3. How does infrared radiation compare to visible radiation ?
A.) Infrared has more energy than visible.
B.) Infrared and visible radiation have similar wavelength and frequency, but are polarized differently.
C.) Infrared has higher frequency than visible.
D.) Infrared has lower frequency than visible
E.) Infrared has shorter wavelength than visible
4. Which of the following could happen when infrared radiation is absorbed by a molecule ?
A.) molecule begins to rotate more rapidly
B.) molecule may glow in the dark
C.) Electrons are promoted from filled to empty molecular orbitals
D.) The orientation of a nuclear spin state changes.
E.) Intra-molecular bond angles change
5. Infrared absorption spectra of organic molecules are often presented as a plot of transmittance versus wavenumber. What is the definition of a wavenumber ?
A.) one wavenumber = one reciprocal micron
B.) one wavenumber = one reciprocal centimeter
C.) wavenumber is the same as wavelength, and can be expressed in any unit of length
D.) one wavenumber = one micron
E.) one wavenumber = one centimeter
6. Which bond would you expect to have the highest vibrational frequency (stretching) ?
A.) C-Br
B.) C-O
C.) C-N
D.) C-C
E.) C-H
7. Which statement is TRUE concerning a Diels-Alder reaction ?
A.) The reaction has a favorable entropy change
B.) It is a [2+2] cycloaddition reaction
C.) Two new C-C sigma bonds form during the reaction
D.) It is a photochemical reaction
E.) It is a multi-step reaction
8. When the following two molecules combine by a Diels-Alder reaction, the product will contain one carbon-carbon double bond. Between which pairs of atoms will this bond be formed ?
A) jk
B) mo
C) fg
D) bd
E) df
9. In the dehydration of 2-methylcyclohexanol, a student begins with 10.042 grams of 2-methylcyclohexanol and an excess of phosphoric acid. The product is a mixture of 1-methylcyclohexene and 3-methylcyclohexene. If the percentage of 1-methylcylohexene in the product mixture is 84.3%, how many grams of 3-methylcyclohexene would be produced ? (assuming 100% yield)
( m.w. 2-methycyclohexanol = 114, m.w. H2O = 18 )
a.) 8.46 b.) 7.13 c.) 1.32 d. ) 11.93 e. ) None of above
10. Suppose that in a proton NMR experiment, you fixed the magnetic field and found a frequency at which a sample absorbed radiofrequency radiation. If you were then to decrease the applied magnetic field, what would you observe ?
A.) The absorption frequency would stay the same, but there would be more splitting of absorption signal.
B.) The absorption frequency would stay the same, but there would be less splitting of absorption signal.
C.) The absorption frequency and splitting both remain unchanged.
D.) The absorption frequency would increase
E.) The absorption frequency would decrease
11. Consider the infrared and proton NMR spectra shown in attached figure 1. Which group of protons is the most magnetically shielded ? (ignore the reference compound)
A.) A
B.) B
C.) C
D.) D
E.) E
12. Referring again to figure 1, which group of protons appears most downfield in the NMR spectrum? (ignore the reference compound)
A.) A B.) B C.) C D.) D E.) E
13. Which compound below is most consistent with the IR and NMR spectra in figure 1 ?
14. Rank the proton groups in the following molecule in order of increasing magnetic chemical shift?
A.) ABCDE
B.) ACBDE
C.) EDCBA
D.) EDBCA
E.) CABDE
15. You have decided that you have 40 wt% of ?-terpinene(C10H16) in a 2.5 gram sample of oil to be submitted to a Diels-Alder reaction. How many grams of maleic anhydride(C4H2O3) will be required to just completely react with the terpinene? (Let the atomic weights of C be 12.00, H be 1.00 and oxygen be 16.00)
