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CÂU HỎI TRẮC NGHIỆM, TIẾNG ANH CÓ ĐÁP ÁN
CÂU HỎI TRẮC NGHIỆM (CĨ ĐÁP ÁN) PHAN ĐỨC TỒN Câu 1: Which of the following is not a true statement? A The operating frequency of an NMR spectrometer depends on the strength of the magnet B All protons in a compound experience the same shielding C The radiation used in NMR spectroscopy is rf radiation D The effective magnetic field is the magnetic field the proton senses E The energy difference between the alpha and beta spin states depends on the strength of the applied magnetic field Câu 2: How many kinds of chemically nonequivalent hydrogen nuclei are there in ethylbenzene? A B C D E Câu 3: Since the chemical shift is defined as the ratio of the “distance downfield from a standard in [Hz]” and the “operating frequency of the spectrometer in [MHz],” what units does chemical shift have? A MHz (megahertz) B KHz (kilohertz) D Hz (hertz) E unitless C ppm (parts per million) Câu 4: In what region of the H NMR spectrum would you find the signal for the acidic hydrogen of a carboxylic acid? A 0–2.5 ppm B 2.5–5 ppm C 5–7.5 ppm D 7.5–10 ppm E 10–12 ppm Câu 5: What is the multiplicity of the methylene hydrogens of a carbon that is attached to a methyl group and to a methoxy group? A singlet B quintet C quartet D triplet E doublet Câu 6: Which signal of C6H5-C(=O)-CH(CH3)2 has the greatest integrated signal area? A It is the aromatic protons that are a singlet B It is the methyl signal that is a triplet C It is the methyl signal that is a doublet D It is the methylene signal that is a multiplet E It is the methine signal that is a septet Câu 7: The four peaks in a quartet occur at chemical shifts a, a + x, a + 2x, and a + 3x (with intensities 1:3:3:1) Under what condition the four peaks of a doublet of doublets (a is coupled to b and to c) also occur at chemical shifts a, a + x, a + 2x, and a + 3x (with intensities 1:1:1:1)? A Jab = Jac B Jab = 1.5 Jac C Jab = Jac D Jab = 2.5 Jac E Jab = Jac Câu 8: Which of the following describes the low temperature 1H NMR spectrum of chlorocyclohexane in which all the H's are replaced by deuterium except for the H bonded to the C that is bonded to Cl? A a sharp singlet B two singlets with equal intensity D two singlets with different intensities C a broad singlet E a doublet Câu 9: The 1H NMR spectrum of which of the following compounds is altered significantly upon addition of a few drops of D2O to the NMR sample? A methyl ethyl ether B propanol D methyl acetate E acetonitrile C propanone Câu 10: What does the bottom-most spectrum of a DEPT 13C NMR spectrum show? A It is a signal for each carbon B It is a signal for each carbon that is covalently bonded to hydrogen(s) C It is a signal for each methyl carbon D It is a signal for each methylene carbon E It is a signal for each carbon that is covalently bonded to a methyl group Câu 11: Each of the following compounds has a singlet in its 1H NMR spectrum Which compound would have its singlet at the highest frequency (farthest downfield)? A 1-bromo-2,2-dimethylpropane D 1,2-dibromoethane B ethyl methyl ether C 2-ethoxy-2-methylbutane E ethyl-tert-butyl ether Câu 12: Which of the following compounds would have the signal for its methylene hydrogens farthest downfield? A ethyl chloride B ethyl iodide D ethyl bromide E ethyl fluoride C ethanol Câu 13: How many signals would you expect to see for 1,3-dinitrobenzene in its H NMR and 13 C NMR spectra? A four in its 1H NMR spectrum and three in its 13C NMR spectrum B two in its H NMR spectrum and three in its 13C NMR spectrum C three in its H NMR spectrum and three in its 13C NMR spectrum D three in its 1H NMR spectrum and four in its 13C NMR spectrum E four in its 1H NMR spectrum and four in its 13C NMR spectrum Câu 14: The 1H NMR spectrum of methyl propyl ketone has what? A signals: a singlet, a triplet, and a quarte B signals: triplets, and a multiplet C signals: triplets, and a quartet D signals: a singlet, triplets, and a multiplet E signals: a singlet, triplets, and a quartet Câu 15: The different kinds of protons in 3-chloro-3-methylpentane have an integral ratio of (looking left to right across the spectrum) what? A 