Aldehydes & Ketones Continued (Chapter 18)

Question 1

Tautomerization of Aldehydes/Ketones

Answer 1

The reversible conversion of an aldehyde/ketone to an enol via α-Hydrogen rearrangement and π-electron transfer.

Question 2

Aldehyde/Ketone → Enol

Enol → Aldehyde/Ketone

Answer 2

Tautomerization

This reversible tautomerization process can occur in acidic conditions and basic conditions.

Question 3

Aldehyde/Ketone → Enolate

Answer 3

Base-Catalyzed Deprotonation

Removal of the α-Hydrogen and subsequent π-electron transfer (C=O→C=C) yields the enolate ion.

Question 4

Enol

Answer 4

A compound containing an alcohol group (—OH) adjacent to an alkene group (C=C).

One carbon atom of the alkene is bonded to the alcohol group subsituent.

Question 5

Enolate

Answer 5

An anionic compoundcontaining an alkoxide group (—O^–) adjacent to an alkene group (C=C).

One carbon atom of the alkene is bonded to the alkoxide group subsituent.

Question 6

How is the α-Hydrogen deprotonation of an aldehyde/ketone possible?

Answer 6

The α-Hydrogen is highly acidic (i.e. pK_a = 16–21)

Resonance stabilization of the deprotonated aldehyde/ketone compound (i.e. an enolate ion) promotes the dissocation of the C—H_α bond.

Question 7

Reagents: Base-Catalyzed Deprotonation of α-Hydrogen

Answer 7

LDA

Lithium Diisopropylamide

Question 8

α-Hydrogen Deprotonation: Kinetic Control vs. Thermodynamic Control

Answer 8

• Kinetic Control: At low temperatures, the base deprotonates the Iess hindered/substituted α-Hydrogen (to form the less stable enolate ion).
• Thermodynamic Control: At room/high temperatures, the base deprotonates the more hindered/substituted α-Hydrogen (to form the more stable enolate ion).

While the base is still more likely to initially depronate the less hindered/substituted α-Hydrogen at room/high temperatures (i.e. thermodynamic control), the reversibility of the deprotonation leads to the more stable enolate ion being the predominant product.

Question 9

Characteristics: Kinetic Control

Answer 9

• Low Temperatures
• Short Reaction Times
• Unreversible

The less stable product isomer is the major product.

Question 10

Characteristics: Thermodynamic Control

Answer 10

• Room/High Temperatures
• Long Reaction Times
• Reversible

The more stable product isomer is the major product.

Question 11

Stability: Aldehye/Ketone vs. Enol

Answer 11

An enol is the less stable isomer of an aldehyde/ketone.

In the presence of acid or base, the enol will tauteromize to the more stable aldehyde/ketone isomer.

Question 12

Methods for Ketone Synthesis

Answer 12

2°/3° Enol Tautomerization

Question 13

Methods for Aldehyde Synthesis

Answer 13

0°/1° Enol Tautomerization

Question 14

Alkyne → Ketone

Answer 14

Hg(II)-Catalyzed Hydration

An enol intermediate is formed (but NOT observed) following alcohol-addition and prior to ketone-yielding tautomerization.

Question 15

Terminal Alkyne → Aldehyde

Answer 15

Hydroboration Oxidation

An enol intermediate is formed (but NOT observed) following alcohol-addition and prior to aldehyde-yielding tautomerization.

Question 16

Reagents: Hg(II)-Catalyzed Alkyne Hydration

Answer 16

HgSO₄, H₂O, H₂SO₄

Question 17

Reagents: Hydroboration-Oxidation Alkyne Hydration

Answer 17

1. BH₃
2. H₂O₂, NaOH

Question 18

Mechanism: Base-Catalyzed Aldehyde/Ketone Tautomerization

Base-Catalyzed Enolization

Answer 18

1. Deprotonation of the α-Hydrogen (and subsequent π-electron transfer) to yield the Enolate ion.
2. Protonation of the aldehydic/ketonic Oxygen to yield the Enol.

Product = Enol

Question 19

Mechanism: Acid-Catalyzed Aldehyde/Ketone Tautomerization

Acid-Catalyzed Enolization

Answer 19

1. Protonation of the aldehydic/ketonic Oxygen to yield the oxocarbenium ion.
2. Deprotonation of the α-Hydrogen (and subsequent π-electron transfer) to yield the Enol.

