311Exam1Key2012 - CHE 311 EXAM 1 KEY(Ch 1-4 Answers in BOLD...

This preview shows page 1 out of 3 pages.

Unformatted text preview: CHE 311 EXAM 1 KEY(Ch. 1-­‐4) Answers in BOLD RED Multiple Choice(60%; 2% each) Please mark the letter of the BEST answer to each question clearly on your answer sheet. Thanks! 1. Which of the following substances is most likely to have ionic bonding between the atoms that form it? a. CH3OH b. BBr3 c. KF d. SeBr2 2. Carbon displays many types of bonding in its millions of compounds. Which statement is true of carbon? a. it forms four bonds b. it rarely forms multiple bonds c. C-­‐to-­‐F bonds are weak d. C-­‐to-­‐C bonds are weak 3. Which of the following species has a negative formal charge on at least one of its atoms? Answer a O a.((((((((((((((((((((((((((((((b.(((((((((((((((((((((((((((c.(((((((((((((((((((((((((((((((((((((d. N CH3 C N 4. O Among Klein’s rules & examples of resonance electron arrow errors, which of these is acceptable? Answer a O a. moving electrons like this: c. moving electrons like this: b. moving a bond like this: d. moving an atom like this: O O H 5. Which is a molecule that is likely to have a significant dipole moment? a. CO2 b. CH3Cl c. CCl4 6. How many structural (constitutional) isomers of C3H4 would there be? a. 3 b. 2 c. 4 d. only 1 7. What orbitals are overlapping to form the C–C bond of ethane, using the usual valence bond concepts? a. 2s + 2p b. 2 x 2p c. 2 x sp3 d. 2 x sp2 8. Which of these is a constitutional isomer of hexane? a. 3-­‐methylpentane b. cyclohexane c. 2,2-­‐dimethylpropane d. 1,4-­‐dimethylbutane 9. The main intermolecular forces in pure alkanes are a. dipole-­‐dipole b. London (dispersion) c. dipole-­‐induced dipole d. hydrogen bonding 10. Incomplete combustion of hydrocarbons produces a. CO or soot b. CO2 c. H2O2 d. alcohols 11. The balanced equation for the complete combustion of nonane requires _____ moles of O2 per mole of nonane. a. 18 b. 12 c. 16 d. 14 12. The sp hybridization of carbon is required to explain the bonding of _____________ in valence bond theory. a. benzene b. alkynes c. alkenes d. cycloalkenes 13. All of the following are isomers of C8H18; when burned fully, which gives off the most energy? Answer b d. CH4 a.########################################################b.#####################################################################c.#################################################d. 14. What is the oxidation state of carbon in CHCl3 ? a. +1 b. –1 c. –2 d. +2 15. Which type of strain is still present in a chair-­‐conformer cyclohexane? a. angle strain b. torsional strain c. van der Waals strain 16. Looking down the C2-­‐C3 bond, which Newman projection is the most stable 2-­‐methylbutane conformer? d H H H CH3 H CH3 H H H CH3 a.##################################################b.############################################c.############################################d. CH3 CH3 H3C CH3 H3C CH3 H3C H H CH3 CH3 H H H d. bond length distortion CHE 311 Exam 1 Page 2 17. What is the main energy factor that makes an eclipsed conformer less stable than a similar staggered one? a. bond length distortion b. van der Waals strain c. hydrogen bonding d. torsional strain 18. The only truly planar cycloalkane is a. cyclohexane b. cyclobutane 19. Cyclopentane reduces its strains by taking one of two conformations: the envelope and the a. half-­‐chair b. twist chair c. bent pentagon d. full boat 20. The most stable conformer of cis-­‐1,3-­‐dimethylcyclohexane has the methyl groups a. both equatorial b. both axial c. axial and equatorial d. staggered and gauche 21. All spiro-­‐compounds contain _______ rings fused at _________ carbon atom(s). a. 2 ; 1 b. 2 ; 2 c. 2 ; 3 22. Which of the following has a bicyclo[3.2.1] ring system? Answer b c. cyclooctane d. cyclopropane d. 3 ; 3 a.##################################################b.############################################c.############################################d. 23. The proper IUPAC name for (CH3)2CHCH2CH2CH2OH would be a. 4,4-­‐dimethyl-­‐1-­‐butanol b. 4-­‐methyl-­‐1-­‐pentanol c. 1,1-­‐dimethyl-­‐4-­‐butanol d. 3-­‐isopropyl-­‐1-­‐propanol 24. Which reagent will be best to convert 2-­‐butanol to 2-­‐bromobutane? a. NaBr b. CaBr2 c. Br2 in CCl4 25. What combination of reagents is used to identify whether an alcohol is 1°, 2, or 3°? a. KBr + H2SO4 b. ZnCl2 + HCl c. Na + F2 d. NaNH2 + H2O 26. Which alcohol is most likely to react with HBr in a reaction involving formation of a carbocation? a. ethanol b. 2-­‐methyl-­‐2-­‐butanol c. 2-­‐butanol d. methanol 27. Which of these alcohols is most likely to react only via an SN2 reaction mechanism? a. ethanol b. 2-­‐methyl-­‐2-­‐butanol c. 2-­‐butanol d. 2-­‐propanol 28. The nucleophile in the substitution reaction of 2-­‐butanol with HCl is a. Cl– ion b. H3O+ ion c. OH– d. H2O 29. A good alternative to HCl for the conversion of alcohols into alkyl chlorides is a. SOCl2 b. NaCl c. AlCl3 d. Cl2 30. When you brominate 2-­‐methylbutane using Br2, the most common monobromination product should be a. 1-­‐bromo-­‐3-­‐methylbutane b. 2-­‐bromo-­‐3-­‐methylbutane c. 1-­‐bromo-­‐2-­‐methylbutane d. 2-­‐bromo-­‐2-­‐methylbutane Problems on next page… d. HBr + heat CHE 311 Exam 1 Page 3 Problems(40%; 20% each) SHOW WORK as requested for each problem: I. Draw both chair conformations of the compound shown below*. Be sure that the axial and equatorial locations of each hydrogen and other substituent are clearly shown in their proper locations and state if one of the two chairs is more stable than the other, with a brief explanation of why. CH3 H H H H CH3 H H H H H H3CH2C H H H H CH3 H H H H H MORE%STABLE: both%groups%are%equatorial CH2CH3 H CH2CH3 H II. GIVE THE STEPS in the mechanism of the reaction shown below, which has been found to be an SN1 reaction under the conditions in which it is run. This means you need to show the structures of any intermediates and use ‘curved arrows’ to indicate electron movement in the steps of the mechanism. CH3 conc.)HBr,)85°C CH3 OH Br DO NOT draw on these structures CH3 CH3 O H O H H Br CH3 –(H2O H The(basic(mechanism(must(show(protonation(to(form incipient(water,(loss(of(water(to(form(the(carbocation, and(attack(by(bromide(to(form(the(alkyl(halide(product. Br– CH3 Br * Note that the structure drawn is NOT a chair conformation as drawn; it just gives the groups and that they are trans. ...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern