Naming carbon compounds (1 Viewer)

[-::Sanni::-]

How do you name this?

F F F H
| | | |
H-C-C-C-C-H
| | | |
H H Cl Cl

Is this called:

1,2-dichloro-2,3,4-trifluorobutane

OR

3,4-dichloro-1,2,3-trifluorobutane ?

 

[JasonNg1025]

Errrr.... do we have to know? I'm pretty sure the Cs are a little weird.. cause they haven't got all 4 bonds filled yet :O
But if you assume full hydrogens, then it's just butane

 

[-::Sanni::-]

Ooops it didn't come out right....

Just imagine that the lines are above and below the C's.

 

[JasonNg1025]

Ok ok ok I see it now

I think 1,2-dichloro-2,3,4-trifluorobutane should be it..

But I'm also wondering, when do you name in order of electronegativity and when do you name alphabetically?

 

[-::Sanni::-]

Yeah that's my problem....

I think electronegativity is first and then alphabetic is next. But I'm not sure! X_x

 

[danz90]

you order the constituent halogen atoms in terms of alphabetical order (dont worry about electronegativity).

always have chloro- before fluoro- etc.

 

[JasonNg1025]

So it's always

Bromo, then chloro, then fluoro, then iodo? And when you put the numbers on (not the di-, tri- tetra-, the numbers symbolising the position), do you give the first halogen the lowest number? Because in this Dot Point question it preferred 4-bromo over 3-bromo

hmmmmm

 

[danz90]

I usually just try and get the lowest-number possible for each halogen.
It really depends on the molecule/isomer thats given.

 

[JasonNg1025]

So you take into account what you'll get when you include all halogens?

In the example above, it was actually a choice between

3-bromo-5-chloro-4,4-difluorohexane

OR

4-bromo-2-chloro-3,3-difluorohexane

 

[danz90]

So you take into account what you'll get when you include all halogens?

In the example above, it was actually a choice between

3-bromo-5-chloro-4,4-difluorohexane

OR

4-bromo-2-chloro-3,3-difluorohexane

the choice is subjective, but I would've picked what the DotPoint answer was.. starting with the 4-bromo, because the other two halogens have quite low-number positions, which is favourable.

The one's in HSC exams aren't as tricky though.. and usually just contain chlorine and/or fluorine atoms, usually not bromo. Although it's important to be aware about halons with Bromine (and that Br is much more destructive than Cl)

 

[JasonNg1025]

So you're saying you look for a generally small group of numbers?

 

[danz90]

So you're saying you look for a generally small group of numbers?

yeah, pretty much.

 

[axlenatore]

So you take into account what you'll get when you include all halogens?

In the example above, it was actually a choice between

3-bromo-5-chloro-4,4-difluorohexane

OR

4-bromo-2-chloro-3,3-difluorohexane

Second 1 you need to keep the numbers at a min