CycloAlkane Nomenclature
 

I am little bit confused in naming the following compound




1) parent name Hexane
2) cyclo
3) subsitutents or ethyl,methy, propyl
4c) 4-ethyl-2methyl-1propylcyclohexane

or is it

1 ethyl 3 methyl 4 propylcyclohexane

I thought as per rule 4c i have to name 1 ethyl-3 methyl 4 propylcyclohexane using alphabetic rule

but the first one is having
lower lower locants

which one is right.

Again the rule says sum of subsitutents is it actual sum ie in above case (4+2+1) and (1+3+4) respectively

Please clarify
Thanks

Shweta

nomenclature
 

4-ethyl-2methyl-1propylcyclohexane is the correct name. You are correct that the name should go in alphabetical order eg. ethyl, methyl propyl and the parent will be cyclohexane. The rule for numbering highly branched alkanes is called the "first point of difference" rule. In the two numbering schemes you use "4-ethyl-2methyl-1propylcyclohexane" or "1 ethyl 3 methyl 4 propylcyclohexane." Your first locant, in either case, is 1 (1 ethyl or 1 propyl) but looking at each numbering scheme, the second locant is either 2 or 3 (2methyl or 3methyl). The first point of difference rule means that even though both numbering schemes start at 1, the scheme that has the lowest number at it's first point of difference is the correct scheme. So 1, 2, 4 is correct while 1,3,4 is not. So numbering should be 1 propyl, 2 methyl, 4 ethyl and to keeep it alphabetic you get 4-ethyl-2methyl-1propylcyclohexane.

Hope this rule helps for any other similar problems,

bw800402