Product = Enol

Question 20

Mechanism: Base-Catalyzed Enol Tautomerization

Answer 20

1. Deprotonation of the enolic alcohol group (—OH) to yield the enolate ion.
2. π-electron rearrangement to yield the anionic α-Carbon aldehyde/ketone.
3. Protonation of anionic α-Carbon to yield the (nonionic) aldehyde/ketone.

Product = Aldehyde/Ketone

Question 21

Mechanism: Acid-Catalyzed Enol Tautomerization

Answer 21

1. Protonation of the enolic alkene group (at the α-Carbon) AND transfer of π-electrons from Oxygen lone pair to Carbon-Oxygen bond (C=O) to yield the oxocarbenium ion.
2. Depronation of oxocarbenium Oxygen yield the (nonionic) aldehyde/ketone.

Product = Aldehyde/Ketone

Question 22

Deuterium Exchange of α-Hydrogens

Answer 22

All α-Hydrogens of an aldehyde/ketone are replaced with Deuterium isotopes.

The acidic α-Hydrogens are the ONLY hydrogen atoms replaced with Deuterium isotopes.

Question 23

Reagents: Deuterium Exchange

Answer 23

D₂O (Excess), OD^–

Question 24

Aldehyde/Ketone → Racemic Mixture

Answer 24

Isomerization of Aldehydic/Ketonic α-Stereoisomer

The isomerization reaction yields (1) the* reagent α-Isomer* and (2) its α-Stereoisomer.

Question 25

*Reagents:* Isomerization α-Stereoisomer

Answer 25

CH₃CH₂O^–, CH₃CH₂OH

Question 26

Aldehyde/Ketone → α-Halogenated Aldehyde/Ketone

Answer 26

Electrophilic α-Halogenation ## Footnote This α-halogenation reaction can occur in *acidic conditions* and *basic conditions*.

Question 27

*Reagents:* Acid-Catalyzed α-Halogenation

Answer 27

X₂, CH₃CO₂H, H₂O (Solvent) ## Footnote Electrophile = **X₂** Acid Catalyst = **CH₃CO₂H**

Question 28

*Reagents:* Base-Catalyzed α-Halogenation

Answer 28

X₂, NaOH, H₂O (Solvent) ## Footnote Electrophile = **X₂** Acid Catalyst = **NaOH**

Question 29

Why do enols react *faster* with electrophiles than simple alkenes?

Answer 29

The alkene group of enols is *more electron-rich* than that of simple alkenes. ## Footnote Since the alcohol substituent of the enol is *electron-donating*, the adjacent alkene group (i.e. α-Carbon) possesses a greater electron density (than a simple alkene).

Question 30

Why do enolates react *faster* with electrophiles than simple alkenes?

Answer 30

The alkenyl α-Carbon of enols is *more electron-rich* than that of simple alkenes. ## Footnote The enolate possesses an anionic α-Carbon resonance form, so the alkenyl α-Carbon possesses a greater electron density (than it would on a simple alkene).

Question 31

*Enolization Reactions:* Acid-Catalyzed vs. Base-Catalyzed | Tautomerization

Answer 31

* **Acid-Catalyzed:** Protonation of the aldehydic/ketonic Oxygen (to form an *oxocarbenium* ion) occurs *first*. * **Base-Catalyzed:** Deprotonation of the α-Hydrogen (to form an *enolate* ion) occurs *first*.

Question 32

*Carbonylization Reactions:* Acid-Catalyzed vs. Base-Catalyzed | Tautomerization

Answer 32

* **Acid-Catalyzed:** Protonation of the α-Hydrogen (to form an *oxocarbenium* ion) occurs *first*. * **Base-Catalyzed:** Deprotonation of the aldehydic/ketonic Oxygen (to form an *enolate* ion) occurs *first*.

Question 33

What conditions will cause the *tautomerization* of enols

Answer 33

Enols will tautomerize in the presence of **acid** *or* **base**. ## Footnote A minor amount of *acid* or *base* is sufficient to catalyze the transformation from the less-stable enol to the more-stable ketone/aldehyde.

