Chapter 22 - Carbonyl Alpha Substitution Reactions

Question 1

A carbonyl compound with a hydrogen atom on its _____ carbon rapidly equilibrates its corresponding _____ isomer.

Answer 1

alpha; enol

Question 2

Tautomers are isomers that interconvert spontaneously and can occur in _____ or _____ conditions.

Answer 2

acidic (H3O+); basic (-OH)

Question 3

Tautomers are _____ isomers.

Answer 3

constitutional

Question 4

Resonance forms are different representations of a _____ compound.

Answer 4

single

Question 5

Most monocarbonyl compounds exist in their _____ form at equilibrium

Answer 5

keto

Question 6

Keto-enol tautomerism of carbonyl compounds is catalyzed by both _____ and _____.

Answer 6

acids; bases

Question 7

In acidic conditions, the carbonyl oxygen is protonated by an acid giving a _____ with two _____ _____.

Answer 7

cation; resonance structures

Question 8

In acidic conditions, loss of _____ from the _____ position by reaction with base A:- gives the enol tautomer and regenerates HA catalyst.

Answer 8

H+; alpha

Question 9

In basic conditions, base (-OH) removes the acidic _____ hydrogen yielding an _____ ion with two resonance structures.

Answer 9

alpha; enolate

Question 10

An enolate ion is when a ( + / - ) charge is given to the _____ carbon with the loss of alpha hydrogen and its resonating structures when the negative charge goes to the _____ _____.

Answer 10

negative; alpha; carbonyl oxygen

Question 11

Carbonyl compound can act as a(n) _____ and donate one of its alpha hydrogens to a sufficiently strong base yielding a(n) _____ _____.

Answer 11

acid; enolate ion

Question 12

Enols behave as _____ and react with _____.

Answer 12

nucleophiles; electrophiles

Question 13

Enols are more _____-rich and correspondingly more reactive than _____. The alpha carbon is the negative charge and is electron rich.

Answer 13

electron; alkenes

Question 14

It is important that the nucleophile be a good _____ _____, meaning it has electrons it wants to share.

Answer 14

Lewis base

Question 15

Aldehydes and ketones can be halogenated at the alpha positions by reactions with _____, _____, or _____ in _____ solution.

Answer 15

Cl2; Br2; I2; acidic

Question 16

If an aldehyde or ketone is treated with D3O+ the alpha-hydrogens are replaced with deuterium at the same rate as _____.

Answer 16

halogenation

Question 17

Reaction of an aldehyde or ketone with D3O+ or X2 both involve a _____ intermediate.

Answer 17

enol

Question 18

Alpha-bromo ketones can be dehydrobrominated by base treatment (pyridine) to yield _____.

Answer 18

alpha,beta-unsaturated ketones (this is just a double bond between the alpha and beta carbons)

Question 19

Alpha,beta-unsaturated ketones occur with alpha and beta being in the _____ carbon chain.

Answer 19

longest

Question 20

Acids, esters, and amides do not react with _____.

Answer 20

Br2

Question 21

Acids, esters, and amides are brominated by a mixture of _____ and _____.

Answer 21

Br2; PBr3 (Hell-Volhard-Zelinskii reaction)

Question 22

_____ converts –COOH to –COBr.

Answer 22

PBr3

Question 23

LDA is used on _____ carbons to form a(n) _____ ion.

Answer 23

alpha; enolate

Question 24

When a hydrogen atom is flanked by two carbonyl groups, its acidity _____.

Answer 24

increases

Question 25

When a hydrogen atom is flanked by two carbonyl groups, the negative charge of enolate _____ over both carbonyl groups.

Answer 25

delocalizes

Question 26

Is the enolate ion a cation or anion?

Answer 26

anion

Question 27

Enolate ions can be looked at either as _____ _____ (C=C–O-) or as _____ _____ (-C–C=O).

Answer 27

vinylic alkoxides; alpha-keto carbanions

Question 28

Most of the time, the (vinylic alkoxides / alpha-keto carbanions) react. This is because they yield a carbonyl compound.

Answer 28

alpha-keto carbanions

Question 29

Aldehydes and ketones undergo _____ alpha-halogenation. Although, it is seldom used.

Answer 29

base-promoted

Question 30

If excess base and halogen are used, a methyl ketone is _____ _____ and then cleaved by base in the haloform reaction.

Answer 30

triply halogenated

Question 31

A halogen-stabilized carbanion acts as a _____ group.

Answer 31

leaving

Question 32

CHX3 is called _____.

Answer 32

haloform

Question 33

CHCl3 is called _____.

Answer 33

chloroform

Question 34

CHBr3 is called _____.

Answer 34

bromoform

Question 35

CHI3 is called _____.

Answer 35

iodoform

Question 36

Alkylation of enolate ions is base-promoted and occurs through a(n) _____ _____ intermediate.

Answer 36

enolate ion

Question 37

Enolate alkylation (R–X) is a(n) _____ reaction. The leaving group X can be _____, iodide, _____, or chloride.

Answer 37

SN2; tosylate; bromide

Question 38

Enolate alkylation (R–X) is a(n) _____ reaction. The R group should be _____ or methyl and preferably should be _____ or benzylic.

Answer 38

SN2; primary; allylic

Question 39

Malonic ester synthesis is for preparing a _____ _____ from an alkyl halide while lengthening the carbon chain by _____ atoms.

Answer 39

carboxylic acid; two

Question 40

A malonic ester is when there are two _____ groups on one CH2.

Answer 40

carbonyl

Question 41

Malonic ester is easily converted into its enolate ion by reaction with _____ _____ in _____.

Answer 41

sodium ethoxide (Na+ -OEt); ethanol (EtOH)

Question 42

The malonic ester derivative hydrolyzes in _____ (and heat) and loses _____ to yield a substituted monoacid.

Answer 42

acid; CO2

Question 43

Esters can be hydrolyzed to a(n) _____ under _____ condition.

Answer 43

acid; acidic

Question 44

Decarboxylation requires a(n) _____ group _____ atoms away from the –COOH.

Answer 44

carbonyl; two

Question 45

1,4-dibromobutane and a malonic ester enolate ion reacts twice with sodium ethoxide and ethanol to form a(n) _____ product.

Answer 45

cyclic (this can occur with other compounds like 1,4-dibromobutane to form 3-, 4-, 5-, and 6-membered rings)

Question 46

What does H3O+ / heat do to a –C(CO2Et)2?

Answer 46

it turns it into a –COOH + CO2 + 2 EtOH

Question 47

Acetoacetic ester synthesis converts an _____ _____ into a _____ _____ having 3 more carbons.

Answer 47

alkyl halide; methyl ketone

Question 48

What does H3O+ / heat do to a –C(CO2Et)?

Answer 48

cleaves it into CO2 + EtOH

Question 49

Ketones, esters, and nitriles can all be alkylated using _____ in _____. (It turns the alpha carbon into an anion by attacking an alpha hydrogen.)

Answer 49

LDA; THF