21. Rank the aromaticities of the following compounds from most stable to least stable. (i) thiophene (ii) benzene (iii) pyrrole (iv) furan (A) ii ＞ i ＞ iii ＞ iv (B) ii ＞ iv ＞ iii ＞ i (C) ii ＞ iv ＞ i ＞ iii (D) ii ＞ iii ＞ iv ＞ i (E) iv ＞ ii ＞ i ＞ iii

3. Why is sodium methoxide not used in the Claisen condensation of ethyl acetate? (A) The methoxide is a weaker base than the ethoxide which is used. (B) sodium methoxide is more difficult to prepare than sodium ethoxide. (C) The methoxide would abstract a proton from the ethyl group of the ester. (D) Use of sodium methoxide would result in transesterification. (E) sodium methoxide can be used as well as sodium ethoxide.

21. Rank the aromaticities of the following compounds from most stable to least stable. (i) thiophene (ii) benzene (iii) pyrrole (iv) furan
(A) ii ＞ i ＞ iii ＞ iv
(B) ii ＞ iv ＞ iii ＞ i
(C) ii ＞ iv ＞ i ＞ iii
(D) ii ＞ iii ＞ iv ＞ i
(E) iv ＞ ii ＞ i ＞ iii

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