5:3 B 4:3:6 C 2:3:3 D 4:6:3 E 4:9 Câu 16: A single hydrogen bonded to a carbon is called what? A a methyl hydrogen B an isolated hydrogen D a single hydrogen E a methine hydrogen C a methylene hydrogen Câu 17: Which hydrogens in CH3CH2-C(=O)-CH2CH(CH3)2 are the most shielded? A the methyl hydrogens of the isobutyl group B the methine hydrogen C the methylene hydrogens of the carbon bonded to oxygen D the methylene hydrogens of the carbon bonded to C=O E the methyl hydrogens of the ethyl group Câu 18: How many signals would you expect to see for 1,2-dinitrobenzene in its H NMR and 13 C NMR spectra? A one in its H NMR spectrum and three in its 13C NMR spectrum B two in its H NMR spectrum and two in its 13C NMR spectrum C three in its H NMR spectrum and three in its 13C NMR spectrum D three in its 1H NMR spectrum and two in its 13C NMR spectrum E two in its 1H NMR spectrum and three in its 13C NMR spectrum Câu 19: How many signals would be present in the 13 C NMR spectrum of methyl propyl ketone? A B C D E Câu 20: Which of the following is not a true statement? A Signals occurring at low frequencies have small ppm values B The chemical shift is independent of the operating frequency of the NMR spectrometer C The splitting of a signal is determined by the number of equivalent hydrogens bonded to an adjacent carbon D The number of peaks in a signal is called the multiplicity of the signal E Equivalent protons split one another Câu 21: Which set of protons in 1-chloropentane are the most shielded? A the hydrogens on C-5 B the hydrogens on C-3 D the hydrogens on C-1 E the hydrogens on C-4 C the hydrogens on C-2 Câu 22: How many signals would you expect to see in the chlorocyclobutane? A B C D H NMR spectrum of E Câu 23: The 1H NMR spectrum of a compound shows three signals, A, B, and C, with integral ratios of 3:6,6:6, respectively How many hydrogens give rise to each signal? A A = 9, B = 20, C = 18 B A = 3, B = 2, C = D A = 2, B = 3, C = E A = 6, B = 4, C = C A = 3, B = 7, C = Câu 24: Which compound has its signal farthest upfield? A methyl fluoride B methyl chloride C methyl bromide D methyl iodide E methanol Câu 25: Which of the following is the correct ratio of the peak intensities of a quartet? A 1:3:3:1 B 1:1:1:1 C 1:2:2:1 D 1:1:2:2 E 1:4:4:1 Câu 26: Which set of hydrogens in vinyl chloride has the smallest coupling constant? A the trans hydrogens B the hydrogens on C-2 C the cis hydrogens Câu 27: Which of the following compounds will show an H NMR spectrum with doublets, a triplet, and a quartet? A CH3CHCl-C(=O)-CH2-CH(=O) C CH3CH2CH2-CH(= B CH3CH2-C(=O)-OCH2CH3 D CH3-C(=O)-CH2CH2CH3 E (CH3)2CH-C(=O)-CH2CH3 Câu 28: What is the multiplicity of the OH group of an alcohol in a solution that contains a trace amount of acid? A quartet B doublet C triplet D singlet E quintet Câu 29: What causes the splitting in a spin-coupled 13C NMR spectrum? A 1H–1H spin–spin coupling B 13C–1H spin–spin coupling C 13C–12C spin–spin coupling D 13C–13C spin–spin coupling E none of the above, since no splitting is observed Câu 30: How many signals would you expect to see in the H NMR spectrum of butane? A B C D E Câu 31: How many signals would you expect to see for 1,4-dinitrobenzene in its H NMR and 13 C NMR spectra? A two in its 1H NMR and two in its 13C NMR spectra B one in its 1H NMR and one in its 13C NMR spectra C one in its 1H NMR and two in its 13C NMR spectra D two in its 1H NMR and one in its 13C NMR spectra E two in its 1H NMR and three in its 13C NMR spectra Câu 32: Which of the following will occur farthest downfield? A the hydrogens of ethene C the hydrogens of H-C(=O)-H B the hydrogens of dimethyl ether D the hydrogens of ethyne E the hydrogens of benzene Câu 33: How can CH3 CH2-C(=O)-OCH3 and CH3-C(=O)-OCH2CH3 be distinguished by H NMR? A They have different numbers of signals B Only CH3-C(=O)-OCH2CH3 will have a singlet, a triplet, and a quartet C The signals for each compound will have different multiplicities D Only CH3CH2-C(=O)-OCH3 will have a singlet, a triplet, and a quartet E It is by the multiplicity of the signal appearing farthest downfield Câu 34: How many signals will vinyl chloride have in its H NMR spectrum? A B C D E Câu 