[blaisem]

Hello, I am trying to figure out the difference between the ethylidene and ethenyl functional groups.  My issue arose when I had to name the substituents on a cyclohexane ring, at which point I encountered the ethylidene group for the first time after entering the structures in question into a database.  I have done several brief searches on the internet, and so far I have seen somewhat inconsistent patterns for the ethylidene group.  The two molecules I had to name were:

Ethylidene group:

http://www.chemsynthesis.com/base/chemical-structure-10632.html

Ethenyl group:

http://www.chemspider.com/Chemical-Structure.63665.html

I also drew a picture of these molecules which I attached.  I can't figure out how to insert it directly into the post, unfortunately.

My issue primarily with the ethylidene group is that I have 1. seen it used in the above link for a double bond directly to an alkyl ring, 2. seen it used in naming 1,1-ethylidene dichloride, as opposed to 1,2-ethylene dichloride, and 3. seen a definition of it as a radical from some online dictionaries. In other words, its manner of use seems inconsistent to me.

I have even seen a methylidene group, which seems consistent with 1. in that it is a double bond between the primary alkyl group and the α-carbon of the substituent; however, I believe this group may also be referred to as methenyl, so I am confused as to which might be correct.  Here is a link to a molecule using methylidene:

http://www.molport.com/buy-chemicals/moleculelink/4-methoxy-2-methylidene-4-oxobutanoic-acid/5657

Anyone able to clarify the rule for the use of this -idene suffix, or link me to someplace where I can read more on it?  I couldn't find a definitive site myself, and I did not see it on the IUPAC site.  Thank you very much.

Edit: I also get an error when using the search box on the forum, so I apologize if this has already been brought up before.

Edit 2: Added my picture! The left molecule is 1,2-diethylidenecyclohexane, and the right molecule is 1,2-diethenylcyclohexane.

[discodermolide]

Hello, I am trying to figure out the difference between the ethylidene and ethenyl functional groups.  My issue arose when I had to name the substituents on a cyclohexane ring, at which point I encountered the ethylidene group for the first time after entering the structures in question into a database.  I have done several brief searches on the internet, and so far I have seen somewhat inconsistent patterns for the ethylidene group.  The two molecules I had to name were:

Ethylidene group:

http://www.chemsynthesis.com/base/chemical-structure-10632.html

Ethenyl group:

http://www.chemspider.com/Chemical-Structure.63665.html

I also drew a picture of these molecules which I attached.  I can't figure out how to insert it directly into the post, unfortunately.

My issue primarily with the ethylidene group is that I have 1. seen it used in the above link for a double bond directly to an alkyl ring, 2. seen it used in naming 1,1-ethylidene dichloride, as opposed to 1,2-ethylene dichloride, and 3. seen a definition of it as a radical from some online dictionaries. In other words, its manner of use seems inconsistent to me.

I have even seen a methylidene group, which seems consistent with 1. in that it is a double bond between the primary alkyl group and the α-carbon of the substituent; however, I believe this group may also be referred to as methenyl, so I am confused as to which might be correct.  Here is a link to a molecule using methylidene:

http://www.molport.com/buy-chemicals/moleculelink/4-methoxy-2-methylidene-4-oxobutanoic-acid/5657

Anyone able to clarify the rule for the use of this -idene suffix, or link me to someplace where I can read more on it?  I couldn't find a definitive site myself, and I did not see it on the IUPAC site.  Thank you very much.

Edit: I also get an error when using the search box on the forum, so I apologize if this has already been brought up before.

If you click "additional options" when posting you will see a button allowing you to upload files.

[blaisem]

@Discodermolide

Thanks, I thought I had uploaded it, but it wasn't working.  Now that I do it again in my edit, it works . Thanks!

[discodermolide]

@Discodermolide

Thanks, I thought I had uploaded it, but it wasn't working.  Now that I do it again in my edit, it works . Thanks!

I would call the molecule on the right 1,2-divinylcyclohexane.
I'm not sure about ethylidene but you could look at this page if it makes any sense, it doesn't to me!
http://www.thefreedictionary.com/Ethylidene

[blaisem]

I would call the molecule on the right 1,2-divinylcyclohexane.
I'm not sure about ethylidene but you could look at this page if it makes any sense, it doesn't to me!
http://www.thefreedictionary.com/Ethylidene

Yeah haha I saw this definition, that is where I read something about it being a radical.  After trying to figure this out, I've realized that a definition from the dictionary websites are pretty ambiguous - and they all share the same definitions!  See Methenyl:

http://www.thefreedictionary.com/Methenyl

Oh well, I guess I'll leave the nomenclature part to someone else.  It's a little reassuring to see I'm not the only one for whom this makes no sense.  Hopefully, I won't be required to know this kind of thing in grad school.

[discodermolide]

I would call the molecule on the right 1,2-divinylcyclohexane.
I'm not sure about ethylidene but you could look at this page if it makes any sense, it doesn't to me!
http://www.thefreedictionary.com/Ethylidene

Yeah haha I saw this definition, that is where I read something about it being a radical.  After trying to figure this out, I've realized that a definition from the dictionary websites are pretty ambiguous - and they all share the same definitions!  See Methenyl:

http://www.thefreedictionary.com/Methenyl

Oh well, I guess I'll leave the nomenclature part to someone else.  It's a little reassuring to see I'm not the only one for whom this makes no sense.  Hopefully, I won't be required to know this kind of thing in grad school.

You will need to know some of it, but there are lots of applications that name compounds for you.