CHEM 233 FINAL EXAM QUESTIONS ANSWERED CORRECTLY LATEST UPDATE 2026

CHEM 233 FINAL EXAM QUESTIONS ANSWERED CORRECTLY LATEST UPDATE 2026 Mass spectrometry separates compounds based on what characteristic? - Answers mass/charge ratio Electrospray ionization mass spectroscopy often results in analyte molecules fragmenting. (T/F) - Answers F The fingerprint region is a difficult to interpret area of an IR spectrum (T/F) - Answers T Which of the following types of carbonyl would generally have a stretch located below 1700 cm-1 - Answers amide (or conjugated carbonyls) The stretch for a C-H bond where the carbon is sp2 hybridized would be located where on an IR spectrum? - Answers just above 3000 cm-1 () Electrospray ionization is a soft ionization technique. (T/F) - Answers T Which of the following electrospray ionization mass spectra corresponds to a compound that contains one chlorine atom? - Answers The one with the 3:1 ratio Which of the following electrospray ionization mass spectra corresponds to a compound that contains one bromine atom? - Answers The one with 2 peaks of the same height Which of the following electrospray ionization mass spectra corresponds to a molecule with a neutral molecular weight of 102 g/mol? - Answers 103 (H+) or 125 (Na+) A non-polar bond will always show a signal in an IR spectrum. (T/F) - Answers F - symmetric bonds will not show up Increasing the mass of atoms connected by a bond results in the absorbance of a higher wavenumber of light. (T/F) - Answers F Select the bond that would absorb the highest wavenumber of light in an IR experiment. C-N single bond C-N double bond C-N triple bond Cannot be determined - Answers C-N triple bond (triple bonds absorb higher ppm) Which of the following wavenumber ranges corresponds to the fingerprint region in an IR spectrum? cm-1 cm-1 cm-1 1500 cm-1 - Answers 1500 cm-1 Which of the following structures would you expect to have a carbonyl stretch above 1700 cm-1 in an IR spectrum? Select all that apply. - Answers ester and aldehyde Which of the following IR stretches would be consistent with the C-H bond in the below structure where the carbon is sp hybridized? (H - C☰C) 3300 cm-1 3100 cm-1 2950 cm-1 2100 cm-1 1700 cm-1 - Answers 3300 cm-1 Which of the following stretches would NOT be present in an IR spectrum of the below compound? Select all that apply. (terminal alkene, sp3 C, carbonyl) 3400 cm-1, broad 3300 cm-1 3100 cm-1 2950 cm-1 2100 cm-1 1700 cm-1 1650 cm-1 - Answers 3400 cm-1, broad 3300 cm-1 2100 cm-1 ( : sp2 C, 1650 : C=C, 1700 : C=O, : sp3 C) When placed inside of a magnetic field, NMR active nuclei act in what way? - Answers They align mostly in the same direction as the applied magnetic field When placed inside of a magnetic field, the magnetic field that electrons generate aligns in the opposite direction of the applied magnetic field. This has what effect on the nucleus the electrons are around? - Answers The electrons shield the nucleus from the magnetic field Proton A couples to Proton B. Proton A posseses a J-value of 3.0 Hz. What do you expect the J-value Proton B posseses to be? - Answers 3.0 Hz A carbon carbon triple bond would contribute how many degrees of unsaturation to a molecule? - Answers 2 How many degrees of unsaturation are present in a molecule with the molecular formula C5H8BrNO - Answers 2 ((2*5 + 2 + 1 - 8 - 1)/2) Is it acceptable to mark the baseline (the starting line 1 cm from the plate bottom) using a pen? Yes, because the ink will be easily distinguishable from any other compounds on the plate. Yes, because the ink will not elute up the plate. No, because the ink will react with the silica plate, causing an explosion. No, because the ink will elute up the plate and potentially obscure important data. - Answers No, because the ink will elute up the plate and potentially obscure important data. Switching from a less polar eluent to a more polar eluent using a normal phase TLC plate will have what consequence? Increasing the polarity of the eluent has no effect on how far compounds elute. Increasing the polarity of the eluent causes all compounds to elute a longer distance. Increasing the polarity of the eluent causes only nonpolar compounds to elute a longer distance. Increasing the polarity of the eluent causes only polar