Thread: Help! Using IUPAC's recommendations to name the following haloalkane.

Hello,

Does anyone know here if the designation of the following haloalkane is correct? (I used the program chemdraw to name it, but I have a problem with finding the parent chain which is explained below).


I think we need to take the red chain as "parent chain", because it contains the principal group chlorine. Then the naming of the substance was probably done wrong by the program chemdraw, right?

Actually I dont know whether Chlorine is the principal group here? In my dutch book it is said that the principal group is the characteristic group that is chose to be the suffix after the root in the designation. But the problem is chlorine cant be a suffix, does that mean its not a principal group in the above molecule?


If that is the case, then the designation right above here is correct anyways, because Chlorine is not the principal group here(?), so this means that according to the rules we use to determine the parent chain we have to look at the longest chain.

Rules for determining the parent chain are:

When in an acyclic compound there is a choice for principal chain, the following criteria are applied successively, in the order listed, until a decision is reached:

(a) Maximum number of substituents corresponding to the principal group. (WE SKIP THIS ONE BECAUSE CHLORINE IS NOT THE PRINCIPAL GROUP? SO WE DETERMINE THE PARENT CHAIN BY LENGHT SINCE WE SKIP THIS STEP)
(b) Maximum number of double and triple bonds considered together.
(c) Maximum length.



Thanks in advance!

The name you have given 5-(chloromethyl)-undecane is correct, the "parent chain" is the 11 carbon chain from the left and turning down towards the bottom with the chloromethyl substituent group on carbon 5. (You number the chain from one end, picking the end to start from such that the carbon with the substituent groups has the lower number).

By principle group it means something like an aldehyde, ketone or acid group that makes it a specific type of molecule (and gives the suffix -anal, -one, -acid etc.), not a substituent group like Cl, Br or (chloromethyl). As this molecule has no principle group you name it from the principle chain. As there are no principle groups and the molecule is saturated, the criterion to use in picking the principle chain is length, and the longest chain is the one mentioned above.

Thank you a lot, you have explained it perfectly! Now I can go on with repeating my material. Also I would like to add that only one functional group can be the principal group.

ok i guess i was wrong

No problem, as to one principle group, there can only be one type, but you can have more than one in number (if they are the same), for example imagine a di-ketone, it has two ketone groups and the parent chain must include both of them even if it is not the longest chain. This is what the rule:

(a) Maximum number of substituents corresponding to the principal group



is saying and this takes precendence over chain length.

I agree with everything, thanks again!

thnx