HWeb27 (9.1-9.2; 9.12-9.18) 28.1. Which of the following cannot be determined about a compound by mass spectrometry? [a]. boiling point [b]. molecular formula [c]. presence of heavy isotopes (e.g., 2H, 13C) [d]. molecular weight 28.2. Which of the following is used to ionize molecules in mass spectrometry? [a]. by an ionizing magnetic field [b]. by a beam of gamma radiation [c]. by a beam of high energy electrons [d]. by placing the molecules in an electric field 28.3. Which of the following is not true? [a]. the most intense peak in the mass spectrum of a compound corresponds to its molecular ion [b]. the molecular ion is a radical cation formed upon removal of an electron [c]. the heaviest ion detected by mass spectrometry is the molecular ion [d]. fragmentation is the process whereby molecular ions break up into smaller speciesHWeb 28 (2.16) 29.1. What type of compound an IR peak at ~3300 cm-1 , but not at ~1720 or 1100 cm-1? [a]. alcohol [b]. carboxylic acid [c]. ketone [d]. ester 29.2. Which of the following types of compound has a strong IR band in the region of 1700 cm-1? [a]. Alkane [b]. Alkene [c]. Alcohol [d]. Ketone 29.3. The combustion analysis of a compound indicates that it has a carbon to hydrogen ratio of one-to-two and that another element is present. The mass spectrum shows a molecular ion at m/z=58. The IR spectrum shows a peaks at approximately 1650 and 1100 cm-1, but no peaks at approximately 1720 or 3300 cm-1. What structure is consistent with this data? A B C DOOHOHOO [a]. A [b]. B [c]. C [d]. DHWeb29 (9.3-9.4) 29.1. Which of the following is not true regarding nuclear magnetic resonance? [a]. Nuclei act as magnets and align with a magnetic field [b]. Nuclei absorb energy when they “flip” from being aligned with a magnetic field to being misaligned. [c]. The radioactive decay of nuclei is observed [d]. The technique aids in the determination of organic structures 29.2. Useful information obtained from a 1H NMR spectrum include: [a]. chemical shift [b]. integration [c]. splitting [d]. all of the above 29.3. Which of the following regions of the electromagnetic spectrum corresponds to the energy difference between the spin states of a nucleus in a magnetic field? [a]. gamma rays [b]. X-rays [c]. radio waves [d]. IRHWeb30 (9.5-9.6) 30.1. How many signals are there in the 1H NMR spectrum of 2-methyl-2-pentanol? [a]. Three [b]. Four [c]. Five [d]. Six 30.2. How many signals are there in the 1H NMR spectrum of p-xylene (1,4-dimethylbenzene)? [a]. Two [b]. Three [c]. Four [d]. Five 30.3. How many signals are there in the 1H NMR spectrum of 1,3,5-trimethylbenzene? [a]. One [b]. Two [c]. Three [d]. FourHWeb31 (9.8) 31.1. What type of peaks are there in the 1H NMR spectrum o-xylene (1,2-dimethylbenzene)? [a]. two singlets [b]. three singlets [c]. a singlet and two doublets [d]. two singlet and a doublets 31.2 What type of peaks would be obtained in a 1H NMR spectrum of isopropyl formate HC(=O)OCH(CH3)3? [a]. three singlets [b]. one quartet, one triplet, one singlet [c]. a singlet, a doublet and a septet [d]. two triplets, one doublet 31.3 What type of peaks would be obtained in a 1H NMR spectrum of ethyl acetate, CH3CO2CH2CH3? [a]. three singlets [b]. one quartet, one triplet, one singlet [c]. two triplets, one doublet [d]. unable to answer; more information is needed.HWeb32 (9.10 + review) 32.1. What is the structure of the compound, C4H7O2Br, which has the following NMR spectra? 1H NMR: 2.89 ppm (triplet, 2H), 3.54 ppm (triplet, 2H), 3.69 ppm (singlet, 3H) 13C NMR: 25.8 ppm, 37.5 ppm, 52.0 ppm, 171 ppm [a]. A [b]. B [c]. C [d]. D 32.2. How many signals appear in the 13C NMR (broadband proton-decoupled) spectrum of 3-bromobenzoic acid? BrCOOH [a]. Four [b]. Five [c]. Six [d]. Seven 32.3 A compound had the following analysis: C=39.75%; H=7.34%; Br=52.90%. Its 13C NMR spectrum shows five peaks. What is the correct structure of this compound? A B C DBrBrBrBr [a]. A [b]. B [c]. C [d]. DHWeb33 (Spectral Problems) 33.1. Which of the following compounds (C6H14N2) gives a 1H NMR spectrum consisting of three signals and a 13C NMR spectrum consisting of two peaks? A B C DNNCH3H3CHNNHCH3H3CNNNH2H2N [a]. A [b]. B [c]. C [d]. D 33.2. The 1H NMR spectrum of a compound has signals at approximately 1.2 (t, 3H), 2.5 (q, 2H), 4.0 (s, 3H), and 7-8 (4 H) ppm. Its IR spectrum had prominent peaks at 3050, 2950, and 1700 cm-1. What is the structure of this compound? H3COOCH2CH3H3COOCH2CH3H3COCH3OCH3A BC DH3CCH2 [a]. A [b]. B [c]. C [d]. D 33.3. The 1H NMR spectrum of a compound has signals at approximately 1.2 (t, 3H), 2.5 (q, 2H), 4.0 (s, 3H), and 7-8 (4 H) ppm. Its IR spectrum had prominent peaks at 3050, 2950, and 1700 cm-1. What is the structure of this compound? OCH3OCH2CH3CH3OOCH2CH3CH3OCH3OCH3CH2CH3A B C D 1. A 2. B 3. C 4.