Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Chemistry 2 > Chemistry Y5: Organic synthesis > Flashcards

Chemistry Y5: Organic synthesis Flashcards

1
Q

Where do curly arrows start from?

A

A lone pair/ bond that will break/ negative charge

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

If a curly arrow leads to 5 pairs on an atom what must you do?

A

Add another curly arrow to break one of the bonds

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

Rank the reactivity of these carbonyl groups:
Aldehyde, Ester, acid chloride, Ketone, amide, anhydride

A
  1. A C
  2. Anhydride
  3. Aldehyde
  4. Ketone
  5. Ester
  6. Amide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Is a carbonyl more reactive if it is electron withdrawing or electron donating?

A

More electron withdrawing

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

What are the 4 ways to react carbonyls?

A
  1. Nucleophilic addition
  2. Nucleophilic addition/ elimination
  3. Nucleophilic addition/ elimination/Nucleophilic addition
  4. Interconverting carbonyl groups having different OX states
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is an example of Nu addition of carbonyls

A

Aldehyde to secondary Alcohol

*Me-MgBr then quench

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is an example of Nu Addition- Elimination in carbonyls

A

Acid chloride to Amide

*R-NH2 (LP on N attack C)
-RNH3
*R-NH2 attacks again (LP attacks H)
-Cl

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

In the Nu Addition-Elimination of Acid chloride to amide what is happening to the electropholicity (reactivity)

A

It is decreasing

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

What is essential for the Nu Addition - elimination reactions of carbonyls

A

A good LG

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

What is a reaction scheme for Nucleophilic addition/ elimination/ addition of an ester?

A

Ester -(ADD)- (ELIM)->
Aldehyde -(QUENCH/ ADD) -> primary alcohol

H3Al+-H- is the Nu
2 lots of H- attack

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

How do you get from an Aldehyde to a carboxylic acid?

A

CrO3, H+ (Jones reagent)

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

How do you get from a carboxylic acid to an Ester

A
  1. MeOH
  2. Cat. H+
    -H2O = LG
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How do you get from a primary alcohol carboxylic acid

A

CrO3. H+ (Jones Oxidation)

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

How do you get from an Ester to a primary alcohol

A
  1. LiAlH4
  2. H2O
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do you get from a primary alcohol to a Ketone

A

PCC, Cl-CrO3⁻
* Ketone is quite reactive so LiAlH4 isn’t needed

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

How do you get from an Aldehyde to a primary alcohol

A

LiAlH4
or
NaBH

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

How do you get from a secondary alcohol to a ketone?

A

CrO3 + ACID (H+, H2SO4, HCl)

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

How do you make acid chloride from carboxylic acid?

A

C. acid —(SOCl2) –> Acid Chloride

:O(H) of C. Acid attacks S of SOCl2
:B attacks H (making e.g. HCl)
Products = Cl- , SO2 (g) bubbles off, AC

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

What are organometallics and what are they used for?

A

They’re Nu’s, and strong bases (Lewis Base)
They are good for C-C bonding
R- M+ (ionic)
The more E+ve the metal the more reactive the Nu

CH3-Li
CH3-MgBr

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

How do you make R-MgBr? What are the conditions?

A

R-Br + Mg (s) —(Et2O DRY) –> R-MgBr

*Solvent must be DRY as OrganoMg reacts with water -> ACID
*Mg should get reduced in this reaction (shd get warm)

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

why is Et2O a v good solvent?

A

It has 2 LPs

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

What are Alkynyl Grignard reagents?

A

R - = - MgBr

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

How do you make Alkynyl Grignard reagents?

A

R - = - H + H3C-MgBr ->
R - = ⁻ + MgBr⁺ + CH4. <—> R - = - MgBr

H3C-MgBr is a waste product so should be used sparingly

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

What are the possible reactions with organomagnesium?