35: Which of the following compounds show(s) three signals in its 1H NMR spectrum? A a: 1-chloro-3-methylbutane B b: 2-chloro-2-methylbutane C c: 2-chloropentane D d: 3-chloropentane E b and d Câu 36: How many signals does 2,2,4-trimethylpentane have in its H NMR spectrum? A B C D E Câu 37: Why does the signal for the hydrogen bonded to oxygen in ethanol appear as a triplet in pure ethanol and as a singlet in ethanol that contains a trace amount of acid? A Photon exchange cause spin decoupling B Spin exchange causes spin decoupling C Chemical exchange causes spin decoupling D Electron exchange causes spin coupling E Hydrogen exchange causes more spin coupling Câu 38: In the 1H NMR spectrum of CH3CH2Cl, the quartet for the CH2 group has a coupling constant of Hz What is the coupling constant for the CH3 triplet? A B 3,5 C D 10,5 E 14 Câu 39: Which of the following is not a true statement? A There are more hertz/ppm on a 360-MHz NMR than on a 60-MHz NMR B The chemical shift in hertz is independent of the operating frequency of the NMR C Coupling constants not depend on the operating frequency of the NMR D "Clean" splitting patterns require the chemical shift difference between peaks to be at least 10 times the coupling constant E Spectra taken at higher operating frequency have higher resolution Câu 40: In the DEPT 13C spectrum of 1,3-diethylbenzene, how many peaks would be observed in the second spectrum from the bottom? A B C D E Câu 41: Which of the following is not a true statement? A Signals occurring at low frequencies will have small chemical shift values B If "a" is more shielded than "b," "a" will appear farther upfield than "b." C Downfield is to the left in an 1H NMR spectrum D If "a" is less shielded than "b," "a" will require a greater frequency than "b." E The chemical shift of a hydrogen will vary with the operating frequency of the NMR spectrometer Câu 42: What would be the multiplicity of the methylene group in CH3CH2-C(=O)-CH(CH3)2? A a singlet B a quartet C a doublet D a doublet of doublets E a triplet Câu 43: How many signals would you expect to see in the 1H NMR spectrum of 1bromopropane and 2-bromopropane? A 1-Bromopropane has and 2-bromopropane has B 1-Bromopropane has and 2-bromopropane has C 1-Bromopropane has and 2-bromopropane has D 1-Bromopropane has and 2-bromopropane has E 1-Bromopropane has and 2-bromopropane has Câu 44: How many signals would you expect to see in the 1H NMR spectrum of 2methylpropene? A B C D E Câu 45: Which of the following compounds is frequently used as an internal reference in H NMR spectroscopy? A TNS B TMS C DMS D DMF E DMSO Câu 46: The H NMR spectrum of a compound shows methyl and methylene signals with relative intensities of 3:1 Identify the compound A CH3CH2Br B (CH3)3CCH2Br D (CH3)2C(CH2Br)2 E (CH3)2CBrCH2Br C CH3C(CH2Br)3 Câu 47: In what region of the 1H NMR spectrum would you expect to find signals that are due to methyl groups? A 0–2 ppm B 2–4 ppm C 4–6 ppm D 6–8 ppm E 8–10 ppm Câu 48: Identify the compound with molecular formula C4H8Br2 whose 1H NMR spectrum consists of singlets, one at 1.97 ppm and one at 3.89 ppm A 1,3-dibromo-2-methylpropane B 1,1-dibromo-2-methylpropane C 1,2-dibromobutane D 1,4-dibromobutane E 1,2-dibromo-2-methylpropane Câu 49: What multiplicity would you expect for the signal of a proton bonded to a carbon that is adjacent to two chemically equivalent methyl groups? A a quintet B a sextet C a triplet D a quartet E a septet Câu 50: Which of the following describes the H NMR spectrum of 1,2-dichloroethane? A one doublet of doublets B one doublet D two doublets E two triplets C one singlet Câu 51: How many lines are there in a doublet of doublets if the two coupling constants are the same? A B C D E Câu 52: The coupling constant between the geminal hydrogens in trans-3-chloropropenoic acid is 14 Hz in an NMR spectrum that was recorded on a 60-MHz spectrometer What would be the coupling constant if the spectrum were measured on a 600-MHz spectrometer? A 1400 Hz B Hz C 1.4 Hz D 14 Hz E 140 Hz Câu 53: Which of the following methyl groups will have the most downfield signal? A CH3OH B CH3CH2CH3 C C6H5-CH3 D CH3-C(=O)-CH3 E CH3Br Câu 54: What is the multiplicity of the hydrogen bonded to oxygen in an NMR spectrum of pure ethanol? A a singlet B a doublet C a quintet D a triplet E a quartet Câu 55: In what region of a 13C NMR spectrum would you find a carbon in an aromatic ring? A 30–40 ppm B 8–35 ppm C 110–170 ppm D 165–175 ppm E 205–220 ppm Câu 56: The chemical shift is calculated using which of the following equations? A δ = distance downfield from TMS (Hz)/operating frequency of the spectrometer (MHz) B δ = distance downfield from TMS(Hz)/magnet strength of the spectrometer C δ = distance upfield from TMS (Hz)/operating frequency of the spectrometer (MHz) D δ = operating frequency of the spectrometer (MHz)/distance downfield from TMS (Hz) E δ = distance downfield from TMS (Hz) X operating frequency of the spectrometer (MHz) Câu 57: In the H NMR spectrum of a compound with molecular formula C5H10O, the integrated peak areas were: 5.4, 3.6, 3.6, and 5.4 What is the ratio of protons in the four peaks? A 3:2:2:3 B 5:4:4:5 C 3:3:2:2 D 9.7:6.5:6.5:9.7 Câu 58: What is the ratio of peak intensities in a clean triplet? A 1:3:1 B 2:1:2 C 1:2:1 D 3:1:3 E 1:1:1 Câu 59: What condition is required in order for signals to have "clean" splitting patterns? A The difference in the chemical shifts of two adjacent protons must be < 10 J B The difference in the chemical shifts of two adjacent protons must be > 10 J C The difference in the chemical shifts of two adjacent protons must be < J D The difference in the chemical shifts of two adjacent protons must be = J E The difference in the chemical shifts of two adjacent protons must be > J Câu 60: Which of the following has the greatest value for its chemical shift in a 13C NMR spectrum? A the alpha carbon of an alkyl halide B a carbonyl carbon C the alpha carbon of an alcohol D a carbon of TMS E the carbon of a benzene ring Câu 61: Why is the signal for the C-2 hydrogen of 2-chloro-3-methylbutane the one that appears farthest downfield? A It is the hydrogen in the middle of the compound B It is the most shielded hydrogen C It is closest to the electron-donating chloro substituent D It has no equivalent hydrogens E It is closest to the electron-withdrawing chloro substituent Câu 62: What is the multiplicity of the CH2 hydrogens in CH3OCH2CH2OCH3 ? A a triplet B a singlet C a doublet D a doublet of doublets E a quartet Câu 63: What would the 1H NMR spectrum of 1,3-cyclohexadiene look like? A signals: a triplet, a multiplet, and a doublet B signals: two doublets and a multiplet C signals: a singlet, a multiplet, and a doublet D signals: a doublet and two triplets E signals: a triplet, a multiplet, and a doublet of doublets Câu 64: Which of the following is not a true statement? A A C-2 hydrogen of 1-chlorobutane shows a signal farther downfield than a signal for a C-1 hydrogen B Protons that are deshielded require a higher frequency to sense the effective magnetic field C Dimethyl ketone shows two signals in its 13C NMR spectrum D Deshielded protons are located farther downfield in an NMR spectrum E Diethyl ketone shows two signals in its 1H NMR spectrum Câu 65: Which of the following describes the 1H NMR spectrum of CH3CH2-CH(=O)? A two triplets and a multiplet B a singlet, a triplet, and a quartet C two doublets and a triplet D a singlet, a doublet, and a quartet E a singlet, a triplet, and a doublet of doublets Câu 66: Which of the following is true? A a: More shielded protons require a lower frequency to come into resonance B b: Protons in electron-rich environments are less shielded C c: B(effective) = B(applied) – B(local) D d: Electron-withdrawing groups shield neighboring atoms E a and c Câu 67: Which set of protons in 1-bromo-5-fluoropentane has the smallest value for its chemical shift? A It is the protons on C-5 B It is the protons on C-2 C It is the protons on C-1 D It is the protons on C-3 E It is the protons on C-4 Câu 68: What would the 1H NMR spectrum of nitrobenzene, C6H5-NO2, look like? A It would have unsplit signal B It would have signals: a doublet and triplets C It would have signals: a doublet, a doublet of doublets, and a triplet D It would have signals: doublets and a triplet E It would have signals: a doublet and a triplet Câu 