北京化工大学：《有机化学》课程教学资源（章节测验，含答案）Chapter 04 Cycloalkanes

1.What would be the name of the following? 5-cyclopentyl-1-methyleyclononane cis-1-cyclopentyl-5-methylcyclodecane cis-5-methyl-1-cyclopentylcyclododecane trans-cyclopentyl-5-methylcyclodecane (5-methylcyclodecyl)cyclopentane Ans: A)cis-1,2-dimethylcyclohexane trans-1,3-dimethylcyclohexane cis-1.4-dimethyleyclohexane Ans: 3.Terpenes can be considered to be built up from what units? c) D) E) Ans:

Page 1 1. What would be the name of the following? CH3 A) 5-cyclopentyl-1-methylcyclononane B) cis-1-cyclopentyl-5-methylcyclodecane C) cis-5-methyl-1-cyclopentylcyclododecane D) trans-cyclopentyl-5-methylcyclodecane E) (5-methylcyclodecyl)cyclopentane Ans: B 2. Which of the following isomers would you expect to have the lowest heat of combustion? (i.e., be most stable) A) cis-1,2-dimethylcyclohexane B) trans-1,3-dimethylcyclohexane C) cis-1,4-dimethylcyclohexane D) cis-1,3-dimethylcyclohexane E) All should have the same heat of combustion. Ans: D 3. Terpenes can be considered to be built up from what units? A) B) C) D) E) Ans: E

4.Which of the following compounds has the highest heat of combustion per CH cyclohexane B) 5.What is the correct IUPAC name for the following molecule: A)1-ethyl-2-methylhexane D)1-ethyl-2-methylcyclohexane 2-ethyl-1-methylcycloheptane Ans: Dethyl-5-methyleyeloe E)1-methyloctane CH(CH3) 3) 9 aa H.C D) CH(CH3). A CH(CH3) Ans:E Page2

Page 2 4. Which of the following compounds has the highest heat of combustion per CH2 group? A) cyclopropane D) cyclohexane B) cyclobutane E) All have equal ΔHcombustion. C) cyclopentane Ans: A 5. What is the correct IUPAC name for the following molecule: A) 1-ethyl-2-methylhexane D) 1-ethyl-2-methylcyclohexane B) 2-ethyl-1-methylcycloheptane E) 1-methyloctane C) 4-ethyl-5-methylcyclohexane Ans: D 6. Which would be the most stable conformation of trans-1-methyl-3-isopropylcyclohexane? A) CH(CH3) H 2 H3C H B) CH(CH3) CH 2 3 H H C) CH(CH3)2 H H3C H D) CH(CH3)2 H CH3 H E) CH H 3 H CH(CH3)2 Ans: E

7.Which one of the following cyclic alkanes has the greatest tendency to have a planar cyclohexan none of the above are planar Ans:A 8.What would be the proper name of the following: (C)3C 才H cis-1-tert-butyl-4-methylcyclohexane trans-1-tert-butyl-4-methylcyclohexane axial.equatorial-1-tert-butyl-4-methylcyclohexane cis-1-isopropyl-4-methylcyclohexane opopy-meyleyclohe 9.The most stable conformation of cis 1.3-dimethylcyclohexane has how many hydrogen atoms in axial positions? A)4 B)5 C)6 D)8 E)none of the above Ans:C 10.Which of the following stituted cyclohexanes could exist in a conformation is-4-dimethylcyclohexane trans-1,3-dimethylcyclohexane cis-1,2-dimethylcyclohexane E) All or none can have both groups equatorial s:A Page 3

Page 3 7. Which one of the following cyclic alkanes has the greatest tendency to have a planar ring? A) cyclopropane D) cyclohexane B) cyclobutane E) none of the above are planar C) cyclopentane Ans: A 8. What would be the proper name of the following: CH3 H H (CH3)3C A) cis-1-tert-butyl-4-methylcyclohexane B) trans-1-tert-butyl-4-methylcyclohexane C) axial,equatorial-1-tert-butyl-4-methylcyclohexane D) cis-1-isopropyl-4-methylcyclohexane E) trans-1-isopropyl-4-methylcyclohexane Ans: A 9. The most stable conformation of cis 1,3-dimethylcyclohexane has how many hydrogen atoms in axial positions? A) 4 B) 5 C) 6 D) 8 E) none of the above Ans: C 10. Which of the following disubstituted cyclohexanes could exist in a conformation that has both groups equatorial? A) cis-1,3-dimethylcyclohexane B) cis-1,4-dimethylcyclohexane C) trans-1,3-dimethylcyclohexane D) cis-1,2-dimethylcyclohexane E) All or none can have both groups equatorial. Ans: A

11. 0v O C) n Done of the above Page

Page 4 11. Which of the following correctly represents cyclopropylcyclohexane? A) B) C) D) E) none of the above Ans: D

hichth olngng systems belongs to the class of compounds calld strod Page 5

Page 5 12. Which of the following ring systems belongs to the class of compounds called steroids? A) B) C) D) E) Ans: B

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Page 6 13. Which of the following could be classified as a terpene? A) B) CHO C) O D) O E) O Ans: E

14.Which of the following could have both methyl groups in an equatorial orientation? Ans:B 15.Which of the following compounds has the lowest heat of combustion per CH2 group? A)cyclopropane cyclobutane

