Question

9.1 Alcohols Worksheet Prior Knowledge: ✓ Acid/base definitions and pka values. ✓ Nucleophile/electrophile definitions and roles. ✓ Substitution and elimination reactions and mechanisms using curved arrows. Leaving group ability. Learning Objectives After completing this activity students should be able to: ✓ Predict the role of an alcohol in the Williamson Ether Synthesis and Fisher Esterification. Determine that protonation of an alcohol affords stronger electrophiles because of better, more stabilized, leaving groups. Conversion of Alcohols to Electrophiles Protonation RCH,OH + H - RCH — Hz, leaving group protonated alcohol Consider the protonation reaction shown in the model above: • What bond is being formed in the protonation reaction? The alcohol is acting as a (circle one) nucleophile / electrophile / acid / base. • Drow curved arrows above to show electron movement to form the protonated alcohol. . For the alcohol and the protonated alcohol shown below, circle the leaving group. Draw the leaving groups that will form when the bond breaks as depicted by the curved arrow. R-O-H R-6-H • Which leaving group would be the best leaving group? Explain.

Answer 1

1. A -O-H bond is being formed, which is a kind of covalent bond. The alcohol is acting as a base.

2. The electron movement is shown in the image given below.

HO HO: R-CH₂ R - che

3. The leaving groups are circled in the image given below, along with the leaving groups that will form when the bond breaks.

& RACH, Lot - R-CH, foH leaving out 4 но

4. H₂O would be a much better-leaving group as compared to the OH^- because the negative charge on the OH^- ion is not stable and there is no other group present that could stabilize the negative charge. However, H₂O doesn't have any charge and is stable.