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76 Cards in this Set
- Front
- Back
Localized Electrons |
electrons that are restricted to a particular locality |
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Delocalized Electrons |
electrons that are shared by more than two atoms (dashed lines in bonds) |
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Are the above localized or delocalized electrons? |
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Are the above localized or delocalized electrons? |
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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). |
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. |
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Benzene is a (planar/nonplanar) molecule with (parallel/nonparallel) p orbitals that overlap on (one/two) side(s). |
Benzene is a planar molecule with parallel p orbitals that overlap on two sides. |
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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. |
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. |
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How should one draw benzene? |
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Resonance Contibutor |
AKA resonance structure or contributing resonance structure a structure with localized electrons that approximates the true structure of a compound with delocalized electrons |
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Resonance Hybrid |
the actual structure of a compound with delocalized electrons; represented by two or more structures with localized electrons (resonance contributors) |
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Electron delocalization is shown by ________ whereas equilibrium is shown by ________. |
Electron delocalization is shown by ↔whereas equilibrium is shown by ⇋. |
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Resonance contributors are (real/imaginary) structures. Resonance hybrids are (real/imaginary) structures. |
Resonance contributors are imaginary structures. Resonance hybrids are real structures. |
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Electron delocalization is most effective for (planar/nonplanar) molecules because this (maximizes/minimizes) the amount of overlap between p orbitals. |
Electron delocalization is most effective for planar molecules because this maximizes the amount of overlapt between p orbitals. |
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Delocalized electrons result from a ___ orbital overlapping the ___ orbitals of ____ adjacent atoms. |
Delocalized electrons result from a p orbital overlapping the p orbitals of two adjacent atoms. |
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List the rules for drawing resonance contributors. |
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. |
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To draw resonance contributors, move only ___ electrons or _____________ toward an sp__ carbon.
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To draw resonance contributors, move only pi electrons or lone-pair electrons toward an sp2 carbon. |
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Draw the resonance contributors. |
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Delocalization makes a molecule (more/less) stable. |
Delocalization makes a molecule more stable. |
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Electrons usually move (towards/away from) the most electronegative atom. |
Electrons usually move towards the most electronegative atom. |
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All resonance contributors (do/do not) contribute equally to the resonance hybrid. |
All resonance contirbutors do not contribute equally to the resonance hybrid. |
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The greater the predicted stability of a resonance contributor, the (more/less) it contributes to the structure of the resonance hybrid. |
The greater the predicted stability of a resonance contributor, the more it contributes to the structure of the resonance hybrid. |
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The more a resonance contributor contributes to the structure of the resonance hybrid, the (more/less) similar the contributor is to the real molecule. |
The more a resonance contributor contributes to the structure of the resonance hybrid, the more similar the contributor is to the real molecule. |
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Separated Charges |
a positive and negative charge that can be neutralized by the movement of electrons |
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Resonance contributors with separated charges are relatively (unstable/stable) and thus (high/low) in energy. |
Resonance contributors with separated charges are relatively unstable and thus high in energy. |
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Delocalization Energy |
the extra stability a compound achieves as a result of having delocalized electrons |
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A resonance hybrid is (more/less) stable than any of its resonance contributors is predicted to be. |
A resonance hybrid is more stable than any of its resonance contributors is predicted to be. |
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The greater the number of relatively stable resonance contributors, the (greater/smaller) the delocalization energy. |
The greater the number of relatively stable resonance contributors, the greater the delocalization energy. |
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The more nearly equivalent the structures of the resonance contributors, the (greater/smaller) the delocalization energy. |
The more nearly equivalent the structures of hte resonance contributors, the greater the delocalization energy. |
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Diene |
a hydrocarbon with two double bonds |
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Isolated dienes have double bonds that are separated by (one/more than one) single bond. |
Isolated dienes have double bonds that are separated by more than one single bond. |
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Conjugated dienes have double bonds that are separated by (one/more than one) single bond. |
Conjugated dienes have double bonds that are separated by one single bond. |
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The most stable alkene has the (largest/smallest) heat of hydrogenation. |
The most stable alkene has the smallest heat of hydrogenation. |
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An increase in delocalization energy means a(n) (increase/decrease) in stability. |
An increase in delocalization energy means an increase in stability. |
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A conjugated diene is (more/less) stable than an isolated diene. |
A conjugated diene is more stable than an isolated diene. |
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Allylic Carbon |
carbon adjacent to sp2 carbon of an alkene |
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Benzylic Carbon |
carbon adjacent to sp2 carbon of benzene ring |
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Allylic Cation |
carbocation with positive charge on allylic carbon |
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Benzylic Cation |
carbocation with positive charge on benzylic carbon |
