Exam 4 Flashcards
1
Q
What are the trends of wavenumber?
A
Frequency increases with increasing bond strength (bond order 1-3) and higher percentage of s character
Decreases with increasing atomic mass and presence of conjugation
2
Q
What is a 1200 cm-1?
A
C-C and C-N
3
Q
What is at 1600 cm-1?
A
C=N (usually intense) and C=C aromatic (usually two skinny spikes, often have squigglies around 2000 and spikes just below 1500, tends to shrink sp2)
4
Q
What is at 1620-1640 cm-1?
A
Conjugated C=C
5
Q
What is at 1660 cm-1?
A
C=C (isolated 1640-1680)
6
Q
What is at 1710 cm-1?
A
C=O of ketones, aldehydes, and carboxylic acids
+huge OH stretch - carboxylic acid
+2 C-H signals ~2700, 2800 aldehyde
(ketones & some aldehydes often have overtones beyond 3000)
7
Q
What is at 1630-1660 cm-1?
A
C=O of amide
8
Q
What is at 2200 cm-1?
A
C=-C <2200 with sp C-H 3300
C=-N >2200 no sp C-H 3300
9
Q
What is at 2700cm-1?
A
First C-H spike of aldehyde
10
Q
What is at 2800-3000?
A
sp3 and 2800- second C-H spike of aldehyde
11
Q
What is at 3000 - 3100cm-1?
A
sp2
12
Q
What is at 3300cm-1?
A
sp
OH when round
NH with spikes, secondary-1 spike, primary- 2 spikes (look for broad NH deformation around 1600)
13
Q
If there is M+2 as large as M+
A
It is Bromine
14
Q
If there is a M+2 a third as large as M+
A
There is a Chlorine
15
Q
If there is a 127 large gap
A
There is an Iodine
16
Q
If there is an odd M+ and some even fragments
A
there is a Nitrogen
17
Q
If there is a M+2 larger than usual (4% of M+)
A
There is a Sulfur
18
Q
Characteristics and function of molecular ions?
A
No fragmentation, usually highest mass and even-numbered.
The value of m/z for the molecular ion gives the molecular weight of the compound
19
Q
What is fragmenation?
A
When instead of the radical cation (the molecular ion) there is a cation fragment (observed) and a radical fragment (not observed)
NOT Random: forms most stable fragments
Odd Numbered
20
Q
Where do aromatic rings fragment?
A
At the carbon next to the aromatic ring (benzylic carbon)
21
Q
How do ethers, amines, and carbonyl compounds fragment?
A
to give resonance stabilized carbons
Oxygen and nitrogen atoms have non-bonding electrons that stabilize positive charge
22
Q
What about the molecular ion of alcohol?
A
It is often very weak or absent
There is a favorable loss of water and common fragment next to carbinol carbon atom giving a resonance-stabilized carbocation
Fragmentation: Alpha cleavage, form water (double bond) –> fragments again
23
Q
What are the rounded masses of C, H, O, N, Cl, Br, I
A
C:12
H:1
O:16
N:14
Cl: 35
Br: 80
I: 127
24
Q
What is the coupling constant 10 Hz?
A
cis
25
What is the coupling constant 15 Hz?
trans
26
What is the coupling constant 2 Hz?
geminal
27
What does the ball park range of 0-1.5 ppm indicate?
Alkane (changes with atoms surrounding)
28
What does the ball park range of 3-4 ppm indicate?
Hydrogens bonded to a C bonded to an halide
29
What does the ball park range of 5.5-6.5 ppm indicate?
alkene
30
What does the ball park range of 6.5-8.5 ppm indicate?
aromatic
31
What does the ball park range of 9-10 ppm indicate?
aldehyde
32
What does the ball park range of 12-13 ppm indicate?
carboxylic acid
33
What does D2O do?
Gets rid of N-H or O-H bonds if present from NMR
34
What do two peaks in the 7-8 range with the roofing effect indicate?
1-4 splitting in aromatic
35
What are the three main things of 1H NMR?
Location: Know Ball Park ranges
Integration: Ratio between protons
Splitting: how many protons are adjacent (past quartet have protons on both sides)
36
Relative deshielding of alkyne and carbonyl?
Carbonyl deshields more
37
What are the aspects of the addition of HX to C=C?
Starting material(s)
Reagents/Conditions
Product(s)
Regioselectivity/Stereoselectivity/Additional Comments
38
What are the aspects of the addition of HX to C=C?
Starting material(s): Molecule with double bond, HX (HCl/Br/I)
Reagents/Conditions: 1) pi attacks H (the electrophile) creating most stable carbocation
2) X- attacks carbocation as nucleophile
Product(s): H on one side and Br on the more stable carbocation side of the pi bond
Regioselectivity/Stereoselectivity/Additional Comments:
Two Steps, if rearrangement is possible it will happen
(will not be used in solution with water or get hydration of C=C)
39
What is Markovnikov's rule?
Electrophile will add to form the most stable carbocation
40
What are the aspects of Hydration of C=C?
Starting material(s): pi bond molecule and H2O
Reagents/Conditions: In protic acid (making H3O)
Product(s): OH on more stable carbocation side and H on other where pi bond was
Regioselectivity/Stereoselectivity/Additional Comments: often use 50% H2SO4 & water, rearrangement occurs
41
What are the aspects of hydration by oxymercuration-demercuration?
Starting material(s): pi bond molecule
Reagents/Conditions: 1) Hg(OAc)2/H2O 2) NaBH4
Product(s): OH on more stable carbocation side and H on other where pi bond was
Regioselectivity/Stereoselectivity/Additional Comments
1) creates OH and Hg(OAc) **trans**
2) replaces Hg(OAc) with H in exact same orientation
MUST put numbers for reagents
42
What are the aspects of alkoxymercurization-demercuration?
Starting material(s): pi bond molecule
Reagents/Conditions: 1) Hg(OAc)2/HO-R 2) NaBH4
Product(s): OR on more stable carbocation side and H on other where pi bond was
Regioselectivity/Stereoselectivity/Additional Comments
1) creates OR and Hg(OAc) **trans**
2) replaces Hg(OAc) with H in exact same orientation
MUST put numbers for reagents
43
What are the aspects of X2 to C=C?
Starting material(s): Halogen Usually Cl2, Br2, I2
Reagents/Conditions: pi bond attacks X and X e- attacks carbon and X bond e- move to other X --> X ion then X- attacks -> trans
Product(s): Trans X on either side of where pi bond was
Regioselectivity/Stereoselectivity/Additional Comments: trans, put both diastereomers/enantiomers
44
What are the aspects of formation of halohydrins?
Starting material(s): X2/H2O
Reagents/Conditions Double bond attack X --> X ion, H2O attack partial positive charge, 2nd H2O attacks H on OH to remove +
Product(s): trans: X/ OH
Regioselectivity/Stereoselectivity/Additional Comments: Exactly the same as halogen addition but different Nu
**When this occurs in NaH (H: -) great base, bad Nu because make gas H2 creates epoxide
45
What are the aspects of free-radical addition of HBr?
Starting material(s): HBr, ROOR
Reagents/Conditions: Heat
Product(s): anti-markovnikov H and Br (Br on lower priority C)
Regioselectivity/Stereoselectivity/Additional Comments:
R-O-O-R --> 2 RO*
RO* + HBR --> ROH + Br*
Pi + Br --> radical on higher priority C and Br on other side of where pi bond was
HBr attacks radical --> antimarkovnikov + Br*
Termination
46
What are the aspects of hydroboration?
Starting material(s): 1)THF.BH3 2) H2O2, -OH
Reagents/Conditions: 1) pi attacks B H attacks C **syn** addition 2) BH2 replaced with OH
Product(s): Syn OH and H on higher priority carbon
Regioselectivity/Stereoselectivity/Additional Comments
Syn
3 alkenes to 1 BH3.THF
47
What is a very common peroxide?