Question 34

*Products of α-Halogenation:* Acid-Catalyzed vs. Base Catalyzed | α-Halogenation of Aldehyde/Ketone

Answer 34

* **Acid-Catalyzed:** Monohalogenated Product * **Base-Catalyzed:** Trihalogenated/Polyhalogenated Product ## Footnote Under *basic conditions*, the α-Halogenation of aldehydes/ketones CANNOT be stopped at the monohalogenated stage.

Question 35

Why is it NOT possible to stop *base-catalyzed* a-Halogenation at the monohalogenated stage? | α-Halogenation of Aldehydes/Ketones

Answer 35

The C—H^α bonds of the *monohalogenated product* are **weaker** (i.e. the α-Hydrogens are *more* acidic) than the C—H^α bonds of the *starting material* (due to the electron-withdrawing effect of the halogen). ## Footnote The monohalogenated product will react *faster* with the halogen electrophile (X₂) than the starting material did. (Each further-halogenated stage will react increasingly faster with the halogen electrophile to eventually halogenate all C—H^α bonds.)

Question 36

Why is it *possible* to achieved the monohalogenated α-Halogenation product? | α-Halogenation of Aldehydes/Ketones

Answer 36

The *alkenyl group* of the *tautomerized monohalogenated product* is **less electron-dense** (i.e. less reactive) than the *alkenyl group* of the *tautomerized starting material* (due to the electron-withdrawing effect of the halogen). ## Footnote The *alkenyl group* of the tautomerized monohalogenated product will attack the halogen electrophile (X₂) **slower** than the alkenyl group of the starting material did.

Question 37

*Reagents:* Carbonyl α-Alkylation | α-Alkylation of Aldehydes/Ketones

Answer 37

1. LDA 2. R—X

Question 38

Aldehyde/Ketone → α-Alkylated Aldehyde/Ketone

Answer 38

Enamine α-Alkylation ## Footnote **Enamine α-Alkylation** does NOT result in poly-α-alkylation *and* can be used to α-alkylate aldehydes AND ketones. (Carbonyl α-Alkylation is *rarely* useful/practical for the synthesis of α-alkylated products.)

Question 39

*Reagents:* Enamine α-Alkylation | α-Alkylation of Aldehydes/Ketones

Answer 39

1. 2° Amine 2. R—X 3. H₂O

Question 40

Why is Carbonyl α-Alkylation is *rarely* useful/practical for the synthesis of α-alkylated products?

Answer 40

Many competing side reactions can potentially occur (e.g. E2 Elimination, Poly-α-Alkylation; Aldehyde Condensation) when the carbonyl α-Alkylation reagents are combined. ## Footnote A more practical/useful alternative to carbonyl α-Alkation is *enamine α-Alkylation*.

Question 41

α,β-Unsaturated Carbonyl Compound

Answer 41

* **α,β-Unsaturated Aldehyde:** A *planar* compound containing an aldehyde group in conjugation with an alkenyl group. * **α,β-Unsaturated Ketone:** A *planar* compound containing a ketone group in conjugation with an alkenyl group. ## Footnote The π-electrons of the carbon-oxygen double bond (C=O) are in conjugation with the π-electrons of the adjacent carbon-carbon double bond (C=C).

Question 42

2 Aldehyde → α,β-Unsaturated Aldehyde | Di-α-Hydrogen Aldehydes OR Tri-α-Hydrogen Aldehydes

Answer 42

Aldol Condensation ## Footnote * A ***trans*** *carbon-carbon double bond* (C=C) is formed between one aldehyde's *α-carbon* and the other aldehyde's *carbonyl carbon*.

Question 43

*Reagents:* Aldol Condensation ## Footnote **Starting Material:** 2 Aldehyde (Identical)

Answer 43

NaOH, Heat (Δ)

Question 44

Aldol

Answer 44

A compound containing an aldehyde group *and* an alcohol group (—OH) on the *β*–carbon.

Question 45

What is the driving force for the dehydration step of Aldol Condensation?

Answer 45

The formation of the *π-conjugated system* within the α,β-unsaturated aldehyde. ## Footnote The charge delocalization of the *π-conjugated system* confers great stability to the unsaturated aldehyde product.

Question 46

2 Aldehyde → Aldol | Mono-α-Hydrogen Aldehydes

Answer 46

Aldol Condensation ## Footnote **2 Aldehyde → Aldol =** Intramolecular

Question 47

Why are aldehydes containing *zero* α-hydrogens unable to undergo Aldol Condensation?

