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JEE Main levelSingle correct optionDifficulty 2 of 3o4181

2-Bromobutane is treated with the following species at the same concentration, temperature and solvent (ethanol). Which causes the fastest E2 elimination?

A $CH X_{3} COO X^{-}$
B $Cl X^{-}$
C $H X_{2} O$
D $C X_{2} H X_{5} O X^{-}$

Answer: D

E2 rate increases with base strength. The conjugate acid pKa values are about 16 for ethanol, 4.8 for acetic acid, -7 for HCl and -1.7 for

H X_{3} O X^{+}

. Ethoxide is by far the strongest base, so it gives the fastest E2.

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