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Orgo 15-17
| Question | Answer |
|---|---|
| In electrophilic aromatic substitution, the electrophile substitutes for a _______ on the benzene ring. | H |
| The bromination of benzene requires a stronger _________ than Br2. Use a strong Lewis acid catalyst, ____________. | electrophile; FeBr3 |
| Addition of Br to benzene is without a catalyst ______thermic. | Endo |
| Chlorination of benzene requires an _____ catalyst. | AlCl3 |
| Iodination of benzene requires an ______ oxidizing agent, like ____________, which oxidizes the iodine to an iodium ion. | acidic; NO2 |
| Use __________ with nitric acid to form the nitronium ion electrophile. NO2+ then forms a sigma complex with benzene and loses H+ to form nitrobenzene | H2SO4 |
| ______________ is a reversible electrophilic aromatic substitution and can be reversed by heating in __________________. | sulphonation; dilute sulphuric acid |
| _________ reacts 25 times faster than benzene. The methyl group is an __________. | Toluene; activator |
| Toluene nitration product mixtures contain mostly ______ and ______ substituted molecules because the __________ is more stable at those positions. | Ortho and para; intermediate |
| Alkyl groups stabilize the sigma complex by ___________, donating electron density through the sigma bond. | Induction |
| Substituents with a lone pair of electrons stabilize the sigma complex by _________. | Resonance |
| -OCH3, also known as ______, is _____-_____ directing. | anisole; ortho-para |
| Aniline reacts with bromine water to yield a __________. Sodium Bicarbonate is added to neutralize the HBr that is also formed. | tribromide |
| Name some activator groups. | O-, -NR2, OH, OR, HNCOR, -R (no lone pairs) |
| Name some activator compounds: | phenoxides, anilines, phenols, phenyl ethers, anilides, alkylbenzenes |
| Electrophilic substitution reactions for nitrobenzene are 100,000 times _________ than for benzene. | Slower |
| Electrophilic substitution for nitrobenzene contains a product mix of mostly the ________ isomer. | Meta |
| _____-directors deactivate all positions on the ring, but the ______ is less deactivated. | Meta; meta |
| In meta-directing deactivators, the atom attached to the aromatic ring will have a ___________________. Electron density is withdrawn ____________ along the sigma bond, so the ring is less __________ than benzene. | partial positive charge; inductively; electron-rich |
| Name some deactivator groups: | NO2, SO3H, CN, Ketones and aldehydes, esters, NR3+ |
| Halogens are ___________ toward electrophilic substitution, but are _____-____ directing. | deactivating; ortho-para |
| Since halogens are very electronegative, they _____ electron density from the ring _____ through the sigma bond. However, they also have _________ that can stabilize the sigma complex by resonance. | withdraw; inductively; lone pairs of electrons |
| Name the activating pi donors: | -NH2, -OH, -OR, -NHCOCH3 |
| Name the activating sigma donors: | -R (alkyl), -BENZENE ring (aryl) |
| The most strongly _____ substituent will determine the position of the next substitution. | activating |
| The _____ Alkylation is the synthesis of alkylbenzenes from alkyl halides and a Lewis acid, usually AlCL3, HF, or BF3. | Friedel-Crafts |
| In the Friedel-Crafts Alkylation, reactions of alkyl halide with Lewis Acid produces a _________, which is the ___________. | carbocation; electrophile |
| Primary Friedel-Crafts Alkylation reactions usually undergo __________________. | hydride shifts |
| A Friedel-Crafts alkylation reaction will fail if benzene has a substituent that is more _____ than the ________. | deactivating; halogen |
| In a Friedel-Crafts acylation, the acylium ion intermediate is resonance stabilized and does not _______ like a _______. | rearrange; carbocation |
| The Friedel-Crafts acylation produces a phenyl _____ that is ____ reactive than benzene. | ketone; less |
| A Clemmensen Reduction is used for the synthesis of ___________. | Alkylbenzenes |
| Acylbenzenes can be converted to alkylbenzenes by treatment with __________ and _________. | aqueous HCl; Zn(Hg) |
