Ortho-nitrobenzoic acid or para-nitrobenzoic acid
2007-03-14 09:44:40 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
para-nitro-benzoic acid is more polar than the respective ortho compound. This is because there is steric hinderance in the case of the ortho- which lowers resonance and thus decreases polarity. Furthermore, the extensive resonance in the para results in two charges that are very far away from each other, increasing the dipole moment to values much higher than you would expect by simply adding the dipole moments of the individual bonds.
Have a look at http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/1955/77/i14/f-pdf/f_ja01619a001.pdf?sessid=6006l3
2007-03-14 10:02:54 · answer #1 · answered by bellerophon 6 · 1⤊ 0⤋
Positioning about the benzene ring makes them have differing polarities. Ortho-nitrobenzoic (1,2 nitro) has two nitro groups right next to each other on the ring and para-nitrobenzoic (1,4 nitro) has them on opposing sides, making ortho-nitrobenzoic more polar. Meta is the other position available, putting the nitro groups two carbons apart from each other on the ring (1,3 nitro).
2007-03-14 16:53:20 · answer #2 · answered by emsviper 2 · 0⤊ 2⤋
p-Nitrobenzoic acid is more polar, because it is stretched out between the C=O at the "top" and the N=O at the "bottom. o-nitrobenzoic acid is hydrogen bonded between the -OH of COOH and the O=N- of nitro. So the division of polaritry is attenuated.
2007-03-14 16:56:13 · answer #3 · answered by steve_geo1 7 · 2⤊ 1⤋
The ortho, because all the electronegative elements are on one side of the molecule. In the para version, they will tend to cancel out.
2007-03-14 16:51:49 · answer #4 · answered by Gervald F 7 · 1⤊ 2⤋