69: How many signals would you expect to see in the 1H NMR spectrum of trans-1,2dichlorocyclopropane? A B C D E Câu 70: How many signals would you expect to see in the 1H NMR spectrum of chlorocyclopropane? A B C D E Câu 71: Which of the hydrogens in CH3OCH2-C6H5-CH3 would show the signal with the lowest value for its chemical shift? (The two substituents on the benzene ring are at the 1- and 4-positions.) A the hydrogens of the methylene group B the hydrogens of the methyl group bonded to the oxygen C the hydrogens on the benzene ring adjacent to the ether group D the hydrogens on the benzene ring adjacent to the methyl group E the hydrogens of the methyl group bonded to the benzene ring Câu 72: Identify the compound with molecular formula C9H12 that has a triplet at 1.21 ppm (3H), a singlet at 2.30 ppm (3H), a quartet at 2.60 ppm (2H), and a singlet at 7.04 ppm (4H) A 1,2,4-trimethylbenzene B isopropylbenzene D 1-ethyl-4-methylbenzene E propylbenzene C 1,3,5-trimethylbenzene Câu 73: What would be the splitting of the protons on the CH2 groups of butane? A triplet of quartets B triplet C single D sextet E doublet Câu 74: Which of the following is the correct order for the coupling constants of vinyl protons? A trans > cis > geminal > long range B geminal > long range > cis > trans C cis > trans > geminal > long range D trans > long range > cis > geminal E trans > geminal > cis > long range Câu 75: NMR relies on? A the absorption of energy by chemical bonds B the absorption of energy by chemical bonds in conjugated p systems C the absorption of energy by the nucleus of any atom D the absorption of energy by the nucleus of some atoms E the absorption of energy by the nucleus of some atoms, exciting their spin state Câu 76: Which of the following statements about shielding is false? A shielding is an increased effect of the external magnetic field due to the induced magnetic field in the molecule B shielding is a decreased effect of the external magnetic field due to the induced magnetic field in the molecule C shielding determines the chemical shift of the atom D the standard reference for measuring shielding effects is TMS E deshielding shifts the signal or peak downfield Câu 77: Electronegative atoms? A shield adjacent protons shifting the peak upfield B deshield adjacent protons shifting the peak downfield Câu 78: Alkenes and arenes protons are? A shielded due to the induced magnetic field of the p electrons B deshielded due to the induced magnetic field of the p electrons Câu 79: Which of the following statements about proton NMR is false? A the number of peaks indicates the number of hydrogen atoms B the multiplicity (or splitting pattern) indicates the number of vicinal protons C the chemical shift indicates the local chemical environment (i.e the presence of electronegative atoms and/or p bonds) D the intensity, or area, of the peak indicates the number of each type of proton E the number of peaks indicates the number of chemically distinct protons Câu 80: Which statement about spin-spin coupling is false? A spin-spin coupling occurs between vicinal protons B spin-spin coupling results in a peak being split in n+1 peaks (where n is the number of vicinal protons) C the coupling constant, J, is the separation between peaks that are split by spin-spin coupling D spin-spin coupling is observable for protons separated by bonds E protons that have the same chemical shift not split each other's signals Câu 81: Groups of peaks can indicate specific functional groups What would a quartet at 3.5 ppm and a triplet at 1.8 ppm indicate? A a -CH(CH3)2 group B a -CH2CH3 group D a -CH2CH2CH3 group E a -O-CH2CH3 group C a -C(CH3)3 group Câu 82: Acidic protons (those on acids, alcohols, and amines) or not couple with their vicinal protons? A they not B they Câu 83: The chemical shifts (in ppm) for 13C-NMR for the following types of carbon atoms are? alcohol, alkene, arene, acid, aldehyde A 50-65, 100-150, 110-175, 160-185, 190-220 B 220-190, 160-185, 110-175, 100-150, 50-65 C 100-150, 50-65, 160-185, 110-175, 190-220 D 100-150, 50-65, 110-175, 160-185, 190-220 E 50-65, 100-150, 160-185, 110-175, 190-220 Câu 84: In the following 13C-NMR the peak