Organic ChemI 3444Q, Columbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 1

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1 olumbia University 92RG24.D EM S3444Q Summer 1992 Professor Irving J. Borowitz Exam No. 4 August13, 1992 Name: Grade: Please use a non-red pen. Answer questions in the provided space. If you write any answers on the back of the page, indicate this on the front of that page. Points appear in parentheses ( ). Good Luck! Question Max. Pts. Points 1. 2 ( 2 2 ) = = = = ( ) 3 2 = = = = = 12 Total = (06) onsider the following two isomers of A: IR cm -1 and 830 cm -1. NMR - (Dl 3 /TMS) ë 1.25 (triplet, 3), ë 2.3 (quartet, 2), ë 2.8 (singlet, 2), ë 3.7 (singlet, 3), ë 7.4 (AB quartet, 4). B: IR cm -1 and 750, 700 cm -1 NMR - (Dl 3 /TMS) ë 1.0 (triplet, 3), ë 1.3 (multiplet, 2), ë 2.8 (singlet, 2), ë 3.8 (triplet, 2), ë 7.2 (singlet, 5). a. alculate ê, the Index of ydrogen Deficiency for the molecular formula b. Sketch the NMR spectra for isomers A and B. A. rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 1

2 δ δ B (16) a. Determine the structure of isomer A, , in Problem 1 above. Fully support your choice by explaining the IR and NMR spectra. b. Determine the structure of isomer B, , in Problem 1 above. Fully support your choice by explaining the IR and NMR spectra. c. Starting with Ph- 2 synthesize : 2 ( 3 ) 2 d. Starting with Ph- 2 synthesize D: 2 ( 3 ) 2 rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 2

3 e. Give a chemical test or reaction which can be used to confirm the identity of. Show the equation and note any visible change. f. Give a chemical test or reaction which can be used to confirm the identity of D. Show the equation. rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 3

4 3. (14) a. If one wishes to prepare 5-methyl-2-hexanone using the acetoacetic ester synthesis, one would use the following alkyl halide(s). (1) 3 2 -Br (2) ( 3 ) Br (3) Br (4) ( 3 ) 2-2 -Br b. Show the above synthesis in detail, using arrows to show the direction of electron flow in the mechanism and including the steps and reagents as well as the structure of the final product. c. Rank the following compounds in order of decreasing acidity (strongest acid to weakest acid). Briefly rationalize your choice (1) (2) (3) (4) l (5) rder: (6) Rationale: d. Fill in the structure for the aldol condensation product formed from 3-pentanone and sodium ethoxide in ethanol after heating and dehydration. Show how it was formed and select the IUPA name: (1) 4-Methyl-4-nonen-3,7-dione (2) 5-Ethyl-4-methyl-5-hepten-3-one (3) 5-Ethyl-4-methyl-4-heptene-3-one (4) 3-Ethyl-4-methyl-3-heptene-5-one (5) 3-Ethyl-4-methyl-2-heptene-5-one rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 4

5 4. (10) a. Which reagent would serve as the basis of a simple chemical test that would distinguish between the pair of compounds listed below: N 3 3 N 2 (1) AgN 3 in 2 (2) Dilute Na (3) Dilute Na 3 (4) PhS 2 l, -, then 3 (5) Dilute l b. Give the equations for the reaction chosen, showing the organic product and noting the differing visible results. c. omplete the following reaction sequence. 3 N 2 1. N 2. u 2 (N) 2 A 3 / 2, B B Br 2 FeBr 3, d. Show and explain the fact that glucose exists in two forms that are interconvertible, à-d-glucopyranose and á-d-glucopyranose. e. Which of the following is/are true of the disaccharide sucrose? (1) It reacts with Benedict s Solution. (2) It hydrolyzes to yield fructose and glucose. (3) It undergoes mutarotation in aqueous solution. rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 5

6 (4) It gives a dark blue color with iodine/ki solution. (5) It is a non-reducing sugar. 5. (10) a. A D-aldotetrose sugar D could be oxidized with N 3 to an optically inactive dicarboxylic acid E. ompound D is subjected it to the modified Kiliani-Fischer Synthesis, whose reaction sequence is: 1. N, 2. 2, Pd/BaS 4, 2. The result of this reaction sequence is the formation of two isomeric aldopentoses F and G. ne of the aldopentoses F could then be oxidized with N 3 to give an optically active diacid, while G, in an analogous oxidation gave rise to an optically inactive acid I. (1) What is the structure of the aldopentose F? 2 2 (1) (2) 2 2 (3) (4) (2) What is the structure of the aldotetrose D? (3) What is the structure of the optically active diacid? b. By showing a part of the amylose portion of starch and of cellulose, and by giving an explanation, differentiate amylose starch and cellulose. rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 6