| Straight-chain alkylation can be accomplished in 2 steps: _____________, then ___________. | acylation, reduction |
| In Nucleophilic aromatic substitution, a nucleophile replaces a ____________ on the aromatic ring. | leaving group |
| ________________ substituents activate the ring for nucleophilic substitution. | electron-withdrawing |
| In the Elemination-Addition Benzyne mechanism, the reactant is halobenzene with no ______________ on the ring. Use a very strong _______ like __________. | electron withdrawing groups; base; NaNH2 |
| Addition of chlorine to the benzene ring may occur with ________. The first Cl2 addition is ______, but the next two add _________. | Heat and pressure (or light); difficult; rapidly |
| What is required for Catalytic Hydrogenation and what are possible catalysts? | Elevated heat and pressure; Pt, Pd, Ni, Ru, Rh |
| In the Birch Reduction, a carbon with an ________ is reduced. However, a carbon with an ________ is not reduced. | Electron withdrawing group; electron releasing group |
| The Birch mechanism begins by forming ____________ using Na and __________. | solvated electrons; NH3 |
| In the Birch Mechanism, addition of an _____, followed by a _____, forms a radical. Addition of a second _________, followed by a ________, gives the product | (electron; proton) both times |
| Alkylbenzenes are oxidized to benzoic acid by ___________ or ______________. | Hot KMnO4 or Na2Cr2O7/H2SO4 |
| In side-chain halogenation, the ___________ position is the most reactive. | benzylic |
| In side-chain halogenation, _________ is not as selective as _______ and results in mixtures. | chlorination, bromination |
| In side-chain halogenation, Br2 reacts only at the ________ position. | Benzylic |
| Benzylic halides are 100 times _______ reactive than primary halides via Sn2 because the ___________ is stabilized by the ring. | more; transition |
| Phenols and phenoxides are (very?/slightly?) reactive. A (strong?/weak?) catalyst (HF) is required for Friedel-Crafts reaction. ___________ occurs without catalyst. | very; weak; tribromination |
| _________ double bonds are separated by one single bond. | Conjugated |
| _________ double bonds are separated by 2 or more single bonds. | Isolated |
| _________ double bonds are on adjacent carbons. | Cumulated |
| A compound with __________ double bonds is 3.7 kcal/mole more stable than one w/ _______ double bonds. | conjugated; isolated |
| The difference between the expected and actual heat of hydrogenation is the ______________. | Resonance Energy |
| In 1,3-Butadiene, the s-____ conformer is MORE stable than the s-_____ conformer. | Trans; cis |
| The carbon adjacent to C=C is _________. It is stabilized by _________. | allylic; resonance |
| In 1,2- and 1,4-Addition to conjugated dienes, _________ addition to the double bond produces the most stable intermediate. For conjugated dienes, the intermediate is stabilized by the ________. | electrophilic; allylic cation |
| In 1,2- and 1,4-Addition to conjugated dienes, the _________ adds to either carbon 2 or 4, both of which have the delocalized _______ charge. | nucleophile; positive |
| At low temperature, the 1-___ version HBr addition to butadiene dominates. This shows ________ control and is because ________. | 2; kinetic; HBr adds to a secondary allylic carbocation faster. |
| At high temperature, the 1-___ version HBr addition to butadiene dominates. This shows ________ control and is because ________. | 4; thermal; it is a more highly substituted and stable alkene |
| Allylic radicals are stabilized by _________. What is the radical stability trend? | 1'< 2' < 3' < 1' allylic |
| Substitution at the allylic position competes with _____ to the double bond. To encourage substitution, what should you use? | addition; use low concentration of reagent with light, heat, or peroxides to initiate free radical formation |
| ________ provides a low, constant concentration of Br2. It reacts with the ____ by-product to produce Br2 and prevent ____ addition. | NBS; HBr; HBr |
| The Diels-Alder reaction produces a _________. A _____ + _______ or _________. | diene; alkene or alkyne with electron-withdrawing group (dienophile) |
| A __________ is a compound containing a double bond that can react with a conjugated diene to give a Diels-Alder adduct. | dienophile |
