[Big-Daddy]

How do we name this group?

It is 2 R groups, with one C atom only between them (bonded to each); from this C atom stems directly a double bond to another C atom, and this latter C atom then connects to another (so there is a methyl group off the double bond, and the double bond coming directly off the main chain).

The problem is that standard naming from the beginning does not work, because by definition of this problem the R groups are the parent chain and so this double bond is a side-substituent. But from what I know of branched naming, the numbering on the chain would start at the first atom exclusively on that chain which has the double bond, whereas now, the atom which connects to the chain (and is itself part of the parent chain, with the double bond substituent coming off it) is the first in the double bond.

Not sure if this is an undergraduate or high school problem but I thought I would post it here. Thanks for the help.

[Arkcon]

I think this is a good topic for the Organic Chemistry forum, so I've moved it.  I don't really know how we'd name something like this.  Unless, since a portion of the molecule is given by R, we're being called on to ignore that part of the molecule, and you just name the unsaturated chain, and mention there are R groups.

[Dan]

It is 2 R groups, with one C atom only between them (bonded to each); from this C atom stems directly a double bond to another C atom, and this latter C atom then connects to another (so there is a methyl group off the double bond, and the double bond coming directly off the main chain).

Please draw.

Smiles tutorial is here, or you can upload a picture as an attachment.

[Big-Daddy]

Here is a picture of the molecule I am talking about:



I have cheekily called the two R groups Ra and Rb - these are not elements, I just don't know how to use SMILES to put in a general "R" group. The point is they could be different and the picture seems to show my idea.

On what Arkcon said: I was wondering what the answer is when the chain coming off must be seen as a branch (due to what is going on in the R groups taking higher priority for naming).

[Borek]

I have cheekily called the two R groups Ra and Rb - these are not elements, I just don't know how to use SMILES to put in a general "R" group.

[Big-Daddy]

I have cheekily called the two R groups Ra and Rb - these are not elements, I just don't know how to use SMILES to put in a general "R" group.

Thank you, this helps a lot as most of my questions involve R-groups!

Anyone know the answer?

[sjb]

Something like ethylidene, by analogy with http://en.wikipedia.org/w/index.php?title=Methylene_group&oldid=542282660 ?

[Big-Daddy]

Something like ethylidene, by analogy with http://en.wikipedia.org/w/index.php?title=Methylene_group&oldid=542282660 ?

Thanks for the link, we are clearly along the right lines now.

How about methylmethylene or methylmethylidene? This seems easier to extend if big groups were to come off the methylene group.

[Dan]

Methylmethylidene is correct (I think).

[Big-Daddy]

Methylmethylidene is correct (I think).

Thank you.