A
  1. Nu addition
  2. Nu addition/ elimination/ addition
  3. Nu addition/eliminaiton
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Nu Addition with organoMg
1. Formaldehyde -> 1. Alcohol 2. Aldehyde -> 2. Alcohol 3. Ketone -> 3. Alcohol Reagents: 1. R''MgBr 2. H2O
26
Nu Addition/elimination/ addition with organoMg
Ester -> Ketone -> 3. Alcohol
27
Nu addition/ elimination with organo Mg
Acid chloride -> Ketone (1eq) AC -> ketone -> 3. Alcohol (2eq) (eqs of R''MgBr)
28
How do you make organoLi
R-Br + 2Li ---(EtO2 DRY)--> R-Li, Li-Br R⁻Li⁺
29
If you want to make a ketone using organoMg what should you start with?
Acid chloride and 1eq of R''MgBr Not Ester as you will get a mixture of Ketone, 3. Alcohol and ester
30
What is the structure of Et2O
H3C-C(H2)-O-C(H2)-CH3
31
What are the 3 types of selectivity?
1. Regioselectivity 2. Stereoselectivity 3. Chemoselectivity
32
What is stereochemistry?
The biological and physical properties of organic molecules depend largely on stereochemical arrangement of functional groups
33
What is the definition of stereoselectivity? And give an example we need to know
preferential formation of 1 stereoisomer over another in a chemical reaction -Conjugate addition
34
in the conjugate addition of a Me group onto an aromatic ring where the stereochemical arrangement is 98% TRANS favoured what organometalic compound should be used as a reagent?
1. Me2CuLi 2. Followed by H+/H2O Me Taken from Me2CuLi and added to aromatic in Meta position (98% TRANS) due to steric hinderence)
35
Enols and ketones are (-------) of each other?
Tautomers Enols tautomerise to ketones
36
How do you make Organocopper reagent?
2MeLi + CuBr ------> Me2CuLi +LiBr
37
What does it mean is a reaction is stereospecific?
If the starting materials differ only in their configuration are converted into stereoisomeric products e.g Dehydroxylation of alkenes -Products always the same just isomers of each other
38
How can you control chemoselectivity?
1. Number of eqs 2. Time 3. Chemoselective agents
39
What is an example of a chemoselective agent?
NaBH4 Sodium Borohydride is less reactive than LiAlH4, it reduces both ketones and aldehydes NOT esters
40
Why is NaBH4 not as reactive as LiAlH4?
Na is not as e+ve as Al Not as reactive Not as strongly ionic
41
What would the reagents be to convert: O =[ Benzene] - Ester to HO-[Benzene]-OH
1. LiAlH4 2. Et2O 3. H2O *Both groups get reduced
42
What would the reagents be to convert: O =[ Benzene] - Ester to HO-[Benzene]-Ester
1. NaBH4 2. Et2O 3. H2O * Ketone reduces *Ester unaffected
43
What would the reagents be to convert: O =[ Benzene] - Ester to O=[Benzene]-C(H2)-OH
Use protecting groups *Ketone unaffected *Ester reduced
44
Why do we need to protect functional groups?
In order to react ONLY the least reactive group
45
What makes a good PG?
* Easy to install * Resists conditions that could damage functionality *Easy to remove under mild and specific condictions- that don't affect other groups * Cheap + sustainable
46
Why do PGs reduce atom economy?
They don't appear in the final product
47
What are orthogonal sets used to remove PGs?
* Acid (HCl, HC3COOH) * Base (OH-, RO-) * Hydrogenation (H2, pd/c) * Fluoride ions (F-) Ideally PGs only belong to 1 Orthogonal set
48
What is the PG for Aldehydes and ketones?
2eqs of R''OH, which forms an acetal + H2O -Diols are often used otherwise acetal formation is entropically unfavourable
49
What is the mechanism for Protection of an Aldehyde or ketone using 2 eqs R''OH
1. Protonate ketone 2. react with OH = Nu attack 3. Proton transfer 4. Lose H2O 5. React with 2nd OH 6. Lose H+
50
State the reagents requires to protect and deprotect a ketone whilst reducing an ester functional group?
1. Diol + Cat. H+ 2. LiAlH4 + H2O 3. H2O + Cat.H+
51
What are the 3 things were trying to protect with PGs
1. Ketones and aldehydes 2.Hydroxyl groups (alcohols+Phenols) 3. Amines
52
What PG do we need to protect hydroxyl groups?
PGs belonging to the orthogonal set: ACID
53
What are the Hydroxyl PGs?
1. THP 2. benzyl (Bn) 3. Acetyl (Ac) 4. (TBS)
54
What do THP protected alcohols resist to?
Ox agents, Hydrogenation, Bases, Nu (grignards reagents), fluorides
55
what are the conditions to protect and deprotect a: primary alcohol <-> Acetal
Protect: Dihydropyran Deprotect: H2O, Cat. H+
56
What are the conditions to protects and deprotect a: Primary alcohol <-> Ether
Protect: "BnBr" Deprotect: H2, pd/c PG = 'Bn"