at 168 ppm is? A an alkane carbon B a carbon attached to an electronegative atom C an sp2 hybridized carbon D an aromatic carbon E a carbonyl carbon in an acid or ester F a carbonyl carbon in an aldehyde or ketone Câu 85: In the following 13C-NMR the peak at 60 ppm is? A an alkane carbon B a carbon attached to an electronegative atom C an sp2 hybridized carbon D an aromatic carbon E a carbonyl carbon in an acid or ester F a carbonyl carbon in an aldehyde or ketone Câu 86: In the following 13C-NMR the peaks at 130 ppm are? A an alkane carbon B a carbon attached to an electronegative atom C an sp2 hybridized carbon D an aromatic carbon E a carbonyl carbon in an acid or ester F a carbonyl carbon in an aldehyde or ketone Câu 87: In the following 13C-NMR the peaks taken together suggest this compound is an ? A an alkane B an alkene C an aromatic ether E an aromatic ketone F an aromatic aldehyde D an aromatic ester Câu 88: In the following decoupled 1H-NMR there are how many unique types of H atoms? A B C D E F Câu 89: In the following 1H-NMR the peak at 12 ppm suggest what functional group? A an aldehyde B an acid D an alkyl halide E an alcohol C an ether Câu 90: In the following 1H-NMR the peaks at - ppm suggest what functional group? A a monosubstituted aromatic ring B an ortho-disubstituted aromatic ring C an meta-disubstituted aromatic ring D an para-disubstituted aromatic ring E an ortho-trisubstituted aromatic ring Câu 91: Combinations of peaks in the IR can give indications of what functional group is present What functional group would correspond to the following combination of peaks? 3500 cm-1 (w) and 1690 cm-1 (s) (w = weak, s = strong) A an acid B an ester C an amine D an amide E an ether Câu 92: Combinations of peaks in the IR can give indications of what functional group is present What functional group would correspond to the following combination of peaks? 3300 cm-1 (s,b) and 1650 cm-1 (s) (b = broad, s = strong) A a phenol B an ester C an amide D an amine E an ether Câu 93: The following IR is of an? A an alkane B an alkene C an alcohol D an acid E an ester F an aromatic ester Câu 94: The following IR is of an? A an alkane B an alkene E an ester F an aromatic ester C an alcohol D an acid Câu 95: The following IR is of an? A an alkane B an alkene E an ester F an aromatic ester C an alcohol D an acid Câu 96: MS relies on? A the absorption of energy by chemical bonds B the absorption of energy by chemical bonds in conjugated p systems C the production of a radical cation D the absorption of energy by the nucleus of some atoms E the absorption of energy by the nucleus of some atoms, exciting their spin state Câu 97: The molecular ion peak in MS is? A the M+ peak B the peak with the largest relative intensity C the M+2 peak D the M+4 peak E the peak with the greatest mass to charge ratio (m/z) Câu 98: A MS with M+ and M+2 peaks with a ratio of 1:0.3 contains? A carbon isotopes B one Cl atom D one Br atom E two Br atoms C two Cl atoms Câu 99: A MS with M+, M+2, and M+4 peaks with a ratio of 1:2:1 contains? A carbon isotopes B one Cl atom D one Br atom C two Cl atoms E two Br atoms Câu 100: The MS can be used to determine all of the following except? A indicate the presence of isotopes B structural features of the compound C the exact structure of the compound D the molecular formula E the molecular weight Câu 101: The index of hydrogen deficiency (IHD) is used to? A indicate the presence of isotopes B determine possible structural features in the molecule C determine the exact structure of the compound D determine the molecular formula E determine the molecular weight Câu 102: Which of the following compounds will give a molecular ion having m/z = an odd number? A CH3CH2OH D CH3CH2NH2 B CH2BrCl C CH3CO2 H E (CH3)2NCH2C≡N Câu 103: What class of compounds is most likely to give a fragment ion at m/z = M-18? A alkenes B cycloalkanes D alkyl iodides E benzene derivatives C alcohols Câu 104: Which of the following compounds is most likely to have its base peak at m/z = 43? A CH3(CH2)4CH3 B (CH3)3CCH2CH3 C cyclohexane D (CH3)2CHCH(CH3)2 Câu 105: Fluorine is monotopic (19F) What would you expect to see in the mass spectrum of F2? A