CHEM Chapter 12 Infrared and Mass Spec (homework). Stafford. S18

Transcription

1 Exhibit 12-4 The following question(s) refer to the mass spectrum shown below. 1. Refer to Exhibit This compound contains C, H, and one other atom. Identify the other atom from the mass spectrum and explain your reasoning. 2. When 2-bromopropane reacts with ethoxide ion, two products are formed; one is the product of S N 2 substitution and the other is the product of E2 elimination. Write the structures of both products, and tell how they could be distinguished using IR spectroscopy. Exhibit 12-6 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 pg. 1

2 b to 2000 cm 1 c to 1500 cm 1 d. below 1500 cm 1 3. N H, C H, and O H stretching and bending motions. Exhibit 12-2 Use the data below to answer the following question(s). Loratidine is the active ingredient in the antihistamine Claritin. Mass spectral analysis of loratidine shows M + at m/z = 382 and M + at m/z = 384 in an approximate ratio of 3:1 in intensity. 4. Refer to Exhibit The mass spectral data indicates that loratidine contains: a. fluorine b. chlorine c. bromine d. iodine 5. The amount of energy in electromagnetic radiation is related to the frequency and wavelength of the radiation. High energy radiation like gamma rays is of: a. low frequency and short wavelength b. low frequency and long wavelength c. high frequency and short wavelength d. high frequency and long wavelength Exhibit 12-5 Refer to the mass spectrum of 2-methylbutane shown below to answer the following question(s). pg. 2

3 6. Refer to Exhibit What peak represents the base peak? 7. Which of the following statements best describes the base peak in a mass spectrum? a. The peak from the most stable radical. b. The peak from the species that has the isotope with the highest atomic number. c. The peak of highest intensity. d. The peak from the molecule minus an electron. Exhibit 12-8 MATCH a structure from the list below to the following IR spectra. Place the letter of the structure in the blank provided. pg. 3

4 8. Exhibit 12-3 For each compound below, what are the masses of the charged fragments produced by the indicated cleavage pathways? 9. Refer to Exhibit Alpha cleavage and dehydration of pg. 4

5 10. Ethyl acetate and 2-butene-1,4-diol both have the molecular formula C 4 H 8 O 2. How would you use infrared spectroscopy to distinguish between the two? Exhibit 12-5 Refer to the mass spectrum of 2-methylbutane shown below to answer the following question(s). 11. Refer to Exhibit What peak represents M +? 12. True or false, both mass spectrometry and infrared spectroscopy involve the interaction of molecules with electromagnetic energy? pg. 5

6 13. Could you distinguish 2,2-dimethylbutane from 2-methylpentane usingmassspectrometry? Exhibit 12-6 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 C C, C O, C N, and C X single-bond vibrations. Exhibit 12-1 Select the most reasonable formula for the compounds with the following mass spectral data. 15. Refer to Exhibit M + at m/z = 101 with a minor M+1 peak a. C 5 H 6 Cl b. C 5 H 12 N 2 c. C 6 H 15 N d. C 9 H 12 O Exhibit 12-7 At what approximate positions might the compounds below show IR absorptions? 16. Exhibit 12-4 The following question(s) refer to the mass spectrum shown below. pg. 6

7 17. Refer to Exhibit Propose a structure for this compound. Exhibit 12-5 Refer to the mass spectrum of 2-methylbutane shown below to answer the following question(s). pg. 7

8 18. Refer to Exhibit Which peak represents the parent peak? Exhibit 12-7 At what approximate positions might the compounds below show IR absorptions? 19. Exhibit 12-8 MATCH a structure from the list below to the following IR spectra. Place the letter of the structure in the blank provided. pg. 8

9 The sugar glucose contains C, H, and O and has a mass of amu as determined by high-resolution mass spectrometry. Glucose contains an equal number of carbon and oxygen atoms. What is the molecular formula of glucose? ( 1 H = amu, 12 C = amu, 16 O = amu) pg. 9

10 22. Predict the m/z position of the parent peak, the peak due to dehydration of the alcohol and -cleavage of the carbonyl in the mass spectrum of the compound shown below. 23. Both methylcycloheptane and ethylcyclohexane have the same molecular mass. Explain how it is possible to distinguish between the two compounds by studying and comparing both their mass spectra. Exhibit 12-5 Refer to the mass spectrum of 2-methylbutane shown below to answer the following question(s). pg. 10

11 24. Refer to Exhibit Propose structures for fragment ions at m/z = 57, 43, and 29. Exhibit 12-2 Use the data below to answer the following question(s). Loratidine is the active ingredient in the antihistamine Claritin. Mass spectral analysis of loratidine shows M + at m/z = 382 and M + at m/z = 384 in an approximate ratio of 3:1 in intensity. 25. Refer to Exhibit Loratidine is known to contain nitrogen. What is the minimum number of nitrogens in loratidine? Exhibit 12-1 Select the most reasonable formula for the compounds with the following mass spectral data. 26. Refer to Exhibit M + m/z = 136 and M + at m/z = 138 of approximately equal intensity a. C 6 H 13 OCl b. C 4 H 9 Br c. C 10 H 16 d. C 9 H 12 O Exhibit 12-3 For each compound below, what are the masses of the charged fragments produced by the indicated cleavage pathways? 27. Refer to Exhibit Alpha cleavage of Exhibit 12-6 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 pg. 11

12 d. below 1500 cm C=O, C=N, and C=C bond absorptions. 29. Examining the infrared spectrum of a compound allows us to: a. determine the types of functional groups present in the compound b. determine the carbon-hydrogen framework of the compound c. determine the molecular weight of the compound d. determine the nature of the conjugated pi electron system in the compound Exhibit 12-4 The following question(s) refer to the mass spectrum shown below. 30. Refer to Exhibit Calculate a possible molecular formula for this compound. Exhibit 12-8 MATCH a structure from the list below to the following IR spectra. Place the letter of the structure in the blank provided. pg. 12

13 What are the charged fragments produced if 4,5-dimethylhex-1-en-3-ol undergoes alpha cleavage? pg. 13

14 33. Cyclohexene and 2-hexyne both have the molecular formula C 6 H 10. How would you use infrared spectroscopy to distinguish between the two compounds? 34. Below is the mass spectrum of an unknown hydrocarbon. In addition, this hydrocarbon shows characteristic absorption at 2100 cm 1 in its IR spectrum. Give the structure of this unknown. Exhibit 12-6 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 pg. 14

15 35. triple bond stretching vibrations. 36. Assume you are carrying out the conversion of 1-bromobutane to 1-butanol. How could you use IR spectroscopy to determine when the reaction is complete? 37. The amount of energy in infrared light corresponds to: a. the amount of energy needed to promote one electron from a bonding to an antibonding molecular orbital b. the amount of energy needed to "flip" the spin of a 13 Cor 1 Hnucleus c. the amount of energy needed to strip a molecule of one electron to generateacationradical d. the amount of energy needed to increase certain molecular motions, such as bond vibrations, in organic molecules pg. 15