organic chemistry

CHE 223/FALL 2020                                                       

PRACTICE EXAM QUESTIONS                                      ANSWER KEY

1. Using curved arrow formalism draw the Lewis structure and all resonance forms for each species:

1. carbonate ion   
2. ozone

• formate anion

• Draw the Molecular Orbital Diagram for F₂; draw its Lewis Structure; give the Net Bond Order of the molecule.

SEE F2 MO DIAGRAM ON BLACKBOARD

• Show how a sp2 hybrid carbon is formed (e.g. show the ground state, first excited state). What is the shape of sp hybrid carbon? Give an example of a compound where the carbon is sp hybridized.

SEE LECTURE SLIDES FOR GS, 1^ST EXCITED STATE, AND HYBRIDIZED STATE. TRIGONAL PLANAR. E.G. ETHYLENE

• Define the following terms and provide an example of each:

a. Stereoisomers          – cmpds with same MF and atom connectivity, but different arrangement in space, e.g. cis and trans-2-butene

b. Constitutional isomers – cmpds with same MF but different constitution/connectivity, e.g. n-butane and 2-methylpropane

c. Polar aprotic solvent – solvent that is polar and has no protons to donate, e.g. THF

d. Dielectric constant – e, the ability of a solvent to stabilize opposite charges. More polar solvents have a higher e, e.g. e for H₂O is higher than that of hexane.

• Calculate the degree of unsaturation for a compound bearing the molecular formula of C₃H₆O; draw all possible stable structures.

• Draw bond-line structures of all monohalogenated products generated when 5-bromo-2,2,8,8-tetramethyl-nonane is treated with Br₂/heat.

• Draw structures for the following:   

a) secondary alcohol

b) tertiary alkyl halide

c) hydride anion

d) urea

e) THF

f) DMF

g) a heterocyclic compound

h) a saturated hydrocarbon compound

i) acetone

j) pyridine

k) potassium ethoxide

l) secondary radical

m) phosphorus oxychloride

n) methylene chloride

• What is the total number of pi bonds found in the following compound?

(A)     8

(B)     9

(C)     10

(D)     11

8. The H–C–O bond angle in H2C=O (formaldehyde) is approximately

(A)     90 degrees

          (B)     109.5 degrees

          (C)     120 degrees

          (D)     180 degrees

• What is a product of the following reaction when the cyclohexanol (shown below) is treated with NaH?

(A)     H+

(B)     H₂

          (C)     NaOH

          (D)     H₂O

10. A hydrocarbon containing no alkene or alkyne linkages has the formula C₁₀H₁₆, How many rings are present in this compound?

(A) 1

(B) 2

(C) 3

(D) 4

11. What is the IUPAC name for the following structure?

(A) 2,5 – dimethyl octane

(B) 4,7 – dimethyl octane

(C) 2 – methyl – 5 – propyl hexane

(D)  2 – propyl – 5 – methyl hexane

12. Fill in the blanks for the following statement: As the alkyl chain of an alcohol _______, its solubility in water ______.

(A) increases, increases

(B) decreases, decreases

(C) decreases, remains the same

(D)  increases, decreases

13. Provide the complete mechanism using CAF for the reaction of 2,2-diethylcyclohexanol treated with aq. H₃PO₄. If more than one product is formed state which is major, minor, very minor, etc. Is the reaction SN1, SN2, E1, or E2? Hint: has a high dielectric constant.

14. Provide the complete mechanism using CAF for the reaction of 2,2-diethylcyclohexanol treated with HBr. If more than one product is formed state which is major, minor, very minor, etc. Is the reaction SN1, SN2, E1, or E2? Hint: has a high dielectric constant.

15. Draw cis-1,2-diisopropylcyclohexane in its most stable chair conformation. Show the ring inversion and identify how many 1,3-diaxial interactions exists in both conformations.