Nomenclature question

[Juggernauts]

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Picture 1) I get why cis-ethyl-3-methylcyclohexane is named with the ethyl group having priority based on the molecular weight being heavier than the methyl group.

Picture 2) But why does ethyl take priority in trans-ethyl-3-i-propylcyclobutane? Shouldn't it be trans-3-ethyl-isopropylbutane?

 

[UCF FINatic]

Picture 1) I get why cis-ethyl-3-methylcyclohexane is named with the ethyl group having priority based on the molecular weight being heavier than the methyl group.

Picture 2) But why does ethyl take priority in trans-ethyl-3-i-propylcyclobutane? Shouldn't it be trans-3-ethyl-isopropylbutane?

1.) I think it has more to do with the longest carbon chain, not on the molecular weight.

2.) I believe it is alphabetical. If you go either way you have the same carbon chain (I don't even think that is relevent here), but e- comes before i-. I believe that is the correct answer.

 

[seunglim87]

for the first structure, ethyl gets the priority b/c of the alphabetical reason. also it can be cis-1-ethly-3-methylcyclohexane, but sometimes you dont write 1 b/c it is given.
the second picture, also, ethyl gets priority over iso-propyl b/c of the alphabetical reason.
The number prefixes such as di-,tri-(di-bromo, you will count "b" for bromo) gets ignored as well as tert- and sec-(tert-butyl, you will cound "b" for butyl), but iso- and cyclo are exceptions (iso-propyl wil be "i", and cyclopentane will be "c")

 

[Mr PS09]

alphabetical my orgo teacher would never let me forget it :/