O Chem Flashcards
1
Q
Define: hydrocarbon
A
Molecule that consists entirely of carbon and hydrogen
2
Q
Define: structural isomers
A
Same molecular formula, but different connectivity of atoms
3
Q
Geometric isomers
A
Double bonded alkene, atoms are connected in same order, but differ in the configuration of atoms around double bond (cis and trans isomers)
4
Q
What state are fats with cis conformations at room temp, and why?
A
Liquid, cis conformation prevents tight packing
5
Q
Define: enantiomer
A
Same chemical structure but differ in their three-dimensional placement of atoms (non-superimposable mirror images), chiral molecules only
6
Q
Which isomer (D or L) of amino acids are found in nature/humans?
A
L
7
Q
Which isomer (D/L) of sugars are found in nature?
A
D
8
Q
What is a carboxylic acid group, and is it acidic or basic?
A
R-COOH, once ionized, it releases H+ into the solution, making it to be considered acidic
9
Q
What is an amino group, and is it considered acidic or basic?
A
R-NH2, it accepts H+ to form NH3+…since it removes H+ from the system, it is considered basic
10
Q
Are hydrogen phosphate groups considered acidic or basic?
A
Acidic, since they release H+ into the solution
11
Q
Which has a higher BP and why? Pentane or hexane?
A
Hexane, longer chain, more molecular weight, more LDF attraction between chains
12
Q
Which has a higher BP and why? Pentane or neopentane?
A
Pentane, neopentane is branched, which decreases its surface area, decreasing ability for LDF
13
Q
Which has a higher BP and why? Hexane or hexanone?
A
Hexanone, since it has a carboxyl group, it has dipole-dipole interactions as well as LDF, increasing BP
14
Q
Which has a higher BP and why? Hexanone or hexanol?
A
Hexanol, it has an OH group, allowing for hydrogen bonding
15
Q
Which has a reaction intermediate: SN1 or SN2?
A
SN1 (two steps)
16
Q
Which is considered bimolecular: SN1 or SN2?
A
SN2
17
Q
Which has a reaction intermediate: E1 or E2?
A
E1
18
Q
Which is considered unimolecular: E1 or E2?
A
E1
19
Q
Which is a more stable carbocation? Allyl or benzyl?
A
Benzyl
20
Q
Which has more cationic stability: allyl or tertiary?
A
Allyl (because of resonance)
21
Q
If the alkyl chain is a methyl group, which will occur (SN1/2 or E1/2)?
A
Only SN2
Not SN1 or E1 because unstable carbocation
Not E2 because no Beta-hydrogen
22
Q
If the alkyl chain is a primary carbon, which will occur (SN1/2 or E1/2)?
A
SN2 more than E2, but both possible
Not SN1 or E1 because unstable carbocation
23
Q
If the alkyl chain is a secondary carbon, which will occur (SN1/2 or E1/2)?
A
SN1 or E1 if a weak nucleophile or base, respectively
SN2 or E2 if strong nucleophile or base
24
Q
Which do SN1/2 reactions prefer: polar protic or aprotic solutions?
A
SN1 prefer polar aprotic
SN2 polar protic
25
Which do E1/2 reactions prefer: polar protic or aprotic solutions?
E1 polar aprotic
| E2 Polar protic
26
If the solution is polar protic, which will be preferred: E2 or SN2?
Either
27
If the alkyl chain is a tertiary carbon, which will occur (SN1/2 or E1/2)?
SN1 or E1 if weak Nucleophile/base
E2 if strong base
Not SN2 because of steric hindrance
28
Is a negatively charged molecule a good or bad nucleophile?
Good/stronger
29
Name some weaker nucleophiles
Neutral: R-OH, H2O, NH3, CH3OH
30
List leaving groups in order from best to worst:
| I-, F-, Cl-, Br-
I-, Br-, Cl-, F-
31
List leaving groups in order from best to worst:
| H2O, OR-, OH-, NH2-, CH3COO-
H2O, CH3COO-, OH-, OR-, NH2-
32
What makes a good leaving group?
Larger size, ability to support/spread out e- cloud
33
Does polar protic allow or not allow H bonding?
