CHEM Review for test 1 (ch12-15). F17. Stafford

Transcription

1 CHEM Multiple Choice Identify the choice that best completes the statement or answers the question. 1. What range of wavelengths corresponds to the infrared region of the electromagnetic spectrum? a nm b nm c m d mm 2. Which of the following bonds (circled) vibrates at the highest frequency? a. 1 b. 2 c. 3 d Which of the following combinations of peaks appears in the 1 H NMR spectrum of diethyl ether, CH 3 CH 2 OCH 2 CH 3? a. a triplet and a doublet b. a quartet and a sextet c. two singlets d. a triplet and a quartet 4. Which C 4 H 9 Br compound gives a triplet at approximately 3.5 ppm in the 1 H NMR spectrum? a. 1 b. 2 c. 3 d What is the relative area of the six peaks in a sexet in an 1 H NMR spectrum? a. 1:2:3:3:2:1 b. 1:3:6:6:3:1 c. 1:5:10:10:5:1 d. 1:6:15:15:6:1 6. Which of the following compounds have enantiotopic protons? 1

2 1. propane 2. butane 3. 2-methylpropane a. only 1 b. only 2 c. only 1 and 2 d. 1, 2 and 3 7. Which of the following is true for pair of homotropic protons? 1. They will appear at the same chemical shift in an achiral (i.e., nonchiral) environment 2. They will appear at the same chemical shifts in a chiral environment a. only 1 b. only 2 c. neither 1 nor 2 d. both 1 and 2 8. Which C 9 H 10 O compound gives the following 1 H NMR spectrum? 2

3 a. 1 b. 2 c. 3 d Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 60? a. 1-hexanol b. 2-hexanol c. hexanal d. hexanoic acid 10. Which of the following arrangements of p atomic orbitals of 1,3-butadiene has the greatest number of nodes? a. 1 b. 2 c. 3 d What is (are) the major organic product(s) formed in the following reaction? a. only 1 b. only 1 and 3 c. only 2 and 4 d. only 1 and Which of the following is(are) formed upon addition of 1 mol of Br 2 to 1,3-cyclohexane? 3

4 a. only 2 b. only 1 and 3 c. only 2 and 4 d. 1, 2 and What is (are) the major organic product(s) formed in the following reaction? a. only 1 b. only 3 c. only 1 and 3 d. only 2 and What are the units of in ultraviolet-visible spectroscopy? a. M 1 cm 1 b. M cm c. J mol 1 M 1 d. none, is a dimensionless quantity 15. Which of the following laws relates absorbance to the concentration of a sample and the pathlength in ultraviolet-visible spectroscopy? a. Buzz-Beer law b. Beer-Lambert law c. Duff-Beer law d. Christopher-Lambert law 16. What is the IUPAC name of the following compound? 4

5 a. 2,4-dibromotoluene b. 2,4-dibromophenol c. 2,4-dibromohydroxybenzene d. 4,6-dibromophenol 17. Which of the following represents the energy levels of the molecular orbitals of benzene? a. 1 b. 2 c. 3 d What is the correct assignment of the names of the following heterocycles? a. 1 = pyrrole; 2 = thiophene; 3 = pyridine b. 1 = thiophene; 2 = furan; 3 = pyrrole c. 1 = pyridine; 2 = thiophene; 3 = furan d. 1 = pyridine; 2 = thiophene; 3 = pyrrole 5

6 19. What is the hybridization of the nitrogen atom of pyridine? a. s b. sp c. sp 2 d. sp Which of the following compounds is antiaromatic? a. ethane b. cyclobutadiene c. benzene d. cyclooctatetraene 21. Which of the following compounds undergoes heterolytic carbon-halogen bond cleavage to form a stable organic cation? a. 1 b. 2 c. 3 d Which of the following has the compounds shown in the correct order of decreasing acidity (i.e., more acidic > less acidic)? a. 1 > 2 > 3 b. 2 > 3 > 1 c. 3 > 2 > 1 d. 1 > 3 > What is the major organic product obtained from the following reaction? 6

