The nucleophilic substitution reaction between 1-bromobutane and sodium hydroxide in ethanol solvent is an SN2 reaction. In an SN2 reaction, the nucleophile attacks the substrate from the opposite side of the leaving group, leading to an inversion of stereochemistry at the reaction center.Balanced chemical equation:C4H9Br + NaOH C4H9OH + NaBrReaction mechanism:Step 1: Nucleophilic attackThe hydroxide ion OH- from sodium hydroxide acts as a nucleophile and attacks the electrophilic carbon atom bonded to the bromine atom in 1-bromobutane. This forms a transition state in which the carbon is partially bonded to both the hydroxide ion and the bromine atom.Step 2: Leaving group departureAs the bond between the carbon and the hydroxide ion strengthens, the bond between the carbon and the bromine atom weakens. The bromine atom leaves as a bromide ion Br- , and the bond between the carbon and the hydroxide ion becomes complete, forming 1-butanol.Overall, the reaction proceeds through a single concerted step with a transition state involving the nucleophile, the electrophilic carbon, and the leaving group. The stereochemistry at the reaction center is inverted due to the backside attack of the nucleophile.