Allow
34
List some polar protic solvents
H2O, CH3OH, NH3
35
List some polar aprotic solvents
DMSO, DMF, Acetone, Acetonitrile
36
What are the 3 steps for a free radical reaction?
Initiation, propagation, termination
37
Define: nucleophilicity
Ability for atom/molecule to give away e- and bond (has extra e- to give away)
38
In a polar aprotic solvent, is I- or F- better nucleophile?
F-
39
In polar protic solvent, is I- or F- better nucleophile?
I-, doesn’t H-bond like F- would
40
Is nucleophilicity a kinetic or thermodynamic step?
Kinetic-how good/fast something is at reacting
41
Is basicity a kinetic or thermodynamic concept?
Thermodynamic, how stable reactants or products are
42
List these in order of strongest to weakest basicity: OH-, Br-, I-, Cl-, F-
OH- (best), F-, Cl-, Br-, I-
43
Define: Zeitsev’s rule
In an elimination reaction, the β C more likely to lose H is one with fewer H attached
44
Electrophiles will have a positive or negative partial/full charge?
Positive
45
Nucleophiles will have a positive or negative partial/full charge?
Negative
46
Define: solvolysis reaction
The solvent acts as the nucleophile in an SN reaction
47
Define: carbocation rearrangement
A tertiary carbocation is more stable than a secondary or primary, so the molecule can move an H or a methyl group to change from a primary or secondary to tertiary carbocation
48
Does a polar protic solvent favor SN1 or SN2?
SN1, the partially negative portion of the electronegative molecule can stabilize the carbocation, and partial positive portion can stabilize anion leaving group
49
Does polar aprotic solvent favor SN1 or SN2?
SN2, need a strong nucleophile which would be stabilized in a polar protic solvent
50
Does a primary substrate favor SN1 or SN2?
SN2, requires decreased steric hindrance
51
Does a secondary substrate favor SN1 or SN2?
SN2 if it is a strong nucleophile and polar aprotic
| SN1 if it is a weak nucleophile and polar protic
52
Does a tertiary substrate favor SN1 or SN2?
SN1, carbocation stabilization
53
Describe an SN1 mechanism
1. Potential H+ transfer, creating good leaving group
2. Loss of a leaving group, carbocation intermediate formed
3. Potential carbocation rearrangement
4. Nucleophile (solvent) attacks electrophile center of carbocation
5. Nucleophile potentially deprotonated
54
Does an SN1 reaction change stereochemistry?
No, creates racemic mixture
55
Does SN2 change stereochemistry?
Yes, switches conformations
56
Describe an SN2 mechanism
1. Nucleophile attacks electrophile (substrate) at same time as loss of a leaving group
57
Describe an E1 mechanism
1. When with an alcohol: protonate OH group, makes good LG (H2O)
2. Loss of a leaving group, creating carbocation intermediate
3. Base takes H+ from β C (C next toC that was attached to LG) to form alkene
58
If a compound has a low pKa of its conjugate acid, is it a good or bad LG?
Good! ie I-
59
Which will be the primary product in an E1 reaction: mono-substituted alkene, di-substituted alkene, or tetra-substituted alkene?
Tetra-substituted (most stable carbocation intermediate)
60
True or false: for an E2 reaction, the β H and X must be on same sides of the double bond plane
False, they must be on different sides of the double bond plane
61
SN2 or E2? Strong nucleophile
SN2
62
SN2 or E2? Strong base?
E2
63
SN2 or E2? Polar aprotic solvent
Either, depending on if Nu or B-
64
SN2 or E2? Polar protic
Neither
65
SN2 or SN1? Primary substrate?
SN2
66
SN2 or SN1? Secondary substrate
Either, depends on strength of Nu
67
SN2 or SN1? Tertiary substrate
SN1, too much steric hindrance for SN2, and best stabilized carbocation
68
Would SH- and SR- be considered a strong/weak nucleophile and/or base?
Strong Nucleophile only, the conjugate acid is too strong to have a strong base
69
Is H- a strong/weak base and/or nucleophile
It is a strong base, and NOT a nucleophile
H2 is a weak acid, making it a strong conj. base
H- is too small to be a nucleophile
70
If a solvent is a strong nucleophile and a strong base, and the substrate is a primary halide, which is favored? SN2 or E2?
SN2
71
Heat favors (substitution/elimination)
Elimination over substitution
72
True or false: ethers allow H-bonding
False
| Ether: ROR
73
Which has a higher BP: alcohol or ether?
Alcohol, ether only allows MINIMAL dipole-dipole interactions
74
Which has a higher BP? CH3OCH3 (methyl methyl ether) or CH3CH2OCH2CH3 (ethyl ethyl ether)?
Ethyl ethyl ether, has larger alkyl groups which allow for increased LDF
75
Describe a Williamson Ether synthesis reaction (starting with R-OH)
1. A strong base deprotonates the OH group, leaving alkoxide nucleophile intermediate (anion)
2. Nucleophile attacks β C of primary alkyl halide (electrophillic center), kicking off halide (SN2)
3. Left with R-O-R’
76
Is a thiol group acidic or basic? A good or bad nucleophile?
Acidic, great nucleophile
77
A compound is aromatic if....?
1. Contains a ring of continuously overlapping p-orbitals (planar) and sp2 hybdridized
2. Has 4n+2 (Huckel’s rule) π e- in ring, when n=0,1,2...
78
Why is a Grignard reagent special?
It can create new C—C bonds
79
Reduction involves addition of __ and subtraction of __.
Addition of H and subtraction of O
80
What is the IR spectra for an OH group?
3300 cm^-1
81
What is the IR spectra for an carbonyl group (C=O)?
1700 cm^-1
82
Is a methyl group hydrophobic or hydrophilic?
Hydrophobic (nonpolar)
83
Is an amine group basic or acidic?
Amine: R-NH2, basic
84
Define: Bronsted Lowry acid
Proton donor
85
Define: Bronsted Lowry base
Proton donor
86
Define: Lewis acid
e- pair acceptor (electrophile)
| Lewis= eLectrons
87
Define: Lewis base
e- pair donor (nucleophile)
| Lewis= eLectrons
88
What happens to an acid when it’s conj. base is more stable?
The more stable the conj. base, the more likely the acid is to donate H+, making it a stronger acid
89
What makes a stable conj. base?
Increased electronegativity in a row
90
The stronger an acid, the (lower/higher) its pKa value
Lower
91
As anion size increases, what happens to electronegativity and bond energy?
Negative charge spreads out more, which decreases electronegativity, which decreases bond energy, making the bonds easier to break
92
When looking at a molecule, how do you determine which H is more acidic?
The H that has more resonance capabilities
93
How does hybridization affect strength of acids and conj. bases?
Increase in s character increases stability of conj. base (there is an increase in e- density closer to the nucleus), which increases acidity
94
Vertical lines on a Fisher projection represent what?
Around chiral center, these molecules are facing AWAY from plane (dashed lines)
95
Horizontal lines on a Fisher projection represent what?
Around chiral center, these molecules are popping OUT from plane (solid lines)
96
Define: meso compound
A compound that has chiral centers but is achiral overall
97
What is the equation for Ka?
Ka = ([H3O+][A-])/([HA])
98
What do strong acids do with their protons?
Donate the H+ very easily
99
For weak acids, where does equilibrium lie?
To the left because not everything gets reacted
100
What is the relationship between pKa and Ka. (Equation)
pKa = -log (Ka)
101
Strong acids have (high or low) Ka and pKa values?
High Ka, low pKa values
102
Equilibrium favors the side with the (weaker/stronger) acid, and the (higher/lower) pKa value?
Weaker, higher
103
How does the anion size of a strong acid compare to a weak acid?
Stronger acid has a larger anion size (e- spread out over larger space, more stable)
104
Is the bond energy of a strong acid low or high?
Low, easier to fully dissociate
105
What solvents can be used to reduce an alkyne?
Product: R-C=C-R or R-C-C-R
H2, Pd (hydrogenation)
Cis, syn addition
Slow, easily stopped to get alkene, or let go to get alkane
H2, Pt
Alkane only product
Na, NH3 (radical intermediate)
Trans, anti addiction
Alkene only product
106
What reagents can be used to reduce Carboxylic acids, and what is the product?