7 a. 1 b. 2 c. 3 d What is the major organic product obtained from the following reaction? a. 1 b. 2 c. 3 d Which of the following represents the energy levels of the molecular orbitals of cyclobutadiene? 7

8 a. 1 b. 2 c. 3 d What are the relative positions of the substituents in the following structure? a. anti b. meta c. ortho d. para 27. What are the relative positions of the substituents in the following structure? 8

9 a. anti b. meta c. ortho d. para 28. Which of the following is true about [10]annulene? a. [10]annulene is planar b. [10]annulene is nonaromatic c. [10]annulene undergoes addition reactions similar to simple alkenes d. [10]annulene has 10 pi electrons 29. Which of the following is not true about [the bridged [10]annulene shown below? a. all of the carbon atoms of bridged [10]annulene are all in the same plane b. bridged [10]annulene is aromatic c. bridged [10]annulene undergoes substitution reactions similar to benzene d. bridged [10]annulene has 10 pi electrons 30. Which of the following does not undergo oxidation in the presence of H 2 CrO 4? a. 1 b. 2 c. 3 d. 4 Completion Complete each statement. 9

10 MATCH each of the following groups of bond-types to the region of the infrared spectrum in which their absorptions occur. Place the letter of the region in the blank to the left of the bond-type. a to 2500 cm 1 b to 2000 cm 1 c to 1500 cm 1 d. below 1500 cm 1 1. C C, C O, C N, and C X single-bond vibrations. 2. C=O, C=N, and C=C bond absorptions. 3. N H, C H, and O H stretching and bending motions. 4. triple bond stretching vibrations. MATCH a structure from the list below to the following IR spectra. Place the letter of the structure in the blank provided

11 Spectrum obtained from: SDBSWeb: 6. Spectrum obtained from: SDBSWeb:

12 Spectrum obtained from: SDBSWeb: MATCH each of the following molecules to the region of the infrared spectrum in which they may show a significant absorption. Place the letter of the region in the blank to the left of the bond-type. a to 2500 cm 1 b to 2000 cm 1 c to 1500 cm 1 d. below 1500 cm CH 3 CH 2 OCH(CH 3 ) 10. For each of the compounds below tell how many signals you would expect the molecule to have in its normal, broadband hydrogen-decoupled 13 C NMR spectra. Enter the numerical value in the blank provided to the left of the structure

13 Predict the splitting of each of the numbered hydrogen atoms in the structure below in a 1 H NMR spectrum. Identify as singlet, doublet, triplet, quartet, quintet, sextet, septet,... Place the correct splitting in the blank to the left of the number Identify the ratio of peak areas upon integration of the 1 H NMR spectrum for A, B, and C respectively. Enter the numbers separated by colons. 13

14 Consider the following structure. blank to the left. Answer the following questions by placing the appropriate number in the 20. The number of nonequivalent hydrogen atoms in this compound. 21. The number of signals in the hydrogen-decoupled 13 C NMR of this compound. 22. The number of nonsinglet splitting patterns in the 1 H NMR of this compound. The following question(s) refer to the mass spectrum shown below. Spectrum obtained from: SDBSWeb: The base peak in this spectrum occurs at a m/z of. 14

15 24. This compound contains C, H, and one other atom. The other atom from the mass spectrum is. Refer to the mass spectrum of 2-methylbutane shown below to answer the following question(s). Spectrum obtained from: SDBSWeb: The peak at a m/z of represents M The peak at a m/z of represents the base peak. 27. The peak at a m/z of represents the following species. 28. The peak at a m/z of represents the following species. 29. The peak at a m/z of represents the following species. +CH 2 CH The mass of the larger charged fragment produced by the dehydration of the following compound occurs at a m/z of. 15

16 31. Cyclohexene and hex-2-yne both have the molecular formula, C 6 H 10. The mass spectrum below belongs to. 32. Alpha cleavage of the following compound will produce a peak at a m/z of. 33. Dehydration of the following compound will produce a peak at a m/z of. Consider the reaction below to answer the following question(s): Enter the appropriate letter in the blank for each the following statements. 16