57
What are the conditions to protect and deprotect a: Primary alcohol <-> Ester
Protect: "AcCl" Deprotect: Cat. NaOMe (base), MeOH (solvent) PG ="Ac"
58
What do Bn protected alcohols resist?
*Ox Agents *Most Nu, Electrophiles and bases *Fluorides
59
What do Ac protected alcohols resist?
*Ox Agents *Mild acids *Electrophiles *Fluorides *Hydorgenation
60
What are Ac PGs removed by?
Mild bases and Nu's (Grig, Org.Li, LiALH4)
61
What are the conditions to protect and deprotect a: Primary alcohol <-> Silyl ether
protect: "TBS-Cl" Deprotect: F- or H+ PG= TBS
62
What do TBS protected alcohols resist?
*Ox agents *Hydrogentation *Electrophiles *Most Nu's
63
What are TBS PGs removed by?
Flourides:TBAF (Tetrabutylammoniumfluoride) Acid: TFA (CF3COOH) (Trifluoroacetic acid)
64
What do the reagents BU4, NF deprotect?
TBS
65
What does the reagent H3O+ deprotect?
THP and TBS
66
What do the reagents Cat. NaOMe and MeOH deprotect?
Ac
67
What do the reagents H2 and pd/c Deprotect?
Bn
68
what are good PGs for Amines, and why?
Carbamates, *Easy to install * Lp conjugated to carbonyl (Not Nu) *Carbamates are not v reactive towards Nu's *Can be converted back to amines
69
What would be a way to show why carbamates aren't good Nu's?
Show the resonance structure -Lp Ends up in a +ve and -Ve charge on the molecule
70
What are the conditions to protect and deprotect a: Primary amine <-> "CBZ" carbamate
Protect: "Cl-cbz" , Na2CO3, H2O Deprotect: H2, pd/c, MeOH PG= cbz
71
What do CBZ carbamates resist to?
*Ox agents *Most E's *Acids *Bases *Most Nu's (NOT grig, orgLi, LiAlH4) *Fluorides
72
What are the conditions to protect and deprotect a: Primary amine <-> "BOC" carbamate
Protect: BOC, NaOH, H2O Deprotect: Acid- TFA (CF3COOH)
73
what do BOC carbamates resist to?
*Ox agents *Most E's *Hydrogenation *Bases *Most Nu's (NOT Grig, orgLi, LiAlH4) *Fluorides
74
Why is the deprotection of BOC and CBZ carbamates irreversible?
The bi-product CO2(g) will bubble off
75
What are proteins?
polymers of AAs linked via peptide bonds
76
What is the basic structure of all AAs?
Glycine H2N-C-C(=O) - OH The C next to the amine group is always chiral All Have primary amines (except Proline which is 2nd)
77
What is the C and N terminus of a peptide?
C = Carboxyl end N = Amino end
78
Why does peptide synthesis require PGs?
*If not an Acyl chloride would form (V. reactive and it would self react) *Or a zwitterionic complex would form = No LP on the N = Not soluble in organic solvents SO, Any 'R' groups with any functionality must be protected * If all reactive groups are protected then a peptide bond will form and HCl will be removed
79
What coupling method is best for peptide sythesis?
DCC (need to know method) -I think will come up on exam! * Forms urea as side product
80
When making an acid chloride why can't BOC be used?
Because the conditions required also generate HCl -ACID = no boc
81
what conditions would you use to deprotect CBZ and ph and make a peptide?
H2, pd/C
82
How would you protect analine's N terminus
boc2O and NaOH
83
How would you protect glycine's C terminus
H-O-Bn and NaOH
84
What is DCC
Its the combination of the BOC protected analine + Bn protected glycine
85
How would you deprotect DCC?
CF3COOH (TFA), H+ and then H2, pd/c
86
What is retreosynthesis?
Disconnect bonds you know how to make (e.g. esters) continues until you reach starting materials -Working backwards
87
What conditions do you need to go from Bn- C(H2)-Br to ph-C(H2)- MgBr
1. Mg 2. Et2O
88
What conditions do you need to go from ph-C(H2)- MgBr to ph-C(H2)-C(CH3₂)-OH
1. acetone (H3C-C(=O)-CH3) 2. H2O 'QUENCH"
89
What conditions do you need to go from ph-C(H2)-C(CH3₂)-OH to ph-C(H2)-C(CH3₂)-O-C(=O)-CH3
1. Acid chloride 2. Pyridine (weak base added to trap HCl generated during ester formation)
90
where do you disconnect in retrosynthesis?
At branching points and remove chains from rings if possible * Look for symmetry
91
In the forward step what must you remeber to mention
QUENCH
92
what size of compound should you try break down into
7 carbons or less -Only 1 functional group
93
What is a synthon
A generalised and frequently imaginary fragment produced by a disconnection
94
Synthons and their synthetic equivalents 1. R+ 2. R- 3. 2nndary alcohol cation 4. R-C(+)=O
1. RBr/ RI 2. RMgBr/ RLi 3. ketone 4. Acid chloride

Chemistry 2 (7 decks)

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