Answer 47

The aldehyde *cannot* be deprotonated at the α-position to yield an enolate.

Question 48

Why are *intermolecular* Aldol Condensation reactions with *ketone* reagents thermodynamically unfavorable?

Answer 48

The *carbonyl carbon* of the ketone is stabilized via hyperconjugation from adjacent alkyl groups, so it is *less electron-deficient* and *less prone* to nucleophilic attack.

Question 49

Why do *intramolecular* Aldol Condensation reactions occur *faster* than *intermolecular* reactions?

Answer 49

The intramolecular Aldol Condensation reaction exhibits favorable *entropic* effects (i.e. the starting reagent forms the α,β-unsaturated aldehyde *and* H₂O).

Question 50

Why are *intermolecular* Aldol Condensation reactions with *ketone* reagents possible?

Answer 50

The intramolecular Aldol Condensation reaction exhibits favorable *entropic* effects (i.e. the starting reagent forms the α,β-unsaturated aldehyde *and* H₂O). ## Footnote The positive *entropic effects* of the condensation reaction override its negative *thermodynamic effects*.

Question 51

*Synthesis Mechanisms:* α,β-Unsaturated Aldehyde

Answer 51

* Aldol Condensation * Allylic Alcohol Oxidation

Question 52

α,β-Unsaturated Carbonyls as Simple Alkenes

Answer 52

An α,β-unsaturated aldehyde/ketone will react as a simple alkene if NONE of the *other* reagents are nucleophiles. ## Footnote The *alkenyl group* of the α,β-unsaturated aldehyde/ketone is NOT involved in the reaction.

Question 53

*Reactions:* α,β-Unsaturated Carbonyls as Simple Alkenes

Answer 53

* Metal-Catalyzed Hydrogenation of Alkene * Electrophilic Halogenation of Alkene * Diels-Alder Reaction

Question 54

α,β-Unsaturated Carbonyls as Simple Aldehydes/Ketones | 1,2-Addition

Answer 54

An α,β-unsaturated aldehyde/ketone will react as a simple aldehyde/ketone if it reacts with any *nucleophilic* organometallic, metal-hydride, hydroxylamine, or hydrazine compound. ## Footnote The nucleophilic compound attacks the α,β-unsaturated aldehyde/ketone at the carbonyl carbon (and does NOT interact with the alkenyl group).

Question 55

*Reactions:* α,β-Unsaturated Carbonyls as Simple Aldehydes/Ketones

Answer 55

* Grignard Reactions * Organolithium Reactions * Metal-Hydride Reduction * Nucleophilic Hydroxylamine Addition * Nucleophilic Hydrazine Addition

Question 56

Hydroxylamine

Answer 56

NH₂OH

Question 57

1,2–Addition | Addition to α,β-Unsaturated Carbonyl

Answer 57

The α,β-unsaturated carbonyl acts as a simple aldehyde/ketone. ## Footnote The nucleophilic compound attacks the α,β-unsaturated aldehyde/ketone at the carbonyl carbon (and does NOT interact with the alkenyl group).

Question 58

1,4–Addition | Conjugate Addition

Answer 58

The *alkenyl group* AND the *aldehyde/ketone group* of the α,β-unsaturated carbonyl are involved in the addition reaction. ## Footnote The nucleophilic compound attacks the α,β-unsaturated aldehyde/ketone at the *β–carbon* to create an *enol* intermediate.

Question 59

*Nucleophiles:* 1,2–Addition

Answer 59

* H₂O * Alcohols * Thiols * 1°/2° Amines * Cyanides * Organocuprates * Grignard Reagents * Enolates ## Footnote The 1,2–Addition pathway is preferred by **stronger nucleophiles**. (Hydroxylamine and Hydrazine are EXCEPTIONS!)

Question 60

*Nucleophiles:* 1,4–Addition

Answer 60

* Grignard Reagents * Organolithiums * Metal Hydrides * Hydroxylamine * Hydrazine ## Footnote The 1,4–Addition pathway is preferred by **weaker nucleophiles**. (Hydroxylamine and Hydrazine are EXCEPTIONS!)

Question 61

α,β-Unsaturated Carbonyls as Alkenyls *and* Aldehydes/Ketones

Answer 61

The α,β-unsaturated aldehyde/ketone experiences 1,4-addition if it reacts with a *weaker* nucleophilic compound. ## Footnote The *weaker* nucleophilic compound attacks the α,β-unsaturated aldehyde/ketone at the *β–carbon* to create an *enol* intermediate. Subsequent deprotonation and π-electron rearragement results in the formation of a *simple* aldehyde/ketone.

