Q 49P Question: Ethyllithium is often ... [FREE SOLUTION]

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Chapter 2: Q 49P (page 140)

Question: Ethyllithium is often used as a base in organic reactions,
(a)Predict the products of the following acid-base reaction,

(b) What is the conjugate acid of? Would you expectto be a strong base or a weak base?

Short Answer

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(a)

(b)

Step by step solution

Bronsted – Lowry concept of acid and base

According to Bronsted-Lowry, an acid can be defined as any substance (molecule or ion) that has the tendency to donate a proton(H⁺) to any substance whereas a base can be defined as any substance (molecule or ion) that has the tendency to accept a proton(H⁺) from any other substance.

Conjugate acid-base pair

The residual part of acid after losing a proton (H⁺) will have a tendency to accept a proton(H⁺) . Therefore, it will behave as a base. These pairs of substances which differ from one another by a proton (H⁺) are known as conjugate acid-base pairs. Consider a general example of an acid:

Prediction of the products and explanation

(a) Bronsted-Lowry acid is a proton (H⁺)donor while Bronsted-Lowry base is a proton (H⁺)acceptor.

(b) The conjugate acid of CH₃CH₂Li is CH₃-CH₃ (or C₂H₆). Ethane (C₂H₆ )is a very weak acid because its pK_a is around 50. Since it is a very weak acid therefore its conjugate base is a very strong base. Hence, CH₃CH₂Li can be expected to be a strong base.