Organic Chem Chap 7

Front 1

Localized Electrons

Back 1

electrons that are restricted to a particular locality

Front 2

Delocalized Electrons

Back 2

electrons that are shared by more than two atoms (dashed lines in bonds)

Front 3

Are the above localized or delocalized electrons?

Back 3

Front 4

Are the above localized or delocalized electrons?

Back 4

Front 5

Kekule proposed that benzene is a ring of ____ carbons with ___ double bonds, which oscillate between carbons so rapidly as to be indistinquishable. He was ultimately (correct/incorrect).

Back 5

Kekule proposed that benzene is a ring of six carbons with three double bonds, which oscillate between carbons so rapidly as to be indistinguishable. He was ultimately incorrect.

Front 6

Benzene is a (planar/nonplanar) molecule with (parallel/nonparallel) p orbitals that overlap on (one/two) side(s).

Back 6

Benzene is a planar molecule with parallel p orbitals that overlap on two sides.

Front 7

Benzene's carbons have a total of _____ p orbitals (___ above and ____ below the plane of the ring) in which each (pi/sigma) electron is shared by ____ carbons.

Back 7

Benzene's carbons have a total of 12 p orbitals (6 above and 6 below the plane of the ring) in which each pi electron is shared by six carbons.

Front 8

How should one draw benzene?

Back 8

Front 9

Resonance Contibutor

Back 9

AKA resonance structure or contributing resonance structure

a structure with localized electrons that approximates the true structure of a compound with delocalized electrons

Front 10

Resonance Hybrid

Back 10

the actual structure of a compound with delocalized electrons; represented by two or more structures with localized electrons (resonance contributors)

Front 11

Electron delocalization is shown by ________ whereas equilibrium is shown by ________.

Back 11

Electron delocalization is shown by ↔whereas equilibrium is shown by ⇋.

Front 12

Resonance contributors are (real/imaginary) structures. Resonance hybrids are (real/imaginary) structures.

Back 12

Resonance contributors are imaginary structures. Resonance hybrids are real structures.

Front 13

Electron delocalization is most effective for (planar/nonplanar) molecules because this (maximizes/minimizes) the amount of overlap between p orbitals.

Back 13

Electron delocalization is most effective for planar molecules because this maximizes the amount of overlapt between p orbitals.

Front 14

Delocalized electrons result from a ___ orbital overlapping the ___ orbitals of ____ adjacent atoms.

Back 14

Delocalized electrons result from a p orbital overlapping the p orbitals of two adjacent atoms.

Front 15

List the rules for drawing resonance contributors.

Back 15

1. Only e- move; never atoms.

2. Only pi e- and lone-pair e- move.

3. Total number of e- does not change. Total charge does not change.

Front 16

To draw resonance contributors, move only ___ electrons or _____________ toward an sp__ carbon.

Back 16

To draw resonance contributors, move only pi electrons or lone-pair electrons toward an sp2 carbon.

Front 17

Draw the resonance contributors.

Back 17

Front 18

Delocalization makes a molecule (more/less) stable.

Back 18

Delocalization makes a molecule more stable.

Front 19

Electrons usually move (towards/away from) the most electronegative atom.

Back 19

Electrons usually move towards the most electronegative atom.

Front 20

All resonance contributors (do/do not) contribute equally to the resonance hybrid.

Back 20

All resonance contirbutors do not contribute equally to the resonance hybrid.

Front 21

The greater the predicted stability of a resonance contributor, the (more/less) it contributes to the structure of the resonance hybrid.

Back 21

The greater the predicted stability of a resonance contributor, the more it contributes to the structure of the resonance hybrid.

Front 22

The more a resonance contributor contributes to the structure of the resonance hybrid, the (more/less) similar the contributor is to the real molecule.

Back 22

The more a resonance contributor contributes to the structure of the resonance hybrid, the more similar the contributor is to the real molecule.

Front 23

Separated Charges

Back 23

a positive and negative charge that can be neutralized by the movement of electrons

Front 24

Resonance contributors with separated charges are relatively (unstable/stable) and thus (high/low) in energy.

Back 24

Resonance contributors with separated charges are relatively unstable and thus high in energy.

Front 25

Delocalization Energy

Back 25

the extra stability a compound achieves as a result of having delocalized electrons

Front 26

A resonance hybrid is (more/less) stable than any of its resonance contributors is predicted to be.

