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Offline rcrandall

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Organic 1 Synthesis Problems
« on: December 06, 2014, 09:05:41 AM »


I have my organic 333 final exam on Tuesday, and my professor has given the class this worksheet of synthesis problems to work out. One of these will be on the exam, as well as a "surprise" synthesis problem.

In working out the first one (methyl cyclohexane into cyclohexanone), I asked a yahoo answers question about this, but something is telling me this is the better place to be  ;)

From yahoo answers, I was told for the first one to Brominate, dehydrohalogenate, oxidize.
In this problem, are you replacing a CH3 with an alcohol, then oxidizing to form (basically) a ketone on a cyclohexane?


Offline Rutherford

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Re: Organic 1 Synthesis Problems
« Reply #1 on: December 06, 2014, 10:20:30 AM »
The product where one hydrogen from the methyl group will be substituted with the halogen is the one you need.

Offline Babcock_Hall

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Re: Organic 1 Synthesis Problems
« Reply #2 on: December 06, 2014, 11:33:12 AM »
From yahoo answers, I was told for the first one to Brominate, dehydrohalogenate, oxidize.
In this problem, are you replacing a CH3 with an alcohol, then oxidizing to form (basically) a ketone on a cyclohexane?


I can't view your diagrams, but I don't know why you think that an alcohol is produced along the way.

Offline Babcock_Hall

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Re: Organic 1 Synthesis Problems
« Reply #3 on: December 06, 2014, 11:36:36 AM »
The product where one hydrogen from the methyl group will be substituted with the halogen is the one you need.
I think that the bromine may add to a different carbon atom from the one you are suggesting, assuming that this is a radical bromination reaction.  However, I cannot see the diagrams provided by the OP, and so I am not certain about the conditions.

Offline rcrandall

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Re: Organic 1 Synthesis Problems
« Reply #4 on: December 06, 2014, 02:54:30 PM »
I don't know how to properly embed photos into this website, sorry (any advice for this? I can see the pictures myself, but this obviously isn't the case for everyone).
(https://answers.yahoo.com/question/index?qid=20141205150945AALqrWb)
I think the pictures work on this website, if you wanted to see them.

I assumed that an alcohol would form because then a keto-enol tautomerism would form the double bond to oxygen. But with synthesis problems, you are "supposed" to work backwards...

Offline gritch

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Re: Organic 1 Synthesis Problems
« Reply #5 on: December 06, 2014, 03:11:25 PM »
You should consider other reactions other than oxidation of alcohols. There are plenty of reactions in Organic 1 to make ketones bur far less that can remove a carbon from the molecule itself. The removing of a carbon from the molecule would seem to be the more mechanistically difficult part. I suggest going through your lecture notes a looking for reactions that break apart molecules and start from there.

Offline kriggy

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Re: Organic 1 Synthesis Problems
« Reply #6 on: December 06, 2014, 03:13:50 PM »
Indeed, you need to get rid of that carbon.
I was able to see the picture before but now I dont see it. I can only suggest IMGUR, it works for me and never had someone that didnt see the picure (on this board)

Offline Babcock_Hall

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Re: Organic 1 Synthesis Problems
« Reply #7 on: December 06, 2014, 03:44:54 PM »
If you dehydrohalogenate the molecule in the picture, there are two possible products, but only one will be useful in this synthesis.  Can you draw the two products out for us and (ideally) explain how to tip the balance toward one or the other?  I agree that working the problem backwards may be helpful.

Offline rcrandall

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Re: Organic 1 Synthesis Problems
« Reply #8 on: December 06, 2014, 03:57:42 PM »
So if you react a methyl cyclohexane with Br2 in the presence of heat, you form a 1-methyl-1-bromo-cyclohexane (my naming might not be perfect).
If you dehydrohalogenate, you can remove a hydrogen from one of the carbons in the ring, or you can remove a hydrogen from the methyl (using a bulky base). The first will create a methyl cyclohexene, and the latter will create a double bonded carbon to a cyclohexane?

Offline rcrandall

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Re: Organic 1 Synthesis Problems
« Reply #9 on: December 06, 2014, 04:07:08 PM »
(I have no idea if I am right in any of this, but I'll keep trying!)
Could you then react with ozone? A double bonded carbon attached to a cyclohexane, react with 1) O3, 2) CH3SCH3  (part 2 came from a list of reagents I have, but the major part is ozone), that double bond to oxygen will cleave, forming an oxygen double bonded to a cyclohexane ring, and an oxygen double bonded to a carbon (so 2 products).

Offline rcrandall

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Re: Organic 1 Synthesis Problems
« Reply #10 on: December 06, 2014, 04:17:52 PM »

Is this image working?

Offline Babcock_Hall

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Re: Organic 1 Synthesis Problems
« Reply #11 on: December 06, 2014, 04:19:42 PM »
Yes, I can see the syntheses.

Offline kriggy

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Re: Organic 1 Synthesis Problems
« Reply #12 on: December 06, 2014, 04:23:24 PM »
So if you react a methyl cyclohexane with Br2 in the presence of heat, you form a 1-methyl-1-bromo-cyclohexane (my naming might not be perfect).
If you dehydrohalogenate, you can remove a hydrogen from one of the carbons in the ring, or you can remove a hydrogen from the methyl (using a bulky base). The first will create a methyl cyclohexene, and the latter will create a double bonded carbon to a cyclohexane?
Yes

(I have no idea if I am right in any of this, but I'll keep trying!)
Could you then react with ozone? A double bonded carbon attached to a cyclohexane, react with 1) O3, 2) CH3SCH3  (part 2 came from a list of reagents I have, but the major part is ozone), that double bond to oxygen will cleave, forming an oxygen double bonded to a cyclohexane ring, and an oxygen double bonded to a carbon (so 2 products).

Indeed you can do that  ;) I think its the way to go.
and btw its better to show a picture than describe a reaction in sentences

Offline rcrandall

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Re: Organic 1 Synthesis Problems
« Reply #13 on: December 06, 2014, 04:27:11 PM »
Yeah, sorry! I thought I had the picture uploaded, but people couldn't see it so I tried posting again (which seems to be working now  ;D )
So 1 down, 6 to go!

Offline rcrandall

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Re: Organic 1 Synthesis Problems
« Reply #14 on: December 06, 2014, 04:48:29 PM »


Just making sure, does anyone see anything wrong with this before I tackle the next problem? (Assuming the picture works...)

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