Solved Practice Exam 5 FA24 Organic Chemistry PDF

# Practice Exam 5 - Fall 2024 ## Multiple Choice 1. Which of the following statements is NOT correct about benzene? - The carbon-carbon bonds have the same length. - It has delocalized electrons. - All of the carbon atoms are *sp²* hybridized. - The carbon-hydrogen bonds...

# Practice Exam 5 - Fall 2024 ## Multiple Choice 1. Which of the following statements is NOT correct about benzene? - The carbon-carbon bonds have the same length. - It has delocalized electrons. - All of the carbon atoms are *sp²* hybridized. - The carbon-hydrogen bonds have the same length. - All twelve atoms lie in the same plane. 2. Nitrogen's lone pair electrons occupy what type of orbital in pyridine? - *s* - *sp²* - *p* - *sp³* - *sp* 3. Which of the following structures, if planar, would be classified as antiaromatic? - **A)** - Aromatic - 6πe - **B)** - Aromatic - 6πe - **C)** - Non Aromatic - sp - **D)** - 6πe - Aromatic - **E)** - 8πe - Anti Aromatic 4. Rank the following in order of increasing *pK*_*a* (from lowest to highest *pK*_*a*). - **Most acidic** - *pK*_*a* ~ 0.4 - **Least acidic** - *pK*_*a* ~ 11 - **Conversely* *ak*_*5**_*2**_*9*** - *pK*_*b* ~ 3 - **Stronger base** - *pK*_*a* ~ 5 - **Weakest base** - *pK*_*a* ~ 13.6 5. Which of the following is aromatic? - cyclopentadienyl cation - cycloheptatrienyl cation - 1,3-cyclohexadiene - cyclobutenyl anion - 1,3,5-hexatriene 6. Which of the following is aromatic? - **A)** - 6πe - **B)** - 12πe - **C)** - 8πe - **D)** - 4πe 7. Which compound below is phenol? - **a)** *NH*_*2* - **b)** *OCH*_*3* - **c)** *CH*_*3* - **d)** *OH* 8. Which sequence correctly ranks the following aromatic rings in order of increasing rate of reactivity in an electrophilic aromatic substitution reaction? - **1)** *CH*_*3* - **2)** *OCH*_*3* - **3)** *CHO* 9. In electrophilic aromatic substitution reactions the nitro group is - a *m*-director since it destabilizes the meta sigma complex more than the *ortho*, *para* - an *o*,*p*-director since it stabilizes the *ortho*, *para* sigma complex more than the *meta* - a *m*-director since it destabilizes the *meta* sigma complex less than the *ortho*, *para* - an *o*,*p*-director since it stabilizes the *ortho*, *para* sigma complex less than the *meta* - none of the above 10. Which of the following species is attacked by benzene in the electrophilic nitration reaction? - *N*_*3*^-* - *NO*_*2* - *NO*⁺ - *NO*_*2*⁺ - *HNO*_*3* 11. Rank the following compounds in order of increasing reactivity towards chlorination with *Cl*_*2*/*AlCl*_*3* (slowest reacting to fastest). - **1)** *CH*_*3* - **2)** *COOH* - **3)** *NH*_*2* - **4)** *CI* - **5)** *CH*_*3* ## Short Answer 19. Which orbital is the lone pair of each *N* in, *sp*^*2* or *p*? 20. Provide the major organic product(s) of the reaction shown below. - *Br*_*2*, *FeBr*_*3* 21. Draw 2,5-dichlorophenol. 22. Draw the major organic product(s) of the reaction shown below. - 1. *CH*_*3**CH*_*2**Cl*, *AlCl*_*3* - 2. *KMnO*_*4* - 3. *Br*_*2*, *FeBr*_*3* 23. Draw the major organic product that results when benzene is treated with the following sequence of reagents: 1. *HNO*_*3*, *H*_*2**SO*_*4* 2. *Br*_*2*, *FeBr*_*3* 24. Draw the major organic product that results when benzene is treated with the following sequence of reagents: 1. *CH*_*3**COCI*, *AlCl*_*3* 2. *Br*_*2*, *FeBr*_*3* 25. Use curved arrow notation to show the detailed, stepwise mechanism for this reaction. - + *AlCl*_*3* ## Answer Key 1. C 2. B 3. E 4. D 5. B 6. A 7. D 8. A 9. C 10. D 11. E 12. C 13. D 14. D 15. D 16. A 17. D 18. D 19. *p* 20. - *Br* - + *Br* 21. - *OH* - *Cl* - *Cl* - *CO*_*2**H* 22. - *Br* 23. - *NO*_*2* - *Br* 24. - *CH*_*3* 25. - *AICI*_*3* - *R-C*=*O* - *R-C*=*O*^+* - *AICI*_*3* - *An acyl cation* - *AICI*_*3* - *HCl* + *AlCl*_*3*