Essay about 2-(2,4-Dinitrobenzyl) Pyridine

1757 Words Mar 2nd, 2013 8 Pages
2-(2,4-Dinitrobenzyl) pyridine

Peter Defnet and Cody Krepps
Department of Chemstry
Juniata College
Huntingdon, PA
September 18, 2012

Abstract: Nitration of 2-benzylpyridine is supposed to yield 2-(2,4-Dinitrobenzyl) pyridine, when electrophilic aromatic substitution is the mechanism. Experiencing many pitfalls, however, has lead to the actual product obtained to contain the expected product, as well as many impurities. This report examines the supposed mechanism for the electrophilic substitution, a mechanism for the product’s photochromic property, as well as an explanation as to why the mechanism happens in this particular sequence.

Introduction:

Nitration of 2-benzylpyridine through electrophilic aromatic substitution
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In the beginning of the reaction, when the 2-benzylpyridine was nitrated, the nitro group had seemingly many choices of where it could have been added. Of the two aromatic structures, however, the one with nitrogen as part of the ring is significantly more deactivating than the benzene because the nitrogen is more electrophilic than carbon. The electronegativity difference causes the electrons in the corresponding aromatic structure to be unevenly distributed and stray toward the nitrogen atom, leaving the ring as a whole less likely to be subject to EAS.

On the more stable benzene ring, the nitro group has two different places it can choose: ortho or para to the alkyl substituent, keeping in mind that one of the ortho positions is blocked by the steric hindrance of the rest of the molecule. This position is shown in figure 3 below. The ortho and para locations are the only two available locations to attach because the alkyl group is an activating group, and in general, an ortho-para director. Once the first nitro group is attached to either of the two possible locations, a second nitro group can attack in the remaining position. The second nitro group only has one possible location choice because the first nitro group that attach is deactivating, meaning it is a meta director. This results in having only one location

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