A) 1.72
B) 1.38
C) 1.0
D) 0.72
E) None of the above
16. Refer back to the reaction in question 15. What would be the theoretical yield of adduct in grams ?
A) 1.72
B) 1.38
C) 1.0
D) 0.72
E) None of the above
For questions 17 and 18, assume that you are trying to identify a chemical compound (compound "X") by a combination of qualitative chemical tests and spectra examination. The compound is known to be one of those listed in Table 1, in which each compound is listed with a corresponding two digit code. The chemical tests that you performed included a 2,4-dinitrophenylhydrazine test, acetyl chloride test, chromic acid test, sodium bicarbonate test, bromine test, and silver nitrate test. The silver nitrate test gave positive results, all other chemical tests were negative. The proton, C-13, and IR spectra for compound X are in the attached figure 2. Identify compound X.
17. From table 1, the first digit of the two digit code corresponding to compound X is :
A.) 1 B.) 2 C.) 3 D.) 4 E.) 5
18. From table 1, the second digit of the two digit code corresponding to compound X is :
A.) 1 B.) 2 C.) 3 D.) 4 E.) 5
You have another compound, compound 'Y", which you need to identify by chemical tests and spectra analysis. The 2,4-dinitrophenylhydrazine test, acetyl chloride test, chromic acid test, sodium bicarbonate test, bromine test, and silver nitrate test all turned out negative. The spectra for compound Y are in attached figure 3. Identify compound Y.
19. From table 1, the first digit of the two digit code corresponding to compound Y is :
A.) 1 B.) 2 C.) 3 D.) 4 E.) 5
20. From table 1, the first digit of the two digit code corresponding to compound Y is :
A.) 1 B.) 2 C.) 3 D.) 4 E.) 5
21. Which of the following statements regarding Grignard reagents is FALSE ?
A) Grignard reagents are stable in anhydrous ether solutions.
B) A Grignard reagent contains electrophilic carbon.
C) Once prepared , a Grignard reagent should be used quickly.
D) The Grignard reagent is an example of an organometallic compound.
E) Grignard reagents tend to act as Bronsted bases.
22. Which of the following statements , regarding the procedures used in the Grignard lab exercise , are TRUE?
A) In order to start the Grignard reaction , it is usually NOT necessary to shake the reaction apparatus after it is assembled and the reagents are added
B) When preparing the Grignard reagent, the cooling water on the reflux condenser need not be turned on as soon as the reaction (ebullition) starts.
C) All glassware used in the Grignard preparation should be carefully dried in an oven before use.
D) While preparing the Grignard reagent , the top of the reflux column and addition funnel should be left open to the atmosphere during the reaction.
E) All glassware used in the Grignard preparation should be cleaned by rinsing with acetone just before assembling the reaction apparatus.
23. You are preparing triphenyl carbinol by a grginard synthesis. First you prepare methyl benzoate, and set aside 4.40 grams of the purified ester for later use. You then prepare the grignard reagent ( phenylmagnesium bromide ) by reacting 1.78 grams of magnesium with 12.01 ml of bromobenzene. You add the 4.40 grams of methyl benzoate to the freshly prepared grignard reagent to form an addition product. Finally, after hydrolyzing the grignard addition product, you obtain 5.27 grams of the final product, triphenyl carbinol. What is the percent yield of triphenyl carbinol ? ( The density of bromobenzene is 1.495 g/ml ) (molecular weights: bromobenzene = 157, methyl benzoate=136, magnesium =24.3, triphenyl carbinol =260)
A.) 62.6
B.) 55.3
C.) 33.4
D.) 6.99
E.) None of the above are close (within 1%)
Table 1 : Chemical Inventory
11 n-pentane 41 1,2-dichloropropane
12 2,2,4-tri-methylpentane 42 2-chloro-2-methylpropane
43 1-bromobutane
21 cyclohexene 44 2-bromobutane
45 1-bromo-3-methylbutane
31 1,2-dimethylbenzene
32 1,3-dimethylbenzene 51 ethanol
33 1,4-dimethylbenzene 52 1-propanol
34 toluene 53 2-propanol
54 1-butanol
55 2-butanol