Chemistry 14C Winter 2016 Final Exam Part A Page 1

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1 hemistry 14 Winter 2016 Final Exam Part A Page 1 1. (6) n the blank after each set of 13 -MR data write the letter of the molecule that is the closest fit. f none of the molecules fit, write none of these. Each molecule can be used only once Molecule A Molecule B Molecule Molecule D Molecule E Molecule F (a) ppm (doublet), ppm (singlet), ppm (doublet), ppm (singlet), ppm (doublet), 69.3 ppm (triplet), 22.6 ppm (triplet), and 10.4 ppm (quartet). Best fit is molecule (b) ppm (singlet), ppm (singlet), ppm (doublet), ppm (singlet), ppm (doublet), 55.2 ppm (quartet), 50.1 ppm (triplet), and 29.1 ppm (quartet). Best fit is molecule (c) ppm (singlet), ppm (doublet), ppm (singlet), ppm (singlet), 60.7 ppm (quartet), 21.9 ppm (quartet), and 16.0 ppm (quartet). Best fit is molecule Questions 2 and 3 refer to these three molecules: Acetamide -Methylacetamide,-Dimethylacetamide 2. (2) Assign the following boiling points by writing numbers after the names: 221 o, 204 o, and 165 o. Acetamide bp = o -Methylacetamide bp = o,-dimethylacetamide bp = o 3. (3) Write the names of three different noncovalent molecular forces that influence the boiling points of these molecules. 4. (2) f the forces you listed in question 3 write the name of the force that has the least influence. Page 1 score =

2 hemistry 14 Winter 2016 Final Exam Part A Page 2 5. (2) The boiling point of,-diethylacetamide is (circle one): (a) Less than 165 o (c) Between 204 o and 221 o (b) Between 165 o and 204 o (d) Greater than 221 o 2 3,-Diethylacetamide 6. (5) ircle 3 or 2 as appropriate, then finish the statement by adding no more than three words to each blank: The most acidic hydrogen of acetamide is 3 / 2. The conjugate base formed by removal of this hydrogen is stable, because nitrogen has larger than carbon. 7. (3) how the one-step reaction mechanism for the formation of the conjugate base of acetamide using 3 - as the base. nclude appropriate curved arrows. f any structure in the mechanism has more than one resonance contributor, show only the most significant contributor (2) By adding, subtracting, or changing into another element up to three atoms, redraw the structure of acetamide in the box so that it is even more acidic. 9. (10) ircle the molecule with the highest boiling point in each set. (a) F (b) ( 2 ) 5 ( 2 ) (c) ( 3 ) 2 ( 3 ) 3 ( 3 ) l (d) (e) 10. (2) Write in the box the name or draw the structure of the molecule with lowest boiling point among all of the molecules in question 9. Page 2 score =

3 hemistry 14 Winter 2016 Final Exam Part A Page (2) onsider the following boiling points, then write the correct conclusion(s) in the blank below = = 2 1-exyne (bp 71 o ) 1-exene (bp 60 o ) 1-Pentyne (bp 40 o ) 1-Pentene (bp 30 o ) (a) Alkynes are more polarizable than alkenes. (b) Alkynes are less polarizable than alkenes. (c) An alkyne is capable of hydrogen bonding whereas an alkene is not. (d) one of these conclusions are reasonable. Letter(s) of correct conclusion(s): 12. (8) n class we were reminded that talian dressing consists of two layers: an upper oil layer and a lower vinegar ( 3 and water) layer. ther chemicals might be added to enhance the flavor or other properties of talian dressing. n the box to the right of each structure shown below write one letter that best describes its distribution in talian dressing. Answer choices: (a) More soluble in vinegar layer than in oil layer (b) More soluble in oil layer than in vinegar layer (c) ighly soluble in both layers (d) ot very soluble in either layer - + a 2 Monosodium glutamate (MG): enhances flavor Ascorbic acid: adds tartness; a preservative 2 Diallyl sulfide: A pungent molecule from onions 2 2 Melamine: falsely increases apparent protein content 13. (4) Understanding the acidity of amino acid side chains is critical to understanding enzyme reaction mechanisms. After each set write the letter of the amino acid with the most acidic side chain in that set Most acidic (a) A B D Most acidic (b) E F G Page 3 score =

