OChem: Naming Alkanes w/ Two Halogens

[informatique]

I just got "Organic Chemistry Odyssey" and started working on the problems.

One nomenclature problem has:

1) 2-bromo-3-flourobutane

the other one is:

2) 2-chloro-3-iodobutane

??????????

Electronegativity= F>Cl>Br>I
Molecular Weight = I>Cl>Br>F

How am I supposed to name dihaloalkanes?? (*I took out R/S configurations...I just need to know the numbering)

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[userah]

it's alphabetical. Chlorine before Iodine. Bromine before Fluorine

 

[Hugh Mannity]

Alphabetical only if each substituent is equally far from the beginning of the end of the chain. Lowest number for first substituent is rule #1 for unbranched alkanes. If equal possibilities, then alphabetical.