| In a Diels-Alder transition state, the diene must be in a _____ conformation. | Cis |
| In a Diels-Alder transition state, the diene's ____ and ___ p orbitals must overlap with the dienophile's p orbitals to form new sigma bonds. Since both sigma bonds are on the same face of the diene, they show ___ stereochemistry. | C1; C4; syn |
| The Endo Rule states that the p orbitals of the _____________ groups on the ___________ have a secondary overlap with the p orbitals of C2 and C3. | electron-withdrawing; dienophile |
| In Diels-Alder reactions using unsymmetrical reagents, the 6-membered ring product will have electrong-donating and electron-withdrawing groups ___ and ___, but not ____. | 1,2; 1,4, NOT 1,3 |
| A __________ reaction takes place in a single step, without intermediates, and involves a cyclic redistribution of bonding electrons. | Pericyclic reaction |
| In Diels-Alder Reactions, the Diene (contributes?/receives?) electrons from its ______. | contributes; HOMO |
| In Diels-Alder Reactions, the Dienophile (contributes?/receives?) electrons from its _________. | receives; LUMO |
| Photochemical induction of cycloadditions is possible because absorption of correct energy photon will promote an electron to _______. | occupy a previously unoccupied energy level. |
| _____-____nm photons excited electrons from a pi bonding orbital to a pi* antibonding orbital. | 200-400 |
| A compound that has a longer chain of __________ double bonds absorbs light at a ________ wavelength. | conjugated; longer |
| Absorbance follows Beer's Law: ________ | A = ECl where E is the molar absorptivity, c is the sample concentration in moles per liter, and l is the length of the light path in centimeters |
| Isolated double bonds generally have UV aborptions in what range? | 170s-180s |
| Conjugated dienes generally have UV absorptions in what range? | 210s-260s |
| Conjugated Trienes generally have UV absorptions in what range? | 250-300s |
| Hydrogenation of one double bond in benzene is ____thermic. | endo |
| An _________ is a cyclic hydrocarbon with a continuous alternation of single and double bonds. | Annulene |
| Benzene has ____ bonding MOs and ___ antibonding MOs. In the ground state, the 6 pi electrons of benzene occupy what? | 3; 3; the 3 bonding MOs |
| The polygon rule states that MOs below the horizontal line through the center of a ring are ___ MOs, on the line are ___ MOs, and above the line are ____ MOs. | bonding; nonbonding; antibonding |
| To be aromatic, a compound must be ______, have one __ orbital on each atom of the ring, be ____ (or nearly) so there is continual overlap, and have a closed loop of _______ pi electrons. | cyclic; p; planar; 4N+2 |
| Antiaromatic compounds have all the properties of aromatic, except what? | The energy of the compound is GREATER than its open-chain counterpart. |
| Nonaromatic compounds do not have what? | A continuous ring of overlapping p orbitals, and may be nonplanar. |
| Huckel's Rule states that if the compound has a continuous ring of overlapping p orbitals and has 4N+2 electrons, it is _________. | aromatic |
| Huckel's Rule states that if the compound has a continuous ring of overlapping p orbitals and has 4N electrons, it is _________. | antiaromatic |
| Why isn't 10 Annulene aromatic even though it has 4N + 2 pi electrons? | It is not planar. |
| With a pKa of 16, cyclopentadiene is much more ____ than other hydrocarbons. | acidic |
| Cyclooctatetraene easily forms a ______, which makes it __________. | dianion; aromatic |
| Pyridine is a heterocyclic aromatic compound with a nonbonding pair of electrons in ____ orbital, making it a weak ____. | sp2; base |
| Pyrrole is __________, but the lone pair of electrons is delocalized, making it very ____ base, while a protonated version is a very ____ acid. | aromatic; weak; strong |
| Pyrimidine has ___ basic nitrogens and ____ nonbasic nitrogens. Imidazole has ___ basic nitrogens and ____ nonbasic nitrogens. Purines have ___ basic nitrogens and ___ nonbasic nitrogens. | (2; 0), (1;1), (3, 1) |
| Pyrrole (5 ring diene, 4 C, :N-H) has ___ pi electrons, Furan (5 ring diene, 4 C, :O:) has ___ pi electrons, and Thiophene (5 ring diene, 4C, :S:) has ___ pi electrons. | All of 6 pi electrons, all are aromatic |