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Allyl Cation |
an unsubstituted allylic cation |
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Benzyl Cation |
unsubstituted benzylic cation |
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Rank the following from most to least stable: Methyl cation Primary carbocation Tertiary carbocation Benzyl cation Secondary carbocation Allyl cation |
Benzyl cation > allyl cation > tertiary carbocation > secondary carbocation > primary carbocation > methyl cation |
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The more stable the base, the (stronger/weaker) its conjugate acid. |
The more stable the base, the stronger its conjugate acid. |
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A nearby electronegative atom stabilizes an anion by ___________________________________. |
A nearby electronegative atom stabilizes an anion by inductive electron withdrawal. |
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Greater stability comes from a(n) (increase/decrease) in delocalization energy. |
Greater stability comes from an increase in delocalization energy. |
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Which acids have a pK_a of the following: <0 : ~5 : ~10 : ~15 : |
<0 : protonated alcohol, protonated water, protonated carbonyl groups ~5 : carboxylic acid, protonated aniline ~10 : protonated amine, phenol ~15 : alcohol, water |
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Electron donation (increases/decreases) acidity. Electron withdrawal (increases/decreases) acidity. |
Electron donation decreases acidity. Electron withdrawal increases acidicty. |
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Substituents with a lone pair on the atom attached to a benzene ring can localize electrons through __________________________________. |
Substituents with a lone pair on the atom attached to a benzene ring can localize electrons through donation of electrons by resonance. |
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List the substituents that commonly donate electrons by resonance. |
NH2, OH, OR, Cl |
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Substituents attached to a benzene ring that are doubly or triply bonded to a more electronegative atom can delocalize electrons through __________________________________________. |
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. |
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List the substituents that commonly donate electrons by resonance. |
C=O, C≡N, SO3H, NO2 |
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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. |
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. |
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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. |
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. |
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For electrophilic addition reactions, one can determine the major product by examining the (number of hydrogens/relative stabilities of individual carbocations). |
For electrophilic addition reactions, one can determine the major product by examining the relative stabilities of individual carbocations. |
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1,2-Addition |
AKA direct addition addition to the 1- and 2-positions of a conjugated system |
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A(n) (isolated/conjugated) diene undergoes only 1,2-addition. |
An isolated diene undergoes only 1,2-addition. |
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1,4-addition |
AKA conjugate addition addition to the 1- and 4-positions of a conjugated system |
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A(n) (isolated/conjugated) diene undergoes both 1,2- and 1,4-addition. |
A conjugated diene undergoes both 1,2- and 1,4-addition. |
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What is the conjugated system? |
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Diels-Alder Reaction |
a [4+2] cycloaddition reaction in which a conjugated diene reactions with a carbon that contains a C=C |
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Dienophile |
an alkene that reacts with a diene in a Diels-Alder reaction |
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Carbons containing carbon-carbon (double/triple) bonds can be used as dienophiles to prepare compounds with two isolated double bonds. |
Carbons containing carbon-carbon triple bonds can be used as dienophiles to prepare compounds with two isolated carbon bonds. |
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List the steps to determine the reactants needed to synthesize a Diels-Alder product. |
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. |
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Aromatic compounds (are/are not) particularly stable because they have (small/large) delocalization energies. |
Aromatic compounds are particularly stable because they have large delocalization energies. |
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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. |
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. |
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Which sp-hybridized carbons have p orbitals? |
Only sp2 and sp carbons have p orbitals |
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Which of these are aromatic? |
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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 |
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Electrophilic Aromatic Substitution |
a reaction in which an electrophile substitutes for a hydrogen of an aromatic ring |
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Aromatic substitution is (more/less) stable than nonaromatic substitution. |
Aromatic substitution is more stable than nonaromatic substitution. |
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Describe the free energy graph of an electrophilic aromatic substitution and electrophilic addition. |
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List the five most common electrophilic aromatic substitution reactions. |
1. Halogenation - Br, Cl, I 2. Nitration - NO2 3. Sulfonation - SO3H 4. Friedel-Crafts acylation - RC=O 5. Friedel-Crafts alkylation - R |
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Describe the steps of the mechanism for electrophilic aromatic substitution.
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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. |
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What substituents exhibit inductive electron withdrawal on alkene rings? |
Substituents which are more electron withdrawing (more electronegative) will exhibit inductive electron withdrawal. |
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What substituents exhibit electron donation by hyperconjugation? |
Substituents that are alkyl substituents can donate electrons via hyperconjugation (donating electrons to empty p orbital(s)) |
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What substituents exhibit electron donation by resonance? |
Substituents that have a lone pair on the atom direct attached to the benzene ring can delocalize that pair into the ring. |
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What substituents exhibit electron withdrawal by resonance? |
Substituents that have the first atom doubly or triply bonded to a more electronegative atom than H can exhibit electron withdrawal by resonance. |