Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

OChem2 > Exam 3 > Flashcards

Exam 3 Flashcards

1
Q

When does nucleophilic addition occur on a carbonyl C?

A

When there is no electronegative atom Z on the carbonyl group

  • Ex: Aldehydes have an H group
  • Ex: Ketones have a CH group of some sort
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

When does nucleophilic acyl substitution occur on a carbonyl C?

A

When there is an electronegative atom Z on the carbonyl group

-Ex: Carboxylic acids, acid chlorides, etc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is substituted on the alpha C (R group) of a carbonyl compound?

A

One of the hydrogens on the alpha C is replaced by the electrophilic group attacking the compound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Tautomerization (definition)

A

The process of converting one tautomer to another (Ex: keto to enol)

  • Catalyzed by both an acid and a base
  • Requires two steps (protonation and deprotonation)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe tautomerization in acid

A

-Protonation PRECEDES deprotonation

  • STEP 1: Carbonyl O deprotonates water (and is protonated itself)
  • STEP 2: -OH Deprotonates the alpha C-H, forming a double bond between the alpha and carbonyl C
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe tautomerization in base

A

-Deprotonation PRECEEDS protonation

  • STEP 1: The -OH deprotonates the alpha C, forming a double bond between the carbonyl C and the alpha C, which pushes the pi bond in the carbonyl group up onto the O
  • STEP 2: Carbonyl O deprotonates H2O (therefore becoming protonated itself)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Does equillibirum favor the side with a weaker acidity or stronger?

A

Favors the side with a weaker acidity (higher pKa)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What does LDA stand for? What is it used for?

A

It is a very strong base (weak nucleophile due to steric hindrance)

It stands for Li(+)N(-)[CH(CH3)2]2

It is used to form enolate in 100% yield

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is an enolate?

A

A carbonyl with a negatively charged alpha C (in the R group)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How would you substitute an electrophile onto a carbonyl compound?

A

STEP 1: A strong base deprotonates the alpha carbon (in the R group)– this makes the enolate (the H is eliminated)

STEP 2: The negatively charged alpha carbon (in the enolate R group) attacks the electrophile, adding it to the alpha C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What happens when an unsymmetrical carbonyl compound is treated with a base?

A

Two enolates are possible

One is formed by removal of a 2’ carbon (first R group), the other formed by the removal of a 3’ carbon (other R group)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Does the removal of a 2’ hydrogen make a kinetic or thermodynamic product?

A
  • Removal of a 2’ hydrogen makes a kinetic product

- Faster, but less stable / higher in energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Does the removal of a 3’ hydrogen make a kinetic or thermodynamic product?

A
  • Removal of a 3’ hydrogen makes a thermodynamic product

- Slower, but more stable / lower in energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How do you favor the kinetic enolate?

A
  • Use a strong nucleophilic base
  • Polar aprotic solvent
  • Low temperature

Ex: Use LDA in THF at -78C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do you favor the thermodynamic enolate?

A
  • Use a strong base
  • Protic solvent
  • Room temperature

Ex: Use -OH in ROH at room temp (25 C)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What solvent would you use for an acid halogenation?

A

X2
———–>
CH3COOH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe acid-catalyzed halogenation at the alpha carbon

A

i) Carbonyl O deprotonates the acid catalyst– The acid catalyst then deprotonates the R group on the carbonyl group (making a double bond b/w carbonyl C and alpha C)
ii) One of the lone pairs on the carbonyl O comes down, forcing the double bond b/w carbonyl C and alpha C attacks the X2
- –The negatively charged X(-) by itself now deprotonates the carbonyl O, making the final product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe base-catalyzed halogenation at the alpha carbon

A

i) The base deprotonates the alpha C, making it negatively charged
ii) The negatively charged alpha C attacks the X2 , finishing the reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe the formation of a haloform

A

**Only occurs with methyl ketones (ketones with a methyl R group)

i) A base (-OH) deprotonates the alpha C, then the negatively charged alpha C attacks the X2
- –This happens one more time
ii) OH adds to the carbonyl C, pushing the pi bond up to the O
iii) The pi bond comes back down and pushes off the R group (the CX situation)
iv) The CX is negatively charged, and it deprotonates the OH group, finishing the reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How would you add a pi bond into a carbonyl hexanone?

A

i) Substitute Br to the alpha C (Br replaces an H)
- –Br2
- ———->
- –CH3COOH

ii) Eliminate the Br to make a pi bond
- –Li2CO3
- ——->
- –LiBr, DMF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How would you add two aldehydes together to form an aldol product? How would you make this aldol product a condensation product?

