Tools are available to switch your figures between Kekul, delocalized and circle forms. You can also force aromatic ring recognition using all resonance bonds. A resonance contributor can be drawn in which a formal negative charge is placed on the carbon adjacent to the negatively-charged phenolate oxygen.īecause of like-charge repulsion, this destabilizes the negative charge on the phenolate oxygen, making it more basic. Detect the aromaticity and anti-aromaticity of your rings and display the number of pi electron contributors. The oxygen atom does indeed exert an electron-withdrawing inductive effect, but the lone pairs on the oxygen cause the exact opposite effect – the methoxy group is an electron-donating group by resonance. Why is this? At first inspection, you might assume that the methoxy substituent, with its electronegative oxygen, would be an electron-withdrawing group by induction. Notice that the methoxy group increases the pK a of the phenol group - it makes it less acidic. Use a resonance argument to explain why picric acid has such a low pK a.Ĭonsider the acidity of 4-methoxyphenol, compared to phenol: The phenol derivative picric acid (2,4,6 -trinitrophenol) has a pK a of 0.25, lower than that of trifluoroacetic acid. Nitro groups are very powerful electron-withdrawing groups. The benzene molecule is best described by the localized. The benzene molecule is best described by the MO theory.E. Benzene, C 6 H 6, is often drawn as a ring of six carbon atoms, with alternating double bonds and single bonds: This simple picture has some complications, however. The charge density of aromatic compounds is diffuse and delocalized such that. Aromatic rings (also known as aromatic compounds or arenes) are hydrocarbons which contain benzene, or some other related ring structure. Detect the aromaticity and anti-aromaticity of your rings and display the number of pi electron contributors. Both the bonding and the bonding are delocalized.D. benzene (6 site), benzene (9 site), nitrobenzene, toluene (10 site). Rank the four compounds below from most acidic to least. The following statements concern molecules that require resonance. Which of the two substituted phenols below is more acidic? Use resonance drawings to explain your answer. The position of the electron-withdrawing substituent relative to the phenol hydroxyl is very important in terms of its effect on acidity.
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