4 hemistry 14 Winter 2016 Final Exam Part A Page (2) Prontosil (structure shown below) was the first commercially available antibiotic, introduced in t was sold as the l salt (prontosil-l). n the structure below, circle the nitrogen atom that is mostly likely to be protonated by l (i.e., the most basic nitrogen atom) (2) onsider this equilibrium and the associated pk a values: Prontosil-l + 2 Prontosil pk a 9 pk a -1.8 Write "<", "nearly equal", or ">" in the blank: For this equilibrium, K eq 1. The tuatara is a reptile whose skins glands produce a diverse set of substance that may help it communicate with other members of its species, as well as defend it against skin fungi. Questions refer to the lipid molecule shown here, which is among more than 150 substances isolated from tuatara skin secretions (2) omplete this sentence by adding no more than ten words: The tuatara skin secretion substance is not a prostaglandin because its structure (2) Answer this question by adding no more than five words: The tuatara skin secretion substance is a member of what lipid category (fatty acid, wax, etc.)? 18. (4) ompared to other lipids of the same type that we have studied in hem 14, the tuatara skin substance has some significant differences. Using no more than ten words in each case, describe two significant differences. ompared to other lipids of the same lipid category mentioned in question 17 that we have studied in hem 14, the tuatara skin substance is different because... ompared to other lipids of the same lipid category mentioned in question 17 that we have studied in hem 14, the tuatara skin substance is different because... Page 4 score =

5 hemistry 14 Winter 2016 Final Exam Part A Page (2) Write the letter of correct statement below concerning the solubility of the tuatara skin substance: (a) t is more soluble in water than in hexane. (c) t is easily soluble in both water and hexane. (b) t is less soluble in water than in hexane. (d) t is poorly soluble in both water and hexane. (e) annot draw any solubility conclusions from the information given. 20. (6) ircle the most acidic hydrogen atom in each molecule. l 21. (2) ircle the atom in this molecule that is the strongest base: P 22. (2) Write the letter of the molecule whose group has the lowest pk a : l 2 Molecule A Molecule B Molecule Molecule D l l Questions refer to an amino acid in a protein, whose partial structure is shown here: X 23. (2) n the structure shown above circle the atom(s) used by this amino acid to accept a hydrogen bond from another amino acid in an α-helix. 24. (2) Write all of the words that describe this amino acid s side chain. Answer choices: Acidic, basic, nonacidic (neutral), hydrophobic, hydrophilic. 25. (1) The stereochemistry of this amino acid s α-carbon is (circle one): natural not natural 26. (1) omplete this statement by writing a single letter or 'cannot determine' in the blank: This amino acid is at the protein's terminus. Page 5 score =

6 hemistry 14 Winter 2016 Final Exam Part A Page (3) Define (use no more than ten words): tandard amino acid 28. (6) omplete each statement using by adding no more than ten words in each case. (a) Among the 20 standard amino acids, glycine is different because it is the only amino acid that... (b) Among the 20 standard amino acids, proline is different because it is the only amino acid that... (c) Among the 20 standard amino acids, cysteine is different because it is the only amino acid that (4) omplete each sentence by writing one word in the blank. Word choices: primary, secondary, tertiary, quaternary. Each word can be used more than once. ot all words will be used. (a) Val-er-Asp describes a tripeptide s structure. (b) The only level of protein structure not possibly influenced by hydrogen bonding is. 30. (6) The following DA segment and accompanying text may have one or more significant errors. learly indicate (circle or arrow) and describe each error (ten words or less). f there are no errors write no errors. The wavy line means "molecule continues beyond this point". Accepts -bond from cytosine P 2 Donates -bond to cytosine Accepts -bond from cytosine The heterocyclic base is guanine (a purine). Page 6 score =