Lecture Quiz 5 - Lectures 21-27 Flashcards
(123 cards)
1
Q
When can carbocation rearrangement happen?
A
whenever we have a carbocation intermediate (Sn1/E1)
2
Q
List the order from best carbocation to worst
methyl, 1, 2, 3*
A
3* - better C+, lower E
2*
1*
methyl
3
Q
When you do SN1/E1 mech with a carbocation, the result is 2 SN1 products and 4 E1 products. How do you determine which product is the major/minor one?
A
Major = rearranged
4
Q
When does a hydride shift typically happen?
A
2C C+ next to a 3 –> will rearrange
5
Q
How many carbons are moved during a hydride shift?
A
Typically don’t more more than 1 carbon.
6
Q
When there is no available H, is it possible to move an alkyl group?
A
Yes - aka alkyl shift
7
Q
Is it possible to move an alkyl group at the same time as a leaving group?
A
Yes = aka concerted rearrangement
8
Q
Gives 3 examples of sp3 oxygens
A
H2O water, ROH alcohol, and ROR’ ether
9
Q
H2O has a (low/high) boiling point.
A
high
10
Q
Alcohol ROH (can/can’t) H-bond, has a ? DP, is (nonpolar/polar), and (is/isn’t) H2O soluble. It is miscible up to (0/1/2/3) carbons
A
ROH:
-can H-bond
-polar
-miscible up to 3C
11
Q
sp3 Oxygens (can/can’t) get protonated. (H2O/ROH/ether) tends to be nucleophilic.
A
sp3 oxygens can get protonated
H2O + ROH tend to be nucleophilic
12
Q
If there are 2 alcohol groups on a molecule, how would you name it?
A
nonane-di-ol
hexane-tri-ol
13
Q
T/F Alcohols are able to act as both acids and bases.
A
True
14
Q
For alcohols, steric hindrance affects>
A
solvation of ion
15
Q
For alcohols, induction….
A
removes/adds electrons to ion
16
Q
What is the pKa range for alcohols that act as acids?
What does ROH turn into?
A
pka 15~18
ROH–> RO-
deprotonated, H leaves, O is (-)
17
Q
For alcohols acting as an acid, larger alkyl groups are typically (better/worser) acids
A
larger alkyl group = worser acid
18
Q
List the following alkyl groups from best acid to worst if bonded to an alcohol.
methyl, 3, 2, 1*
A
methyl-O- oxygen has more space for solvation, easier to make ion or keep the (-) charge
1-O-
2-O-
3*-O- minimal solvation. alkyl groups are sterically hindered, charge is unsupported, harder to form weaker conjugate acid, better conjugate base
19
Q
Alcohols range from pka 15-18. Where would 1* and methyl typically fall on this spectrum? What about 2* and 3*?
A
pka15 = 1* and methyl // better acid
pka18 = 2* and 3* // worser acid
20
Q
For alcohols acting as a base, what is the pka range?
A
pka -2~-4
21
Q
Would a tertiary alcohol be a better acid than a primary alcohol? What about base?
A
primary alcohol would be a better acid AND base. tertiary alcohols have minimal solvation and there’s steric hindrance so it’s harder for them to form ions.
22
Q
pka is affected by ?
A
solvation
23
Q
1*ROH/ROH2+ has a
(low/mod/high) pka, and (poor/mod/good) solvation
A
mod pka (15 + -2)
good solvation
24
Q
3*ROH/ROH2+ has a
(low/mod/high) pka, and (poor/mod/good) solvation
A
extreme pka, poor solvation b/c of hindrance
(18 + -4)
25
induction has a (subtle/extreme/no) effect on pka
subtle effect
More EN neighbors, larger # of EN atoms, and closer EN atoms would have more effect
26
T/F Alcohols are generally not very water soluble and have moderate to low boiling points due to low mass.
False
27
T/F The variance in pka between primary and tertiary alcohols is due to solvation of the resulting alkoxide or alkyloxonium ions.
True
28
T/F Alcohols can form hydrogen bonds with more of themselves
True
29
T/F Industrial reactions tend to make large volumes of complex molecules.
False because they make SIMPLE molecules
30
T/F Laboratory synthesis works generally the same for a functional group regardless of the alkane backbone of the molecule.
True
31
T Industrial reactions tend to use gaseous reagents and recycleable metal surface catalysts.
True - they tend to use gas phase and solid phase catalysts
32
T/F Laboratory synthesis is able to work with molecules with multiple functional groups and/or stereochemistry.
True
33
Between industrial and laboratory scale, which one avoids purification?
Industrial = avoid purification
Lab = puridication, distillation, chromatography, crystallyization
34
What substance phase do laboratories usually deal with?
solution phase
35
To form a primary alcohol from an RX, what nucleophiles would be used? This is via?
NaOH, H2O
SN2 - minimal E2 contamination, only 1 regioisomer
36
To form a tertiary alcohol from a R-X, what nucleophile would be used? This is via?
H2O
Sn1/E1, lose steroeochem at reacting C - going to have E1 product, and can possibly do C+ rearrangement (possible though unlikely)
37
To form a secondary alcohol from a R-X, what nucleophiles would be used? Via?
1) CH3COONa
2) NaOH, H2O
38
Redox is the (transfer/exchange) of electrons
exchange of e-
39
Oxidation is the (loss/gain) of e-
(loss/gain) of EN atoms
or
(loss/gain) of H bonds
Ox = loss of e-, gain of EN bonds, loss of H bonds
40
Reduction is the (loss/gain) of e-
(loss/gain) of EN atoms
or
(loss/gain) of H bonds
Red = gain of e-, loss of EN atoms or gain of H bonds
41
What is the most reduced redox molecule? (Easy/hard) to be selective, leads to?
CH4 - alkane
hard to be selective
42
What is the most oxidized redox molecule?
C=O=C
43
List order from most reduced to most oxidized
alcohol, carboxylic acid, carbonyl (aldehyde/ketone), alkane, and carbon dioxide
alkane
alcohol
carbonyl
carboxylic acid
carbon dioxide
44
oxidizing agent causes something else to be (reduced/oxidized) and itself gets (reduced/oxidized).
oxidizing reagent causes something to be oxidized and itself gets reduced
45
reducing agent causes something else to be (reduced/oxidized) and itself gets (reduced/oxidized).
reducing agent causes something else to be oxidized and itself gets reduced
46
we can create alcohols from carbonyls via?
hydride reagents
(ex: LiAlH4 or NaBH4)
47
LiAlH4 is (less/more) aggressive and a (weaker/stronger) reducing agent than NaBH4
LiAlH4 = more aggressive, stronger red agent
NaBH4 = more moderate red agent
48
To convert a 1*ROH to an aldehyde, you need to (oxidize/reduce)/
oxidize 1*ROH to aldehyde
49
To convert 2*ROH to ketone, you need to (oxidize/reduce)
oxidize 2*ROH to ketone
50
When you oxidize a tertiary alcohol, is there a reaction?
NO REACTION
can't remove any C-H bonds to form another CO, can't remove H2
51
To reduce aldehyde to a primary alcohol, you can use 1) LiAlH4 and 2) H3O+. Which molecule donates the H-? What about the H+?
LiAlH4 donates the H-
H3O+ donates the H+
52
LiAlH4 is a _______ ______ donor
covalent hydride donor
53
Describe the first and second step of reducing an aldehyde to a 1*ROH
1st step = hydride adds, irreversible
2nd step = protonate
54
T/F NaBH4 is mellower so it can exist with ROH, not H3O+. and it gets a transition state.
True
55
How many steps is LiAlH4? What about NaBH4?
LiAlH4 = 2 step process
NaBH4 = 1 step process
56
The transition state of NaBH4 is similar to the reverse of (Sn1/SN2/E1/E2) and has a _______ bond formation
reverse of E2
concerted bond formation
57
When oxidize a 2*ROH to a ketone, we stop at ketone because we run out of
C-H
58
To convert a primary alcohol to carboxylic acid, we can use
Jones Reagent to oxidize 1*ROH
59
True/False When we convert 1*ROH to carboxylic acid, we get an aldehyde transition state.
True
60
T/F Oxidation of a primary alcohol gives a ketone.
False
will get an aldehyde instead of ketone
2*ROH gets ketone
61
T/F Many organic reactions involve oxidizing an alkane to an alcohol directly
False
62
True/False Primary, secondary, and tertiary alcohols can all be formed by reduction of C=O with LiAlH4.