17 34. The nucleophile in this reaction is. 35. The electrophile in this reaction is. 36. The kinetically controlled product in this reaction is. 37. The product that results from 1,4-addition is. 38. The product that results from following mechanistic step is. 39. Consider the following spectrum for a conjugated diene. If a similar spectrum were taken for a conjugated tetraene, the max would be than 217 nm. 40. Based on the following table. Compound max (nm) W 190 X 340 Y 560 Z 250 Compound has the largest energy difference between the HOMO and LUMO. Consider the reaction below to answer the following question(s). 17

18 Fill in the blank in the question with the appropriate letter. 41. The dienophile in the reaction is. 42. The diene in the reaction is. 43. This is an example of a(n) reaction. A. sigmatropic reaction B. electrophillic addition C. Diels-Alder reaction D. Cope rearrangement Answer the following questions concerning sulfathiazole below by filling ieach blank with the appropriate response. 44. The hybridization of the nitrogen atom in sulfathiazole is. A. sp B. sp 2 C. sp Assuming that the sulfur atom is sp 2 -hybridized, there are -electrons in the sulfathiazole ring. 46. According to Hückel criteria, sulfathiazole is predicted to be. Consider the cycloheptatrienyl anion. appropriate word. Complete the following questions by filling in the blank with the 47. According the Hückel criteria this anion would be classified as. 48. This anion has electrons. 49. Consider the following two compounds. 18

19 B A An ether solution containing these two substances was mixed with an aqueous 1 M NaOH solution. Substance will be found in the basic layer. 50. Consider the following compound. When treated with acidic K 2 Cr 2 O 7 the product would be classified as a. Consider the following structure. 51. If named as an annulene, the name would be [ ] annulene. 52. This structure contains electrons. 53. Using the Hückel criteria, the compound would be. Consider the following structure. The 1 H NMR spectrum of [14]annulene at 60 C shows two peaks, one at 0 ppm and one at 7.6 ppm. 54. The NMR data would seem to indicate that this compound is. 55. The ratio of peak areas, respectively for the 7.6 ppm and 0 ppm, peaks would be. 19

20 Matching The following questions pertain to the display of NMR spectra. Match a term to each description below. a. TMS b. high-field or upfield side c. MHz d. delta ( ) e. low-field or downfield side f. chemical shift g. intensity 1. When looking at a NMR spectrum the right-hand part of the chart is the. 2. The exact place on the spectrum at which a nucleus absorbs is called its. 3. The calibration standard for 1 H and 13 C NMR is. 4. NMR spectrum are calibrated using an arbitrary scale that is divided into units. 5. The vertical axis of spectrum displays the of the signal. Problem 1. Provide the structure of three compounds with the molecular formula C 4 H 8 O that give an absorption peak at cm -1 in the infrared spectrum, but no significant peaks at cm -1 or at cm Provide the structure of four compounds with the molecular formula C 5 H 10 O which give a strong absorption peak at cm -1 in the infrared spectrum, but no significant peaks at cm Provide a brief explanation to account for the observation that 1-butyne gives a significantly stronger peak at ~1250 cm -1 in the infrared spectrum than 2-butyne.. 4. Provide a brief explanation to account for the observation that the frequency of the C=O stretching absorption in the infrared spectrum of 2-butanone is higher than that of 3-buten-2-one. 5. Provide a brief explanation to account for the observation that the frequency of the C=O stretching absorption in the infrared spectrum of N,N-dimethylacetamide, CH 3 CON(CH 3 ) 2, is higher than that of methyl acetate, CH 3 CO 2 CH How could you distinguish between 1-hexyne and 2-hexyne by infrared spectroscopy? 7. How could you distinguish between 1-butanol and diethyl ether by infrared spectroscopy? 20