BPO: benzoyl peroxide
Ph-=O-O-O-=O-Ph
48
What are the aspects of catalytic hydrogenation?
Starting material(s): Pi bond molecule
Reagents/Conditions: H2 (g) with catalyst (Pt, Pd, Ni, or Pd/c)
Product(s): No pi bond, syn Hydrogens on either side of where pi bond was
Regioselectivity/Stereoselectivity/Additional Comments:
Syn addition
49
What are the aspects of addition of carbenes to C=C (Simmons Smith)
Starting material(s): Pi bond molecule
Reagents/Conditions: CH2I2/Zn (Cu)
Product(s): Molecule with syn addition cyclopropyl (Zn I, by product)
Regioselectivity/Stereoselectivity/Additional Comments: Syn addition
50
What is a carbene? What are the three methods of making a carbene?
C with lone pair of e- and empty P orbital: Both wants and doesn't want electrons --> cyclopropyl
1) Diazomethane H2C=N(+)=N (-)
2) Simmons-smith reagent: ICH2ZnI (carbenoid, more stable way to make carbene)
3) Alpha elimination: HCX3, haloform --> :CBr2
51
What are the aspects of addition of carbenes to C=C? (alpha elemination)
Starting material(s): Pi bond molecule
Reagents/Conditions: HCX3, -OH
Product(s): molecule with three membered ring and X2 coming off of C
Regioselectivity/Stereoselectivity/Additional Comments
Syn addition, X remains in product
52
What are the aspects of epoxidation?
Starting material(s): Pi bond molecule
Reagents/Conditions: Peroxyacids (Peracids)
Product(s): molecule with epoxide (& acid by product)
Regioselectivity/Stereoselectivity/Additional Comments
Syn
53
What is an epoxide?
Three membered ring with an O in the middle aka oxirane
54
What is the one peroxyacid you should know?
mCPBA
PhCO3
Ph 1-=O-O-O-H 3-Cl
Probably most common reagent
55
What are the aspects of acid-catalyzed ring opening of epoxides?
Starting material(s): molecule with epoxide
Reagents/Conditions: Acid (mainly H3O) epoxide O picks up H, H2O attacks backside of most stable carbocation electron goes to epoxide O makes alcohol
Product(s): Trans alcohols where epoxide was
Regioselectivity/Stereoselectivity/Additional Comments:
Trans
56
When a full carbocation is created...
Watchout for rearrangement
57
What are the aspects of dihydroxylation?
Starting material(s): pi bond molecule
Reagents/Conditions: OsO4 and H2O2 or R3N(+)O(-)
Product(s): Syn OH on either side of where pi bond was
Regioselectivity/Stereoselectivity/Additional Comments: Syn addition
also could use permanganate: KMnO4 with -OH,H2O
same product
58
What are the aspects of oxidative cleavage by KMnO4?
Starting material(s): Pi bond molecule
Reagents/Conditions: KMnO4, heat, conc.
Product(s): IF R groups only: ketones, If H groups: Acid
Regioselectivity/Stereoselectivity/Additional Comments
Created carbonic acid if two hydrogens to stay aldehyde to stay more reactant use ozonolysis
59
What are the aspects of ozonolysis?
Starting material(s): Pi bond molecule
Reagents/Conditions: 1) O3 (-78*C) 2) Me2S or Ph3P (no smell)
Product(s): 1) create ozonide 2) created ketone and aldehyde
Regioselectivity/Stereoselectivity/Additional Comments
60
What are the aspects of cationic polymerization?
Starting material(s): monomer with double bond
Reagents/Conditions: (electrophile) acid
Product(s): polymer (no cap) terminates with weak base elimination reaction
Regioselectivity/Stereoselectivity/Additional Comments
61
What are the aspects of radical polymerization?