A

i) Take two identical aldehydes, add -OH
ii) This results in ONE of the two carbonyl compounds becoming protonated, and the OTHER aldehyde loses an H in order to attach to the 1st aldehyde

Ex: Aldehyde + Aldehyde (Me-C(H)=O) –> Me-C(OH)(H)-CH2-C(H)=O

THEN, Add more OH and heat to get rid of the previously protonated OH, leaving an H in its place, and making a double bond b/w the first aldehyde and the C group bonding the two aldehyde groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Mechanism of aldol synthesis

A

i) Base (OH) deprotonates methyl group on Aldehyde– this creates a double bond b/w the carbonyl C and the methyl C & pushes the C=O bond up to the O
ii) Pi bond of C=O comes back down, forces double bond b/w the carbonyl C and methyl C to attack the carbonyl C of the second aldehyde (which pushes the 2nd aldehyde’s pi bond up to its O)
iii) The negatively charged O on the second aldehyde deprotonates water

That’s it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Mechanism of aldol condensation

A

i) OH deprotonates the CH2 holding the two aldeyde groups together, makes the C there negatively charged
ii) That negative charge moves over to become a pi bond b/w the carbonyl C of the first aldehyde and the CH – This entirely pushes off the OH group on the first aldehyde

That’s it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What must you have in order to create an aldol from an aldehyde?

