I. Qualitatively Predicting Favorable Direction of Hydrate EquilibriumII. HemiacetalsI. Mechanism of Acetal to KetoneII. Mechanism of Acetal to Ketone NOT doable in Basic ConditionsI. Mechanism of Acetal to Ketonea. This must be done in acidic conditions only!b. The first step: lone pair of electrons of one acetal oxygen attack proton (protonation of the acetal)i. Forms carbocation intermediate, which is possible in the aqueous conditions (formed water)ii. Carbocation forms from the breaking of the acetal ring.c. Lone pair of electrons on the non-protonated O reform pi bond, making carbocation neutral, but O now has a positive charge.d. Lone pair of electrons on surrounding water molecule attack partial positive carbon, breaking pi bond, kicking electrons back onto oxygene. Deprotonation of the H from the newly attached water molecule occurs when the lone pair on oxygen attacks H from water, making a good leaving group.i. The leaving group is H – O – R bond (O has positive charge)f. Lone pairs of O that was part of water makes pi bond, kicking off the leaving group.g. Water deprotonates the H on the ketone O, and you regenerate your hydronium catalyst, and ethylene glycol.II. Mechanism of Hemicetal to Ketone NOT doable in Basic Conditionsa. A hemiacetal cannot be made into ketone because OH would be a poor leaving group, making a very unstable alkoxide. So this is not energetically favorable, period.i. The transition state for an alkoxide leaving group has an extremely high-energy barrier.b. But if you de-protonate the alcohol of the hemi-acetal, then you raise the energy of that species and give it a “leg up” in overcoming the energy barrier.c. An acetal would not be able to do this anyway because there is no alcohol to de-protonate.CHEM 0320 1st Edition Lecture 17Outline of Last Lecture I. Qualitatively Predicting Favorable Direction of Hydrate Equilibrium II. Hemiacetals Outline of Current Lecture I. Mechanism of Acetal to Ketone II. Mechanism of Acetal to Ketone NOT doable in Basic Conditions Current Lecture These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.I. Mechanism of Acetal to Ketone a. This must be done in acidic conditions only!b. The first step: lone pair of electrons of one acetal oxygen attack proton (protonation of the acetal)i. Forms carbocation intermediate, which is possible in the aqueous conditions (formed water) ii. Carbocation forms from the breaking of the acetal ring.c. Lone pair of electrons on the non-protonated O reform pi bond, making carbocation neutral, but O now has a positive charge.d. Lone pair of electrons on surrounding water molecule attack partial positive carbon, breaking pi bond, kicking electrons back onto oxygen e. Deprotonation of the H from the newly attached water molecule occurs when the lone pair on oxygen attacks H from water, making a good leaving group. i. The leaving group is H – O – R bond (O has positive charge)f. Lone pairs of O that was part of water makes pi bond, kicking off the leaving group.g. Water deprotonates the H on the ketone O, and you regenerate your hydronium catalyst, and ethylene glycol.II. Mechanism of Hemicetal to Ketone NOT doable in Basic Conditions a. A hemiacetal cannot be made into ketone because OH would be a poor leaving group, making a very unstable alkoxide. So this is not energetically favorable, period.i. The transition state for an alkoxide leaving group has an extremely high-energy barrier. b. But if you de-protonate the alcohol of the hemi-acetal, then you raise the energy of that species and give it a “leg up” in overcoming the energy barrier.c. An acetal would not be able to do this anyway because there is no alcohol to