1. LiAlH4
2. H+
Reduces all carbonyl groups, produces alcohol(s) (reduced oxidation state)
1. BH3
2. H+
Chemoselective to reduce carboxylic acids ONLY, produces primary alcohol but leaves aldehydes and ketones alone (reduced oxidation state)
107
What reagents can be used to oxidize aldehydes?
1. Ag+, OH-, NH3 (Tollen’s reagent [Ag(NH3)2]+)
2. H+
Produces a carboxylic acid (silver cation gets reduced)
**only aldehydes react with Tollen’s reagent, not ketones
1. Na2Cr2O7
2. H2SO4, H2O
Oxidizes alcohols to ketones, and aldehydes to carboxylic acids
108
What is Tollen’s reagent and what does it react with?
[Ag(NH3)2]+
Reacts only with aldehydes, not ketones
109
What must an alcohol have to be oxidized, and what results?
An alpha H, increasing number of bonds to oxygen
110
What results from the oxidation of alcohols (primary, secondary, tertiary)?
Primary: produces aldehyde (which can further be oxidized to produce CA)
Secondary: produces ketone
Tertiary: no reaction (no alpha H)
111
What is the atomic trend on the periodic table for acidity?
As go across period, increasing electronegativity increases acidity
As go across group, increasing size increases acidity
112
When comparing species, what does charge indicate about acidity/basicity
Full/partial + more acidic
| Full/partial - more basic
113
What is ROOR also known as?
Peroxide
114
Define: syn addition
Addition of atoms is on same side of double bond (resulting in alkane, but with same 3D direction)
115
Define: anti-addition
Addition of molecules on opposite sides of double bond, resulting in atoms facing different directions (into vs. out of plane)
116
How is formal charge calculated?
FC = (# e- unbound atom it should have) - (# e- in actual bonded atom)
ie: CH3
FC of C = 4-3 = +1
117
How is oxidation state calculated?
OS = (# e- unbound atom should have) - (# e- it TAKES from bond, taking into account electronegativities)
Ie: CH3OH
OS of C: 4-6 = -2 (should have 4 valence e-, but steals both e- in each C-H bond since C is more electronegative). Does not have an e- in the C-O bond since oxygen takes both e-
OS of each H: 1-0 = +1
OS of O: 6-7 = -1
118
What allows for resonance to occur?
Lone e- pairs next to pi bond
119
List the carboxylic acid derivatives in order from most to least reactive: acid anhydride, ester, acid chloride, carboxylate ion, thioester, amide
1 (most). acid chloride (e- withdrawing)
2. acid anhydride (e- withdrawing)
3. Thioester (weakly e- donating)
4. Ester (alkoxy (-OR) group is weakly e- donating)
5. Amide (very strongly donating)
6. Carboxylate ion (not reactive because the negative charge repels approach of other nucleophiles)
120
What happens to solubility of alcohols as they get longer?
Longer R chain means less soluble because less H-bonding
121
What happens to BP of alcohols as they get longer?
Longer R chain increases BP (because of H bonding and LDF)
122
What is the spectroscopy value for a C-H bound to a triple bond?
3300 cm^-1
123
What is the spectroscopy value for a C-H bound to a double bond?
3100 cm^-1
124
What is the spectroscopy value for a C-H bound to a single bond?
2400 cm^-1
125
What is the spectroscopy value for an aromatic C=C?
1450-1600 cm^-1
126
What is the spectroscopy value for an sp2 hybridized C-H?
3100 cm^-1
127
What is the spectroscopy value for an sp3 hybridized C-H?
2900 cm^-1
128
What is the spectroscopy value for an sp hybridized C-H?
2100 cm^-1
129
What is the spectroscopy value for C=O?
1715 cm^-1
130
What is the spectroscopy value for O-H?
3500 cm^-1
131
What is the spectroscopy value for an acyl chloride?
1850 cm^-1
132
What is the spectroscopy value for an acid anhydride?
1760-1790 cm^-1
133
What is the spectroscopy value for an ester?
1745- 1810 cm^-1
134
What is the spectroscopy value for an aldehyde?
1725 cm^-1
135
What is the spectroscopy value for a ketone?
1715 cm^-1
136
What is the spectroscopy value for a carboxylic acid?
1710 cm^-1
137
What is the spectroscopy value for an amide?
1650-1690 cm^-1