| As the number of aromatic rings increases, the resonance energy per ring ____________, so (larger?/smaller?) polynuclear hydrocarbons will add Br2. | decreases; larger |
| Benzene + OH = _________; Benzene + CH3 = ________; Benzene + NH2 = __________ | Phenol; Toluene; Aniline |
| Benzene + OCH3 = _________; Benzene + CH=CH2 = _________; Benzene + C0CH3 = ___________ | Anisole; Styrene; Acetophenone |
| "_______" indicates the benzene ring attachment. "_______" indicates a benzene ring with an additional carbon. | Phenyl; benzyl |
| Benzene have ____ melting points than alkanes. Why? | higher; because they are more symmetrical and back better into crystals |
| Boiling points of Benzenes are dependent on _______. For disubsituted benzenes, what is the increasing trend of boiling point? | para < meta < ortho |
| Benzene rings are ____ dense than nonaromatics, ____ dense than water. | more; less |
| Benzenes show a C=C IR stretch at _______, a C-H stretch at ________, and an H NMR at _____. | 1600; ~3030; 7-8 |
| What is the common name for the 2-propenyl group, -CH2-CH=CH2? | Allyl group |
| What is the isomerization of a double bond that occurs through the delocalization of an allylic intermediate? | Allylic Shift |
| What is the theory of pericyclic reactions that states that the MOs of the reactants must flow smoothly into the MOs of the products, suggesting there must be bonding interactions that help stabilize the transition state? | Conservation of Orbital Symmetry |
| What is an overlap of orbitals that contributes to bonding? Generally referring to overlap of lobes with similar phases. | Constructive overlap |
| What is a reaction of two alkenes or polyenes to form a cyclic product? Often take place through concerted interaction of the pi electrons in two unsaturated molecules. | Cycloaddition |
| ________ is the overlap of the p orbitals of the electron-withdrawing group of the dienophile with those of one of the central atoms of the diene, helping to stabilize the transition state. With cyclic dienes, favors endo products. | Secondary overlap |
| What is an organic compound that is not aromatic? | Aliphatic |
| What are different forms of an element with different properties? | Allotropes |
| What is the aromatic group that remains after taking a hydrogen atom off an aromatic ring? | Aryl group |
| What are orbitals that have the same energy? | Degenerate |
| What is a cyclic compound in which one or more of the ring atoms is not carbon? | Heterocyclic |
| What is a substituent that makes the aromatic ring more reactive (usually toward electrophilic aromatic substitution) than benzene? | Activating group |
| What is a carbonyl group with an alkyl (R) group attached? | Acyl group |
| What is a substituent consisting of an alkyl group bonded through an oxygen atom? | alkoxy group |
| What is a reactive intermediate in some nucleophilic substitutions that can be drawn with a highly trained triple bond in the 6-membered ring? | Benzyne |
| What is a partial reduction of a benzene ring by sodium or lithium in liquid ammonia? The products are usually 1,4-cyclohexadienes | Birch Reduction |
| What is the replacement of a hydrogen on an aromatic ring by a strong electrophile? | Electrophilic aromatic substitution |
| What is stabilization of a reactive intermediate by donation or withdrawal of electron density through sigma bonds? | Inductive stabilization |
| What is the replacement of a hydrogen atom by a nitro-group? | Nitration |
| What is the replacement of a leaving group on an aromatic ring by a strong nucleophile? Usually takes place by an addition-elimination mechanism or by a benzyne mechanism. | Nucleophilic aromatic substitution |
| What is an intermediate in electrophilic aromatic substitution or nucelophilic aromatic substitution with a sigma bond between the electrophile or nucleophile and the former aromatic ring? | Sigma complex |
| The sigma complex bears a delocalized ________ charge in electrophilic aromatic substitution, and a delocalized _________ charge in nucleophilic aromatic substitution. | positive; negative |
Created by:
jgold37