Page 7 14. Which of the following could have both methyl groups in an equatorial orientation? A) CH3 CH3 B) CH3 CH3 C) CH3 CH3 D) H3C CH3 E) CH3 H3C Ans: B 15. Which of the following compounds has the lowest heat of combustion per CH2 group? A) cyclopropane D) cyclohexane B) cyclobutane E) All have equal ΔHcombustion. C) cyclopentane Ans: D

Which,if either,of the two isomers of the compound shown below would be more (trans) (cis) Cis is more stable Neither is stable. rans is more stable There is no way to predict this oth are equally stable 17.Although five-and six-membered rings are generally the most stable,why is cyclopentane less stable than cyclohexane? A) The angles in cyclopentane deviate significantly from the tetrahedral angle. Five-membered rings have trans annular interactions. red rings have eclipsing hydrogen o s closer to 109 ns 18.Which of the following correctly shows the Newman projection along a C-C bond in cyclohexane?(the squiggles indicate where the rest of the ring is attached) CH2 H CH A H, CH-Z E AB)B C)C D)DE Page 8

Page 8 16. Which, if either, of the two isomers of the compound shown below would be more stable? (trans) (cis) A) Cis is more stable. D) Neither is stable. B) Trans is more stable. E) There is no way to predict this. C) Both are equally stable. Ans: B 17. Although five- and six-membered rings are generally the most stable, why is cyclopentane less stable than cyclohexane? A) The angles in cyclopentane deviate significantly from the tetrahedral angle. B) Five-membered rings have trans annular interactions. C) Five-membered rings have eclipsing hydrogens. D) Planar cyclohexane has bond angles closer to 109°. E) Larger rings are always more stable than smaller rings. Ans: C 18. Which of the following correctly shows the Newman projection along a C-C bond in cyclohexane? (the squiggles indicate where the rest of the ring is attached) H CH H 2 H CH H 2 H H H H CH2 CH2 H H CH2 H CH2 H H H H H CH CH2 2 H H H CH2 CH2 H A BC D E A) A B) B C) C D) D E) E Ans: D

19.Which of the following cyclic alkanes can be ring-opened under hydrogenation conditions H, eyelic hydrocarbon linear hydrocarbon Pd A)cyclopropane D)cyclohexane cyclobutane E)more than one of these C cyclopentane Ans: 20.Which of the following statements about conformations of methyleyelohexane is true? CHs AN CH A)The energy barrier to interconvert these is too high to be achieved at room temperature. 9 The two forms are in equilibrium and are present in equal amounts at room temperature. The two forms are not in equilibrium but are present in equal amounts at room D) emperatu ms are in equilibrium but are not present in equal amounts at room atur E)The two forms are not in equilibrium and are not present in equal amounts at room temperature. Ans:D 21.Cyclohexanes exhibit a higher than their straight-chain analogs.(Choose the D) All of these R e are co of the se are correc Ans:D .Which conformation of cyclohexane exprinc thmon A) Chair B)Planar C)Boat E)All of these are Page 9

Page 9 19. Which of the following cyclic alkanes can be ring-opened under hydrogenation conditions? cyclic hydrocarbon H2 Pd linear hydrocarbon A) cyclopropane D) cyclohexane B) cyclobutane E) more than one of these C) cyclopentane Ans: E 20. Which of the following statements about conformations of methylcyclohexane is true? CH3 CH3 A) The energy barrier to interconvert these is too high to be achieved at room temperature. B) The two forms are in equilibrium and are present in equal amounts at room temperature. C) The two forms are not in equilibrium but are present in equal amounts at room temperature. D) The two forms are in equilibrium but are not present in equal amounts at room temperature. E) The two forms are not in equilibrium and are not present in equal amounts at room temperature. Ans: D 21. Cyclohexanes exhibit a higher_______than their straight-chain analogs. (Choose the correct answer) A) boiling point D) All of these are correct. B) melting point E) Two of these are correct. C) density Ans: D 22. Which conformation of cyclohexane experiences the most transannular strain? A) Chair B) Planar C) Boat D) Twist boat E) All of these are stable. Ans: C

23.Which of the following is o in its most stable conformation? h C D E)All of these are in their most stable conformation. Ans:A 24.What isthe poteial energy changeo fromstbomaion? 45 Kcal/mol Ans:C 25.Which of the following structures represent cis-1,4-dimethyleyclohexane? H CHa A)I&ⅡB)I&llC)Ⅱ&lⅢlD)all of the above E)none of the above Ans:B Page 10

Page 10 23. Which of the following is not in its most stable conformation? A) Cl CH3 B) I CH2CH3 C) H3C OCH3 D) HOOC Br E) All of these are in their most stable conformation. Ans: A 24. What is the potential energy change to convert from a twist-boat to boat conformation? A) –14 Kcal/mol D) 14 Kcal/mol B) 0 Kcal/mol E) 45 Kcal/mol C) 1.4 Kcal/mol Ans: C 25. Which of the following structures represent cis-1,4-dimethylcyclohexane? H CH3 CH3 H I CH3 H CH3 H II CH3 H H H3C III A) I & II B) I & III C) II & III D) all of the above E) none of the above Ans: B