A

There needs to be an alpha Hydrogen on the R group of the aldehyde

—AKA there needs to be a hydrogen directly attached to the alpha carbon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Acetoacetic acid ester synthesis definition
A stepwise method for converting ethyl acetoacetate into a ketone having one or two alkyl groups on the alpha carbon
26
What does ethyl acetoacetate look like?
A carbonyl with the following R groups: - Methyl - C(H2)-COOEt
27
What reacts in a Claisen reaction?
Two molecules of an ester react with each other in the presence of an alkoxide base (such as 1) NaOHEt 2) H3O+) - Claisen reactions are SUBSTITUTIONS - Only esters with 2 or 3 alpha hydrogens on the alpha carbon undergo this reaction
28
Claisen Reaction Mechanism
i) Base deprotonates the CH3 (R-group) to make negatively charged CH2 ii) The negatively charged CH2 attacks the carbonyl C of the second ester, pushing the pi bond of the second ester up to its O iii) The negative charge comes back down from O and pushes off the OR group of the second ester iv) The base deprotonates the CH2 group holding together the two esters, making a negatively charged CH v) Addition of a strong acid re-protonates the CH2
29
What is formed in a Dieckmann reaction?
- A five or six membered ring - It is an intramolecular Claisen Rxn - 1, 6 Diesters form 5-membered rings - 1,7 Diesters form 6-membered rings
30
What is the very basic mechanism of a Dieckman reaction?
Ex: Using a 1,7 Diester -The 1 and 6 carbons fuse, the non-CH2 R group is booted off of the 1 carbon, the R group remains on the 6 carbon
31
Dieckman rxn using a 1,7 Diester Mechanism
i) The -OEt base deprotonates the 6-Carbon, making it negatively charged ii) This negatively charged C attacks the carbonyl 1-Carbon, pushing the carbonyl C=O pi bond up to the O iii) The pi bond comes back down and pushes off the OR group on the 1-Carbon iv) To complete the reaction, the remaining H on the 6-C is removed by base, and then re-protonated by H3O+
32
Michael Reaction Mechanism
i) The -OEt base deprotonates the alpha carbon of the carbon (r group) which contains multiple O groups ii) This now negatively-charged alpha C attacks the Beta carbon of the second a-B-unsaturated carbon compound (ex: a benzene ring with a pi bond attached to the Beta carbon); This pushes the pi bond up to the alpha carbon iii) The now-negatively charged alpha carbon of the unsaturated carbon compound will deprotonate the base which had deprotonated in the first step, this will complete the reaction
33
Robinson Annulation Mechanism - Part 1
i) Base removes the most acidic hydrogen (the one between the two carbonyl groups) making that carbon negatively charged ii) This negatively charged carbon attacks the unsaturated (pi bond) Beta carbon of a carbonyl compound, making the alpha carbon of the unsaturated compound negatively charged (the pi bond next to it bumps onto it) iii) That negatively charged carbon deprotonates a water to become neutral
34
Robinson Annulation Mechanism - Part 2 (Intramolecular)
i) -OH deprotonates the H on the only carbon remaining unattached at the end of the molecule, making that C negatively charged ii) This negatively charged C attacks the carbonyl C of the other half of the compound, pushing the pi bond of that carbonyl up to its O iii) The now negatively charged O deprotonates a water to become OH iv) The -OH deprotonates the alpha C adjacent to the C which contains the OH group (the C that was deprotonated at the very beginning of the reaction), making it negatively charged v) The negative charge becomes a pi bond between this carbon and the carbon containing the OH group, which pushes the OH group off, ending the reaction
35
Are primary and secondary amines H-bond donors or acceptors?
1' and 2' amines are both donors and acceptors of H-bonds
36
Are 3' amines H-bond donors or acceptors?
3' amines are only H-bond acceptors
37
What four elements can undergo H-bonding?
F, Cl, O, and N No other elements are e-negative enough
38
How can an amine act as a base?
The lone pair on N will deprotonate an acid
39
What three acids can protonate an amine?
- HCl - H2SO4 - Carboxylic acids ---Must be strong acids
40
Is a more stable compound more acidic or more alkaline?
A more stable compound is more alkaline (less acidic)
41
What two compounds are good Sn2 electrophiles?
- 1' Halide | - CH3I
42
Can you mix a 1:1 ratio of amine and Sn2 electrophile?
NO!! -You must have one or the other in excess in order to drive the reaction
43
What does the Gabriel synthesis make?
Synthesizes 1' amines via nucleophilic substitution
44
What three reagents would you use to do a Hoffman Elimination starting with an amine?
1) CH3I - ----------> 2) Ag2O 3) Heat
45
What two sets of reagents can you use to reduce a nitro group (NO2)?
H2, Pd/C -------------> OR Fe, HCl -----------> Makes 1' amine
46
What set of reagents can you use to reduce a nitrile?
1) LiAlH4 - -------------> 2) H2O Makes 1' amine
47
What set of reagents can you use to reduce an amine?
1) LiAlH4 - ------------> 2) H2O **Can be used for 1', 2', and 3' amines
48
What reagent do you use in gabriel synthesis?
Pthalamide It's a 5-membered ring with a nitrogen at the top (as part of the ring), which has a =O group on each C to either side of the N, then that ring is attached to a benzene ring
49
Is the N-H bond of an imide acidic or basic?
Super acidic
50
Are amines lewis acids or lewis bases?
Amines are lewis bases --They cannot undergo Friedel-Crafts reactions --Must add protecting group to let it undergo F.C.
51
What reagents would you use to substitute an NH2 group into an OH group on a benzene ring?
H2O, Heat | --------------->
52
What reagents would you use to substitute out an NH2 group for a halide on a benzene ring?
CuCl or CuBr or KI
53
What reagent would you use to substitute out an NH2 for an H on a benzene ring?
H3PO2
54
What reagents do you use to create a diazonium salt from an NH2 group?
NaNO2 ------------> HCl
55
What does a diazonium salt look like?
N(triplebond)N(+) Cl(-)
56
Basic mechanism of a Michael Reaction
Adds an H to the alpha carbon of a carbonyl Eliminates an H from the Beta carbon of a carbonyl, and adds the deprotonated carbonyl from step 1 in its place
57
Hydrolysis of a Nitrile in Base - Mechanism
i) Base (-OH) attacks C in R-C(triplebond)N -- This pushes one of the pi bonds between C and N onto the N ii) The now-negatively charged N deprotonates water to become neutrally charged (forms an imidic acid) iii) Base deprotonates the OH on the C, which results in a negative charge on that O iv) The negative charge on O comes down to form a pi bond b/w C and O, pushing the remaining pi bond b/w C and N onto the N and making it negatively charged v) The negatively charged N deprotonates water to become neutrally charged vi) H2O and -OH are added and this changes out the NH2 group for a negatively charged O group (so you end up with a carbonyl with one of its R groups as a negatively charged O)
58
Reduction of a Nitrile with LiAlH4 and H2O - Mechanism
i) H3LiAl-H protonates the C in the nitrile group (R-C(triplebond)N), shoving one of the pi bonds b/w C and N onto the N and negatively charging it ii) Negatively charged N bonds to AlH3 - -----Molecule: RHC=N-Al(-)H3 iii) H3LiAl-H protonates the C again, causing the remaining pi bond b/w C and C to attack another equivalent of LiAlH3 v) The addition of water will leave the molecule as follows: RH2C-NH2 OVERALL: Both the C and the N have two hydrogens added to them and only a sigma bond remains between them
59
When LDA is added to a methyl ketone and then a second compound is added to the mixture, what does it do?
i) LDA deprotonates the methyl R group on the ketone, leaving a -CH2 ii) The new group attaches at that point
60
What reagents do you need for a Micheal Synthesis?
1) OR' or OH - -----------------> 2) H2O
61
What reagents do you need for a Claisen Synthesis?
1) NaOR' - ------------> 2) H3O+
62
What reagents do you need for an Aldol Synthesis?
1) OH, H2O - ----------------> 2) H3O+
63
What reagents do you need for a Robinson Synthesis?
OH -------> H2O

OChem2 (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions