316 CHAPTER EIGHT Nucleophilic Substitution FIGURE 8.5 The su1 mecha nism for hydrolysis of tert- The Overall Reaction butyl bromide (CH3)3CBr 2H,O (CH3)3COH H3o+ B rf-Butyl bromide Water tert-Butyl alcohol Hydronium ion Bromide ion Step 1: The alkyl halide dissociates to a carbocation and a halide ion. CH3)3C tert-Butyl bromide rt-Butyl cation Bromide ion Step 2: The carbocation formed in step I reacts rapidly with a water molecule. Water is a nucleophile. This step completes the nucleophilic substitution stage of the mechanism and yields an alkyloxonium ion H (CH3)3C H3)3C-0: tert-Butyl cation Water Step 3: This step is a fast acid-base reaction that follows the nucleophilic substitution Water acts as a base to remove a proton from the alkyloxonium ion to give the observed product of the reaction, tert-butyl alcohol. (CH3)3C (CH3)2C-0 H-O: rI-Buty r-Butyl alcohol (CH3)3C-Br Br, H,O Br.2H,0 (CH3)3CO…H…OH2,Br (CH3)3CBr, 2H.O FIGURE 8.6 Energ (CH3) COH, illustrating the Sn1 Br, HO nism for hydrolysis of tert- Reaction coordinate Back Forward Main MenuToc Study Guide ToC Student o MHHE Website316 CHAPTER EIGHT Nucleophilic Substitution (CH3)3C±Br ±£ (CH3)3C Br The Overall Reaction: Step 1: The alkyl halide dissociates to a carbocation and a halide ion. Step 2: The carbocation formed in step 1 reacts rapidly with a water molecule. Water is a nucleophile. This step completes the nucleophilic substitution stage of the mechanism and yields an alkyloxonium ion. slow (CH3)3C O ±£ (CH3)3C±O tert-Butyl cation fast H H Water tert-Butyloxonium ion H H H H Step 3: This step is a fast acid-base reaction that follows the nucleophilic substitution. Water acts as a base to remove a proton from the alkyloxonium ion to give the observed product of the reaction, tert-butyl alcohol. (CH3)3C±O O ±£ (CH3)3C±O H±O tert-Butyloxonium ion fast Water tert-Butyl alcohol H Hydronium ion tert-Butyl bromide tert-Butyl bromide tert-Butyl cation Bromide ion Water (CH3)3CBr 2H2O ±£ (CH3)3COH H3O Br tert-Butyl alcohol Hydronium ion Bromide ion H H H H 2H2O Potential energy Reaction coordinate (CH3)3C - - - Br (CH3)3C - - - OH2, Br, H2O (CH3)3C Br, 2H2O (CH3)3CBr, 2H2O (CH3)3CO - - - H - - - OH2, Br H (CH3)3COH2, Br, H2O (CH3)3COH, Br, H3O Eact δ δ δ δ δ δ FIGURE 8.6 Energy diagram illustrating the SN1 mecha￾nism for hydrolysis of tert￾butyl bromide. FIGURE 8.5 The SN1 mecha￾nism for hydrolysis of tert￾butyl bromide. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website