Using the information below explain why CN- is a stronger Bronsted base even though in the reaction given it is only 300 fold more nucleopihlic. ### Nucleophiles and Reaction Rates#### Nucleophile ComparisonThe table below contrasts two nucleophiles, Br⁻ and CN⁻, by examining the pKa of their conjugate acids and their second-order rate constants in a specific chemical reaction:| Nucleophile Name | pKₐ of Conjugate Acid | k (Second Order Rate Constant, M⁻¹·s⁻¹) ||------------------|-----------------------|----------------------------------------|| Br⁻ | -8 | 1.3 || CN⁻ | 9.4 | 3.2 x 10² |#### Chemical ReactionThe reaction under study is depicted as follows:\[ \text{Nuc:}^- + \text{CH}_3\text{I} \xrightarrow{\text{DMF, 25 °C}} \text{Nuc-CH}_3 + \text{I}^- \]- **Nuc:⁻** represents a generic nucleophile.- The reaction is carried out in dimethylformamide (DMF) at 25 °C. This comparison illustrates how different nucleophiles can vary significantly in terms of their basicity and reaction rates.

Bronsted base is the species that accept proton. For accepting proton the species should have high electron density. With increase in the nucleophilic charecter of the species, its rate of nucleophilic substitution reaction increases. Species having greater electron density surrounding it, will act as good nucleophile. Thus among Br- and CN-, CN- has high electron density surrounding it as CN- acts as good nucleophile rather than Br-. As CN- has higher electron density surrounding it, thus it can act as good bronsted base rather than Br-.