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O Chem Flashcards

1
Q

Define: hydrocarbon

A

Molecule that consists entirely of carbon and hydrogen

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2
Q

Define: structural isomers

A

Same molecular formula, but different connectivity of atoms

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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)

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4
Q

What state are fats with cis conformations at room temp, and why?

A

Liquid, cis conformation prevents tight packing

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5
Q

Define: enantiomer

A

Same chemical structure but differ in their three-dimensional placement of atoms (non-superimposable mirror images), chiral molecules only

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6
Q

Which isomer (D or L) of amino acids are found in nature/humans?

A

L

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7
Q

Which isomer (D/L) of sugars are found in nature?

A

D

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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

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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

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10
Q

Are hydrogen phosphate groups considered acidic or basic?

A

Acidic, since they release H+ into the solution

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11
Q

Which has a higher BP and why? Pentane or hexane?

A

Hexane, longer chain, more molecular weight, more LDF attraction between chains

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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

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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

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14
Q

Which has a higher BP and why? Hexanone or hexanol?

A

Hexanol, it has an OH group, allowing for hydrogen bonding

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15
Q

Which has a reaction intermediate: SN1 or SN2?

A

SN1 (two steps)

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16
Q

Which is considered bimolecular: SN1 or SN2?

A

SN2

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17
Q

Which has a reaction intermediate: E1 or E2?

A

E1

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18
Q

Which is considered unimolecular: E1 or E2?

A

E1

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19
Q

Which is a more stable carbocation? Allyl or benzyl?

A

Benzyl

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20
Q

Which has more cationic stability: allyl or tertiary?

A

Allyl (because of resonance)

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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

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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

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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

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24
Q

Which do SN1/2 reactions prefer: polar protic or aprotic solutions?

A

SN1 prefer polar aprotic

SN2 polar protic

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25
Q

Which do E1/2 reactions prefer: polar protic or aprotic solutions?

A

E1 polar aprotic

E2 Polar protic

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26
Q

If the solution is polar protic, which will be preferred: E2 or SN2?

A

Either

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27
Q

If the alkyl chain is a tertiary carbon, which will occur (SN1/2 or E1/2)?

A

SN1 or E1 if weak Nucleophile/base
E2 if strong base
Not SN2 because of steric hindrance

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28
Q

Is a negatively charged molecule a good or bad nucleophile?

A

Good/stronger

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29
Q

Name some weaker nucleophiles

A

Neutral: R-OH, H2O, NH3, CH3OH

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30
Q

List leaving groups in order from best to worst:

I-, F-, Cl-, Br-

A

I-, Br-, Cl-, F-

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31
Q

List leaving groups in order from best to worst:

H2O, OR-, OH-, NH2-, CH3COO-

A

H2O, CH3COO-, OH-, OR-, NH2-

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32
Q

What makes a good leaving group?

A

Larger size, ability to support/spread out e- cloud

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33
Q

Does polar protic allow or not allow H bonding?

A

Allow

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34
Q

List some polar protic solvents

A

H2O, CH3OH, NH3

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35
Q

List some polar aprotic solvents

A

DMSO, DMF, Acetone, Acetonitrile

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36
Q

What are the 3 steps for a free radical reaction?

A

Initiation, propagation, termination

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37
Q

Define: nucleophilicity

A

Ability for atom/molecule to give away e- and bond (has extra e- to give away)

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38
Q

In a polar aprotic solvent, is I- or F- better nucleophile?

A

F-

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39
Q

In polar protic solvent, is I- or F- better nucleophile?

A

I-, doesn’t H-bond like F- would

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40
Q

Is nucleophilicity a kinetic or thermodynamic step?

A

Kinetic-how good/fast something is at reacting

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41
Q

Is basicity a kinetic or thermodynamic concept?

A

Thermodynamic, how stable reactants or products are

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42
Q

List these in order of strongest to weakest basicity: OH-, Br-, I-, Cl-, F-

A

OH- (best), F-, Cl-, Br-, I-

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43
Q

Define: Zeitsev’s rule

A

In an elimination reaction, the β C more likely to lose H is one with fewer H attached

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44
Q

Electrophiles will have a positive or negative partial/full charge?

A

Positive

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45
Q

Nucleophiles will have a positive or negative partial/full charge?

A

Negative

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46
Q

Define: solvolysis reaction

A

The solvent acts as the nucleophile in an SN reaction

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47
Q

Define: carbocation rearrangement

A

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

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48
Q

Does a polar protic solvent favor SN1 or SN2?

A

SN1, the partially negative portion of the electronegative molecule can stabilize the carbocation, and partial positive portion can stabilize anion leaving group

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49
Q

Does polar aprotic solvent favor SN1 or SN2?

A

SN2, need a strong nucleophile which would be stabilized in a polar protic solvent

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50
Q

Does a primary substrate favor SN1 or SN2?

A

SN2, requires decreased steric hindrance

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51
Q

Does a secondary substrate favor SN1 or SN2?

A

SN2 if it is a strong nucleophile and polar aprotic

SN1 if it is a weak nucleophile and polar protic

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52
Q

Does a tertiary substrate favor SN1 or SN2?

A

SN1, carbocation stabilization

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53
Q

Describe an SN1 mechanism

A
  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
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54
Q

Does an SN1 reaction change stereochemistry?

A

No, creates racemic mixture

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55
Q

Does SN2 change stereochemistry?

A

Yes, switches conformations

56
Q

Describe an SN2 mechanism

A
  1. Nucleophile attacks electrophile (substrate) at same time as loss of a leaving group
57
Q

Describe an E1 mechanism

A
  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
Q

If a compound has a low pKa of its conjugate acid, is it a good or bad LG?

A

Good! ie I-

59
Q

Which will be the primary product in an E1 reaction: mono-substituted alkene, di-substituted alkene, or tetra-substituted alkene?

A

Tetra-substituted (most stable carbocation intermediate)

60
Q

True or false: for an E2 reaction, the β H and X must be on same sides of the double bond plane

A

False, they must be on different sides of the double bond plane

61
Q

SN2 or E2? Strong nucleophile

62
Q

SN2 or E2? Strong base?

63
Q

SN2 or E2? Polar aprotic solvent

A

Either, depending on if Nu or B-

64
Q

SN2 or E2? Polar protic

65
Q

SN2 or SN1? Primary substrate?

66
Q

SN2 or SN1? Secondary substrate

A

Either, depends on strength of Nu

67
Q

SN2 or SN1? Tertiary substrate

A

SN1, too much steric hindrance for SN2, and best stabilized carbocation

68
Q

Would SH- and SR- be considered a strong/weak nucleophile and/or base?

A

Strong Nucleophile only, the conjugate acid is too strong to have a strong base

69
Q

Is H- a strong/weak base and/or nucleophile

A

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
Q

If a solvent is a strong nucleophile and a strong base, and the substrate is a primary halide, which is favored? SN2 or E2?

71
Q

Heat favors (substitution/elimination)

A

Elimination over substitution

72
Q

True or false: ethers allow H-bonding

A

False

Ether: ROR

73
Q

Which has a higher BP: alcohol or ether?

A

Alcohol, ether only allows MINIMAL dipole-dipole interactions

74
Q

Which has a higher BP? CH3OCH3 (methyl methyl ether) or CH3CH2OCH2CH3 (ethyl ethyl ether)?

A

Ethyl ethyl ether, has larger alkyl groups which allow for increased LDF

75
Q

Describe a Williamson Ether synthesis reaction (starting with R-OH)

A
  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
Q

Is a thiol group acidic or basic? A good or bad nucleophile?

A

Acidic, great nucleophile

77
Q

A compound is aromatic if….?

A
  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
Q

Why is a Grignard reagent special?

A

It can create new C—C bonds

79
Q

Reduction involves addition of __ and subtraction of __.

A

Addition of H and subtraction of O

80
Q

What is the IR spectra for an OH group?

A

3300 cm^-1

81
Q

What is the IR spectra for an carbonyl group (C=O)?

A

1700 cm^-1

82
Q

Is a methyl group hydrophobic or hydrophilic?

A

Hydrophobic (nonpolar)

83
Q

Is an amine group basic or acidic?

A

Amine: R-NH2, basic

84
Q

Define: Bronsted Lowry acid

A

Proton donor

85
Q

Define: Bronsted Lowry base

A

Proton donor

86
Q

Define: Lewis acid

A

e- pair acceptor (electrophile)

Lewis= eLectrons

87
Q

Define: Lewis base

A

e- pair donor (nucleophile)

Lewis= eLectrons

88
Q

What happens to an acid when it’s conj. base is more stable?

A

The more stable the conj. base, the more likely the acid is to donate H+, making it a stronger acid

89
Q

What makes a stable conj. base?

A

Increased electronegativity in a row

90
Q

The stronger an acid, the (lower/higher) its pKa value

91
Q

As anion size increases, what happens to electronegativity and bond energy?

A

Negative charge spreads out more, which decreases electronegativity, which decreases bond energy, making the bonds easier to break

92
Q

When looking at a molecule, how do you determine which H is more acidic?

A

The H that has more resonance capabilities

93
Q

How does hybridization affect strength of acids and conj. bases?

A

Increase in s character increases stability of conj. base (there is an increase in e- density closer to the nucleus), which increases acidity

94
Q

Vertical lines on a Fisher projection represent what?

A

Around chiral center, these molecules are facing AWAY from plane (dashed lines)

95
Q

Horizontal lines on a Fisher projection represent what?

A

Around chiral center, these molecules are popping OUT from plane (solid lines)

96
Q

Define: meso compound

A

A compound that has chiral centers but is achiral overall

97
Q

What is the equation for Ka?