False - Can use NaBH4 to reduce C=O to get tertiary
63
T/F Reducing agents are difficult to handle since many of them react violently with the oxygen and water in the air.
True
64
What reagent would we use to oxidize a 1*ROH to an aldehyde?
PCC, CH2Cl
PCC pyridinium chlorochromate in CH2Cl solvent
65
Why would we use PCC as opposed to Jones Reagent?
PCC has no H2O present so if our goal is to get aldehyde from 1*ROH or a ketone from a 2*ROH, we need to use PCC.
We would only use Jones reagent when carboxylic acid is our goal. H2O is present in it so we go from OH to COOH
66
T/F PCC can oxidize 1*ROH to aldehyde and 2*ROH to keton
True
67
Is PCC a better reagent than Jones Reagent?
No, it just doesn't have H2O present. Plus, it's gentler and easier to work with
68
What are the 2 extreme agents?
Oxidizing agent = H2CrO4(aq) chromic acid
Reducing agent = LiAlH4
69
We can form carbanions via ??? reagents
organometallic reagents
70
T/F PCC can oxidize primary, secondary, and tertiary alcohols to C=O.
False
71
sp3 carbanion is a (weak/strong) base so we need to add a (acid/base)
C- is strong base
must add base
72
What is RMgBr?
A Grignard reagent (RMgX)
aka organomagnesium
73
What organometallic reagents can we use to get a carbanion?
RMgBr and RLi
and we can also se R-Cl, R=Br, or R-I
74
Why doe need to be very careful about Li?
It catches on fire
75
76
Organometallic reagents are formed by reacting a ??? with Li or Mg
haloalkane R-X
RMgX or RLiX
77
Reacting a ketone with a Grignard reagent will give a (primar/secondary/tertiary) alcohol
ketone
+ 1) RMgX, 2) H3O+
=3*alcohol
78
aldehyde
+ 1) RLiX, 2) H3O+
=2*alcohol
79
We prefer (linear/convergent) synthesis and which has (fewer/more) steps in a sequence
convergent synthesis preferred due to fewer steps and higher yield
80
T/F Analysis of the target compound when a starting material is not given is called retrosynthetic analysis
True
81
Williamson ether synthesis makes (linear/cyclic/both) ethers.
both linear and cyclic
82
If we're making a linear molecule it will (never/sometimes/always) be symmetrical and (never/sometimes/always) use unhindered primary alcohols.
sometimes be symmetrical
always use unhindered 1*ROH
83
T/F Alkoxide are good Nu-
True -- do SN2 with 1*RX
84
If we have a hindered 1*, 2*, or 3* ROH, we use what mech?
E2
85
If we want 100% completion or a higher yield, we must use a (weak/mod/strong) base to get an alkoxide ion.
STRONG BASE
86
When ROH act as weak bases, they get
protonated by strong acids
87
Nucleophilic acids have a conjugate (acid/base) as a Nu-
conjugate base is Nu-
88
T/F HBr and Hi are better nucleophilic acids than HCl
True
89
For non-nucleophilic acids, its conjugate base is?
a Nu-
90
When we use a nucleophilic acid (ex: HCl, HBr, HI) with an ROH, what mech will we do?
1*ROH, 2*ROH, 3*OH
Nucleophilic acid
1*ROH = SN2
2*/3*ROH = SN1
91
Why is there no E2 product when we react a 2*/3*ROh with a nucleophilic acid?
There will be an electrophilic addition so e get a reverse alkene formation. Basically, the alkene is a good Nu- and will pick up the H again, which reverses the rxn. So we can do E 1 but the rxn doesn't last long
92
When we use a NON-nucleophilic acid (ex: H2SO4,H3PO4,PTsOH,TFA) with an ROH, what mech will we do?
1*ROH, 2*ROH, 3*OH
NON-nucleophilic acid
1*ROH = E2, especially at high Temp, S favored b/c disorder increases (1 starting particle to 2 ending particles)
2*/3*ROH = E1, perfers more stable alkene
93
When we react a NON-nucleophilic acid with an ROH via E1 mechanism, what rxn happens
dehydration rxn, loss of H2O to form C=C
94
What is the problem with carbocations?
