Classify the reagents shown in bold in the following equations as nucleophiles or electrophiles :
(a) `CH_3 COOH + HO^(-) to CH_3 COO^(-) + H_(2) O`
(b) `CH_3 CH_2 Br + HS^(-) to CH_3 CH_2 SH+ Br^(-)`
(c ) `C_6 H_6 + CH_3 CO^(+) to C_6 H_5 COCH_(3)`
(d) `CH_3 COCH_(3) + CN^(-) to CH_3 underset(underset(CN)|)overset(overset(OH)|)C - CH_(3) `

Explanation

To classify the reagents in the given equations as nucleophiles or electrophiles, we will analyze each reaction step by step.

### Step-by-Step Solution:

**(a)** `CH₃COOH + HO⁻ → CH₃COO⁻ + H₂O`

1. **Identify the reagents**: Acetic acid (CH₃COOH) and hydroxide ion (HO⁻).
2. **Determine the role of HO⁻**: The hydroxide ion (HO⁻) acts as a nucleophile because it donates a pair of electrons to the proton (H⁺) in acetic acid, resulting in the formation of water (H₂O).
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