The spectrum contains one peak at m/z = 38 B The spectrum contains peaks at m/z = 38 and 19 of equal intensities C The spectrum contains one peak at m/z = 19 D The spectrum contains peaks at m/z = 38 and 19, and these are probably of different intensities Câu 106: Bromine possesses two isotopes (79Br and 81Br) in an approximate 1:1 ratio In the mass spectrum of Br2, how many peaks will the parent ion contain? A B C D Câu 107: Using appropriate software, it is possible to simulate the isotopic pattern associated with a given molecular formula The simulated mass spectrum of the parent ion of CH4 shows peaks at m/z = 16 and 17 with relative intensities ≈100 : 1.1 What is the main origin of the peak at m/z = 17? A 13C incorporated into CH4 B 3H incorporated into CH4 C 2H incorporated into CH4 D CH5 formed in the mass spectrometer Câu 108: Fluorine is monotopic (19F), and chlorine consists of two isotopes (35Cl and the mass spectrum of ClF, how many peaks does the parent ion contain? A B C 37 Cl) In D Câu 109: The mass spectrum of diethyl sulfide, (CH3CH2)2S, shows several groups of peaks with intense lines at m/z = 90, 75, 61, 46 and 29 Which statement is inconsistent with these data? A The mass spectrum suggests that diethyl sulfide fragments by cleavage of both C–C and C–S bonds B The parent ion is visible in the mass spectrum of diethyl sulfide C The mass spectrum suggests that diethyl sulfide fragments by sequential loss of the ethyl groups to leave an S atom D The mass spectrum suggests that one fragmentation pathway for diethyl sulfide is by loss of an ethyl group Câu 110: A simulation of the isotopic pattern for the parent peak in the mass spectrum of acetonitrile (CH3CN) gives peaks at m/z = 41, 42 and 43 with relative intensities 100.00 : 2.65 : 0.02 An experimental mass spectrum shows intense or relatively intense peaks at m/z = 38, 39, 40 and 41 What is the likely reason for the difference between the two sets of data? A The simulation of an isotopic distribution pattern for a molecule is unreliable B In the mass spectrometer, C–C bond cleavage occurs C In the mass spectrometer, C–N bond cleavage occurs D In the mass spectrometer, C–H bond cleavage occurs Câu 111: The highest mass peak in the mass spectrum of PF3 comes at m/z = 88 and is a single peak Which statement is consistent with these data? A Fragmentation of PF3 occurs in the mass spectrometer B P–F bond cleavage is facile in the mass spectrometer C Either P or F, but not both, is monotopic D F and P are monotopic Câu 112: But-2-yne has the structure H3C–C≡C–CH3 Major peaks in the mass spectrum of but2-yne appear at m/z = 54, 39 and 27 Which of the following is inconsistent with these data? A But-2-yne fragments by cleavage of a C–C bond B But-2-yne fragments by loss of a methyl group C The highest mass peak corresponds to [C4H6]+ D But-2-yne fragments by loss of two methyl groups Câu 113: Which of the following statements is incorrect? A Isotopic distribution patterns are observed in mass spectra B Mass spectrometry provides direct structural data C Mass spectrometry gives information about fragmentation patterns D Parent ions are not always observed in the mass spectra of compounds Câu 114: The highest mass peaks in the mass spectrum of SbF3 are at m/z = 178 and 180 Which is the correct explanation for this observation? A F has two isotopes, and Sb is monotopic B Sb has two isotopes, and F is monotopic C The peak at m/z = 178 is a fragment ion D The sample is impure Câu 115: The mass spectrum of acetone (CH3COCH3) shows major peaks at m/z = 58, 43 and 15 What can be deduced from these data? A The parent ion is observed, and fragmentation involves loss of CO B The parent ion is observed, and fragmentation involves cleavage of two C–C bonds C The parent ion is observed, and fragmentation involves cleavage of a C–C bond D The parent ion is not observed Câu 116: The base peak in a mass spectrum is: A the lowest mass peak B the peak corresponding to the parent ion C the highest mass peak D the peak set to 100% relative intensity Câu 117: Bromine has two isotopes 79Br and 80 Br, each ≈50% abundant In the mass spectrum of tribromomethane (CHBr3), the highest mass peaks