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Pitt CHEM 0320 - Direction of Hydrate Equilibrium and Introduction to Hemiacetals
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I. Analyzing Ketone StructureII. Consequences of the Structures of Ketones and AldehydesIII. Hydrate EquilibriumIV. Hydrate Formation in Basic vs. Acidic ConditionsI. Qualitatively Predicting Favorable Direction of Hydrate EquilibriumII. HemiacetalsI. Qualitatively Predicting Favorable Direction of Hydrate Equilibriuma. Applying understanding of electron donating groups and electron withdrawing groups:i. When you have strong electron withdrawing group(s), there is an increased favorability towards the hydrate formation. Energy of the molecule is raised, so to the highly positive character present on the carbonyl carbon.ii. When you have 2 electro-neutral groups on the carbonyl (formaldehyde), they are not donating any electron density and the carbonyl is susceptible to equilibrium.iii. Reference: Aldehyde1. Only one electron donating group, methyliv. When you have two electron-donating groups, the electrophilicity of the carbonyl C is lower than the reference, and so there is a dramatic decrease in favorability towards the hydrate formation.II. Hemiacetalsa. Hemi means half, so a single C atom derived from a ketone/aldehyde has half OH/OR. A full acetal has OR/OR attached to same C.b. The reactions are not new; the only difference is the type of nucleophile and electrophile involved in the reactions.i. Mechanism forward: ketone + CH3ONa (in basic conditions)  hemiacetal1. Use the best nucleophile available! Lone electrons on alkoxide ion attack carbonyl C (partial positive), kicking off electrons to oxygen, forming methanol.2. Lone electrons on the negatively charged oxygen attack and deprotonate methanol. Forming the hemiacetal and regenerating the basic catalyst.ii. Mechanism reverse : propose a mechanism! Notice the consistencies. And propose a mechanism for forward/reverse in acidic conditions.c. The most famous hemiacetal of all: GLUCOSE!CHEM 0320 1nd Edition Lecture 16Outline of Last Lecture I. Analyzing Ketone Structure II. Consequences of the Structures of Ketones and Aldehydes III. Hydrate Equilibrium IV. Hydrate Formation in Basic vs. Acidic Conditions Outline of Current Lecture I. Qualitatively Predicting Favorable Direction of Hydrate Equilibrium II. Hemiacetals 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. Qualitatively Predicting Favorable Direction of Hydrate Equilibrium a. Applying understanding of electron donating groups and electron withdrawing groups: i. When you have strong electron withdrawing group(s), there is an increased favorability towards the hydrate formation. Energy of the molecule is raised, so to the highly positive character present on the carbonyl carbon.ii. When you have 2 electro-neutral groups on the carbonyl (formaldehyde), they are not donating any electron density and the carbonyl is susceptibleto equilibrium. iii. Reference: Aldehyde1. Only one electron donating group, methyliv. When you have two electron-donating groups, the electrophilicity of the carbonyl C is lower than the reference, and so there is a dramatic decrease in favorability towards the hydrate formation.II. Hemiacetalsa. Hemi means half, so a single C atom derived from a ketone/aldehyde has half OH/OR. A full acetal has OR/OR attached to same C.b. The reactions are not new; the only difference is the type of nucleophile and electrophile involved in the reactions.i. Mechanism forward: ketone + CH3ONa (in basic conditions)  hemiacetal1. Use the best nucleophile available! Lone electrons on alkoxide ion attack carbonyl C (partial positive), kicking off electrons to oxygen, forming methanol.2. Lone electrons on the negatively charged oxygen attack and deprotonate methanol. Forming the hemiacetal and regenerating the basic catalyst. ii. Mechanism reverse : propose a mechanism! Notice the consistencies. And propose a mechanism for forward/reverse in acidic conditions. c. The most famous hemiacetal of all:


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Pitt CHEM 0320 - Direction of Hydrate Equilibrium and Introduction to Hemiacetals

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