ch. 22

Question 1

Malonic Ester Synthesis

Answer 1

Converts an alkyl halide into a carboxylic acid with the addition of two carbon atoms (RX –> RCH2CO2H)

Heating in HCl causes hydrolysis and decarboxylation of alkylated malonate to yield a substituted monocarboxylic acid.

Question 2

Acetoacetic Ester Synthesis

Answer 2

Converts an alkyl halide into a methyl ketone with an addition of three carbon atoms (RX –> RCH2COCH3)

Heating in HCl hydrolyzes the ester and decarboxylates the acid to yield a ketone.

Question 3

Keto-enol Tautomerism

Answer 3

carbonyl compounds in equilibrium with enols

Question 4

Enol Tautomers

Answer 4

can’t be isolated in pure form, present only a small extenet at equilbrium,contain highly nucleophilic double bonds, and are very reactive with electrophiles in an alpha-substitution rxn

Question 5

Hell-Volhard-Zelinskii (HVZ) Reaction

Answer 5

Alpha bromination of carboxylic acids treated with Br2 and PBr3

Question 6

What can the alpha-halogenated products of the HVZ reaction undergo?

Answer 6

base-induced E2 elimination to yield a beta-unsaturated carbonyl compound.

Question 7

Alpha hydrogen atoms of carbonyl compounds are…

Answer 7

weakly acidic; can be removed with strong bases (LDA) to yield nucleophilic enolate ions

Question 8

Most useful reaction of enolate ions

Answer 8

SN2 alkylation with alkyl halides

Question 9

What can carbonyl compounds be directly alkylated by?

Answer 9

treatment with LDA and an alkyl halide

Question 10

Aldehyde/Ketone holgenation reagent

Answer 10

CH3CO2H (acetic acid)

Question 11

HVZ bromination reaction reagent

Answer 11

1. Br2, PBr3

2. H2O

Question 12

Dehydrobromination of alpha-bromo ketone reagent

Answer 12

pyridine,heat

Question 13

Haloform reaction reagent

Answer 13

X2,NaOH (base)

X2=Cl2, Br2, I2

Question 14

Malonic ester synthesis reagent

Answer 14

1. Na+ -OEt (strong base), ethanol
2. RX (alkyl halide)
3. H3O+ (aqueous acid), heat

Question 15

Direct alkylation reagent (ketones, esters, nitriles)

Answer 15

1. LDA in THF

2. R’X

Question 16

Tautomerism

Answer 16

rapid equilbration of carbonyl compounds with hydrogens bonded to their alpha carbons and corresponding enols

Question 17

Tautomers

Answer 17

Individual tautomers; isomers

Question 18

Acid-Catalyzed Enolization

Answer 18

carbonyl carbon is protonated to form an intermediated that can lose a hydrogen from its alpha carbon to yield a neutral enol

Question 19

Base-catalyzed Enol formation

Answer 19

acid-base rxn between a base and alpha hydrogen; enolate ion is protonated to yield an enol, protonation can occur on either carbon/oxygen; only hydrogen on alpha positions of carbonyl compounds are acidic

Question 20

Enols are ____ and behave as ____.

Answer 20

electron-rich double bonds; nucleophiles

Question 21

Are enols more or less reactive than alkenes? Why?

Answer 21

Enols are more reactive than alkenes due to the electron-donating enol -OH group.

Question 22

Are enolates or enols more reactive? Why?

Answer 22

Enolates are more reactive than enols because they are more nucleophilic.

Question 23

Hydrogens alpha to carbonyl group are ___? Why?

Answer 23

weakly acidic; due to overlap of filled p orbitals with carbonly group p orbitals

Question 24

Which resonance forms of the enolate ion formation has lower energy?

Answer 24

Form with negative charge on oxygen

Question 25

What is needed for enolate ion formation?

Answer 25

Strong bases (LDA); alkoxide ions are too weak to use

Question 26

What can enolates react with? And what do they yield?

Answer 26

1. Carbon; yields an alpha-substitued carbonyl carbon

2. Oxygen; yields an enol derivative

Question 27

Alkylation features

Answer 27

form a new C-C bond; alkyl groups must by methyl, primary, allylic, or benzylic

Question 28

Decarboxylations are only common in?

Answer 28

Beta-keto acids and malonic acids