21 8. How could you distinguish between methyl butanoate and pentanoic acid by infrared spectroscopy? 9. Label three peaks in the following spectrum with the bond that gives rise to them, and identify the functional group that is present in the compound (the compound has a formula of C 6 H 14 O)? 10. Label three peaks in the following spectrum with the bond that gives rise to them, and identify the functional group that is present in the compound (the compound has a formula of C 5 H 10 O 2 )? 11. Label three peaks in the following spectrum with the bond that gives rise to them, and identify the functional group that is present in the compound (the compound has a formula of C 4 H 9 NO)? 21

22 12. Identify the compound (C 4 H 6 O 2 ) that gives the following 1 H NMR spectrum. 13. Identify the compound (C 4 H 8 O 2 ) that gives the following 1 H NMR spectrum. 14. Identify the compound (C 3 H 7 Cl) that gives the following 1 H NMR spectrum. 22

23 15. Identify the compound (C 3 H 7 Cl) that gives the following 1 H NMR spectrum. 16. Identify the compound (C 4 H 8 O) that gives the following 1 H NMR spectrum. 17. Identify the compound (C 4 H 8 O) that gives the following 1 H NMR spectrum. 23

24 18. Identify the compound (C 8 H 10 O 2 ) that gives the following 1 H NMR spectrum. 19. Identify the compound (C 8 H 11 N) that gives the following 1 H NMR spectrum. 20. Identify the compound (C 8 H 10 ) that gives the following 1 H NMR spectrum. 24

25 21. Identify the compound (C 8 H 10 ) that gives the following 1 H NMR spectrum. 22. Identify the compound (C 8 H 10 ) that gives the following 1 H NMR spectrum. 23. What is the most likely molecular formula of a compound that has a molecular ion in the EI mass spectrum with m/z of 97 and an M+1 peak that is 6.6% of the intensity of the molecular ion peak? 25

26 24. What is the most likely molecular formula of a compound (that contains only C, H and O) which has a molecular ion in the EI mass spectrum with m/z of 104 and an M+1 peak that is 5.5% of the intensity of the molecular ion peak? 25. What is the most likely molecular formula of a compound that has a molecular ion in the EI mass spectrum with m/z of 136, with a M+1 and M+2 peaks that are 4.4% and 49% of the intensity of the molecular ion peak, respectively. 26. What is the most likely molecular formula of a compound that has a molecular ion in the EI mass spectrum with m/z of 120, with a M+1 and M+2 peaks that are 6.6% and 24% of the intensity of the molecular ion peak, respectively. 27. Provide the mass of the three most prominent fragment peaks that are observed in the EI mass spectrum of 2-hexanone, CH 3 CH 2 CH 2 CH 2 COCH 3 (molecular ion m/z = 100) and describe the processes that lead to each of these fragments. 28. Provide the mass of the three most prominent fragment peaks that are observed in the EI mass spectrum of methyl pentanoate, CH 3 CH 2 CH 2 CH 2 CO 2 CH 3 (molecular ion m/z = 116) and describe the processes that lead to each of these fragments. 29. Which C 5 H 12 O compound give the following EI mass spectrum? 30. Which C 5 H 12 O compound give the following EI mass spectrum? 26

27 31. Which C 6 H 12 O carbonyl-containing compound shows a molecular ion peak at m/z 100 and significant fragment peaks at m/z 85, 58, 57, 43 and 42 in the EI mass spectrum? 32. Which C 6 H 12 O carbonyl-containing compound shows a molecular ion peak at m/z 100 and significant fragment peaks at m/z 71, 58, 57, 43 and 29 in the EI mass spectrum? 33. What is the IUPAC name of the following compound? 34. What is the IUPAC name of the following compound? 35. What are the two major organic products obtained from the following reaction? 36. What are the two major organic products obtained from the following reaction? 37. Provide the structures of the constitutional isomers of the two major organic products obtained from the following reaction? 38. What is the major organic product obtained from the following reaction? 39. Draw two resonance structures of the reactive intermediate that accounts for the formation of 1,2- and 1,4-addition products upon reaction of 1,3-butadiene with one equivalent of bromine. 27