Starting material(s): Double bond monomer
Reagents/Conditions: ROOR'
Product(s): polymer with R-O- cap
Regioselectivity/Stereoselectivity/Additional Comments
62
What are the aspects of anionic polymerization?
Starting material(s): Double bond polymer
Reagents/Conditions: -OH (something to make negative charge)
Product(s): polymer with OH cap
Regioselectivity/Stereoselectivity/Additional Comments
63
What are the aspects of olefin metathesis?
Starting material(s): terminal double bonds
Reagents/Conditions: Shrock or Grubbs
Product(s): cis/trans combinations and = (ethylene gas)
Regioselectivity/Stereoselectivity/Additional Comments
64
What are the types of olefin metathesis and what do they entail?
1) Cross Metathesis: break two terminal double bonds and put back together (crosses two molecules)
2) Ring Closing Metathesis (RCM): break two terminal double bonds on long chain and put together in ring (looses two carbons and creates ethylene)
3) Ring Opening Metathesis Polymerization (ROMP) break double bond in ring then polymerization fragments are on same side (i.e. both wedges)
65
What is the name of the most simple alkyne?
acetylene (without 1 H acetylide)
**Make sure triple bonds are LINEAR**
66
What is the relative acidity of H on ethyl, ethylene, and aceytlene?
Ethyl least, acetylene most acidic
because of increasing s character sp3, sp2, sp, 25%, 33% 50%
Most S character, more easily support carboanion
67
What deprotonates acetylene?
NaNH2
It is a really strong base
(-)NH2 N attacks H on acetylene creating carbanion
68
What is the carbanion of a triple-bonded carbon?
A great nucleophile that really likes to attack carboneals
69
What is the most common synthesis of alkynes? What are the conditions?
Sn2, LG must be unhindered (must be a Me or 1*)
70
What is one of the most versatile reaction organic chemists will see?
Addition of nucleophile to carboneal
71
What are the different types of alcohols that can be made with triple-bonded carbanions?
R-=- : (-)
+ ketone --> 3* alcohol
+ aldehyde --> 2* alcohol
+ formaldehyde --> 3* alcohol
72
How are alkynes made?
Dehydrohalogenation with dihalides either
1) vicinal (ie 1,2)
2) geminal (on same C)
73
What are the common reagents to make alkynes?
(VERY STRONG BASES)
1) KOH fused with heat to continue slow second step
2) NaNH2 that will deprotonate alkyne to force the completion and fully make the product of a terminal alkynes (add H2O to protonate)
The first step is fast but the second is slow
74
Major points of hydrogenation for alkynes?
Reactants: 2 eq H2 with Pt/Pd/Ni
Intermediate: Syn double bond
Product: Four H added where bond was
1) Stop at syn double bond
Lindlar's catalyst Pd/BaSO4 and quinone and CH3-OH
2) Stop at trans double bond
NH3 (l) + Na*, strips electron from NH3
e- adds to double bond creates trans double bond (half arrow and double arrow) to keep e- pair and lone e- as far away as possible
e- pair attacks H-NH2, another e- adds , e- pair attacks H-NH2
75
Major points of X2 addition to alkyne?
X2: cis/trans mix of 2 X across double bond
excess X2: four X where bond was
76
Major points of addition of HX to alkyne?
Markovnikov
HX --> cis/trans mix
Excess HX leads to carbocation with resonance then geminal addition of two X
Anti-Markovnikov
HBr, ROOR, Heat leads to geminal addition of two X
77
Major points of hydration of alkyne?
Markovnikov
HgSO4, H2SO4, H2O
(no work up step because acid supplies H)
forms enol and Hg 2+ (electrons taken from Hg to satisfy carbocation)
Enols do not like to exist
-Terminal alkyne --> ketone
Anti-Markovnikov (Hydroboration)
1) Sia2 BH 2) H2O2, NaOH to form aldehyde
78
What do enols do?
They tautomerize to form a more stable ketone