Back 26

A resonance hybrid is more stable than any of its resonance contributors is predicted to be.

Front 27

The greater the number of relatively stable resonance contributors, the (greater/smaller) the delocalization energy.

Back 27

The greater the number of relatively stable resonance contributors, the greater the delocalization energy.

Front 28

The more nearly equivalent the structures of the resonance contributors, the (greater/smaller) the delocalization energy.

Back 28

The more nearly equivalent the structures of hte resonance contributors, the greater the delocalization energy.

Front 29

Diene

Back 29

a hydrocarbon with two double bonds

Front 30

Isolated dienes have double bonds that are separated by (one/more than one) single bond.

Back 30

Isolated dienes have double bonds that are separated by more than one single bond.

Front 31

Conjugated dienes have double bonds that are separated by (one/more than one) single bond.

Back 31

Conjugated dienes have double bonds that are separated by one single bond.

Front 32

The most stable alkene has the (largest/smallest) heat of hydrogenation.

Back 32

The most stable alkene has the smallest heat of hydrogenation.

Front 33

An increase in delocalization energy means a(n) (increase/decrease) in stability.

Back 33

An increase in delocalization energy means an increase in stability.

Front 34

A conjugated diene is (more/less) stable than an isolated diene.

Back 34

A conjugated diene is more stable than an isolated diene.

Front 35

Allylic Carbon

Back 35

carbon adjacent to sp2 carbon of an alkene

Front 36

Benzylic Carbon

Back 36

carbon adjacent to sp2 carbon of benzene ring

Front 37

Allylic Cation

Back 37

carbocation with positive charge on allylic carbon

Front 38

Benzylic Cation

Back 38

carbocation with positive charge on benzylic carbon

Front 39

Allyl Cation

Back 39

an unsubstituted allylic cation

Front 40

Benzyl Cation

Back 40

unsubstituted benzylic cation

Front 41

Rank the following from most to least stable:

Methyl cation

Primary carbocation

Tertiary carbocation

Benzyl cation

Secondary carbocation

Allyl cation

Back 41

Benzyl cation > allyl cation > tertiary carbocation > secondary carbocation > primary carbocation > methyl cation

Front 42

The more stable the base, the (stronger/weaker) its conjugate acid.

Back 42

The more stable the base, the stronger its conjugate acid.

Front 43

A nearby electronegative atom stabilizes an anion by ___________________________________.

Back 43

A nearby electronegative atom stabilizes an anion by inductive electron withdrawal.

Front 44

Greater stability comes from a(n) (increase/decrease) in delocalization energy.

Back 44

Greater stability comes from an increase in delocalization energy.

Front 45

Which acids have a pK_a of the following:

<0 :

~5 :

~10 :

~15 :

Back 45

<0 : protonated alcohol, protonated water, protonated carbonyl groups

~5 : carboxylic acid, protonated aniline

~10 : protonated amine, phenol

~15 : alcohol, water

Front 46

Electron donation (increases/decreases) acidity. Electron withdrawal (increases/decreases) acidity.

Back 46

Electron donation decreases acidity. Electron withdrawal increases acidicty.

Front 47

Substituents with a lone pair on the atom attached to a benzene ring can localize electrons through __________________________________.

Back 47

Substituents with a lone pair on the atom attached to a benzene ring can localize electrons through donation of electrons by resonance.

Front 48

List the substituents that commonly donate electrons by resonance.

Back 48

NH2, OH, OR, Cl

Front 49

Substituents attached to a benzene ring that are doubly or triply bonded to a more electronegative atom can delocalize electrons through __________________________________________.

Back 49

Substituents attached to a benzene ring that are doubly or triply bonded to a more electronegative atom can delocalize electrons through withdrawal of electrons by resonance.

Front 50

List the substituents that commonly donate electrons by resonance.

Back 50

C=O, C≡N, SO3H, NO2

Front 51

The more electron donating the substituent, the (more/less) it decreases the acidity of a COOH, an OH, or an +NH3 group attached to a benzene ring.

Back 51

The more electron donating the substituent, the more it decreases the acidity of a COOH, an OH, or an +NH3 group attached to a benzene ring.

Front 52

The more electron withdrawing the substituent, the (more/less) it increases the acidity of a COOH, an OH, or an +NH3 group attached to a benzene ring.

Back 52

The more electron withdrawing the substituent, the more it increases the acidity of a COOH, an OH, or an +NH3 group attached to a benzene ring.

