O chem questions

[student1982]

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Hi, these are just some old questions that I wrote down but don't quite understand. Anybody care to explain these questions. thank you
1) 4-fluoro1,1-dimethylcyclohexane
How come the methyl is prioritize first over flouride?

2) Why can't F- make H-bond, something about it being too electronegative?

3) 3-phenyl-1-propene
why is the propene used as the main chain? will phenyl always be used as a substituent?

 

[Flipper405]

1. It's not so much that the methyl is prioritized... it's that you have to number the substituents with the lowest possible sum. if you chose 4 for methyl, it would be 4+4+1 vs, 1+1+4.

2. no idea about that... i've read that F- actually works well with hydrogen bonds.

3. The alkene has priority.

 

[TheWiredNerv]

2. F can H bond.

 

[joonkimdds]

1. It's not so much that the methyl is prioritized... it's that you have to number the substituents with the lowest possible sum. if you chose 4 for methyl, it would be 4+4+1 vs, 1+1+4.

2. no idea about that... i've read that F- actually works well with hydrogen bonds.

3. The alkene has priority.

I am also confused with #1.
shouldn't fluride be prioritized?

How about I put a similar example?

C-C-C-C-C-C

it still has hexane as a parent chain
so let's say we put 2 methyl groups on first carbon.
and how about we put OH instead of F?
do we call it 1,1-dimethyl-4-hexanol or 6,6-dimethyl-2hexanol?

I am sure the order of priority is
OH> alkene > halogen > alkyl
if this order is correct, F is halogen so it was supposed to be prioritized than alkyl(dimethyl).

and if we follow this priority rules, I guess I can answer the #3 by saying that there is nothing higher priority than alkene except OH.

 

[TheWiredNerv]

I believe the hydroxy group takes priority and must have the lowest number.

 

[Flipper405]

I am also confused with #1.
shouldn't fluride be prioritized?

How about I put a similar example?

C-C-C-C-C-C

it still has hexane as a parent chain
so let's say we put 2 methyl groups on first carbon.
and how about we put OH instead of F?
do we call it 1,1-dimethyl-4-hexanol or 6,6-dimethyl-2hexanol?

I am sure the order of priority is
OH> alkene > halogen > alkyl
if this order is correct, F is halogen so it was supposed to be prioritized than alkyl(dimethyl).

and if we follow this priority rules, I guess I can answer the #3 by saying that there is nothing higher priority than alkene except OH.

The thing is, there are lots of things that have higher priority than alkenes.

For your example, I don't think your two options are even equivalent... but yes, alcohols take priority so you would have to number that carbon as low as possible.

With #1 from the OP, I guess nomenclature is kinda quirky... but the point is that there is no priority concerns with the compound.

"Alkyl groups and halogens are given equal priority when naming alkyl halides" - from some powerpoint off google

If you review your ochem book, there might be some more details on the basic nomenclature rules.

 

[drdeeeena]

I am also confused with #1.
shouldn't fluride be prioritized?

How about I put a similar example?

C-C-C-C-C-C

it still has hexane as a parent chain
so let's say we put 2 methyl groups on first carbon.
and how about we put OH instead of F?
do we call it 1,1-dimethyl-4-hexanol or 6,6-dimethyl-2hexanol?

I am sure the order of priority is
OH> alkene > halogen > alkyl
if this order is correct, F is halogen so it was supposed to be prioritized than alkyl(dimethyl).

and if we follow this priority rules, I guess I can answer the #3 by saying that there is nothing higher priority than alkene except OH.

If you add the two methyl on the first C then you will end up with a heptane so ur cpd will be 6-methyl-3-heptanol

its really important that you choose the longest chain for your naming, so when you add the methyl your long chain will change from 6C to 7C. Please note that adding methyl on the first or the last carbon will chained the length of the chain.
As for the order of your priority group list, its correct.

ALWAYS choose the naming with the lowest number possible!

Hope this helps