Sunday, March 6, 2011

Electrophilic Aromatic Substitution Reaction in an Article

 In an attempt to find a peer reviewed article/ journal that discussed electrophilic aromatic substitution reactions, I accessed the JSTOR database, available through the school's website. Upon searching for the reaction, I found one titled: Electrophilic Mercuration and Thallation of Benzene and Substituted Benzenes in Trifluoroacetic Acid Solution. The article discussed the electrophilic aromatic substitution of a benzene ring with Hg(OCOCF3)2 to form C6H5Hg(OCOCF3), which is then introduced with NaBr(aq) to form C6H5HgBr. That compound was then introduced to Br2 in CHCl3 to form bromobenzene. The following is a link to the article, which includes the reaction mechanism.

 http://www.jstor.org/stable/67683?seq=3&Search=yes&searchText=aromatic&searchText=reactions&searchText=chemistry&searchText=substitution&searchText=electrophilic&list=hide&searchUri=%2Faction%2FdoBasicSearch%3Facc%3Don%26Query%3Dchemistry%2Belectrophilic%2Baromatic%2Bsubstitution%2Breactions%26gw%3Djtx%26acc%3Don%26prq%3Dchemistry%2Belectro-synthetic%2Baddition%2Breactions%26hp%3D25%26wc%3Don&prevSearch=&item=1&ttl=206&returnArticleService=showFullText&resultsServiceName=null 

In electrophilic aromatic substitution, a hydrogen atom on a benzene ring is replaced by an electrophile. In this mechanism, the carbon atom is attacked by the Hg atom in Hg(OCOCF3)2. The hydrogen atom on that carbon is then deprotonated by the NaBr (aq).  The new substituent then undergoes halogenation to produce the bromobenzene product.
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2 comments:

  1. Dr. MMarch 8, 2011 at 8:19 PM

    Interesting Bethany,

    You actually found a case that used (toxic) metal ion salts to produce organometallic intermediate compounds. When we get to Grignard rxns later this term you'll see some similarities...

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  2. John HarboldMarch 8, 2011 at 9:12 PM

    Bethany very nice article with a kind of confusing but great multistep synthesis. It was very difficult to find a peer reviewed article with a synthesis within jstor and Im glad to see that you have found one. The substitution portions of the reaction are spot on and were discussed very well within the blog. Halogenation is a common form of the substitution which specifically shows the end product of bromobenzene in this instance. Great job!

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