Molecular Orbitals - Worksheets

Worksheet 1. 2. 3. 4. 5. 6. 7. The Stability of the Allyl Radical The Allyl Cation Alkadienes & Polyunsaturated Hydrocarbons 1,3-Butadiene: Electron Delocalization The Stability of Conjugated Dienes Electrophilic Attack on Conjugated Dienes: 1,2 and 1,4-Addition The Diels–Alder Reaction: a 1,4-Cycloaddition Reaction of Dienes 1) 1,3-Butadiene has how many electrons in its ground state bonding  molecular orbitals? a) 1 b) 2 c) 3 d) 4 e) 0 Answer: D 2) 1,3-Butadiene has how many electrons in its ground state antibonding  molecular orbitals? a) 1 b) 2 c) 3 d) 4 e) 0 Answer: E 3) Which carbocation would be least stable? 1 I II IV III a) I b) II c) III d) IV e) V Answer: E 4) Which carbocation would be most stable? a) b) c) d) e) Answer: C 5) Which carbocation would be least stable? a) b) c) 2 V d) e) Answer: D 6) Which carbocation would be most stable? a) I b) II c) III d) IV e) V Answer: C 7) Which of the following compounds would be the most stable? I II III IV a) I b) II c) III d) IV e) They are all of equal stability. Answer: A 8) Which diene would be least stable? 3 I II III IV V a) I b) II c) III d) IV e) V Answer: C 9) Which alkene would you expect to be most stable? a) CH2=CHCH2CH2CH=CH2 CH2 CHCH2 H C H CH3 CH2CH CH2 b) CH3 C c) C H H H CH3 C d) C H C C C H CH3 CH3 H H C H H C H e) C C CH3 Answer: E 10) Arrange these hexadienes in order of expected decreasing stability. I II IV III V a) V > II > I > III > IV b) III > IV > II > I > V c) IV > III > II > V > I d) IV > III > I > II > V 4 e) I > II > IV > III > V Answer: D 11) Arrange these hexadienes in order of expected increasing stability. I II III IV V a) V < II < I < III < IV b) III < IV < II < I < V c) IV < III < II < V < I d) IV < III < I < II < V e) I < II < IV < III < V Answer: A 12) Select the structure of the conjugated diene. II I IV III V a) I b) II c) III d) IV e) V Answer: C 5 13) Select the structure of the isolated diene. III II I IV V a) I b) II c) III d) IV e) V Answer: D 14) Keeping in mind stereochemistry, how many products are formed by the reaction of one equivalent of HBr with 2-methyl-1,3-cyclohexadiene? a) 2 b) 4 c) 6 d) 8 e) 10 Answer: C 15) The accompanying diagram, which describes the fate of the intermediate in a reversible reaction, implies that: 6 a) the less stable product forms more rapidly. b) the more stable product forms more rapidly. c) product B will predominate at equilibrium. d) the intermediate has a short lifetime. e) No conclusions can be drawn as to either reaction rate or product stability. Answer: A 16) Draw the structure of major product when the following molecule is treated with HCl at room temperature. 7 15) The accompanying diagram implies that: E B A reaction coordinate a) the formation of A from B would be favored at high temperature. b) the more stable product forms more rapidly from the intermediate species. c) the formation of B from the intermediate is the rate-limiting step in the transformation of A into B d) the formation of B from A is not a concerted reaction. e) All of these statements are true. Answer: E 16) Which of these dienes can undergo the Diels-Alder reaction? a) b) c) d) e) All of these choices can undergo the Diels-Alder reaction. Answer: A 8 17) From the standpoint of reactivity, which is the poorest choice of dienophile to react with 2,3dimethyl-1,3-butadiene in a Diels-Alder reaction? O O I O II H3CO III O O H3CO O OCH3 OCH3 O IV V a) I b) II c) III d) IV e) V Answer: B 18) What is the product of the following reaction? CH CH2 O + CH3C O C C ? CCH3 COCH3 COCH3 COCH3 COCH3 COCH3 COCH3 I II III COCH3 COCH3 COCH3 COCH3 IV V a) I b) II 9 c) III d) IV e) V Answer: A 19) Which reaction would produce the following compound? a) I b) II c) III d) IV e) None of these choices. Answer: B 10 20) Which reaction would produce the following compound? a) I b) II c) III d) IV e) None of these choices. Answer: D 11 21) Which of the following pairs of compounds could be used as the basis for a Diels-Alder synthesis of the compound shown below? CO2CH3 CO2CH3 I 2 CH3CH CHCH3 II III + CH3CH CH2 + CH2 CHCO2CH 3 + CO2CH 3 IV + CH2 CHCO2CH 3 a) I b) II c) III d) IV e) More than one of these choices. Answer: D 12