Sciencemadness Discussion Board

a,b-dichlorocinnamic acid

Deathtillation - 15-5-2013 at 09:06

Some time ago I have tried to chlorinate the cinnamic acid.
I have constructed an apparatus consisting of a gas generator charged with MnO2 and fitted with the dropping funnel with HCl and the generator was connected by all jointed glass with U-tube reactor, where a concentrated solution of cinnamic acid in chloroform (CHCl3 - 1,5 g in 15 ml) was placed. I have started stirring in the U-tube gas reciever with cinnamic solution and streamed very slowly the chlorine by adding the concentrated HCl to manganese dioxide and heating the bottom of the generator flask. The yellowish gas was streamed during 12 hours very slowly through a U tube, but it did not appear it was dissolved or absorbed in the U-tube.
I thought it would be a classical Ae reaction, like addition of chlorine to ethylene, but the cinnamic showed to be totally unreactive towards chlorine. I also was surprised the chlorine did not dissolve in chloroform.

Where is my mistake? What have I done wrong?
Should I have use a traditional reactor with gas tube going to the bottom of the solution? I hav used a U-tube reciever for chlorine because I wanted to be sue it would not suck back in to the chlorine generator and the chlorine will slowly distill to a U-tube reciever.
Or maybe the chlorine should have been dried before passing into the chloroform solution of cinnamic acid?
Or maybe the stream of chlorine should be considerably faster?

I haven't found examples of this reaction in the literature somewhy.
Any suggestions would be helpful!


[Edited on 15-5-2013 by Deathtillation]

Dr.Bob - 15-5-2013 at 10:53

There are few examples of this reaction in chloroform with only chloride. I put a few below. Most use a harsher chlorination agent as a catalyst or reagent. Some have oxidants, some include bromine as a catalyst and some use thionyl chloride as the Cl source. The straight chlorine ones are mostly in German, but appear to use acetic acid as the solvent and higher temps (50-60C). Bromine is much more reactive, it may be OK at RT, but chlorine is not nearly as reactive in many cases, which may explain the harsher conditions. This is just a few of 21 citations I found with a quick search.

2,2,6,6-tetramethyl-piperidine-N-oxyl; trichloroisocyanuric acid; sodium hydrogencarbonate; sodium bromide in water; acetone :
Luca, Lidia De; Giacomelli, Giampaolo; Masala, Simonetta; Porcheddu, Andrea
Journal of Organic Chemistry, 2003 , vol. 68, # 12 p. 4999 - 5001

Buckles,R.E. et al. Journal of Organic Chemistry, 1960 , vol. 25, p. 24 - 26

With chlorine
Field,L.; Carlile,C.G. Journal of Organic Chemistry, 1961 , vol. 26, p. 3170 - 3176

Stelling Zeitschrift fuer Physikalische Chemie (Leipzig), 1934 , vol. 24, p. 407,417

With iodobenzene dichloride in chloroform
Heating; Lasne,M.-C. et al. Bulletin de la Societe Chimique de France, 1972 , # 12 p. 4592 - 4596

With chlorine; acetic acid; lithium chloride
Cabaleiro,M.C. et al. Journal of the Chemical Society [Section] B: Physical Organic, 1968 , p. 1022 - 1026

Durrans Journal of the Chemical Society, 1923 , vol. 123, p. 1427



[Edited on 15-5-2013 by Dr.Bob]

Nicodem - 16-5-2013 at 06:44

Quote: Originally posted by Deathtillation  
The yellowish gas was streamed during 12 hours very slowly through a U tube, but it did not appear it was dissolved or absorbed in the U-tube.
I thought it would be a classical Ae reaction, like addition of chlorine to ethylene, but the cinnamic showed to be totally unreactive towards chlorine. I also was surprised the chlorine did not dissolve in chloroform.

Do you mind explaining how did you measure the absorbed chlorine and how did you monitor the chlorination reaction?
Quote:
I haven't found examples of this reaction in the literature somewhy.

Though electron poor alkenes like cinnamic acid are much less reactive toward the electrophilic addition reactions, there are many examples in the literature (see how many references Dr.Bob provided). Even if you search for "cinnamic acid chlorination" in Google, the second hit gives a study of this reaction with the experimental. Possibly you lack the literature searching skills to find the articles. In such case I suggest you to read the forum guidelines, as they contain useful instructions on how to do literature work.