compounds to elute a longer distance. - Answers Increasing the polarity of the eluent causes all compounds to elute a longer distance. Select all of the following compounds that are not considered highly polar, that is they do not form hydrogen bonding interactions alkanes amines carboxylic acids alcohols alkenes ethers - Answers alkanes, alkenes, ethers You develop and visualize a TLC with two lanes. The compound in lane 1 eluted a distance of 3.0 cm. The compound in lane 2 eluted a distance of 6.0 cm. The solvent front eluted a distance of 12.0 cm. Calculate the retention factor of the compound in lane 1 to the hundredths place. (1 pt) - Answers .25 You wish to analyze the purity of a compound via TLC. If you wanted polar compounds to remain near the bottom (baseline) of the plate, what kind of TLC plate would you use A reverse phase TLC plate because the polar stationary phase will interact with polar compounds more strongly. A normal phase TLC plate because the nonpolar stationary phase will interact with nonpolar compounds more strongly. A reverse phase TLC plate because the nonpolar stationary phase will interact with polar compounds more strongly. A normal phase TLC plate because the polar stationary phase will interact with polar compounds more strongly. - Answers A normal phase TLC plate because the polar stationary phase will interact with polar compounds more strongly. You decide to use a plastic-backed TLC plate coated in silica gel. Which of the following choices is the stationary phase? A. The silica gel on the TLC plate B. The plastic of the TLC plate C. The solvent vapors in the developing chamber D. The substance or mixture to be separated E. The liquid solvent in the developing chamber - Answers A You are deciding which solvents to use to develop your TLC plate. Order the following solvents from most polar to least polar where 1 is most polar and 3 is least polar. - Answers isopropanol (H bonding), acetone (dipole), toluene (van der waals) You develop and visualize a silica gel TLC plate and are not satisfied with the results. Which of the following experimental parameters would result in a change in retention factors if you were to modify them in a properly performed TLC analysis? Mark all that apply. changing the TLC plate stationary phase length of the TLC plate changing the solvent system polarity width of TLC plate - Answers changing the TLC plate stationary phase, changing the solvent system polarity You developed the silica gel TLC plate using 100% ethyl acetate. Which of the following solvent systems would result in higher retention factors if you were to analyze the sample via TLC the same way again? The structures of ethyl acetate, ethanol, and hexane are shown below. 100% ethanol 50% ethanol/50% ethyl acetate 100% hexanes 50% hexanes/50% ethyl acetate - Answers 100% ethanol 50% ethanol/50% ethyl acetate Your silica gel TLC plate, shown below, was visualized using UV light. Performing other analytical techniques on your sample reveal that there are four compounds present, yet you see only three spots. What can you definitively say about the unseen fourth compound? A. The fourth compound does not visualize in iodine B. The fourth compound is not polar C. The fourth compound is polar D. The fourth compound does not E. The fourth compound does not visualize under UV light - Answers E. The fourth compound does not visualize under UV light Which of the following is an accurate description of the CEC method? A single enantiomer of alcohol is reacted with both enantiomers of HBTM A single enantiomer of alcohol is reacted with only one enantiomer of HBTM Both enantiomers of alcohol are reacted with both enantiomers of HBTM A single enantiomer of HBTM is reacted with both enantiomers of an alcohol - Answers A single enantiomer of alcohol is reacted with both enantiomers of HBTM Upon being added, the butyric anhydride reacts with what first? HBTM the unknown alcohol triethylamine toluene - Answers HBTM (makes reactive intermediate) What is the purpose of the phenyl group on the stereocenter of HBTM? To act as a pi-stacking recognition point for the approaching alcohol To block one face of the HBTM catalyst, forcing approach of the alcohol from the other side To coordinate with the triethylamine to facilitate deprotonation