Front 53

For electrophilic addition reactions, one can determine the major product by examining the (number of hydrogens/relative stabilities of individual carbocations).

Back 53

For electrophilic addition reactions, one can determine the major product by examining the relative stabilities of individual carbocations.

Front 54

1,2-Addition

Back 54

AKA direct addition

addition to the 1- and 2-positions of a conjugated system

Front 55

A(n) (isolated/conjugated) diene undergoes only 1,2-addition.

Back 55

An isolated diene undergoes only 1,2-addition.

Front 56

1,4-addition

Back 56

AKA conjugate addition

addition to the 1- and 4-positions of a conjugated system

Front 57

A(n) (isolated/conjugated) diene undergoes both 1,2- and 1,4-addition.

Back 57

A conjugated diene undergoes both 1,2- and 1,4-addition.

Front 58

What is the conjugated system?

Back 58

Front 59

Diels-Alder Reaction

Back 59

a [4+2] cycloaddition reaction in which a conjugated diene reactions with a carbon that contains a C=C

Front 60

Dienophile

Back 60

an alkene that reacts with a diene in a Diels-Alder reaction

Front 61

Carbons containing carbon-carbon (double/triple) bonds can be used as dienophiles to prepare compounds with two isolated double bonds.

Back 61

Carbons containing carbon-carbon triple bonds can be used as dienophiles to prepare compounds with two isolated carbon bonds.

Front 62

List the steps to determine the reactants needed to synthesize a Diels-Alder product.

Back 62

1. Locate double bond in project; delete that pi bond and add pi bonds on either side of it.

2. Delete the sigma bonds between the diene side of the cycloalkene and add a pie bond between the two carbons that just had a sigma bond deleted.

Front 63

Aromatic compounds (are/are not) particularly stable because they have (small/large) delocalization energies.

Back 63

Aromatic compounds are particularly stable because they have large delocalization energies.

Front 64

For a compound to be aromatic, it must be ____________ and __________, and it must have an (interrupted/uninterrupted) cloud of an (odd/even) number of pi electrons.

Back 64

For a compound to be aromatic, it must be cyclic and planar, and it must have an uninterrupted cloud of an odd number of pi electrons.

Front 65

Which sp-hybridized carbons have p orbitals?

Back 65

Only sp2 and sp carbons have p orbitals

Front 66

Which of these are aromatic?

Back 66

Front 67

Back 67

A is not: it does not have an uninterrupted cloud of pi electrons

B is not: it does not have an odd number of pi electrons

C is the only aromatic compound

D is not: it is not cyclic

Front 68

Electrophilic Aromatic Substitution

Back 68

a reaction in which an electrophile substitutes for a hydrogen of an aromatic ring

Front 69

Aromatic substitution is (more/less) stable than nonaromatic substitution.

Back 69

Aromatic substitution is more stable than nonaromatic substitution.

Front 70

Describe the free energy graph of an electrophilic aromatic substitution and electrophilic addition.

Back 70

Front 71

List the five most common electrophilic aromatic substitution reactions.

Back 71

1. Halogenation - Br, Cl, I

2. Nitration - NO2

3. Sulfonation - SO3H

4. Friedel-Crafts acylation - RC=O

5. Friedel-Crafts alkylation - R

Front 72

Describe the steps of the mechanism for electrophilic aromatic substitution.

Back 72

1. Electrophile (Y+) adds to nucleophilic benzene ring, forming a carbocation intermediate.

2. Base in the mixture (:B) removes a proton (H+) from the carbocation intermediate and the electrons that held the proton move into the ring to re-establish aromaticity. H+ is always removed from the carbon that formed the bond with the electrophile.

Front 73

What substituents exhibit inductive electron withdrawal on alkene rings?

Back 73

Substituents which are more electron withdrawing (more electronegative) will exhibit inductive electron withdrawal.

Front 74

What substituents exhibit electron donation by hyperconjugation?

Back 74

Substituents that are alkyl substituents can donate electrons via hyperconjugation (donating electrons to empty p orbital(s))

Front 75

What substituents exhibit electron donation by resonance?

Back 75

Substituents that have a lone pair on the atom direct attached to the benzene ring can delocalize that pair into the ring.

Front 76

What substituents exhibit electron withdrawal by resonance?

Back 76

Substituents that have the first atom doubly or triply bonded to a more electronegative atom than H can exhibit electron withdrawal by resonance.