Question 62

Why are Grignard reagents able to attack at the α,β-unsaturated carbonyl at the β–carbon OR the carbonyl carbon?

Answer 62

Grignard reagents are *medium-strength* nucleophiles (i.e. *weaker* nucleophiles than organolithium reagents and *stronger* nucleophiles than organocuprate reagents). ## Footnote Since the Grignard reagent is a *weaker* nucleophile than the 1,2–preferring organolithium reagent and a *stronger* nucleophile than the 1,4–preferring organocurprate reagent, it has the ability to perform *both* types of nuclephilic addition.

Question 63

*Reactions of α,β-Unsaturated Carbonyls:* Grignard Reagents | Nucleophilic Addition to α,β-Unsaturated Carbonyls

Answer 63

Grignard reagents can undergo *1,2-addition* AND *1,4-addition* to α,β-unsaturated aldehydes/ketones. ## Footnote Grignard reagents are *weaker* nucleophiles than the 1,2–preferring organolithium reagents and *stronger* nucleophiles than the 1,4–preferring organocurprate reagents.

Question 64

Why do *stronger* nucleophiles prefer to undergo 1,2–Addition? | Nucleophilic Addition to α,β-Unsaturated Carbonyls

Answer 64

* The *carbonyl carbon* is ***more positively charged*** than the *β-carbon*, so the nucleophile will attack the carbonyl carbon faster/earlier. * Attack of the *stronger* nucleophilic compound is *highly exothermic* due to the formation of the robust C—Nu bond, so the reaction is ***irreversible***. ## Footnote The carbonyl carbon has a greater *partial positive* charge (than the β-carbon) since it is directly bonded to the electronegative Oxygen aotm.

Question 65

*1,2–Addition:* Thermodynamic Control vs. Kinetic Control | Nucleophilic Addition to α,β-Unsaturated Carbonyls

Answer 65

Kinetic Control ## Footnote The nucleophile will always attack the *carbonyl carbon* first due to it possessing a greater partial positive charge. (Unless the nucleophilic addition reaction is *reversible*, the less stable 1,2-addition product will predominate.)

Question 66

*1,4–Addition:* Thermodynamic Control vs. Kinetic Control | Nucleophilic Addition to α,β-Unsaturated Carbonyls

Answer 66

Thermodynamic Control ## Footnote Although the nucleophile will always attack the *carbonyl carbon* first, the addition reaction becomes *reversible* under thermodynamic control. (The thermodynamically more stable 1,4-addition product will predominate since any 1,2-addition reaction will be reversible.)

Question 67

*Addition to α,β-Unsaturated Carbonyls:* Hydroxylamine and Hydrazine

Answer 67

Hydroxylamine and Hydrazine prefer to undergo ***1,2–addition*** to the α,β-unsaturated aldehyde/ketone (despite being *weaker* nucleophiles) since the 1,2–product is thermodynamically more stable. ## Footnote The Oxime (i.e. the 1,2-addition product of Hydroxylamine) and Hydrazone (i.e. the 1,2-addition product of Hydrazine) are stabilized via conjugation between the OH/NH₂ π-electrons and the C=N π-bond.

Question 68

During the *protonation step* of 1,4–addition, why does the *enolate* become protonated faster than the α-carbon? | Nucleophilic Addition to α,β-Unsaturated Carbonyls

Answer 68

The enolate (with a *full* negative charge) is more negatively charged than the α–carbon (with a *partial* negative charge).

Question 69

Oxime

Answer 69

A compound containing a Carbon double-bonded to a Nitrogen (C=N) that is single-bonded to an alcohol group (—OH). | R₂—C=N—OH

Question 70

*Reagents:* Organocuprate Preparation ## Footnote **Organocuprate =** R₂CuLi

Answer 70

2 R—Li + CuI

Question 71

Reactions of Organocuprates

Answer 71

* β–Alkylation (via Acid Workup) * α,β–Dialkylation (via Addition of Alkyl Halide)

Question 72

α,β-Unsaturated Carbonyl → 1,5-Dicarbonyl

Answer 72

Michael Addition ## Footnote The Michael Addition reaction occurs under *basic conditions* ONLY.

