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Topic: 3,4,5-triiodotoluene synthesis  (Read 8307 times)

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Offline xmayer

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3,4,5-triiodotoluene synthesis
« on: October 14, 2011, 09:13:58 AM »
Can someone help me which reagents are needed to get it from benzene?

Offline discodermolide

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Re: 3,4,5-triiodotoluene synthesis
« Reply #1 on: October 14, 2011, 09:19:02 AM »
Can someone help me which reagents are needed to get it from benzene?

Not from benzene!
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Offline Nosterius

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Re: 3,4,5-triiodotoluene synthesis
« Reply #2 on: October 14, 2011, 09:30:13 AM »
Hi Xmayer,

Is it part of a written exercice, or do you want to actually make it in the lab?

As Discodermolide pointed out, if you can, we would advise starting from another reagent than benzene, such as one already bearing substituent(s). Toluene, for exemple, would be a better starting point since there is already the methyl group installed on the aromatic ring.

Offline xmayer

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Re: 3,4,5-triiodotoluene synthesis
« Reply #3 on: October 14, 2011, 09:43:48 AM »
Hi Xmayer,

Is it part of a written exercice, or do you want to actually make it in the lab?

As Discodermolide pointed out, if you can, we would advise starting from another reagent than benzene, such as one already bearing substituent(s). Toluene, for exemple, would be a better starting point since there is already the methyl group installed on the aromatic ring.
Hi, it's just a written exercise. Well ok, i can get toulene with friedel-crafts alkylization.

Offline discodermolide

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Re: 3,4,5-triiodotoluene synthesis
« Reply #4 on: October 14, 2011, 09:58:52 AM »
Hi Xmayer,

Is it part of a written exercice, or do you want to actually make it in the lab?

As Discodermolide pointed out, if you can, we would advise starting from another reagent than benzene, such as one already bearing substituent(s). Toluene, for exemple, would be a better starting point since there is already the methyl group installed on the aromatic ring.
Hi, it's just a written exercise. Well ok, i can get toulene with friedel-crafts alkylization.

A Friedel-Crafts with benzene will give you a mess. I don't advise it unless you have very specific conditions.
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Offline fledarmus

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Re: 3,4,5-triiodotoluene synthesis
« Reply #5 on: October 14, 2011, 10:26:53 AM »
Hi Xmayer,

Is it part of a written exercice, or do you want to actually make it in the lab?

As Discodermolide pointed out, if you can, we would advise starting from another reagent than benzene, such as one already bearing substituent(s). Toluene, for exemple, would be a better starting point since there is already the methyl group installed on the aromatic ring.
Hi, it's just a written exercise. Well ok, i can get toulene with friedel-crafts alkylization.

A Friedel-Crafts with benzene will give you a mess. I don't advise it unless you have very specific conditions.

I second this. Benzene is relatively unreactive, and every methyl group you add makes it more reactive. Toluene as it is formed will react faster than the benzene it is formed from, and you will end up with a whole mess of various alkylation patterns.

Offline xmayer

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Re: 3,4,5-triiodotoluene synthesis
« Reply #6 on: October 15, 2011, 04:57:07 PM »
Is it good if I do a diazonium salt then with E substitution a iodobenzene? Halogens has o-,p- directional so can I get a trisubstituated benzene if do the previous reaction again, finally Friedel-Crafts alkylization?

Offline discodermolide

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Re: 3,4,5-triiodotoluene synthesis
« Reply #7 on: October 15, 2011, 05:45:26 PM »
Is it good if I do a diazonium salt then with E substitution a iodobenzene? Halogens has o-,p- directional so can I get a trisubstituated benzene if do the previous reaction again, finally Friedel-Crafts alkylization?

Do you mean a Sandmeyer reaction? That would require aniline.
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Offline Nosterius

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Re: 3,4,5-triiodotoluene synthesis
« Reply #8 on: October 15, 2011, 09:59:35 PM »
Xmayer,

What is your present synthetic plan for this molecule?

I would personnaly aim to make 4-methylaniline as an intermediate. From there, do you see how you can form your desired compound?

Offline xmayer

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Re: 3,4,5-triiodotoluene synthesis
« Reply #9 on: October 16, 2011, 06:22:56 AM »
 From 4-methylanaline with iodo-chloride and zinc-chloride get a 2,6-diiodo, then with Sandmeyer make iodide from amino group, maybe this?

Offline discodermolide

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Re: 3,4,5-triiodotoluene synthesis
« Reply #10 on: October 16, 2011, 09:16:57 AM »
From 4-methylanaline with iodo-chloride and zinc-chloride get a 2,6-diiodo, then with Sandmeyer make iodide from amino group, maybe this?

But you are not starting from benzene as your original post required!
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Offline xmayer

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Re: 3,4,5-triiodotoluene synthesis
« Reply #11 on: October 16, 2011, 07:29:57 PM »
Hope this good for a written exercise, but revise me if not! Thank you

Offline fledarmus

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Re: 3,4,5-triiodotoluene synthesis
« Reply #12 on: October 16, 2011, 08:59:42 PM »
I think that you will find that a methyl group is a stronger o,p director than the iodo group, especially considering the size of the iodo group that you are trying to substitute next to. Would you like to try changing the order of your reactions?

Offline nox

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Re: 3,4,5-triiodotoluene synthesis
« Reply #13 on: October 16, 2011, 09:03:14 PM »
Also, your proposed sequence to make 4-methylaniline from benzene is very unlikely to work out the way you intend it to.

Offline Nosterius

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Re: 3,4,5-triiodotoluene synthesis
« Reply #14 on: October 17, 2011, 08:28:30 AM »
Xmayer: you have a nice overall scheme now. As others pointed out, you will need to start from benzene.

First, do the methylation of benzene. It will not be a clean reaction, but you can always argue that benzene vs toluene vs xylenes can be purified by distillation. Then proceed with your reactions until 4-methylaniline is obtained.

What is the better directing group between methyl, iodo and amino? Consider using it to direct your iodination reaction. If you now plan to halogenate your molecule while an amino group is present, you should protect your amino group as an acetanilide before reacting it with ICl; you will minimize side-reactions such as oxydations.

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