Choice the best choice for the following questions: 1. In the planar conformatio

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Choice the best choice for the following questions: 1. In the planar conformation of 1, 3- butadiene, the electrondensity in the conjugated system is a. localized within each individual pi bond b. localized between each pi bond c. delocalized over the entire molecule d. indeterminate due to the Heizenberg uncertaintyprinciple e. none of these descriptions is accurate 2. The resonance energy of a system is best decribedas... a. the additional energy required to resonate a + or a- chargeover several atoms b. the additional stability which arises when conjugation ispresent in a molecule c. the additional energy required for alternate pi systems tocommunicate with each other d. the amount of stabilization which is lost when electrons are delocalized over atoms other than the carbons wherethe double bonds were originally assigned e. none of these descriptions is accurate 3. Which statement below best explains why Sn2 reactionson allyl bronide proceed forty times faster than correspondingreactions on ethyl bromide? a. allylic systems are generally less hindered, thus have lesssteric congestion at the transition state, which leads to a fasterrate b. the pi bond in allylic Sn2 reactions provides additionalelectron density to the sytem which makes the leaving roup morelabile to detachment, thus increasing the rate. c. when the substrate is allylic, resonance stabilizationthrough conjugation with the adjacent pi bond occurs in thetransition state. This delocalization lowers the energy ofthe transition state resulting in an enhanced rate. d. bromine leaves the allylic system in the Sn2, as a radical,thus one energetically huge step is already accomplished inadvance. This enhances rate. e. Allylic pi bonds form a complex with the solvent inan Sn2 reaction, lowering the overall energy of the system,including the energy of activation. Thus the collision energyof the nucleophile is considerably lowered and the rateincreased. 4. Benzene undergoes a substiution reaction with br2 whilecyclohexene undergoes an addition reaction beacuse... a. Cyclohexene is an isolate pi system, benzene is a conjugatesystem b. addition of Br2 to benzene would result in the destructionof aromaticity c. Substitution of Br for H allows for preservation of thearomatic conjugated ring syster, while addition does not. d. All of the above are valid reasons e. none of the above are valid reasons 5. In electrophilic aromatic substituion reactions, thehydroxyl moeity is an ortho/ para- director becuase a. It donates e- density to the ring by induction anddestabilizes the meta- sigma complex b. it donates e- density tot eh ring by resonance andstabilizes the ortho/ para- sigma complex c. it donates e- density to the ring by induction anddestabilizes the ortho/ para - sigma complex d. it donates e- density to the ring by resonance anddestabilizes the meta- sigma complex e. it withdraws e- density from the ring by induction anddestabilizes the meta- sigma complex Choice the best choice for the following questions: 1. In the planar conformation of 1, 3- butadiene, the electrondensity in the conjugated system is a. localized within each individual pi bond b. localized between each pi bond c. delocalized over the entire molecule d. indeterminate due to the Heizenberg uncertaintyprinciple e. none of these descriptions is accurate 2. The resonance energy of a system is best decribedas... a. the additional energy required to resonate a + or a- chargeover several atoms b. the additional stability which arises when conjugation ispresent in a molecule c. the additional energy required for alternate pi systems tocommunicate with each other d. the amount of stabilization which is lost when electrons are delocalized over atoms other than the carbons wherethe double bonds were originally assigned e. none of these descriptions is accurate 3. Which statement below best explains why Sn2 reactionson allyl bronide proceed forty times faster than correspondingreactions on ethyl bromide? a. allylic systems are generally less hindered, thus have lesssteric congestion at the transition state, which leads to a fasterrate b. the pi bond in allylic Sn2 reactions provides additionalelectron density to the sytem which makes the leaving roup morelabile to detachment, thus increasing the rate. c. when the substrate is allylic, resonance stabilizationthrough conjugation with the adjacent pi bond occurs in thetransition state. This delocalization lowers the energy ofthe transition state resulting in an enhanced rate. d. bromine leaves the allylic system in the Sn2, as a radical,thus one energetically huge step is already accomplished inadvance. This enhances rate. e. Allylic pi bonds form a complex with the solvent inan Sn2 reaction, lowering the overall energy of the system,including the energy of activation. Thus the collision energyof the nucleophile is considerably lowered and the rateincreased. 4. Benzene undergoes a substiution reaction with br2 whilecyclohexene undergoes an addition reaction beacuse... a. Cyclohexene is an isolate pi system, benzene is a conjugatesystem b. addition of Br2 to benzene would result in the destructionof aromaticity c. Substitution of Br for H allows for preservation of thearomatic conjugated ring syster, while addition does not. d. All of the above are valid reasons e. none of the above are valid reasons 5. In electrophilic aromatic substituion reactions, thehydroxyl moeity is an ortho/ para- director becuase a. It donates e- density to the ring by induction anddestabilizes the meta- sigma complex b. it donates e- density tot eh ring by resonance andstabilizes the ortho/ para- sigma complex c. it donates e- density to the ring by induction anddestabilizes the ortho/ para - sigma complex d. it donates e- density to the ring by resonance anddestabilizes the meta- sigma complex e. it withdraws e- density from the ring by induction anddestabilizes the meta- sigma complex

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