A

Ka = ([H3O+][A-])/([HA])

98
Q

What do strong acids do with their protons?

A

Donate the H+ very easily

99
Q

For weak acids, where does equilibrium lie?

A

To the left because not everything gets reacted

100
Q

What is the relationship between pKa and Ka. (Equation)

A

pKa = -log (Ka)

101
Q

Strong acids have (high or low) Ka and pKa values?

A

High Ka, low pKa values

102
Q

Equilibrium favors the side with the (weaker/stronger) acid, and the (higher/lower) pKa value?

A

Weaker, higher

103
Q

How does the anion size of a strong acid compare to a weak acid?

A

Stronger acid has a larger anion size (e- spread out over larger space, more stable)

104
Q

Is the bond energy of a strong acid low or high?

A

Low, easier to fully dissociate

105
Q

What solvents can be used to reduce an alkyne?

A

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
Q

What reagents can be used to reduce Carboxylic acids, and what is the product?

A
  1. LiAlH4
  2. H+
    Reduces all carbonyl groups, produces alcohol(s) (reduced oxidation state)
  3. BH3
  4. H+
    Chemoselective to reduce carboxylic acids ONLY, produces primary alcohol but leaves aldehydes and ketones alone (reduced oxidation state)
107
Q

What reagents can be used to oxidize aldehydes?

A
  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
Q

What is Tollen’s reagent and what does it react with?

A

[Ag(NH3)2]+

Reacts only with aldehydes, not ketones

109
Q

What must an alcohol have to be oxidized, and what results?

A

An alpha H, increasing number of bonds to oxygen

110
Q

What results from the oxidation of alcohols (primary, secondary, tertiary)?

A

Primary: produces aldehyde (which can further be oxidized to produce CA)
Secondary: produces ketone
Tertiary: no reaction (no alpha H)

111
Q

What is the atomic trend on the periodic table for acidity?

A

As go across period, increasing electronegativity increases acidity

As go across group, increasing size increases acidity

112
Q

When comparing species, what does charge indicate about acidity/basicity

A

Full/partial + more acidic

Full/partial - more basic

113
Q

What is ROOR also known as?

114
Q

Define: syn addition

A

Addition of atoms is on same side of double bond (resulting in alkane, but with same 3D direction)

115
Q

Define: anti-addition

A

Addition of molecules on opposite sides of double bond, resulting in atoms facing different directions (into vs. out of plane)

116
Q

How is formal charge calculated?

A

FC = (# e- unbound atom it should have) - (# e- in actual bonded atom)

ie: CH3
FC of C = 4-3 = +1

117
Q

How is oxidation state calculated?

A

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
Q

What allows for resonance to occur?

A

Lone e- pairs next to pi bond

119
Q

List the carboxylic acid derivatives in order from most to least reactive: acid anhydride, ester, acid chloride, carboxylate ion, thioester, amide

A

1 (most). acid chloride (e- withdrawing)

  1. acid anhydride (e- withdrawing)
  2. Thioester (weakly e- donating)
  3. Ester (alkoxy (-OR) group is weakly e- donating)
  4. Amide (very strongly donating)
  5. Carboxylate ion (not reactive because the negative charge repels approach of other nucleophiles)
120
Q

What happens to solubility of alcohols as they get longer?

A

Longer R chain means less soluble because less H-bonding

121
Q

What happens to BP of alcohols as they get longer?

A

Longer R chain increases BP (because of H bonding and LDF)

122
Q

What is the spectroscopy value for a C-H bound to a triple bond?

A

3300 cm^-1

123
Q

What is the spectroscopy value for a C-H bound to a double bond?

A

3100 cm^-1

124
Q

What is the spectroscopy value for a C-H bound to a single bond?

A

2400 cm^-1

125
Q

What is the spectroscopy value for an aromatic C=C?

A

1450-1600 cm^-1

126
Q

What is the spectroscopy value for an sp2 hybridized C-H?

A

3100 cm^-1

127
Q

What is the spectroscopy value for an sp3 hybridized C-H?

A

2900 cm^-1

128
Q

What is the spectroscopy value for an sp hybridized C-H?

A

2100 cm^-1

129
Q

What is the spectroscopy value for C=O?

A

1715 cm^-1

130
Q

What is the spectroscopy value for O-H?

A

3500 cm^-1

131
Q

What is the spectroscopy value for an acyl chloride?

A

1850 cm^-1

132
Q

What is the spectroscopy value for an acid anhydride?

A

1760-1790 cm^-1

133
Q

What is the spectroscopy value for an ester?

A

1745- 1810 cm^-1

134
Q

What is the spectroscopy value for an aldehyde?

A

1725 cm^-1

135
Q

What is the spectroscopy value for a ketone?

A

1715 cm^-1

136
Q

What is the spectroscopy value for a carboxylic acid?

A

1710 cm^-1

137
Q

What is the spectroscopy value for an amide?

A

1650-1690 cm^-1

MCAT (17 decks)

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