Chapter 22 - Carbonyl Alpha Substitution Reactions Flashcards
A carbonyl compound with a hydrogen atom on its _____ carbon rapidly equilibrates its corresponding _____ isomer.
alpha; enol
Tautomers are isomers that interconvert spontaneously and can occur in _____ or _____ conditions.
acidic (H3O+); basic (-OH)
Tautomers are _____ isomers.
constitutional
Resonance forms are different representations of a _____ compound.
single
Most monocarbonyl compounds exist in their _____ form at equilibrium
keto
Keto-enol tautomerism of carbonyl compounds is catalyzed by both _____ and _____.
acids; bases
In acidic conditions, the carbonyl oxygen is protonated by an acid giving a _____ with two _____ _____.
cation; resonance structures
In acidic conditions, loss of _____ from the _____ position by reaction with base A:- gives the enol tautomer and regenerates HA catalyst.
H+; alpha
In basic conditions, base (-OH) removes the acidic _____ hydrogen yielding an _____ ion with two resonance structures.
alpha; enolate
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 _____ _____.
negative; alpha; carbonyl oxygen
Carbonyl compound can act as a(n) _____ and donate one of its alpha hydrogens to a sufficiently strong base yielding a(n) _____ _____.
acid; enolate ion
Enols behave as _____ and react with _____.
nucleophiles; electrophiles
Enols are more _____-rich and correspondingly more reactive than _____. The alpha carbon is the negative charge and is electron rich.
electron; alkenes
It is important that the nucleophile be a good _____ _____, meaning it has electrons it wants to share.
Lewis base
Aldehydes and ketones can be halogenated at the alpha positions by reactions with _____, _____, or _____ in _____ solution.
Cl2; Br2; I2; acidic
If an aldehyde or ketone is treated with D3O+ the alpha-hydrogens are replaced with deuterium at the same rate as _____.
halogenation
Reaction of an aldehyde or ketone with D3O+ or X2 both involve a _____ intermediate.
enol
Alpha-bromo ketones can be dehydrobrominated by base treatment (pyridine) to yield _____.
alpha,beta-unsaturated ketones (this is just a double bond between the alpha and beta carbons)
Alpha,beta-unsaturated ketones occur with alpha and beta being in the _____ carbon chain.
longest
Acids, esters, and amides do not react with _____.
Br2
Acids, esters, and amides are brominated by a mixture of _____ and _____.
Br2; PBr3 (Hell-Volhard-Zelinskii reaction)
_____ converts –COOH to –COBr.
PBr3
LDA is used on _____ carbons to form a(n) _____ ion.
alpha; enolate
When a hydrogen atom is flanked by two carbonyl groups, its acidity _____.
increases
When a hydrogen atom is flanked by two carbonyl groups, the negative charge of enolate _____ over both carbonyl groups.
delocalizes
Is the enolate ion a cation or anion?
anion
Enolate ions can be looked at either as _____ _____ (C=C–O-) or as _____ _____ (-C–C=O).
vinylic alkoxides; alpha-keto carbanions
Most of the time, the (vinylic alkoxides / alpha-keto carbanions) react. This is because they yield a carbonyl compound.
alpha-keto carbanions
Aldehydes and ketones undergo _____ alpha-halogenation. Although, it is seldom used.
base-promoted
If excess base and halogen are used, a methyl ketone is _____ _____ and then cleaved by base in the haloform reaction.
triply halogenated
A halogen-stabilized carbanion acts as a _____ group.
leaving
CHX3 is called _____.
haloform
CHCl3 is called _____.
chloroform
CHBr3 is called _____.
bromoform
CHI3 is called _____.
iodoform
Alkylation of enolate ions is base-promoted and occurs through a(n) _____ _____ intermediate.
enolate ion
Enolate alkylation (R–X) is a(n) _____ reaction. The leaving group X can be _____, iodide, _____, or chloride.
SN2; tosylate; bromide
Enolate alkylation (R–X) is a(n) _____ reaction. The R group should be _____ or methyl and preferably should be _____ or benzylic.
SN2; primary; allylic
Malonic ester synthesis is for preparing a _____ _____ from an alkyl halide while lengthening the carbon chain by _____ atoms.
carboxylic acid; two
A malonic ester is when there are two _____ groups on one CH2.
carbonyl
Malonic ester is easily converted into its enolate ion by reaction with _____ _____ in _____.
sodium ethoxide (Na+ -OEt); ethanol (EtOH)
The malonic ester derivative hydrolyzes in _____ (and heat) and loses _____ to yield a substituted monoacid.
acid; CO2
Esters can be hydrolyzed to a(n) _____ under _____ condition.
acid; acidic
Decarboxylation requires a(n) _____ group _____ atoms away from the –COOH.
carbonyl; two
1,4-dibromobutane and a malonic ester enolate ion reacts twice with sodium ethoxide and ethanol to form a(n) _____ product.
cyclic (this can occur with other compounds like 1,4-dibromobutane to form 3-, 4-, 5-, and 6-membered rings)
What does H3O+ / heat do to a –C(CO2Et)2?
it turns it into a –COOH + CO2 + 2 EtOH
Acetoacetic ester synthesis converts an _____ _____ into a _____ _____ having 3 more carbons.
alkyl halide; methyl ketone
What does H3O+ / heat do to a –C(CO2Et)?
cleaves it into CO2 + EtOH
Ketones, esters, and nitriles can all be alkylated using _____ in _____. (It turns the alpha carbon into an anion by attacking an alpha hydrogen.)
LDA; THF
