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Author: Subject: Preparation of Quinoline
Magpie
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[*] posted on 23-11-2017 at 16:53
Preparation of Quinoline


November 23, 2017

A. Introduction
This preparation is from Brewster (ref 1) with an expected yield of 10-12g.

Nitrobenzene + aniline + 3 glycerol = quinoline + 11H2O

B. Procedure
Everything proceeded as described in Brewster, a reference that can be found in the forum library.

C. Yield

My yield is 11.2g. The % yield is 89.2%.

D. Discussion

This procedure uses several unit operations, ie, oxidation, ring closure, steam distillation (twice), diazotization, neutralization, liquid-liquid extraction, and distillation. For this reason I feel that this would be a good experiment for someone wishing to practice his organic lab skills. Also, for this reason this experiment is quite laborious and time-consuming.

If you don’t know the chemical structure of quinoline I invite you to look it up. It is a double ring heterocycle with a nitrogen in one ring.

E. Photographs
The following pictures show the progress of the synthesis. One shows off my new 1L mantle and another my microburner I picked up for $1 at a university surplus sale. It was perfect for providing just enough heat to keep the reactants boiling for 40 minutes, unattended.

quinoline reaction vessel.JPG - 118kB
Reaction Vessel

quinoline reaction at low boil.JPG - 131kB
Reaction at Low Boil for 40 Minutes

quinoline steam distillation to remove nitrobenzene.JPG - 158kB
Steam Distillation to Remove Unused Nitrobenzene

quinoline separated from distillate.JPG - 157kB
Quinoline Removed from Steam Distillate

F. Reference
1. “Preparation of Quinoline by the Skraup Synthesis," Unitized Experiments in Organic Chemistry, 1960, by Brewster et al, Experiment 81, p. 191.

Questioins, comments, and suggestions are welcomed.







[Edited on 24-11-2017 by Magpie]




The single most important condition for a successful synthesis is good mixing - Nicodem
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clearly_not_atara
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[*] posted on 23-11-2017 at 17:41


Interesting. I like the pictures although I would hope that you could at least include e.g. a photograph of the procedure in Brewster if you're going to use it as your whole writeup :p I didn't actually have access to the References forum before I read this



[Edited on 04-20-1969 by clearly_not_atara]
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Dr.Bob
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[*] posted on 23-11-2017 at 18:06


That is a nice prep, from simple chemicals, awesome job. I have only made a few of those in many years of work, so that is a good yield for such a tough reaction, with several steps.
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Magpie
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[*] posted on 23-11-2017 at 18:57


Quote: Originally posted by clearly_not_atara  
Interesting. I like the pictures although I would hope that you could at least include e.g. a photograph of the procedure in Brewster if you're going to use it as your whole writeup :p I didn't actually have access to the References forum before I read this


Brewster is in th forum library. I state this in my write up.

Thanks, Dr Bob. I was surprised by my yield also, as this is such a dirty looking process.

[Edited on 24-11-2017 by Magpie]




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ninhydric1
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[*] posted on 23-11-2017 at 19:07


Beautiful write-up as usual Magpie; always admired your work. By the way, what do you plan to do with quinoline you produced? It is a versatile reagent with a variety of uses as is and as a precursor to other compounds.



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Magpie
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[*] posted on 23-11-2017 at 19:59


Thank you Ninhydric. I plan to use this for the purification of thionyl chloride per Len1’s book.



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Aqua-regia
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[*] posted on 24-11-2017 at 07:06


This is crazy good yield. Did you controlled the purity of quinoline? Cause i prepared several times subsituted and unsubtituted quinoline likewise with skraup methode and never had result over 60-65%.
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[*] posted on 24-11-2017 at 08:26


The final step is to separate the quinoline (bp 237°C) from 30mL of CCl4 (bp 77°C) by distillation. There is no other purification step.

Aqua-regia: What do you do with quinoline?




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[*] posted on 24-11-2017 at 09:47


Ok i see. I afraid you have with aniline contaminated quinoline. The final purification step is maybe missing. You removed with steam the unreacted nitrobenzene this is correct. After basicifying again, steam distillation, goes quinoline +aniline over. This ist the point.

Removing of aniline you have 2 ways:
a) you can diasotizing your aniline and by heating decomp. to phenol, after basicifying with steam removing the quinoline.
b) crude quinoline based of 0,23 molar starting aniline by mass 1:4 cc HCl solution treating, heating to 60 degrees and treating with 35 g ZnCl2/60 ml 10% HCL. Cooling, salt is settle, filtering, and the solid is a salt of quiniline. Basicifying again quinoline will free, and extract.



I preparated from quinoline mainly few kind of dyes. Also used for purification of SOCl2.
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[*] posted on 24-11-2017 at 10:23


I can vouch for the ZnCl2 complex method, and it gives a clean product by 1H-NMR. Instructions can be found in Vogel. Alternatively, OrgSyn describes a diazotisation method to remove any unreacted aniline.
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[*] posted on 24-11-2017 at 10:47


Yes , agree.
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Magpie
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[*] posted on 24-11-2017 at 11:11


Yes, the aniline is converted to phenol by diazotization using NaNO2.

What dyes did you make from quinoline?




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[*] posted on 24-11-2017 at 12:55


Quinoline Yellow WS water soluble yellow dye.
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[*] posted on 24-11-2017 at 14:37


Magpie,

Nice job!

If aniline is the contaminant, why not treat the mixture with acetic anhydride to form acetanilide which would allow an acid/base workup to isolate quinoline and recover the excess aniline? Just a thought.

AvB
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[*] posted on 24-11-2017 at 15:13


Thanks AvB. If there was much aniline to recover I might do that.



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[*] posted on 26-11-2017 at 12:23


@Magpie, nice work! I have been looking at this synthesis for some time as a route to related heterocyclics. Since the purpose of the nitrobenzene is as an oxidizing agent what is it reduced to? Aniline? If the latter, does this form early enough in the reaction to compete with the existing amine? This may not seem important but if I were to start out with a substituted aniline would I end up with a mixture of quinoline and a substituted quinoline?

Most of the older preparations used arsenic acid but this is problematic these days, I have seen a few method that use iodine but this sounds messy and looking at your yield (even with a bit of aniline contamination) nitrobenzene looks attractive.

I bought some sodium 3-nitrobenzenesulphonate through our own Mario as an oxidizing agent for this reaction. Presumably if it forms an amine that competes the product would be a quinoline sulphonic which is probably water soluble so easily separated.
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[*] posted on 26-11-2017 at 13:42


Brewster indicates that the NB is converted to aniline and that it is used in the synthesis of quinoline.



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