CHEM 334 CONCEPT QUESTIONS -- MADUKWE QUESTIONS
AND CORRECT DETAILED ANSWERS (VERIFIED ANSWERS)
ALREADY GRADED A+
The pKa of the carbon next to one C=O is Ans✓✓✓20-25
Give two reasons why the carbon next to a C=O is acidic. Ans✓✓✓1.
C=O is an EWG
2. The conjugate base is stabilized by resonance
The carbon next to a C=O is more or less acidic than an alcohol.
Ans✓✓✓Less acidic. pka of alpha carbon = 19-20 pka or alcohol is 16-
18
A carbon in between two C=O's has a pKa of _________ and is more or
less acidic than an alcohol Ans✓✓✓9-10, MORE
Draw the two resonance structures for an enolate. Ans✓✓✓(picture)
Which resonance structure is more stable and which is more reactive
Ans✓✓✓The negative charge on the oxygen is more stable because the
O is more electronegative than carbon, negative charge on carbon is
more reactive
Describe the origins of the names enol and enolate Ans✓✓✓En(alkene)-
ol(alcohol), En(alkene)-ol(alcohol)-ate(negative charge on oxygen)
, In the reaction of an enol or enolate with an electrophile, the electrons
forthe new bond between the enol/enolate and electrophile come
from________ (give name of source of these electrons) Ans✓✓✓C=C
bond
What is the reason that the lone pair on the oxygen of an enolate does
not attack the electrophile? Ans✓✓✓The lone pair and negative charge
on oxygen is usually coordinated to the metal counterion (Na+, Li+, K+)
LDA is an example of what type of reagent? Ans✓✓✓Very strong bulky
base, forms kinetic enolates
If a ketone has two different α-carbons, the deprotonation of which α-
carbon would give the thermodynamic enolate, the more or less
substituted α-carbon? Ans✓✓✓(pic)
Why is the thermodynamic enolate more stable than the kinetic enolate?
Ans✓✓✓The C=C is more substituted and therefore more stable
How can you form the kinetic enolate? Ans✓✓✓Using a strong base
that irreversible deprotonates an alpha carbon
Which always forms first, the kinetic or thermodynamic enolate?
Ans✓✓✓Kinetic enolate forms first from the deprotonation of the
sterically less hindered alpha carbon
AND CORRECT DETAILED ANSWERS (VERIFIED ANSWERS)
ALREADY GRADED A+
The pKa of the carbon next to one C=O is Ans✓✓✓20-25
Give two reasons why the carbon next to a C=O is acidic. Ans✓✓✓1.
C=O is an EWG
2. The conjugate base is stabilized by resonance
The carbon next to a C=O is more or less acidic than an alcohol.
Ans✓✓✓Less acidic. pka of alpha carbon = 19-20 pka or alcohol is 16-
18
A carbon in between two C=O's has a pKa of _________ and is more or
less acidic than an alcohol Ans✓✓✓9-10, MORE
Draw the two resonance structures for an enolate. Ans✓✓✓(picture)
Which resonance structure is more stable and which is more reactive
Ans✓✓✓The negative charge on the oxygen is more stable because the
O is more electronegative than carbon, negative charge on carbon is
more reactive
Describe the origins of the names enol and enolate Ans✓✓✓En(alkene)-
ol(alcohol), En(alkene)-ol(alcohol)-ate(negative charge on oxygen)
, In the reaction of an enol or enolate with an electrophile, the electrons
forthe new bond between the enol/enolate and electrophile come
from________ (give name of source of these electrons) Ans✓✓✓C=C
bond
What is the reason that the lone pair on the oxygen of an enolate does
not attack the electrophile? Ans✓✓✓The lone pair and negative charge
on oxygen is usually coordinated to the metal counterion (Na+, Li+, K+)
LDA is an example of what type of reagent? Ans✓✓✓Very strong bulky
base, forms kinetic enolates
If a ketone has two different α-carbons, the deprotonation of which α-
carbon would give the thermodynamic enolate, the more or less
substituted α-carbon? Ans✓✓✓(pic)
Why is the thermodynamic enolate more stable than the kinetic enolate?
Ans✓✓✓The C=C is more substituted and therefore more stable
How can you form the kinetic enolate? Ans✓✓✓Using a strong base
that irreversible deprotonates an alpha carbon
Which always forms first, the kinetic or thermodynamic enolate?
Ans✓✓✓Kinetic enolate forms first from the deprotonation of the
sterically less hindered alpha carbon