Question 73

Aldehyde/Ketone → 1,5-Dicarbonyl

Answer 73

Michael Addition ## Footnote The Michael Addition reaction occurs under *basic conditions* ONLY.

Question 74

*Reagents:* Michael Addition ## Footnote **Starting Materials:** α,β-Unsaturated Carbonyl + Aldehyde/Ketone

Answer 74

CH₃CH₂O^–, CH₃CH₂OH ## Footnote The α,β-unsaturated carbonyl *must* consist of four carbons.

Question 75

Ethoxide Deprotonation in Michael Addition

Answer 75

Since the ethoxide base is relatively *unhindered*, it will deprotonate the *most substituted* α-carbon (to form the most stable enolate intermediate).

Question 76

α,β-Unsaturated Carbonyl → Cyclic α,β-Unsaturated Ketone

Answer 76

Robinson Annulation ## Footnote The Robinson Addition mechanism occurs under *basic conditions* and at *high temperatures* ONLY.

Question 77

Aldehyde/Ketone → Cyclic α,β-Unsaturated Ketone

Answer 77

Robinson Annulation ## Footnote The Robinson Addition mechanism occurs under *basic conditions* and at *high temperatures* ONLY.

Question 78

*Mechanism:* Robinson Annulation

Answer 78

1. Deprotonation of α-Carbon to Aldehyde/Ketone 2. 1,4–Addition of Enolate to α,β-Unsaturated Carbonyl 3. Protonation of Internal α-Carbon to Enolate 4. Deprotonation of Terminal α-Carbon to Ketone 5. Ring Formation via Attack by Terminal α-Carbon of Enolate 6. Protonation of Oxide 7. Deprotonation of α-Carbon to Ketone 8. Leaving of Hydroxyl via π-Electron Rearragement | Michael Addition + Intramolecular Aldol Condensation

Question 79

*Reagents:* Robinson Annulation ## Footnote **Starting Materials:** α,β-Unsaturated Carbonyl + Aldehyde/Ketone

Answer 79

1. CH₃CH₂O^–, CH₃CH₂OH 2. CH₃CH₂O^–, Δ (Heat) ## Footnote The α,β-unsaturated carbonyl *must* consist of four carbons.

Question 80

1,5-Dicarbonyl → Cyclic α,β-Unsaturated Ketone | Step 2 of Robinson Annulation

Answer 80

Intramolecular Aldol Condensation

Question 81

[4 + 2] Annulation

Answer 81

Robinson Annulation ## Footnote The addition of an aldehyde/ketone to a **four-carbon** α,β-unsaturated carbonyl yields a six-membered cyclic α,β-unsaturated carbonyl.

Question 82

In what cases can Robinson Annulation NOT occur?

Answer 82

Robinson Annulation is impossible in cases where NO α-Hydrogens to the non-cyclic ketone are present. ## Footnote **E.g.** Robinson Annulation is impossible with compounds containing a *phenol* group adjacent to the non-cyclic ketone.

Question 83

Synthons with Nucleophilic α-Carbon

Answer 83

* Enol * Enolate * Enamine * Phosphorus Ylide

Question 84

Synthons with Electrophilic β-Carbon

Answer 84

* α,β-Unsaturated Aldehyde * α,β-Unsaturated Ketone

Question 85

Synthons with Carbanion

Answer 85

* Grignard Reagents * Organolithium Reagents * Organocupric Reagents * Cyanides

Question 86

Synthons with Carbocation

Answer 86

* Alkyl Halides * Epoxides

Question 87

*Examples:* Carbon-Nucleophiles

Answer 87

* Enol * Enolate * Enamine * Grignard Reagent * Organolithium Reagent * Organocupric Reagent * Cyanide * Phosphorus Ylide

Question 88

*Examples:* Carbon-Electrophiles

Answer 88

* Alkyl Halide * Aldehyde (Carbonyl Carbon) * Ketone (Carbonyl Carbon) * α,β-Unsaturated Aldehyde (β-Carbon) * α,β-Unsaturated Ketone (β-Carbon) * Epoxide * Imine * Iminium

Question 89

Protection Groups

Answer 89

* **Aldehyde/Ketone:** Acetal OR Thioacetal * **Hydroxyl Group:** Ether * **Amine:** Amide