28 40. Draw two resonance structures of the reactive intermediate that accounts for the formation of 1,2- and 1,4-addition products upon reaction of 1,3-butadiene with one equivalent of HBr. 41. How would you be able to distinguish between 1,3-cyclohexadiene and 1,4-cyclohexadiene using ultraviolet spectroscopy? 42. Which of 1,3-cyclohexadiene and 1,4-cyclohexadiene has the greatest heat of hydrogenation (i.e., the most exothermic reaction with H 2 in the presence of a catalyst). Provide a brief explanation for your choice? 43. What is the IUPAC name of the following compound? 44. What is the IUPAC name of the following compound? 45. What is the IUPAC name of the following compound? 46. What is the IUPAC name of the following compound? 28

29 47. What is the major organic product obtained from the following reaction? 48. What is the major organic product obtained from the following reaction? 49. What is the major organic product obtained from the following reaction? 50. What are the two major organic products obtained from the following reaction? 51. List all of the requirements of a molecule for it to be considered aromatic. 29

30 52. Provide a brief explanation of why furan (below) is aromatic. Your answer should identify the hybridization of the oxygen atom and account for which electrons are in the pi system. 53. Provide a brief explanation of why the cyclopentadienyl anion (below) is aromatic. Your answer should identify the hybridization of each carbon atom and account for which electrons are in the pi system. 30

31 Answer Section MULTIPLE CHOICE 1. ANS: C 2. ANS: D 3. ANS: D 4. ANS: A 5. ANS: C 6. ANS: B 7. ANS: D 8. ANS: B 9. ANS: D 10. ANS: C 11. ANS: D 12. ANS: C 13. ANS: B 14. ANS: A 15. ANS: B 16. ANS: B 17. ANS: C 18. ANS: C 19. ANS: C 20. ANS: B 21. ANS: D 22. ANS: B 23. ANS: C 24. ANS: A 25. ANS: A 26. ANS: C 27. ANS: D 28. ANS: A 29. ANS: A 30. ANS: D COMPLETION 1. ANS: d 2. ANS: c 31

32 3. ANS: a 4. ANS: b 5. ANS: F 6. ANS: D 7. ANS: A 8. ANS: b 9. ANS: d 10. ANS: a 11. ANS: 3 three 12. ANS: 5 five 13. ANS: 6 six 14. ANS: 5 five 15. ANS: 5 five 32

33 16. ANS: singlet 17. ANS: quartet 18. ANS: triplet 19. ANS: 3:1:6 20. ANS: 3 three 21. ANS: 3 three 22. ANS: 0 zero 23. ANS: ANS: Br bromine Bromine 25. ANS: ANS: ANS: ANS: 43 33

34 29. ANS: ANS: ANS: cyclohexene Cyclohexene 32. ANS: ANS: ANS: A 35. ANS: B 36. ANS: D 37. ANS: C 38. ANS: D 39. ANS: greater longer 40. ANS: W 41. ANS: B 42. ANS: A 34

35 43. ANS: C 44. ANS: B 45. ANS: six ANS: aromatic 47. ANS: antiaromatic 48. ANS: 8 eight 49. ANS: B 50. ANS: quinone 51. ANS: ANS: ANS: antiaromatic 54. ANS: aromatic 55. ANS: 5:2 5 to 2 5/2 35

36 MATCHING 1. ANS: B 2. ANS: F 3. ANS: A 4. ANS: D 5. ANS: G PROBLEM 1. ANS: Any three of the following: 2. ANS: Any four of the following: 3. ANS: 2-Butyne is a symmetrical molecule and stretching of the triple bond does not give rise to a change in the bond dipole moment. 4. ANS: The C=O bond of 3-buten-2-one is weaker in 2-butanone by virtue of the existence of an additional resonance structure with a C O single bond. 36