Irritating, lose stereochemistry, can get side rxns (SN1/E1), , can rearrange
95
How do we avoid carbocations?
change SN1 to Sn2
96
1*ROH react with ??? via ??? mechanisms to form haloalkanes
HBr or HI via SN2
form haloalkane with nucleophilic acid + 1*ROH via Sn2
97
3*ROH react with ??? via ??? mechanisms to form alkenes.
H2SO4 via E1
Form an alkene by E1 mech with nonnucl acid+ 3*Roh
98
2*ROH react with ??? via ??? mechanisms to form haloalkanes.
This reaction (does not/does) also give alkenes as a product because ??
HBr or HI via SN1
does not give alkene product b/c this mechanism can for alkenes but they react with the acid reagent
99
T/F Carbocation rearrangements will always start with the formation of a carbocation
False
100
1*ROH react with ??? via ??? mech to form alkenes
H2SO4 via E2 to form alkene
101
One advantage of SOCl2 is it (does not/does) undergo carbocation rearrangements
does not undergo carbocation rearr
102
When we want to form a haloalkene from a 2*/3*ROH, what can we do to avoid the carbocation rearrangement?
IF Sn1 = carbocation rearrangement :(
IF Sn2 = avoids C+ rearr
Must change from Sn1 to SN2 and use SoCl2, Pcl5, PBr3, or PI3 which convert the ROH to a good leaving group.
103
T/F PCl5, SOCl2, and HCl are all interchangeable and will give the same products
False
104
Ethers generally are water (insoluble/soluble). Ethers generally have (low/mod/high) boiling points for their size.
Ethers = H2O insoluble and low BP
105
A cyclic ether which forms a 4 member ring will have the IUPAC name
oxacyclobutane
106
Rank for IUPAC priority:
ROH, R-X, ether, alkane
ROH -- highest priority
alkane, R-X, and ether
107
T/F Formation of ethers via acid catalysis prefers very high temperatures (e.g. 180 degrees C)
False
108
T/F Formation of ethers with acid catalysis tends to form symmetrical ethers.
True
109
T/F Williamson ether synthesis is commonly used to form secondary and tertiary linear ethers.
False
110
T/F The major factor between formation of ethers vs alkenes from alcohols with acid catalyst is enthalpy.
False
111
Enthalpy prefers (minimal/maximal) ring strain so a (smaller/larger) ring is preferred.
Enthalpy = minimal ring strain preferred
Larger/med ring preferred
112
Entropy prefers if the ends are (closer/further apart) so a (smaller/larger) ring is preferred.
Entropy = wants closer ends
Smaller rings preferred
113
Entropy is a bigger factor at (lower/higher) temperatures
Higher
114
When temp is 180*C, there is (less/more) energy and entropy is (less/more) of a factor. We would use (substitution/elimination) mech.
180*C = more E, Entropy more significant
1*ROH = E2
2*ROH/3*ROH = E1
115
When temp is 135*C, there is (less/more) energy and entropy is (less/more) of a factor. We would use (substitution/elimination) mech.
135*C = less E, Entropy less significant
1*ROH = Sn2
2*ROH/3*ROH = Sn1
116
Linear ethers generally do not react with ??? and do react with ???. This means they make (poor/good) solvents for most reactions.
NR w/ base, Nu-, ox agent, red agent (harder to protonate)
R w/ strong acids, O2
good solvents
117
Which ether breaks faster? 1*ether or 2* ether. Which one prefers to do SN2 mechanisms in the presence of HX.
1*ether breaks faster
Sn2
118
Which ether breaks faster? 3*ether or 2* ether. Which one prefers to do SN2 mechanisms in the presence of HX.
3*ether breaks faster
Sn1
119
For ether rxns, we get mixes when we have
1*/1*, 2*/2*, or 3*/3* because it means the nucleophile can come in on both sides
120
When the sides of the ethers aren't equally substituted:
3* --> ___ mech @ which side
Sn1 at 3* side
121
For an ether rxn, when there is no 3*, is CH3 faster or slower than 1*?
Ch3 faster - via Sn2
122
When we have only 2* for ether rxns, we do ??? mech and we get a mix of products.
SN1 rxn
123
Rings generally react like linear versions of the same function group. What is the exception?
lots of ring strain
