OChem question..

[FLY]

I have 2 questions, and this is my webassignment and if I make like a simple little mistake, my answer will be wrong and out of 3 submissions I already used up 2...

1. 2-Ethyl-5,5-dimethylcyclohexanol is treated with thionyl chloride. Provide the substitutive name of the major organic product.

my ans: 1-choro-2-ethyl-5,5-dimethylcyclohexane
but something is wrong with it?? can somebody find it??

3. 3,3,5-triethyl-5,6-dimethylcycloheptanol is treated with phosphorus tribromide. Provide the substitutive name for the product of this reaction.

my ans:
6-bromo-1,1,3-triethyl-3,4-dimethylcycloheptane
but this is wrong too..

(RESPONSE FORMAT: in your response use all small-case letters, place one comma between adjacent numbers, use dashes between numbers and names and between names and numbers.)
Thanks..

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[wolferman]

•••quote:••• my ans: 1-choro-2-ethyl-5,5-dimethylcyclohexane
••••Well, I'm not sure if you just mistyped when posting this thread, but you have "choro" down instead of "chloro".

 

[BUmiken12]

FLY,
I have no clue about the first one (I've never heard of thionyl chloride), but I think I have some idea of the second. Phosphorus tribromide is used to add bromide while making the -OH the leaving group. After the hydroxyl group leaves a carbocation is formed and therefore, carbocation rearrangements need to be taken into account. There would quite possibly be a double hydride shift so that the carbocation can be on a tertiary carbon and the Bromide can be a tertiary substituent. Therefore, I would get:
4-bromo-1,1,3-triethyl-3,4-dimethylcycloheptane. I think this is right, but can someone else verify this??

 

[Street Philosopher]

SOCl2 reacts to substitute the alcohol. That should answer your first question.

nevermind: i did the reaction and got your answer (except the spelling error)

the only thing I can think of is maybe the reaction involves a carbocation (i.e. rearragements) and the Cl goes with the ethyl group...

 

[Jameson]

Your number assignments for your first question are wrong...I think that it should be 3-ethyl-2-chloro-1,1-dimethylcyclohexane. For your second question you may be on your own there because I am really not familiar with that rxn.

 

[wolferman]

If Newton is right, then all you need to do is make sure your constituents are alphabetized per IUPAC rules.

3-ethyl-2-chloro-1,1-dimethylcyclohexane
becomes...
2-chloro-3-ethyl-1,1-dimethylcyclohexane

 

[Jameson]

Ah yes, thank you wolferman! I swore I had them alphebetized but I obviously need to go back to grade school!!!!

 

[FLY]

Ok, for those of you that helped .. thanks..

The right answers were..

1. 3-chloro-4-ethyl-1,1-dimethylcyclohexane

3. not sure which is the right answer yet, but I know that the following answers are wrong...

1-bromo-3,3,5-triethyl-5,6-dimethylcycloheptane
6-bromo-1,1,3-triethyl-3,4-dimethylcycloheptane
4-bromo-1,1,3-triethyl-3,4-dimethylcycloheptane

 

[omores]

Alrightee, I'll give 3 a go, even though it's been a few years...

Step One: remove -OH and form carbocat on C1.

Step Two: double hydride shift to form tertiary carbocat on C6

Step Three: add bromide to C6 to keep the methyl group company

Step Four: reassign numbers: bromo- is first alphabetically, and also gives you the lowest set of numbers all round, so C6 becomes C1.

Here's what the ring looks like now: bromo and methyl on C1 (formerly C6), methyl and ethyl next door on C2 (formerly C5), and two ethyls two doors down on C4 (formerly C3). Note: none of the other substituents have moved; it's just the numbering that's changed.

This gives us 1-bromo-2,4,4-triethyl-1,2-dimethylcycloheptane.

Or maybe it doesn't...

<img border="0" alt="[Laughy]" title="" src="graemlins/laughy.gif" /> <img border="0" title="" alt="[Eek!]" src="eek.gif" /> <img border="0" alt="[Laughy]" title="" src="graemlins/laughy.gif" /> <img border="0" title="" alt="[Eek!]" src="eek.gif" /> <img border="0" alt="[Laughy]" title="" src="graemlins/laughy.gif" />

 

[Elysium]

Sorry I can't help, but I just wanted to let you know that I HATE webassign with a passion. I think it's evil and it's just pure laziness (and an unwillingness to grade problems) on the part of the teachers. We're doing webassign for physics and it totally blows (if it's off by 1 sig fig, it's just wrong)
I feel your pain!

 

[FLY]

It sure is a pain in the ass and we complained to him today...

But he got a good point thou..

This is the first year that we are doing web assings for Orgo. and the avg. score for Test one was a 79.7 when compared to 55-65 all the previous years...

I hate it but it's really helping me... Since I never used to do any of those text problems...

 

[Catalyst]

I think the answer is 1-bromo-5,6-dimethyl-3,3,5-triethylcycloheptane. PBr3 converts the alcohol (R-OH) to the alkyl halide (R-Br). The name arises from the carbon having bromine being named as priority #1 (because of bromine's atomic number), and the dimethyl part goes alphabetically before the triethyl part.. is this the right answer?

Probably the only pre-med on the face of the earth that loves organic chemistry..

Sachin

 

[Catalyst]

Ehh, I take that back, I think I'm wrong, maybe I don't know what the hell I'm talking about after all haha..

Sachin