37 5. ANS: The C=O bond of the amide is weaker than that of the ester. Nitrogen is less electronegative than oxygen, and therefore a better electron pair donor. Accordingly, the resonance contributor in which the nitrogen has donated a pair of electrons to the carbonyl carbon atom is an important contributor to the structure. 6. ANS: 1-Hexyne, a terminal alkyne, has a stronger peak for the C C stretching vibration than 2-hexyne, an internal alkynes. 7. ANS: The infrared spectrum of 1-butanol has a strong and broad peak at cm -1 for the O H bond. This peak is absent in the spectrum of ethers. 8. ANS: The infrared spectrum of pentanoic acid has a very broad peak at cm -1 for the O H bond. This peak is absent in the spectrum of esters. 9. ANS: O-H: ~3300 cm -1 C-H: ~2900 cm -1 C-O: ~1060 cm -1 Functional group: alcohol 37

38 10. ANS: O-H: cm -1 C-H: ~2900 cm -1 C-O: ~1700 cm -1 Functional group: carboxylic acid 11. ANS: N-H: ~3500 cm -1 C-H: ~2900 cm -1 C=O: ~1680 cm -1 Functional group: amide 12. ANS: methyl propionate, CH 3 CH 2 CO 2 CH ANS: ethyl acetate, CH 3 CO 2 CH 2 CH ANS: 2-chloropropane 15. ANS: 1-chloropropane 16. ANS: butanal 17. ANS: 2-butanone 18. ANS: 3-phenylpropanoic acid, PhCH 2 CH 2 CO 2 H 19. ANS: 1-phenylethanamine, PhCH(NH 2 )CH 3 38

39 20. ANS: p-xylene (1,4-dimethylbenzene) 21. ANS: m-xylene (1,3-dimethylbenzene) 22. ANS: o-xylene (1,2-dimethylbenzene) 23. ANS: C 6 H 11 N 24. ANS: C 5 H 12 O ANS: C 4 H 9 Br 26. ANS: C 6 H 13 Cl 27. ANS: 85: loss of CH 3 (15) by -cleavage 72: loss of CH 2 =CH 2 (28) by McLaferty rearrangement 43: loss of C 4 H 9 (57) by -cleavage 28. ANS: 88: loss of CH 2 =CH 2 (28) by McLaferty rearrangement 85: loss of CH 3 O (31) by -cleavage 59: loss of C 4 H 9 (57) by -cleavage 29. ANS: 2-pentanol 30. ANS: 2-methyl-2-butanol 39

40 31. ANS: 4-methyl-2-pentanone 32. ANS: 2-methylpentanal 33. ANS: (E)-2,3-dimethyl-2,4-hexadiene 34. ANS: (E)-2,3-dimethyl-1,3-pentadiene 35. ANS: 36. ANS: 37. ANS: 38. ANS: 39. ANS: 40

41 40. ANS: 41. ANS: 1,3-Cyclohexadiene, in which the two pi-bonds are conjugated, absorbs at a higher wavelength than 1,4-cyclohexadiene. 42. ANS: 1,4-Cyclohexadiene has a greater heat of hydrogenation. This is because 1,3-cyclohexadiene is stabilized by conjugation of the two pi bonds. 43. ANS: 3-bromo-4-nitrophenol 44. ANS: 4-chloro-3-nitrobenzoic acid 45. ANS: 3,4-dichloroaniline 46. ANS: 4-bromo-2-propylbenzonitrile 47. ANS: 41

42 48. ANS: 49. ANS: 50. ANS: 51. ANS: An aromatic molecule has an uninterrupted cycle of overlapping p orbitals (i.e., the cyclic structure should be planar) that contains 2n+2 (i.e., 2, 6, 8,...) electrons 52. ANS: The oxygen is sp 2 hybridized. One lone pair is in a p orbital and is part of the pi system, along with one electron in the p orbital on each of the four carbon atoms. The other lone pair of the oxygen is in an sp 2 orbital, which is in the plane of the ring and not involved in the pi system. 42

43 53. ANS: The all five carbons are sp 2 hybridized. The lone pair is in a p orbital and is part of the pi system, along with one electron in the p orbital on each of the other four carbon atoms for a total of six pi electrons. 43