are at m/z = 250, 251, 252 and 253 The ratio of the intensities of these peaks is: A : : : B : : : C : : : D : : : Câu 118: Which list below gives only spin active nuclei? A 1H, 13C, 19F B 2H, 12C, 19F C 1H, 12C, 19F D 1H, 2H, 12C Câu 119: Vicinal coupling is: A coupling between 1H nuclei attached to adjacent C atoms B coupling between H nuclei in an alkene C coupling between H nuclei attached to the same C atom D coupling between 1H nuclei in an alkane Câu 120: Which statement corresponds to the case where the chemical shift difference between two coupling protons is less than 5-times the coupling constant? A An AX pattern is observed B An AB pattern is observed C An undistorted binomial splitting pattern is expected D A first-order spectrum is expected Câu 121: A 1H-1H coupling constant for a doublet in a compound X is measured as 5.0 Hz on a 500 MHz NMR spectrometer Which of the following statements is incorrect? A For this doublet, the coupling constant measured in Hz depends on the field strength of the spectrometer B For this doublet, the coupling constant is 5.0 Hz when the spectrum of X is recorded on a 250 MHz NMR spectrometer C The difference Δδ for the two components of this doublet is 0.05 ppm when measured on a 100 MHz spectrometer D The difference Δδ for the two components of this doublet depends on the field strength of the spectrometer Câu 122: Which statement is correct about the vibrational ground state of an H2 molecule? A The molecule is in its lowest vibrational level but is not vibrating B The molecule is vibrating C In its vibrational ground state, the molecule has no vibrational energy D The molecule is static in its ground state Câu 123: The force constants for CO and CS are 1902 and 849 N m–1 respectively Which statement is incorrect? A Less energy is required to dissociate CS than CO B The wavenumber associated with the stretching of CO is higher than that of CS C Stretching the bond in CO requires less energy than stretching the bond in CS D The trend in bond energies for CO and CS follows the trend in force constants Câu 124: Which statement is incorrect about CO2? A CO2 has two degenerate bending modes of vibration B CO2 is linear C The IR spectrum of CO2 shows four absorptions D CO2 has two stretching modes of vibration Câu 125: Which statement is incorrect about H2O? A H2O has three IR active modes of vibration B H2O has four degrees of vibrational freedom C H2O undergoes symmetric and asymmetric stretching modes of vibration D H2O is non-linear Câu 126: Which is the correct sequence of wavenumbers associated with the stretching of the following bonds? A C–I > C–Cl < C=O < C≡N B C–I < C–Cl < C=O < C≡N C C–I > C–Cl > C=O < C≡N D C–I > C–Cl > C=O > C≡N Câu 127: n-Propylbenzene contains C(sp2)–H and C(sp 3)–H bonds The IR spectrum of propylbenzene contains strong or medium absorptions at 3085, 3064, 3028, 2960, 2931 and 2873 cm–1 as well as bands below 1600 cm–1 Which statement is incorrect? A Absorptions at 2960, 2931 and 2873 cm–1 are assigned to the stretching of the C(sp3)–H bonds B Absorptions at 3085, 3064 and 3028 cm–1 are assigned to the stretching of the C(sp2)–H bonds C Each absorption can be assigned to the stretching mode of a particular bond in the propylbenzene molecule D Stretching of the C(sp3)–H bonds gives rise to absorptions at lower wavenumbers than stretching of the C(sp 2)–H bonds Câu 128: The IR spectrum of CBr4 has a strong absorption at 667 cm–1 Which is the correct assignment of this absorption? A The symmetric stretching of the four C–Br bonds B A bending mode C The asymmetric stretching of the four C–Br bonds D The stretching of one C–Br bond Câu 129: The IR spectrum of liquid cyclohexanol contains a broad band at 3331 cm–1 Which of the following statements correctly describes what happens if the IR spectrum is re-recorded after D2O has been added to the alcohol? A A new band near to 2500 cm–1 is observed B A new band near to 3800 cm–1 is observed C The absorption at 3331 cm–1 becomes more intense D The absorption at 3331 cm–1 becomes very sharp Câu 130: For which of the following molecules could a pure rotational spectrum not be observed in the gas phase? A N2 B CO C HCl D CO