Sciencemadness Discussion Board

m-(trifluoromethyl)aniline

Jor - 14-6-2010 at 01:11

I really want to this chemical for a particular reason (wich I will reveal when I have it, and I think it will be quite nice to see for most of you :) ).
I can buy 100mL for about 30 EUR, but I can also buy 50mL trifluorotoluene for 10 EUR. Wiki says the amino-derivative can be made my nitration and reduction of the trifluorotoluene.
I have been searching for exact procedures, but I cannot find any.

Can you guys help me out with this. I was thinking adding the trifluorotoluene dropwise to a heated 1:1 HNO3:H2SO4 mixture (or adding the HNO3 to a solution of trilfuorotoluene in H2SO4, if it dissolves), then quenching the reaction with water (just like nitrobenzene synthesis). The nitro-derivative should separate, as the solubility is 0,4g/L. Then seperate, wash with water, and use this crude product in the next step, reduction with sodium dithionite, I think in alkaline environment ? The solubility of the amine is 5g/L, but I think it will be lowered by adding some salt.

I'd like to avoid distillation, as currently it does not fit in my fume hood (I bought a large NS29 setup a long time ago and don't have money for a smaller set up. And I won't do this reaction outside my fume hood, as I really don't like boiling these compounds outside of my hood, both are nasty (the nitro-derivative is T+).
The product doesn't need to be very pure, as I need it for a pure visual effect ;)




[Edited on 14-6-2010 by Jor]

Lambda-Eyde - 14-6-2010 at 01:28

Do you have any references claiming the nitration of benzotrifluoride will occur at STP and with reasonable yields? It seems to me that the trifluoromethyl group would strongly deactivate the benzene ring towards electrophilic substitution (nitration).

DJF90 - 14-6-2010 at 01:44

If you can buy the necessary material for a good price like that then why bother with the benzotrifluoride? It does make a good high temperature alternative to DCM though!.

Jor - 14-6-2010 at 02:55

It is because I only need a small amount of the compound (purely for a visual effect in a test tube, a really nice one ;) ), and the benzotrifluoride is much cheaper. Also, I can probably use benzotrifluoride for other things.
Besides, the synthesis seems like a nice challenge. But I'm not sure what conditions are needed.

DJF90 - 14-6-2010 at 03:50

I would aim for conditions similar to the nitration of nitrobenzene ( http://www.versuchschemie.de/topic,10466,-1%2C3-Dinitrobenzo... ), as the -NO2 and -CF3 groups are quite similar in deactivation of the aromatic ring.

Check this paper, claims 69% yield using NO2, Br2 in H2SO4. Should be doable.

Cheprakov, A. V.; Makhon'kov, D. I.; Rodkin, M. A.; Beletskaya, I. P.
1988 , vol. 24, # 2 p. 217 - 223
Zhurnal Organicheskoi Khimii, 1988 , vol. 24, # 2 p. 248 - 255

Also see the following paper... not very friendly though.
[Edited on 14-6-2010 by DJF90]

[Edited on 14-6-2010 by DJF90]

Attachment: Superelectrophilic nitrating agents.pdf (282kB)
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Nicodem - 14-6-2010 at 04:17

The mononitration of benzotrifluoride with HNO3/H2SO4 is described in EP0295674. They use 1.2 equivalents of fuming HNO3, but I think using conc. HNO3 should work as long as you use a bit more H2SO4 or a higher temperature (see below). Probably using KNO3 instead of fuming HNO3 would work as well. In addition, here are also two CA abstracts regarding the nitration:
Quote:
Preparation of m-trifluoromethylaniline from benzotrifluoride by nitration and normal pressure catalytic hydrogenation. Wang, Yanyong; Yang, Dongpeng; Zhang, Hongpeng; Zhou, Liming; Guong, Xiaoping. The Chemical Research Institute, Institute of Chemical Defence of CPLA, Beijing, Peop. Rep. China. Jingxi Shiyou Huagong (2003), (1), 40-43. Publisher: Jingxi Shiyou Huagong Bianjibu, CODEN: JSHIBF ISSN: 1003-9384. Journal written in Chinese. CAN 141:227195 AN 2004:31056 CAPLUS

Abstract: m-Trifluoromethylaniline was prepd. from benzotrifluoride (phCF3) by nitration and normal pressure catalytic hydrogenation. The purity was above 99% and the total yield reached to 89%. The optimum ratio of nitrating agent is PhCF3:HNO3:H2SO4 = 1:1.05:1.3(mol), the purity and yield of m-trifluoromethyl nitrobenzene were 98.0% and 90.7% resp. The optimum conditions of catalytic hydrogenation are as follows: wt. of 5% Pd/C catalyst used in the substrate = 2%, trifluoromethylnitrobenzene:abs. ethanol = 0.10 mol:100 mL, reaction temp. 45°, stirring speed 240 r/min, the purity and the yield of m-trifluoromethylaniline were 99.3% and 98.5% resp.


Process for the mononitration of benzotrifluorides. Lobo, Marcos Souza; Scholze, Jakson Goi; Araujo, Marcelo Aguiar; Alvares, Paulo Sergio Martins; Rahmeier, Luis Henrique Sanfelice. (Milenia Agro Ciencias S.A., Brazil). Braz. Pedido PI (2002), 8 pp. CODEN: BPXXDX BR 2000002090 A 20020102 Patent written in Portuguese. Application: BR 2000-2090 20000510. Priority: . CAN 137:169311 AN 2002:669748 CAPLUS

Abstract: Benzotrifluorides 4-XC6H4CF3 (X = H, Cl, F, Br, iodo) underwent mononitration to give 4,3-X(O2N)C6H3CF3 by treatment with 65-98% HNO3 in excess (1.1:1 to 4:1 molar ratio) in the absence of a solvent at 0-150 for 1-18 h. Thus, nitration of p-chlorobenzotrifluoride using 3-fold moles 98% HNO3 for 3 h at 90 afforded 95% 3-nitro-4-chlorobenzotrifluoride (purity 98%).


I could find no specific example of the reduction to the m-aminobenzotrifluoride using sodium dithionite, but the general procedure should work. Almost invariably catalytic hydrogenation, usually with Pd-C and at the atmospheric pressure, is used in the literature and patent examples. Though related only due to the sulfur, there is an example of a reduction using sodium sulfide in Journal of Labelled Compounds and Radiopharmaceuticals, 28 (1990) 1441-1448.