Naming Organic Compounds #-yl

newyorkcity

Hi all,

I have a question regarding the nomenclature of organic compounds. What is the significance of -5-yl in

bicyclo[2,1,0]pent-5-ylbicyclo[3,3,0]octane

? In general, what is the significance of the # in -#-yl in compounds?

Additionally, in (E)-1,2-diiodo-1methylcyclohexane, does the E indicate trans, whereas a Z would indicate cis? As in the two iodine atoms are on the first and second carbons, and they are both trans to each other (both axial)?

Thanks guys!

newyorkcity

I think I figured this out. So I think the -#-yl (when used with bicyclo subunits) denotes the carbon on the subunit that attaches to the main compound.

In the case presented above, the bicyclo[2,1,0]pentyl is not attached via a bridgehead C but rather one C over, but since the 'cyclopropyl' side is attached to the bicyclo[3,3,0]octane, we need to first go around the larger 'cyclobutyl' portion of the bicyclo[2,1,0]pentyl, thus getting a -5-yl. Note that I am using 'cyclobutyl' and 'cyclopropyl' as rough descriptors of the portions of the bicyclo[2,1,0]pentyl I am trying to reference; I can't think of a better way to accomplish this without an image.

Similarly, if we had 5-methylbicyclo[3,3,0]oct-2-yl-4-methylnonane, this would indicate that there is a methyl on the bridgehead of methylbicyclo[3,3,0]oct-2-yl and the bond to the main nonane chain is on the second carbon (one over from the bridgehead carbon) of the methylbicyclo[3,3,0]oct-2-yl.

Can someone confirm this analysis?