken

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Why is Hydroxyethyl cellulose not an alcohol?
« on: October 18, 2021, 03:42:07 AM »
I'm just a curious layperson, chemistry was my least-favorite of the natural sciences in high school.

I have a personal care product that is labelled as "alcohol free," but when reading the ingredients list I came across "Hydroxyethyl cellulose" (HEC). I was looking up all the ingredients, and became curious about this one due to the "alcohol free" claim. I recognize "ethyl" as somehow being related to alcohol. So I read the Wikipedia page about alcohol, and read "When a higher priority group [than the hydroxyl group] is present in the compound, the prefix hydroxy- is used in its IUPAC name."

I tried researching about functional groups, but I didn't get much other than a list of the order of functional groups. I'm too unknowledgeable and inexperienced to recognize these functional groups in chemical substances; I can compare which atoms are in the molecules, and not much else.



From the image on the Alcohol page, it seems to me that any substance with a "hydroxyl functional group bound to a saturated carbon atom" should be an alcohol. But this can't be right, because cellulose (seems to me to) have this property and obviously isn't an alcohol. I'm a bit fuzzy on what "saturated" means, but some quick searching led me to believe that it means a carbon atom with four single bonds. Because a carbon atom with a double bond is unsaturated by definition.

Because HEC has hydroxyl groups by virtue of its name, I wonder if it is more of a technical/definitional distinction to not classify it as an alcohol. Although I guess simply having a hydroxyl group is not enough, but looking at the ball and stick model and counting bonds it seems to me that it is indeed an alcohol according the above definition.

TL;DR: Would you call HEC an alcohol, and why/why not? Does HEC not share properties with most alcohols?

Offline rolnor

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Re: Why is Hydroxyethyl cellulose not an alcohol?
« Reply #1 on: October 18, 2021, 03:45:46 AM »
Its an alcohol. Its impossible to define any properties of alcohols, its suck a wide group of compounds. Its just any compound with a hydroxyl on a carbon somewhere in the molecule, except a hydroxyl group on a carbon in a aromatic ring, then its a phenol.
« Last Edit: October 18, 2021, 06:12:14 AM by rolnor »

Offline Orcio_87

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Re: Why is Hydroxyethyl cellulose not an alcohol?
« Reply #2 on: October 18, 2021, 05:21:26 AM »
It is an alcohol, but it does not cause drunkness - that is why labelled as "alcohol free".

Offline DrCMS

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Re: Why is Hydroxyethyl cellulose not an alcohol?
« Reply #3 on: October 18, 2021, 05:24:15 AM »
a personal care product that is labelled as "alcohol free,"

By this they mean it contains no ethanol.  To a lay person alcohol ≡ ethanol.

Offline roastchicken

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Re: Why is Hydroxyethyl cellulose not an alcohol?
« Reply #4 on: October 22, 2021, 07:21:52 AM »
Thank you for the responses!

Its an alcohol. Its impossible to define any properties of alcohols, its suck a wide group of compounds.

Interesting! I guess this makes intuitive sense given the lax requirements for belonging to the group. At least, that's how I (a layperson) rationalize it.

By this they mean it contains no ethanol.  To a lay person alcohol ≡ ethanol.

That's a good point. I guess I got so caught up in researching "chemical alcohol" that I forgot about this.

Offline Borek

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Re: Why is Hydroxyethyl cellulose not an alcohol?
« Reply #5 on: October 22, 2021, 07:44:42 AM »
lax requirements for belonging to the group

They aren't lax, they are quite precise - it is just that the properties of the compounds that fit the definition vary immensely.

A bit like defining mammals as the ones having mammal glands and then being surprised by how much bat differs from the whale ;)
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