query (1 Viewer)

[pLuvia]

When naming haloalkanes do you name them favouring the element that is most electronegative, so example
CCl₃CBrF₂
Would this be: 1-bromo 2,2,2-trichloro 1,1-difluoroethane?

 

[Gecko888]

Apparently the first thing to do is to find which way yields the lowest set of numbers. In this case I think both directions are the same. Then, if both directions are the same, you give the lowest number to the first named halogen, which is bromine anyway. I thought I read before somewhere it was electronegativity too...maybe there are conflicting sources

 

[onebytwo]

i thought it was to do with alphabetical order, which would mean your right.

 

[pLuvia]

That too, but I'm just confused with the electronegativity aspect, as the books say it and my teacher too says this. But when I did a question in the Success One it contradicts all my sources I think the answers are wrong, but I need to make sure, as I've seen other mistakes in their answers

 

[tennille]

I've always been taught to name them in alphabetical order, even at uni. But then again, I'm not that great with nomenclature (maybe I'm missing something).

Have you checked any websites at all?

 

[pLuvia]

I don't know if you guys are talking about the same thing as me, sorry if I was unclear but this is what I should have meant.

Let's say there's this haloalkane
CH₃CHBrCH₃CH₂Cl

Now would you name this, from the most electronegative element which is the Cl, so you would start counting from there.

I know that you have to name via alphabetical order, but there's that problem with counting from the electronegative side or not.
For this example, would you name it:
3-bromo,1-chlorobutane (this is what I think it is, since it yields the lowest set of numbers)
or
2-bromo, 4 chlorobutane

 

[Gecko888]

An example of conflict is 113 trichloro 133 trifluoro propane. This could also be 133 trichloro 113 trifluoro propane. According To Conquering Chemistry the second one is correct. Spotlight is unclear on this, although I think in some questions they seem to suggest the first name. Other books are split between the two.

Anyway, search IUPAC for confirmation. I tend to believe the second name is correct.

 

[mitsui]

I don't know if you guys are talking about the same thing as me, sorry if I was unclear but this is what I should have meant.

Let's say there's this haloalkane
CH₃CHBrCH₃CH₂Cl

Now would you name this, from the most electronegative element which is the Cl, so you would start counting from there.

I know that you have to name via alphabetical order, but there's that problem with counting from the electronegative side or not.
For this example, would you name it:
3-bromo,1-chlorobutane (this is what I think it is, since it yields the lowest set of numbers)
or
2-bromo, 4 chlorobutane

the first number should always be the smallest number possible
ie.
2nd answer is correct