2 1. Circle the correct answer: (40 pts; 4 pts/each) (1) 2-Butyne (CH3C=CH3) does not show IR absorption in the region 2100-2200 cm-1 because: a. C-H stretches occur at lower frequencies. b. C=C stretches occur at about 1640 cm-1. c. there is no change in the dipole moment when the C=C bond stretches. d. there is a change in the dipole moment when the C=C bond stretches. (2) When a high-energy electron impacts molecules in the ionization chamber, what type of species is initially produced? a. cation; b. anion ; c. radical; d. radical cation; e. radical anion (3) How many nuclear spin states are allowed for the 13C nucleus? a. 1; b. 2; c. 3; d. 4; e. 10 (4) 1H nuclei attached to or near electronegative atoms tend to be relative to 1H nuclei that are not. a. shielded; b. deshielded; c. conjugated; d. split (5) The Williamson ether synthesis proceeds via an mechanism. a. SN1; b. SN2; c. E1; d. E2 (6) Which compound would show a larger than usual M+2 peak? a. CH3CH2OH; b. CH3CH2Cl; c. CH3CH2I d. CH3CH2F (7) Which will occur at the lowest frequency: a. a C-O stretch; b. a C=O stretch; c. a C-H stretch; d. an O-H stretch (8) If two signals differ by 1.0 ppm in a 300 MHz spectrometer, how do they differ in ppm in a 100 MHz spectrometer? a. 0.33 ppm; b. There’s no difference; c. 1.0 ppm; d. Cannot determine3 (9) Ethers have significantly lower boiling points than their corresponding alcohol isomers because of their: a. lack of polarity; b. lack of H-bonding; c. volatility; d. effective packing (10) Epoxide’s high ring strain makes it susceptible to a. hydrolysis; b. electrophilic attack; c. ring-opening; d. nucleophilic attack 2. Which of the following two compounds gives the IR spectrum shown? What kind of absorption gives the broad band at ~3300 cm-1? (10 pts) OHOHOAB Answer: A (5 pts); O-H stretching (5 pts) 3. What m/z value would you predict for the base peak in the mass spectrum of each of the following compounds? Draw the structure of the carbocation corresponding to each base peak. (10 pts) (a)(b)m/z = 57 (2 pts)m/z = 43 (2 pts)structure of carbocation:structure of carbocation:or (CH3)3C+or (CH3)2CH+(3 pts)(3 pts)4 4. The mass spectra of three isomeric ethers, A, B, and C, are shown below. Match the compound with the spectra. (15 pts, 5 pts/each) OCH3A BOCH3CH3OC C (5 pts)B (5 pts)A (5 pts)5 5. Match each of the following 1H NMR spectra with one of the following compounds: (15 pts, 5 pts/each) AB COC CH3CH3CH2CH3CCH3CH3NO2OC CH2CH3CH3CH2CH3CH2CH2NO2CH3CH2NO2CHBrCH3CH3DEF F (5 pts)D (5 pts)A (5 pts)6 6. Match each of the following 1H NMR spectra with the corresponding compound. (10 pts) OOAB (a)(b)3.002.50 2.00 1.501.00 Compound A gives spectrum (b) . (5 pts) Compound B gives spectrum (a) . (5 pts) 7. The 1H NMR spectrum for a compound with formula C8H18 shows only one peak at 0.86 ppm. The 13C NMR spectrum has two peaks, a larger one at 26 ppm and a smaller one at 35 ppm. Draw the structure of this compound. (6 pts) or (CH3)3CC(CH3)3(5 pts)7 8. Please draw the structures of the alkyl halide and alcohol needed for the preparation of each of the following ethers. (12 pts) CH2CCH3CH3CH3O(a)AlcoholAlkyl halide(b)AlcoholAlkyl halideCH2OCH2XCCH3CH3CH3HOCH2-XHO(X = Cl, Br, or I)(X = Cl, Br, or I)(3 pts) (3 pts)(3 pts) (3 pts) 9. Give the major product of the following reactions: (12 pts) OHCH3CH3HCH3OHH2SO4(1) CH3O-Na+(2) H+/H2O(a)(b)CH2Oexcess HBr(c)OHCH3CH3HHOHCH3CH3HOCH3OHHCH3CH3HCH3OCH2Br HO(4 pts)(4 pts)(2 pts)(2 pts)It's not necessary to show perspective of each structure (but doesn't hurt. Showing structures as line-angle formulas is fine. 10. Extra credit. How might the two trimethylcyclohexane isomers (A and B) shown below be most readily distinguished using NMR? Pleas briefly explain. (10 pts) A B The all cis (left) isomer A has three equivalent methyl groups. (2 pts) The 1H or 13C NMR spectrum of this isomer will show one signal for the methyl groups. (3 pts) The other (cis, cis, trans) isomer B has two types of methyl groups, with two being equivalent and the third one non-equivalent to the other two. (2 pts). The 1H or 13C NMR spectrum of this isomer will show two different signals for the methyl groups. (3 pts) H3C