7 c. Give a simple chemical test and its visible result that would distinguish the two polysaccharides. 6. (12) a. Which of the following statements regarding lipids is not true? (1) Lipids are soluble in non-polar organic solvents. (2) All lipids have the same functional groups. (3) Lipids have very little in common except their solubility. (4) Lipids include waxes, terpenes, steroids, and triglycerides. (5) Many lipids have biological roles. b. Natural "fatty acids" are biosynthesized in living organisms from: (1) Glycerol (2) Alkenes with cis-double bonds (3) Acetyl-S-oA (4) Isopentyl pyrophosphate (3-methyl-3-butenyl-PP) and dimethylallyl pyrophosphate (3-methyl-2-butenyl-PP) (5) Unbranched alkanes with even numbers of carbon atoms. c. Which of the following is a female sex hormone? (1) Ergosterol (2) ortisone (3) Androsterone (4) holic acid (5) Estradiol (6) ortisol d. Which of the following is a male sex hormone? (1) Ergosterol (2) Testosterone (3) Estradiol (4) ortisone (5) holic Acid (6) Estrone e. holesterol and other steroids are made biosynthetically from the triterpene: (1) aryophyllene (2) á-arotene (3) à-farnesene (4) Squalene (5) holic Acid. f. utline the key steps by which a -4 sample small acid is biosynthesized on the way to becoming a "fatty acid." rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 7

8 7. (08) a. Define isoelectric point giving its important characteristics. b. Using the following table of pk a values, find the amino acid which would have its isoelectric point pi closest to 3.0. alculate the exact pi and show your calculation. amino acid pk a1 (-) pk a2 (-N 3 ) pk3 (-R) alanine lysine phenyl alanine tyrosine glutamic acid cysteine c. hoose the structure that corresponds to the answer you have chosen. (The structures are randomly placed below compared to the order in the table above). rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 8

9 _ N 3 N N 3 2 _ N (1) (2) (3) N 3 N 3 N S 2 (4) (5) (6) 8. (12) a. Synthesize alanine from direct appropriate precursors by two different methods, such as ammonolysis, Gabriel Synthesis, Strecker synthesis, or acetamidomalonate synthesis. N 3 3 b. Show how Sanger s method using 2,4-dinitrofluorobenzene, 2,4-DNFB, can be used to identify the N-terminal amino acid in the dipeptide Val-Phe. N 2 ( 3 ) 2 N Val - Phe 2 Ph _ rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 9

10 c. The secondary structure of proteins is derived from: (1) peptide linkages (2) disulfide linkages (3) hydrogen bond formation (4) hydrophobic reactions (5) acid-base interaction d. The primary structure of proteins refers to its. 9. (12) a. Which reagent(s) below are used to "protect " the amino group of an amino acid which is to be joined to a second amino acid by a peptide bond. 3 l l 3 2 l 2 - l ( 3 ) 3 l (1) (2) (3) (4) (5) b. Synthesize the dipeptide gly-val using either the straight organic synthetic method with the mixed anhydride as the activating group or the Merrifield automated solid state peptide synthesis with DI (dicyclohexylcarbodiimide) as the activating group. Show all steps including protection, activation, reaction, and removal of the protecting groups. (Ignore the fact that in the standard synthetic method, the valine is used as the methyl ester). :N 2 ( 3 ) 2 N Gly - Val rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 10

11 c. Which of these amino acid residues is expected to prefer the interior of a protein to the exterior when the protein is in aqueous medium? (1) threonine (2) valine (3) serine (4) aspartic acid (5) lysine d. The occurrence of this amino acid in a chain disturbs the à-helix: (1) proline (2) alanine (3) histidine (4) methionine (5) tyrosine rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 11

12 Scrap Paper Best wishes for a successful career and an enjoyable remainder of the summer. 08/13/92 Grace and Irv Borowitz rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 12

13 Scrap Paper rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 13 rganic hemi 3444Q, olumbia U, Su92, Exam 4 - Final Exam, 08/13/92; Dr. I.J. Borowitz 13