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SAMPLE ORGANIC CHEM 2423 EXAM #1( Ch. 1-4) DIRECTIONS- Please answer all questions in the space provided as completely and clearly as possible. Show all your work for the writing portions of the exam. PART I- Multiple Choice (3 points each) ____1. How would you best describe the C-C bonds in H3C-CH2-CH3? A. sp3-sp B. sp2-sp3 C. sp3-sp3 D. sp-sp ____2. Which of the following molecules contains an sp-hybrized N-atom? B. NH4+ A. NH3 C. CH3NH2 D. HCN ____3. Which of the following statement is(are) correct? A. the maximum number of electrons possible for a set of p-orbitals is 6? B. the ground state electron configuration of carbon 1s2 2s2 2px1 2py1 2pz0 . C. the total number of bonding electron pairs in BF3 is 3. D. All of these ____4. What is the formal charge on the N-atom in nitromethane, CH3NO2, in the most important resonance forms of this molecule? B. –2 A. +1 C. –1 D. +2 ____5.Which one of the following notations does not represent an acceptable condensed structural formula of propanol, C3H8O? A. CH3-CH2-CH2OH C. CH3-CH2-CH2-O-H B. CH3-CH2-CH2-OH D. CH3CH2CH2OH ____6. Which is the correct order of increasing bond polarity? (Consider the electronegativities of the halogens.) A. H-F < H-Cl > H-Br > H-I C. H-F > H-Cl < H-Br < H-I B. H-F < H-Cl < H-Br < H-I D. HI < H-Br < H-Cl <H-F ____ 7. Which of the following conformation is the most stable conformation of butane, view the molecule from the central carbons? CH3 H H H A. I only H CH3 CH3 H H H CH3 H H CH3 CH3 H H I II III B. II only C. III only H D. all of these ____ 8. Which of the following cyclohexane conformation is(are) consider to be cis conformation? A. I only III II I B. II only C. I and II D. I, II, and III ____ 9. What is the IUPAC name of neopentane? A. 2-methyl-butane C. 1,1-dimethylpropane B. 3-methyl-butane D. 2,2-dimethylpropane ____10. Which structure is tert.-butyl bromide? A. Br-CH(CH3)-CH2-CH3 C. Br-CH2-CH(CH3)2 B. Br-C(CH3)3 D. Br-C(CH3)2-CH2-CH3 ____11. Which one of the alkanes would you suspect to have the lowest boiling point? A. 2-methylpropane B. pentane C. nonane D. butane ____ 12. Which reaction describes the complete combustion of propane? A. B. C. D. C3H8 + 5 O2 C3H8 + 3 O2 C3H8 + 3.5 O2 C3H8 + 4.5 O2 3 CO2 + 4 H2O 3 CO2 + 3 H2O 3 CO + 4 H2O 3 CO2 + 3 H2O ____13. Which conformation of cyclohexane corresponds to the most stable structure? A. half chair B. chair C. twist-chair D. none of these ____14. Name the compound CH3-C(CH3)2-CClH-CH3 according to IUPAC nomenclature. A. 3-chloro-1,2-dimethylbutane C. 3-chloro-2,2-diethylbutane B. 3-chloro-2,2-dimethylbutane D. 2-chloro-3,3-dimethylbutane ____15.What is the barrier to rotation about the C-C bond in ethane? A. about 1.0 kcal/mol C. about 2.0 kcal/mol B. about 3.0 kcal/mol D. about 2.5 kcal/mol ____16. An axial methyl group in cyclohexane suffers from what disadvantage? A. one 1,3-diaxial interactions C. two 1,3-diaxial interactions B. two 1,2-diaxial interactions D. one 1,2-diaxial interactions ____17. Among the following pairs of isomers, identify the pair of constitutional isomers. A. neopentane and isopentane B. isobutane and 2-methylpentane C. neopentane and isobutane D. isopentane and 2,2-dimethylbutane ____18. How many tertiary hydrogen atoms are there in Cl-CH2-C(CH3)2-CH(CH3)-C(CH3)3? A. 6 B.3 C. 2 D. 1 ____19. Consider the structure of trans-1,4-dimethylcyclohexane. Which statement is fully correct? A. B. C. D. Trans methyl groups favor chair and both are equatorial. Trans methyl groups favor chair and both are axial. Trans methyl groups favor twist-boat conformation. Trans methyl groups favor chair and are axial and equatorial. ____20. Which statement is written incorrectly? A. B. C. D. Acetic acid (pKa =4.73) is stronger acid than water(pKa =15.75). The conjugate acid to (CH3)3N: is (CH3)3NH+. An electron pair donor substance considers being a Lewis acid. The stronger the acid, the weaker the conjugate base. PART II- Show your work (8 points each) 21. Naming and Structures CH3CH2 _______________________________ cis- 1-ethyl-3-methylcyclohexane CH3 __________________________________ 5-ethyl-4-isopropyldecane 22. Draw all the possible resonances (at least two) for the following compound: CH3 .. 23. Identify the functional groups in the following compound and name each functional group. CO - O - CH2 -CH3 O - CH = CH3 24. Complete the following reactions and write the major products. a) CH3 - CH2 - CH - CH3 + O2 CH3 + b) Cl2 / light CH3 c) + O2 + d) Cl2 /light 25. Given that Ka for HCN is 4.9x10 –10 and Ka for water 1.80x10-16, will the following reaction occur? (will the products be favored at equilibrium?). Please explain for complete credit. HCN + OH- ? CN - + H2O BONUS Question(10 points)- Show all your work. Please draw five isomers (constitutional or/and geometrical) of cyclobutane derivatives of the formula C5H9Cl. Please name each isomer. ORGANIC CHEM 2423 EXAM #1 ( Answers) 1. C 2. D 3. D 4. A 5. C 6. D 7. A 8. A 9. D 10. B 11. A 12. A 13. B 14. B 15. B 16. C 17. A 18. D 19. A 20. C trans –1-ethyl-3- methylcyclohexane 21. Naming: 3,4-diethyloctane Structures : CH2CH3 CH3 22. CH3 CH3 CH3 .. .. .. 23. CO - O - CH2 - CH3 ester alkene O - CH = CH2 ether aromatic 24. a) CH3 - CH2 - CH - CH3 + 8 O2 5 CO2 + 6 H2O CH3 + HCl + Cl2 /light b) CH3 CH3 Cl c) d) + 6 O2 4 CO2 + 4 H2O + Cl2 /light Cl 25. K = Ka (reactant acid) / Ka(product acid) = (4.9x10 -10)/(1.80x110 -16) = 2.72x106 > 1.0 products will be favored () Cl Cl CH3 CH3 cis-1-chloro-2-methylcyclobutane 1-chloro-1-methylcyclobutane CH3 CH3 trans-1-chloro-2-methylcyclobutane Cl Cl CH3 cis -1-chloro-3-methylcyclobutane Cl trans-1-chloro-3-methylcyclobutane