Organic Chemistry 3540

Transcription

1 rganic Chemistry 3540 December 8, 2004 (8 Pages, 13 Parts) ame 1. (8%) Many organic compounds found in living systems are complex molecules which can be characterized, in part, by simply listing the chemical class or the specific products of the complete hydrolysis of the complex molecule. Such products might include:. amino acids;. deoxyribose; C. glucose; D. glycerol; E. long chain saturated acids; F. long chain unsaturated acids; G. nitrogen bases;. phosphate ion; and I. ribose.. Some products J. might not be in the previous list. dditionally, some organic compounds found in living systems are complex molecules but which cannot be hydrolyzed at all L. ydrolysis involves the breaking of specific bond types which might include: M. acetal;. amide;. anhydride; P. ester; and R. hemiacetal.. Some bonds S might not be in this list. nd, compounds which are not hydrolyzed as bond type T.."Characterize" the following groups of naturally occurring molecules by placing in front of the compound the appropriate letter (or letters) above of the product(s) of complete hydrolysis of the naturally occurring molecule..give the bonding which is broken during such hydrolysis by placing after the compound the appropriate letter (or letters) of the bond(s) broken during complete hydrolysis. a. b. c. d. alkaloid cellulose starch simple protein 2. (10%) ptically active aldopentose was strongly oxidized with nitric acid to give optically inactive diacid. Degradation of gave optically active aldotetrose C. Degradation of C gave D-glyceraldehyde. itric acid oxidation of C gave optically active diacid D. Give Fischer projections of,, C, and D.

2 3. (4%) Each amino acid has its own unique isoelectric point, the p at which it is essentially electrically neutral. Four amino acids and their isoelectric points are shown below (The structures, of course, are not shown in the zwitterionic forms.). C C 2 C 2 C C 3 C S C 2 C 2 C C Glu = Met = C C C 2 (C 2 ) 4 C C 2 la = 6.01 Lys = mino acids can separated by electrophoresis. Give the amino acid or acids of these four which: a. migrates towards the negative electrode in electrophoresis at p = b. migrates towards the positive electrode in electrophoresis at p = c. does not migrate towards the either electrode in electrophoresis at p = (7%) Draw the two dimensional structure of the tetrapeptide, Met-Glu-Lys-la. 5. (10%) In a study of rat liver aldehyde oxidase, a decapeptide was involved. Give the basic structure of the decapeptide based on the following analytical data. Edman degradation gave Gly. Carboxypeptidase analysis gave Val. Complete hydrolysis: sn =1; Gly = 1; Ile = 1; Pro = 2; Ser = 1; Trp = 1, Tyr = 1; Val = 2. Partial acid hydrolysis gave a complex mixture from which only two tripeptides were isolated in high enough yield and purity to be sequenced. They are: sn-ile-pro Ser-Tyr-Val Chymotrypsin hydrolysis (to the right of Phe, Tyr, and Trp) gave three small peptides with the following composition: sn, Ile, Pro, Val Gly, Ser, Tyr Pro, Val, Trp

3 6. (8%) Give simple chemical tests which will distinguish between the following. Give the formulas of reagents you would DD and tell what you would SEE. a. 2 b. 2 C 3 2 c. d. C 3 7. (4%) For each of the following examples, state if the example is an example of the primary, secondary, tertiary, or quaternary structure of the protein: a. folding of the helix in a globular protein b. association of four globins and four hemes in hemoglobin c. the amino acid sequence d. shape of a portion of the backbone, i.e., α-helix

4 8. (10%) Synthesize the following two compounds starting from benzene and compounds containing no more than two carbon atoms. a. b. I 9. (6%) The reaction of furan with bromine goes under milder conditions than benzene. Like benzene, it does not give addition product T. Like benzene, it gives a substitution product and it gives isomer V and not Z. 2, 0 o a. Is the resonance energy of furan greater than or less than benzene? T b. Explain, using appropriate structural drawings, why V is formed in preference to Z. V Z

5 10. (7%) Compound (C 7 17 ) is insoluble in 5% a but is soluble in 5% Cl. has 5 peaks in its C-13 MR spectrum. To determine the structure of, was treated with nitrous acid. Two fractions, and C (C 7 14 ) were collected by preparative gas chromatography. oth and C decolorized a solution of bromine in carbon tetrachloride. Detailed examination of revealed that it was a mixture of two cis-trans stereoisomers. Each stereoisomer of had 5 peaks in their C-13 MR spectra and C had 6 peaks. Treatment of with hot, acidic permanganate gave D (C ) and E (C ). D had two peaks in its C-13 MR spectrum and E had three peaks in its C-13 MR spectrum. Treatment of C with hot, acidic permanganate gave F (C 3 6 ) and G (C 4 8 ). F had two peaks in its C-13 MR spectrum and G had four peaks in its C-13 MR spectrum. oth F and G gave an orange-red precipitate with 2,4-DP. was treated with an excess of methyl iodide to give a salt, (C I). was treated with silver oxide to give I (C ), a compound as basic as a. eating I gave only and no C. a. Determine the structures of,, C, D, E, F, G,, and I. b. Suggest a reason why the nitrous acid treatment of gave two products while the heating of I gave only one product.

6 11. (12%) In each of the following, give the letter of the correct answer: a. Stronger base: b. Stronger base: 2 2 c. Stronger base: C 2 d. Product: 2, 300 o C e. bsorbs UV-Visible photon of a lower energy: C 3 3 C C 3 3 C C C 2 C f. D-glyceraldehyde: C C C 2 C C 2 C 2 C g. Edman degradation of a polypeptide reveals:. The amino end ( terminus) of the peptide.. The carboxyl end (C terminus) of the peptide. C. The amino acid to the right of Phe, phenylalanine.

7 C 3 M C 2 C 2 C C 2 C 2 h. For the reaction of M,, and with enedict s reagent:. nly M gives a positive test.. nly gives a positive test. C. nly gives a positive test. D. nly M and give a positive test. E. nly M and give a positive test. F. nly and give a positive test. G. ll three give a positive test. i. hexose: C 2 C 2 j. The β-pleated sheet is most significantly associated with which structure of a protein?. Primary structure. Secondary structure C. Tertiary structure D. Quaternary structure k. n aldose: C 2 C 2 l. pyranose C 2 C 2

8 12. (5%) There are various bonds and attractions which are responsible for the unique conformation of an enzyme. List five of these bonds and attractions. 13. (9%) For each of the following, give the letter of only one compound which contains the structural feature requested. ote that some compounds contain more than one structural feature. a. acetal b. -acetal c. amide d. hemiacetal e. deoxy sugar f. pyranose g. furanose h. aldose i. ketose j. aldopentose E C 2 G I C 2 C 2 C 3 C 3 F J 3 C C 2 S 2 C 2 k. l. ketohexose undergoes mutarotation K. Structure ot Given bove m. nonreducing sugar